INSTRUCTOR'S SOLUTIONS MANUAL to accompany product design for Engineers Devda Shetty.

Chapter 1 Exercises 1.1.

Suggest possible improvements you would like to see made to a common household item. a. Let us consider a common household item like an ironing board cover. I would like to see an effective means of stretching it tight over the ironing board so it doesn’t bunch up and cause wrinkles. The commonly used elastic border is insufficient to accomplish this. The solutions would be Velcro patches on the cover that engage stick-on patches on the underside of the ironing board, or grommets in the edge of the cover that wraps under the board so that an elastic cord could be attached from edge to edge under the board to keep the cover pulled tight. b. Another example of household product is “Refrigerator”. Although lot of innovations have taken place, there are customer needs that need to be addressed. With the large size of many of today’s refrigerators, food can get pushed out of sight and forgotten. That is until they go bad and the smell lets you know that you have a problem. An improvement I’d like to see would be an internal air sampling device that tests for a few common bacteria that indicate food spoilage.

1.2.

List several tools and techniques required for product development. How would you use them effectively?

Concept Development Phase

• • • • •

Market Studies Voice of the Customer Quality Function Deployment Axiomatic Design TRIZ

Design & Development

• • • • • •

Function Analysis Design for Manufacturing Design for Disassembly and Maintenance Product Modeling by CAD/CAM Simulation & Optimization, Six-sigma Design for Life-cycle

Analysis & Testing

• • •

Failure Mode Effects Evaluation Robust Design Rapid Prototyping

Process of Product Creation

• • •

Workplace Design, Flexible Automation, Value Stream mapping Design for Supply Chain

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1.3.

List two examples of promising products that have failed and briefly describe the reasons for it. a. Electric Automobile – In the early development of automobiles, about 1900, electric automobiles were a significant proportion of those made.

However, gas engine technology far outstripped battery technology, and gasoline was cheap, and pollution was not considered, so by 1920, no electric automobiles were manufactured in the US. The interest in electrical automobiles is on the rise in the last 10 years. b. New Coke – The Coca-Cola Company replaced its original formula and brand “Coke” with a sweeter “New Coke”. It failed because Coca-Cola did not adequately research the taste in other than small sips at a time, and did not consider the taste preferences and emotional attachment of its most loyal customers to the original Coke formula.

1.4.

Examine the 1998 case study of Breakfast Mates from Kellogg. Identify the reasons for the product to be withdrawn.

Reasons for the Product’s Withdrawal: 1. Warm milk: The product was advertised as ‘aseptically pack-aged and did not need refrigeration’. Aseptic processing is the process by which a sterile (aseptic) product (typically food or pharmaceutical) is packaged in a sterile container in a way that maintains sterility. However, consumers did not like the idea of warm milk 2. Cool milk: In order to accommodate for the consumer’s preference for cool milk, Kellogg’s eventually decided to place Cereal Mates in refrigerators to imply that consumers should have the milk cold. According to Robert McMath, president of New Product Works has has the following quotation which led to more confusion.

‘This decision inevitably caused a problem in that Cereal Mates was not in a location where you would generally expect to find breakfast cereal. The expense of trying to re-educate the consumer to look for cereal in the dairy case proved too enormous – way beyond, apparently, what Kellogg’s wanted to spend on selling the new line,’ 3. Advertising: Kellogg complicated matters further with the advertising campaign for Cereal Mates. The TV advertisements featured young kids helping themselves to the product, while their parents were still in bed. However, the packaging of the product was not child-friendly 4. Taste: Since the milk was warm, it did not taste good.

5. Price: Cereal Mates was considered too expensive by many consumers.

1.5.

What role does research play in product design? Indicate four sources of research and the desired information that you can expect from each source.

Research is the key factor in the design and successful market launch of the product.

The companies that spend a higher percentage of revenue on research have a good possibility of keeping up with the market forces worldwide.

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Four sources of research are: 1. Internet 3. Patents

2. Reference books, journals, Standards and trade catalogs 4. Use of simulation tools

1. Internet: This relatively new-research tool has proven to be very effective. Internet can facilitate and provide information on a range of competitive products, research publications. The Internet facilitates companies to conduct research and release new designs much faster. With the Internet connection becoming available in more and more countries, the Internet based technology provides new opportunity. For market research on new products, the resources available from the Internet are unlimited. The technology can help the product to get to the market as quickly as possible and explore the best possible alternatives. The advances in software and hardware have made it possible to animate prototypes and create design alternatives, adding a whole new dimension of utility to the practice. The Internet can be utilized to contact suppliers, vendors and contractors.

The Internet provides an extremely inexpensive and widely distributed format for distributing and soliciting product information and feedback. Distributing Internet based models via local networks, wide-area networks, or the Internet is very easy If the research is focused on customers, the use of Internet tools in early focusgroup sessions can yield effective feedback from potential customers, leading to higher market acceptance for the ultimate product. Traditional communication and collaboration often result in significant expenses from travel, personnel relocations, and telecommunications. Internet communication addresses most of these needs by enabling real-time linking of multiple sites in one virtual product; the result is a far more efficient use of time than traditional meetings. Access via the World Wide Web is simple and intuitive with the help of standard browsers available today.

Tools The most popular search tools for finding information on the Internet include Web search engines, meta search engines, Web directories, and specialty search services. A Web search engine uses software known as a Web crawler to follow the hyperlinks connecting the pages on the World Wide Web. The information on these Web pages is indexed and stored by the search engine. To access this information, a user enters keywords in a search form and the search engine queries its algorithms, which take into consideration the location and frequency of keywords on a Web page, along with the quality and number of external hyperlinks pointing at the Web page.

A Meta search engine enables users to enter a search query once and it runs against multiple search engines simultaneously, creating a list of aggregated search results. Since no single search engine covers the entire web, a meta search 3 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

engine can produce a more comprehensive search of the web. Most meta search engines automatically eliminate duplicate search results. However, meta search engines have a significant limitation because the most popular search engines, such as Google, are not included because of legal restrictions.

A Web directory organizes subjects in a hierarchical fashion that lets users investigate the breadth of a specific topic and drill down to find relevant links and content. Web directories can be assembled automatically by algorithms or handcrafted. Human-edited Web directories have the distinct advantage of higher quality and reliability, while those produced by algorithms can offer more comprehensive coverage. The scope of Web directories are generally broad, such as DOZ, Yahoo! and The WWW Virtual Library, covering a wide range of subjects, while others focus on specific topics.

Specialty search tools enable users to find information that conventional search engines and meta search engines cannot access because the content is stored in databases. In fact, the vast majority of information on the web is stored in databases that require users to go to a specific site and access it through a search form. Often, the content is generated dynamically. As a consequence, Web crawlers are unable to index this information. In a sense, this content is "hidden" from search engines, leading to the term invisible or deep Web. Specialty search tools have evolved to provide users with the means to quickly and easily find deep Web content. These specialty tools rely on advanced bot and intelligent agent technologies to search the deep Web and automatically generate specialty Web directories, such as the Virtual Private Library.

Advantage of using Internet for product related research: •

Shortening of the product definition phase involving the customer, marketing and design engineering.

•

Provides instantaneous access to knowledge and experience from different locations and disciplines during design and development stage to achieve high quality results quickly.

•

Exploring and building on ideas in the product implementation stage involving trade-off decisions between manufacturing, tooling and design engineering.

•

Improved design coordination with remote and non-remote partners.

Disadvantages: •

Internet security

•

Bandwidth 4

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•

Exposed proprietary information

There are other research search mechanisms such as Google including Research at Google; Google Research Blog; Think with Google; Google Research Programs; Google Scholar; Google Research on Twitter; Google Research Scientist 2. Reference books, journals, Standards and trade catalogs: In the early stages of research, many reference books will be useful as they provide analytical techniques and abstract ideas. Published literature includes scientific journals, conference proceedings, trade magazines, government reports, and new product reports. The state of the art information is available from scientific journals.

Many good ideas are published in trade journals, which are usually oriented towards a specific discipline. However, there are some trade journals that are targeted at product designers. Handbooks cataloging technical information can also be very useful reference as research tool. Examples of reference standards are: SME Handbook of product design, Standards Handbook of Mechanical Engineers etc.

Electronic database searches are another research tool to gather information from the published literature. The database can be accessed through on-line sources or in the form of CD-ROM storage devices 3. Patents: The patent literature is a good source of information. Patents are the sources of readily available sources of information that contains drawings and explanations of how many products work. The patents are also useful to check what concepts are already protected and must be avoided for certain period. Since there are a few millions of patents, a patent search narrows the area of interest. A patent search on a specific topic is done in three steps.

1. Identify the class and/or subclass of the area of interest.

2. Find the numbers of the specific patents that have been filed in the specific class that has been identified.

3. For a specific patent number, the information is available from the patent itself or from the official gazette announcement.

4. Use of simulation tools: Interactive product simulation can assist the product designers in conducting more efficient research. Use of Interactive product simulation procedures assists the research and development of department’s efforts. They can provide earlier access 5 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

to prototypes, faster updates than with physical models, enterprise distribution of information in an easy-to-understand format. They can support existing processes, and provide long-term value that extends beyond the finalization of product designs. In the design and detailing phase of product development, during which the primary need is to conduct frequent design reviews, Internet based simulation tools provide a means of integrating work from many different people and processes for group review and feedback. Instant on-line model changes on 3D models allow design optimization and lower manufacturing costs through immediate understanding of impact and implications of design alternatives.

As users can add real-time animations to the virtual product and edit them to indicate part paths and sequences as well as check for collision and clearances, cross-disciplinary collaborative design reviews can quickly evaluate individual ideas in the context of overall product assembly, maintenance and usability. The use of interactive tools in early product research can yield more-effective feedback from potential customers, leading to higher market acceptance for the ultimate product.

1.6.

With the help of sketches, show the basic concepts that can be used in the development of a product. What strategies would you use to have an effective design as speedily as possible?

Product Considered: Three Dimensional Vision Sensor (3D Sensor Development and Validation for Robotics and Unmanned Vehicle Applications. The sensor will be a part of the mobile Robot which has the capability to recognize objects within six feet) Objectives: The objectives of product design strategy should be to create a product with the basic objectives of achieving the desired functions with quality and greatest impact to the organization. The design of the product has a major impact on the cost.

• Make sure that the project goals are well defined and everyone understands what is to be committed in achieving them.

• Team goals are as important as individual goals. The environment should be comfortable for team action. Variety of viewpoints are encouraged.

Team members should communicate regularly; diversity of opinions should be encouraged.

• The product related decisions are made by consensus and supported by team members.

• Follow a predetermined agenda with time estimates. Focus on ideas, not personalities.

Background: The need for three dimensional sensing can be applied to various markets and has scores of applications including unmanned ground vehicles or mobile robots. Three dimensional technologies allows the capabilities such as mapping out a room or given area and scanning 6 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

for an object such as a bomb or a person, to report back to the military and act accordingly to the situation. A great advancement is in the safety for ground troops and be able to recognize things that the human eye may not see at first glance.

Unmanned vehicles have been deployed in several defense and security applications to provide information about unknown, unstructured environments with minimal risk to human life. These vehicles instrumented with sensors are capable of avoiding obstacles to navigate in an unknown environment, reporting concerns in different scenarios such as a battlefield, civilian security, disaster management, or in a patrol/surveillance mission. In such missions, a 3D environment map of the surveyed area of interest is useful feedback for organizing future action and deployment of army resources in a much more efficient manner.

State-of-the-art unmanned ground vehicles are capable of understanding and adapting to arbitrary road terrain for navigation. The robotic mobility platforms mounted with sensors detect and report security concerns for subsequent action. Often, the information based on the localization of the unmanned vehicle is not sufficient for deploying army resources. In such a scenario, a three dimensional (3D) map of the area that the ground vehicle has surveyed in its trajectory would provide a good spatial knowledge for directing resources in an efficient manner Navigation sensors for robots - such as lasers, radar, flash lidar, high-definition lidar and stereovision cameras - often are extremely expensive and perform poorly under the harsh terrain, lighting, precipitation and abrasion conditions met outdoors. Two-dimensional sensors such as planar range-finding lasers work well with robots indoors. However, in less predictable outdoor spaces, robots require 3D sensing to handle organic obstacles and cliffs. Most 3D sensors, such as high-definition flash lidars, are power-hungry and expensive, limiting their applicability. There is a definite need for a reliable, low cost, energy efficient 3D sensor for robotic navigation purposes.

Basic Design Concepts and Principles of Operation: The design methodology consists of the development of a laser based 3D sensor with unique illumination and positioning of sensors.

Fig. 1. Telescopic robot with the mounted laser sources and sensors

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On the top of that tube have to be mounted seven identical sensors where one of them must be located along the tube and to be tightened to it rigidly. The other six sensors with the combination of first one must be used for creation the entire 3D image of object’s frontal and top sides. These six sensors have to be located on the small platform, adjusted on the top of the detector C (Fig. 1.)

R

γ

S C γ

L

P

Fig. 2. Location of the sensors on the top of the telescopic tube

Fig. 3. Location of sensors by the right side (R) and left side (L) detector holders

Sensor Design

Divergent light source (visible or infrared) is used with circular exit of the source surrounded by the sensors/photodetectors. The shape of the sensors also is considered as a circular one, which must be tangent to the cylindrical surface of the light source and the sensors’ cylindrical holder (Fig. 4.)

Fig. 4. Location of the laser source and 12 Sensors/Photodetectors 8 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

Here the vertexes of the central angles α coincides with the center of the circles and that angle indicates the angular occupation of each sensor. If the radius of the light source is R than the radius of the sensors holder will be R + 2r where r is the radius of the sensor.

The efficiency of each detecting system might be determined as the ratio of the total area, occupied by the given ceria of sensors and the area between two circles that is the circle of the light source and detectors holder. Hence, the efficiency of detecting system might be found through this formula.

n ⋅π ⋅ r 2 n r π sin α E= = ⋅ = ⋅ π ⋅ (R + 2 ⋅ r )2 − π ⋅ R 2 4 (R + r ) 4 α , where n =

(1)

π r sin α = . α is the number of detectors and R+r

On the base of formula (2) let us calculate the efficiency with the several values of angle

α:

Table 1.

1)

o

then n = 4 ,

r ≈ 2.414 ⋅ R ,

E ≈ 0.707

o

then n = 6 ,

r ≈ R,

E ≈ 0.750

then n = 8 ,

r ≈ 0.62 ⋅ R ,

E ≈ 0.765

then n = 12 ,

r ≈ 0.35 ⋅ R

E ≈ 0.778

then n = 16

r ≈ 0.24 ⋅ R

E ≈ 0.780

if α = 45

2) if α = 30

3) if α = 22 .5 4) if α = 15 5)

o

o

if α = 11 .25

o

From these values, we can calculate and improve efficiency.

∆E = Eα =450 − Eα =600 ≈ 0.058 ∆E = Eα =300 − Eα =450 ≈ 0.043 ∆E = Eα =22.50 − Eα =300 ≈ 0.015 ∆E = Eα =150 − Eα =22.50 ≈ 0.013

(3)

∆E = Eα =11.50 − Eα =150 ≈ 0.002 It can be concluded that increasing the number of sensors leads to the decreasing of diameters of the sensors and in result of that increasing the efficiency of detection system.

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Timeline Task

Months 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Methodology Experiment and analysis Validation and testbed Report

Fig. 5. Conceptual sketches and prototype

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1.7.

Explain how you would select a team to undertake the product design for a multicomponent product.

Product design process is of complex and interdisciplinary nature. Carrying out a project on product design requires gathering a team of people with diverse expertise. It is important that the group dynamics of participants should be of right caliber. The methodology used by the product team would determine the quality of final product and its innovativeness and competitiveness. A good team leader is essential to coordinate the team members effectively so that the group can be kept focused. In selecting a product design team, various factors to be considered are: • Composition of team members • Creation of an environment for design discussions • Management of the team • Methodology and approach Team Chemistry: The team must have clearly defined goals: the rules of the game must be set for budgets, staffing, and responsibilities. The team should begin with a small, manageable problem. The disciplines that are related to the product should be included. The team member must develop an atmosphere that is conducive to free thinking. Most importantly, the team must have strong leadership. Teams generally make better decisions than individuals, especially in situations that are relatively broad and far-reaching in scope (e.g., strategic planning). Because of the diversity in background, experience and skills of the team members, they are more likely to consider a wider range of alternatives to solving problems and be more creative in their solutions. The very nature of team dynamics and consensus approaches to problem-solving means that teams are likely to take longer time to make their decisions. When dealing with sensitive issues, team has more potential power than any one of the individuals.

Team Selection: Next to the selection of the project, the single most important task is to choose the right players to serve on the team. As with any type of team, having the right combination of individual skills, attitudes and leadership will have a dramatic impact on the outcome of a project. It is also very important to have a good understanding of how teams should, and can work together in meeting their goals.

Teams are composed of highly motivated individuals from various areas of the company who may never have worked together. Regardless of whether concurrent engineering is used to develop a new product or process, or modify an existing one, some start-up problems must be anticipated. If people in the various functional departments are comfortable with traditional design approaches, the switch to teamwork may be difficult. In the traditional approach, each department has a welldefined piece of action. Each function adds its value as the project is passed from 11

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department to department, often with minimal interaction. Problems naturally arise, often resulting in some level of controversy. Genuine communication is not likely to occur under these conditions. For most employees of manufacturing companies, people from other departments are like strangers. Only rarely have they been required to share ideas or interact with each other during the early phases of a project.

Leaders of multifunctional or cross-functional teams are faced with the challenge of optimizing team performance. For leaders to have a reasonable chance of success, any team project must be preceded by adequate managerial preparation.

An underlying foundation in the concept of teamwork must be developed within the organization prior to commissioning any team.

Team Leader: Picking the right team leader is absolutely critical to a project’s success. The leader needs to have a combination of knowledge and qualities that will bring out the best in the team. Some of the qualities to look for are listed below: • • • • • • •

Respected technical specialist in one functional area Open to change.

Strong desires to contribute toward positive change Willingness to listen to ideas of others and to evaluate those ideas objectively; Good level of creativity; Effective oral communication; Assertiveness and persistence; Willingness and desire to work with others in problem solving.

Once members have been recruited, various amounts of team training should be considered. This, of course, will depend on the magnitude of the project and the experience of the leader and members in team solutions. Depending on the size and resources of the organization, the team leader could perform the selected training, or external consultants, an internal education department, or other qualified personnel could perform the training. Special training in team dynamics, cost reduction, or value engineering techniques only can improve the probability and degree of team success.

1.8.

Draw the functional diagram of an entire product. With examples, illustrate the difference between constraints and engineering specifications.

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Utility knife

Function Diagram of Utility knife A constraint is a limitation, within which the system must operate. The system may be constrained to such factors as cost, safety, compatibility with other products, and use of specific electronic and mechanical parts as other devices, interfaces with other instruments and test equipment, and development schedule.

The engineering specifications are detailed parameters describing how the system should work. For example, a requirement may state that the system should fit into a pocket,

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whereas a specification would give the exact size and weight of the device. For example, suppose we wish to build a motor controller.

1.9.

From the perspective of engineering design, what are the differences and similarities between a system and a product?

A system is an arrangement of physical components connected or related in such a manner as to form and/ or act as an entire unit. System can be controlled and modified. A product is the result of creation an idea where the final output will be in the form of a device or gadget. The product could be a physical entity or software algorithm satisfying the needs.

The characteristics of a system are: 1. It has distinct parts and parts involve a broad range of physical phenomenon.

2. The parts have observable attributes.

3. Parts are designed by different locations and by different designers.

4. The parts operate interactively.

The products and/or components are used to create a system.

Designing a product involves one in a constant decision-making process, which includes problem solving in a sequential fashion, and analysis of the constraints at each step.

Designing a product is providing a set of rules for reorganizing the elements of creation toward some greater purpose, known as “design intent.” The process of creating a product is very much influenced by the process of designing, as well as the overall product cost.

The cost of a product grows from conception, through the stages of technical research, design, development, market testing, use, maturity, until finally, its disposal. An organization has greatest control over a product at the early stages of its creation, when the market, its factory cost, operational cost and life cycle are determined. At this stage, a product’s status can be unstable as the organization tries to optimize the distinctiveness of the product for greater market acceptance. Naturally, a product’s features determine its performance and cost. The speed of a product’s development process, market testing, and manufacturing, are important factors in a product’s life cycle.

Industrial designers view design as a product. The solution of a design problem may take several forms. It may be a particular device or a product, such as an automobile, submarine or a space shuttle. The solutions for a design problem could be a process such as a technique for preserving food, or a new procedure for cutting metals. It could also be a procedure or a set of action plans. Although various professions define it differently, in general, design is some answer to a problem, an answer that has visible form or shape, or function. There is a powerful trend in product design toward material substitution, in using new, synthetically designed materials which have the highly desirable characteristics of toughness, lightness, durability, and flexibility. These technological advances are spurred by higher rates of productivity and, therefore, higher return rates on investment. In all these cases, the new technology exerts a more serious impact on the environment than the older one if we are not careful. Thus, the major cause of environmental crises has been these technological “improvements,” which have originated from a faulty design, failing to take the environment into account, in the quest for narrowly defined efficiencies. There should 14 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

be concern at the corporate level for the larger consequences of design can be understood and is being excused on the basis of economic exigencies. By neglecting such safety factors in design, we end up borrowing on the future, running an environmental repair and clean up. Rapid developments are currently taking place in certain research and development fields will have tremendous effects on product design. The changes we have witnessed in the electronic industry in the last thirty years, from the vacuum tube to the present day computer chip, are just a glimpse of what is in store for the future. Wide spectrums of information technologies, biotechnologies, along with other new materials are influencing the market significantly.

1.10.

Using web-based research, identify five corporations and their product lines.

In what way do these products support each corporation’s strategy?

• • • • •

Five corporations are Pratt & Whitney Jacobs vehicle systems Wiremold Company ABB Trumpf Inc.

Pratt & Whitney Pratt & Whitney is a leader in the design, manufacture and support of engines for commercial, military and general aviation aircraft, space propulsion and power systems. Pratt & Whitney is focused on continuously improving products and processes to deliver the performance and reliability the customers expect. It is an ISO9001-certified company.

Commercial Aviation Large Commercial Engines JT8D JT9D PW2000 PW4000-100" PW4000-112" V2500 GP7000 Parts Pratt & Whitney Canada Engines PT6A - Large JT15D PT6B Parts

PT6A - Small PW300 PT6C

Military Aviation F100 F117 PW4000 JT8D-219

PW4000-94" PW6000

PW100 PW500 PW200

PW800 PT6T/T400 PW900

F119 Parts

F135

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FT8 ST6L-72 ST5

ST30 ST6L-79 Brush Seals

Space & Missile Propulsion RL10 RD180 Orbus 21D

MK-72 Booster

ST6L-90 ST6L-81

ST40 ST18

Space Shuttle Turbo pumps Booster Separation Motors

THAAD National Missile Defense (NMD) System

Pratt and Whitney is also involved in maintenance services, spare parts, field services, support systems Jacobs’s vehicle systems As the world's leading manufacturer of engine brakes, Jacobs continues to push design, manufacturing, and performance standards beyond accepted limits. As Jacobs pursues incremental improvements, each hurdle represents the next standard. Each achievement becomes the basis of yet another. Quite simply, defying limits is the energy and spirit of Jacobs. No other manufacturer can match our products' track record & proven reliability. Since 1961, over 2 million Jake Brake retarders have been specified & installed and proven in over 1 trillion miles of driving.

Their engine brakes are used in Caterpillar C-10, C-12 & 3176/B Engines Caterpillar 3306 Engines, Caterpillar 3406B/C/E Engines Cummins N14 Engines Wiremold Company The Wiremold Company, founded in 1900 and headquartered in West Hartford, Conn., is a leading manufacturer of wire and cable management systems, power and data quality products, and data/communications connectivity systems. The Wiremold Company has embarked upon an aggressive program of quality improvement and product introduction using the “Kaizen” philosophy.

The Wiremold Company is developing and introducing new products faster than ever before. And strategic acquisitions of companies such as Walker Systems, Interlink Technologies, Brooks Electronics, Shape Electronics, and Sentinel Lighting have added new solutions that meet today’s challenges. This company mainly concentrates on power, data transfer devices, and wiring systems like

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WallSource Box, Nonmetallic Raceway, Metal Raceway, AnySize Raceway, Aluminum Raceway, Prewired Raceway, Plugmold.

ABB (Asea Brown Boveri Ltd.) ABB's strategy is to offer more value for customers while building a leaner organization. ABB is a global leader in power and automation technologies that enable utility and industry customers to improve performance while lowering environmental impact. ABB is moving all of its offerings to a common architecture, to deliver Industrial IT-enabled products and services that allow customers to optimize their operations and link up in real time with their suppliers and customers.

The result is a leap in efficiency, quality and competitiveness.

The products are in wide categories like Utilities, Process Industries, Manufacturing and Consumer Industries, Oil, Gas and Petrochemicals, - Power Technology Products, Automation Technology Products, and Financial Services.

TRUMPF Inc. TRUMPF Inc. is the North American subsidiary of TRUMPF GmbH +Co. KG. based near Stuttgart, Germany. With more than 566 employees, TRUMPF Inc. is the largest subsidiary within the TRUMPF Group. TRUMPF Inc. is dedicated to serving the fabricating machinery, OEM laser and laser marking needs of the American, Canadian and Mexican markets and is the largest manufacturer of fabricating machinery in the United States. The TRUMPF Group of companies has subsidiaries in 23 countries and with about 5,600 employees generates sales in excess of $1.1 billion. The TRUMPF Group is a world leader in sheet metal fabrication machinery and industrial lasers. The products are: • Machine Tools: TRUMPF offers computer controlled machine tools for flexible sheet metal and material processing.

• Laser Technology: High powered CO2 and solid-state lasers are ideal for cutting, welding or marking applications in industrial fabrication.

• Electronics: This includes dc power supplies and radio-frequency generators for laser, induction and vacuum technology.

• Medical Technology: This field includes surgery tables, systems for physical therapy, and systems for high frequency and laser surgery.

• Power Tools: In this field TRUMPF offers power tools for cutting, fastening and shaping.

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Chapter 2 Exercises 2.1.

Conduct a complete QFD analysis on a household product of your choice such as a dishwasher, washing machine, or refrigerator. The analysis should include the voice of the customer and the product’s ranking compared to that of competitors. Briefly explain your reasoning for the selection.

Product considered: Refrigerator Voice of the Customer: A. Energy efficient. Low importance.

B. Aesthetically pleasing. High importance.

C. Easy to clean. High importance.

D. Labor saving. Medium importance.

E. Reliable. High importance.

F. Quiet. High importance.

G. Cost. Medium importance.

Requirements Energy efficient

Aesthetically pleasing

What Low electrical consumption Low cooling loss when door is open Refined handles and exterior details Finish options

Easy to clean

Exterior Interior

Labor saving

Additional options

Convenience

Reliable

Long design life

Low Cost

Warranty High Value

How High efficiency compressor Temperature barrier Design includes ergonomic considerations Stainless, wide variety of colors Built-in cabinet option Fingerprint resistant Stable shelving Spill guards to contain spill on one shelf Ice maker (cube and chip) Water dispenser Night light Controls are ergonomically designed and located Components with 15 year design life Minimize vibration or redesign components to eliminate source 15 year, parts and labor Market value for dollar spent versus absolute cost

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Quiet

High efficiency compressor Sound isolation Vibration dampers Ice Maker Low noise pump, sound isolation A QFD chart with detailed market analysis and survey might capture a few more customer requirements.

2.2.

Compressor

Select a simple product of your choice (such as a can opener or umbrella) and identify the parts and objectives.

Product 1: Hand Held Cheese Slicer

Wire

Roller

Handle

Parts

Objectives Power Input, Control Cutting Guide Cutting Blade

Handle Roller Wire Product 2: Electric Kettle Parts

Objectives Main component of kettle for assembly.

Used to boil small quantity of water for domestic use.

Used for energizing.

Made of thermoplastic elastomers and facilitates handling of kettle.

These parts are interlocked with snap-fit with the base.

Base Reservoir Toggle switch Handle Grip Rear Cover and lid

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2.3.

Create a figure that shows the elements of a QFD chart. Explain how a cascade of these charts can be used to cover the total design and development process.

The typical product selected here is: Sports Bicycle.

Before the QFD chart is drawn, the basic customer requirements are identified.

Customer Requirents/Voice of the customer: • affordable, • easy to pedal, • adjustable positions, • lightweight, • aesthetically pleasing, • comfortable seat, • ability to ride on and off the road Elements of House of Quality The central body of the house of quality consists of WHATS (Customer needs), HOWS (what we control), and a matrix of relationships between the WHATS and HOWS. Figure shows the essential elements of a general house of quality. The customer requirements/needs/wants are listed horizontally and are known as WHATS. The counterpart technical characteristics are listed vertically and are known as HOWS. The interrelationship matrix (WHATS against the HOWS) is shown where horizontal and vertical axes meet. The roof of the matrix shows the correlation between the HOWS and HOWS. The bottom of the house of quality gives an indication of the technical characteristics against the technical bench marking (HOWS against the HOW MUCH).

Four Phases of QFD The four phases of QFD are: • Product planning phase • Part deployment phase • Process deployment phase • Product deployment phase

Correlation Matrix

• Strong Relationship = 9 ο Medium Relationship =3 ∆ Weak Relationship = 1 Customer Requirements

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3

Lightweight

4

•

Smooth ride Target values

5

ο X

ο •

∆

∆ X

Make a Snap Fit

Multi-suspension system

Standard components • ∆

Quick release fastener

Use of light weight material 2 5

ο •

Inexpensive Easy to pedal Adjustable positions

ο ∆ ο

∆

ο

X

• X

ο X

House of Quality In the product planning phase, customer attributes are drawn based on surveys, interviews, observations, field contacts, focus groups, employee feedback, publications, and sales records and are converted into product characteristics. A relationship matrix between the customer requirements and the product characteristics is drawn. This matrix will have data from market evaluation that includes customer expressed importance ratings and data on competitor’s products. The matrix will have information on data on current product strengths and weaknesses, measurable targets to be achieved, and selling points. In the part deployment phase, the product characteristics are translated into component characteristics.

At this stage, the characteristics of the final product are converted into part details at the component level. In the process deployment phase, the process plan for the manufacture of the component, sub-assembly, and assembly are identified as well as quality parameters. In the production deployment phase, the output from the process deployment charts provides a measure of critical product and process parameters. At this stage production operations for all critical components are identified

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Customer Requirements

Design Requiremen

Design Requirements

Four Phases of QFD

1. DESIGN

2. DETAILS Process Requiremen

Parts

Process

Production Requiremen

Customer Satisfaction

3. PROCESS

4. PRODUCTION

2.4.

Generate a number of concepts for a potato peeler and then create a product design.

The four-step concept generation methodology is used to generate a number of concepts for a potato peeler as follows:

1. Clarifying the problem • Understanding the current situation • Decompose the system into logical sub-components • Examine customer feedback 2. Search Externally • Patents • Literature • Experts • Benchmarking Search Internally • Review historical design data • Consultation • Brainstorming 3. Explore Systematically • Combine and Classify 23 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

4. Reflect on the Solutions & Process • Constructive feedback; Focus on each component individually The four-step concept generation methodology can be applied to the potato peeler as follows: • •

• • •

2.5.

Clarifying the problem: How to peel potatoes quickly, easily, safely, and cheaply. The problem is broken down into four critical sub-problems.

External search: An external search would consist of obtaining currently available potato peelers and evaluating their performance. Tests will be run to quantify their performance.

Internal search would consist of reviewing the internal knowledge and brainstorming on potato peeler design methods.

Explore: Organize, compile, and analyze the information.

Solution: A design of new potato peeler would be presented. Its performance would be compared with other potato peelers. Feedback from the analysis will be analyzed for further refinement.

Show a simple QFD-matrix relationship identifying three customer requirements and three design features.

In Quality Function Deployment analysis, it is very important that the product features have a strong relationship with the customer requirements. The degree to which the product features satisfy the customer requirements is quantifiable and is useful to the successful application of QFD. Three customer requirements for the potato peeler would be: 1. Maximize the rate of peeling of potatoes.

2. Minimize the risk of injury from using the potato peeler.

3. Minimize the effort (translates into strain) required to peel the potato.

Three design elements of the potato peeler would be: a. Blade length b. Guard configuration c. Swivel configuration Other customer requirements and design features certainly exist, but looking at the three items above, we can recognize a direct relationship. The relationship in three items can be identified as (1-a. 2-b, 3-c). As an example, the blade length affects the rate at which potatoes can be peeled. The guard configuration affects the likelihood that the user will cut their finger. A swivel reduces the operator strain because the blade will follow the contour of the potato, rather than having them bend their wrist to follow the contour.

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2.6.

If you are designing a technologically integrated product, identify the key criteria.

Design criteria for smart lamp: Examples of typical criteria are: • • • • • • • •

2.7.

Must have modern design Adjustable height and flexible gooseneck for precise direction of light Must be of suitable size to be used as a desk lamp and must not occupy much space Must be low voltage and energy saving Must appeal to both a male and female market Must be able to move to different locations easily Includes modern and traditional features Must have an inconspicuous switch

You are interested in creating a sustainable product. However, the supply chain influences its features. Prepare a survey for the supply chain companies to identify the issues of sustainability.

Survey Questions: The company developing a product should participate in a survey to see that the customer is satisfied. The survey should contain questions related to the quality of the product.

Some of the typical questions are as follows: • Does the company track, report, and communicate “costs of poor quality” to everyone in the company on a regular basis?

• Is the information system on quality computer-based or manual?

• Does a company have a formal quality evaluation program?

• Does the company have measurable, time-based quality objectives set on a regular basis by the management of the company?

• Are the product returns due to damage during shipping a problem?

• What performance measures are used to assess quality?

• What is the organizational structure for communication on quality issues and specific improvements?

• Does the company have an up-to-date quality manual that clearly defines the processes, procedures, and resources that assure the quality of products and processes?

• Is the company ISO-9000 certified, and has it passed subsequent audits?

• What role has quality played in product standardization?

• Has standardization increased the throughput and efficiency of the organization?

• Has standardization generated better usage of tools/instruments?

• What difficulties (technical, financial, personnel, production, and quality) were encountered in implementing process standardization?

25

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• • • • • • •

2.8.

Does the company certify suppliers?

What role have the suppliers played in the quality function?

What resources were necessary to effectively use suppliers in the quality function?

What is the percentage of on-time delivery from major suppliers?

What quality assurance tasks have been delegated to suppliers?

Do suppliers participate in product design activities?

What effect did quality improvements have on supplier process standardization?

Write the design specification for a smart air-pump station for filling automobile tires. This example requires the design of a new “Smart Air Pump Station” for filling automobile tires to the right pressure. The design features include the exact car manufacturer’s recommended tire pressure in an internal database without requiring more input from the customer than a basic knowledge of their car’s make, model, and year. There will be little possibility of inflating tires to the wrong pressure even in extreme and temperature conditions.

Design specification for a Smart Air Pump: • • • • • • • • • • • •

2.9.

15 inch LCD (liquid crystal display) touchscreen monitor for easy viewing to display user instructions, fees, and advertisements.

Computer located inside housing for programming and creating database of recommended tire pressure values.

Ergonomic features such as “easy grip” for user comfort.

Automatically inflates or deflates tires to the car-maker’s recommended tire pressure.

Shuts off once the desired pressure is reached.

Recognizes outside temperature (hot or cold) in order to determine the proper adjusted tire pressure.

Half inch thickness plywood housing with white color vinyl siding covering and ventilation channels for air compressor and desktop computer fan.

Protection from weather conditions by providing vinyl siding.

Retractable air hose.

Attractive and aesthetic look.

Audio and visual interactive units.

All weatherproof enclosures.

Write the design specification for creating the next generation of dishwasher.

Design specification of a modern dishwasher: • •

Large interior capacity makes room for larger dinnerware Energy Efficiency Class 26

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• • • • • • • • • • • • • • • • • • • • • •

2.10.

Noise level: 44 dB – 48 dB Efficient water consumption Different cleaning temperatures Water management system Load sensor with overload protection Detergent automation Self-cleaning filter system Push button top controls Attractive display inside Acoustic end of cycle indicator Real-time clock Electronic delay timer: 1-24 hours LED rinse aid refill indicator Anti-fingerprint surface coating Large size baskets 6 foldable plate racks in top basket 8 foldable plate racks in bottom basket 2 cup shelves in bottom basket Glass rack in bottom basket and glass care protection system Components with life time guarantee Childproof door lock Servo lock for effortless door closing

The design team decided to implement a full QFD chart for designing a garden implement such as weed cutter. It can be used in maintaining quality gardens. The requirements include (a) durability, (b) adequate power requirement, (c) light weight, (d) consistent starting, and (e) easy maintenance. Develop customer requirements and engineering parameters.

Compare your design to a commercially available product.

Product considered: Weed Cutter The product features can vary depending on the customer views. For some customers the major requirement could be dependability, ergonomic design, and cost as shown below. These requirements can also be broken down as secondary requirements. For example, dependability can be broken down as 1. String trimmer starts every time, and 2. String trimmer lasts 10 years. The importance of these secondary requirements can be shown by ranking them from 1 to 5.

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Voice of the Customer Survey What

Rank

Start Every Time

5

Solid state Ignition

Last 10 Years

4

High Quality Critical Parts

Requirement

How

Dependable

Light Weight Materials Weight

3

Ergonomic

Cost

Design Parts for Light Weight Balance

Fasten Lifting Strap at C.G.

Shape

4

Survey different types of customers for best design shape

Manufacturing process

3

Design For Manufacturability

Suppliers

Find Lowest Cost Suppliers

Ranking: 1 (Lowest Importance) - 5 (Highest Importance) The QFD chart created for String Trimmer is shown in Figure below.

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Chapter 3 Exercises 3.1.

Pick any product of your choice and construct a morphological chart for it.

Indicate one of its subsolutions and explain a brief reasoning for it.

Table 1. Chosen Product: Hand-held Wood Saw (Circular Saw)

Feature

Means

Handle

‘T’ type

Circular Grip

Horizontal Offset

Twist Grip

Input Power

Elec.

(AC)

Elec. (DC)

Gasoline

Natural Gas

Output Power

Electric Motor

Internal Combustion

External Combustion

Spring Motor

Cutting

Toothed Blade

Abrasive Blade

Laser

Shear

Guiding

Flat Plate

Curved Plate

Spherical Plate

Cable

Muscle

Parallel Rule

Common Optional Product 1. The proposed general type of Circular Saw is powered with 110V AC and uses an electric motor to drive a circular blade with sharp teeth for shearing the wood fiber. There is typically a flat plate to allow for a consistent blade angle for the duration of the cut, and the saw has a handle ergonomically suited to the majority of users.

Product 2 (with additional features). To differentiate a new product from the sizable competition requires uniqueness and some superior qualities without any weaknesses that would interfere with functionality. The proposed product would be a natural gas powered micro steam engine that powers a micro generator to activate a modestly powered CO2 laser. This would be completely portable and quiet, would make no sawdust, and would never need sharpening. The twist grip (similar to a motorcycle throttle) would serve to vary the output for different 31 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

thicknesses of material. There are some technical issues that have to be addressed.

3.2.

A customer has requested a weed cutter that can function for prolonged cycles with little maintenance. It must be lightweight in construction and durable. Go through the steps of attribute listing and create a morphological chart for this product.

Product: Weed cutter Voice of the Customer Survey Table 2. Ranking: 1 (Lowest Importance) - 5 (Highest Importance)

Requirement

What Start Every Time Dependable Last 10 Years

Ergonomic

Rank 5 4

Weight

3

Balance

Cost

Geometry

4

Mfg. Processes Suppliers

3

How Solid state Ignition High Quality Critical Parts Light Weight Materials Design Parts for Light Weight Fasten Lifting Strap at C.G. Test with wide variety of People to Find Optimum Geometry Design For Manufacturability Find Lowest Cost Suppliers

The process of designing a weed cutter starts with defining the needs of the customer and a niche in the market. A weed cutter is a common device used for cutting grass and weeds in small areas, tight corners, and around sharp corners.

Based on this need which general lawn mowers cannot fill, a need for the “weed cutter” exists. The voice of the customer is generally based on surveys and customized interviews with the prospective customers. Based on these, a house of quality can be generated.

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Table 3. Morphological Chart Function Cuts grass Power

Means Rotating Blades Gasoline

Holding method

Scissors

Laser

Electric

Hydro

Manual

Handle bars

Broom style

Harness mechanism

Blade safety

Blade shielded

Plastic blades

Switch on/off type Motor type

Push and hold button Gear box

Toggle switch

Wheel supported at back Emergency stop if hardness exceeds Knob

DC Motor

Pneumatic

Solar Power

Push and hold lever Magnetic

The next generation of weed cutters could use lasers to slash through grass instead of rotating blades. The laser source is carefully designed by a protective shield. It could be solar powered with rechargeable battery with magnets that spin the laser beam around. The source can be turned on by a lever on a handle bar set up so that it is easy to maneuver around sharp corners and along walls.

3.3.

Develop some new design concepts for a “comfort bicycle” and contrast them to the design of a mountain bicycle.

In this example, “Comfort Bicycle” is represented as “Indoor Bicycle Trainer.” The bicycle industry is a hi-tech, multi-million dollar industry that touches many customer requirements such as mountain bikes, sport bikes, and indoor bikes to name a few. The demand for such a wide range of categories arises from the riders and from competitions. Bicycles are often designed using cutting edge materials and computer software to accurately simulate the forces a bike frame is subjected to, allowing the designer to reduce the weight of the bike without compromising its overall strength.

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Customer Requirements for “Indoor Bicycle Trainer”: The market analysis shows many bicycle enthusiasts train hard to maintain the necessary level of fitness required to compete. The customers are interested in replicating the resistive forces that a bike is subjected to in order to allow the cyclist to train in a protective indoor environment. This type of need has resulted in products such Indoor Bicycle Trainers.

Figure 1. Indoor Bicycle Trainer

Problem Statement The design of an indoor bicycle trainer is required to simulate the forces a rider feels when cycling outdoors. These forces not only vary due to the characteristics of the road,trail, and ascending-descending motions, but also the rider’s position on the bike. However, there are two main types of forces which come into play when a cyclist is in motion. The types of forces experienced can be categorized as follows: Balancing Forces: The rider feels pedaling forces, caused by such things as friction, gravity, and bumps, through the pedals as he or she applies pressure to move the bike forward. Balancing forces are those minute body movements with weight shifts and steering actions required to keep the bike traveling in the desired direction. Designing an indoor trainer to replicate these various forces is very difficult. The focus of the design will be the aspect which can most improve the rider’s fitness by simulating the pedaling forces.

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Problem Definition: “Design a bicycle trainer that can simulate the pedaling forces experienced by a rider who is traveling on their bike in a straight line on a Flat Road with a regular surface.”

Functional Requirements: The next step of the design process is to formalize a set of product requirements.The establishment of these requirements is a critical phase of the design process, as the design concepts generated will be evaluated against each criterion individually. The product should simulate the pedaling forces experienced by the rider traveling in a straight line.

Simulating the forces a rider feels while pedaling is more complicated than first imagined. It doesn't just involve applying a resistance force, f or it also involves simulating the effect which the forward movement of the rider has on the forces felt through the pedals.

The force that a rider applies (Pedaling Force) is transmitted through a gearing system to the rear wheel, which causes the desired forward motion of both the rider and the bike as a single mass. This moving body has an inherent resistance applied, caused by various forces such as gravity (due to an incline), friction in the drive train, and wind drag. The mass of the bike and the rider also dictates the force required to accelerate the bicycle (F = MA). A rider of a fixed mass can only apply a set force; there is a maximum possible acceleration which can be generated. The replication of this attribute will directly affect the realistic feel of an indoor trainer, as it will prevent the unrealistic surges which the rider will feel when applying large forces through the pedals.

As opposed to Mountain Bikes, the forces that the indoor trainer must simulate should not only represent the range of resistive forces experienced, but also prevent the rider from accelerating at a rate greater than real/life conditions.

• • •

The indoor trainer should prevent forward motion of the bicycle during operation.

The final design should retail for no more than $250.

The final design should be easily portable and allow for compact storage.

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Concept Generation: The first step is to generate a Morphological Chart, allowing for the alternate solutions for each of the key areas to be displayed in a table. This table was generated with the help of Osborn Checklist to ensure that all the various options were generated.

Table 4. Morphological Chart

Key Area:

Means:

Resistance

Magnetic

Electric Motor

Fluid

Drive Engagement

Tire Surface

Rim Surface

Drive Train

Energy Storage

Flywheel

Spring

Electrical Energy

Bicycle Mount

On both wheels

Front Fork and Rear Wheel

Rear Wheel Only

Wind

Evaluation of the principles: Several types of indoor trainers are commercially available in the market each performs the same role slightly differently in the quest to simulate the feel of real cycling. There are three main types of trainer available, each being categorized by the method in which they provide resistance to the pedaling motion supplied by the rider:

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Pedals

Wind Resistance Trainers

Magnetic Resistance Trainers Fluid Resistance Trainers Figure 2. Different Principles

Attribute Listing: The key similarities of the various designs shown are that they address the Pedaling Forces and the Acceleration Considerations. A wind resistance based trainer uses the pedaling motion to drive what is in essence a small fan. The design of this fan varies considerably from each manufacturer, although most prefer the compactness of a Turbo Fan type.

Fluid based trainers work on a similar principle as the wind based trainers, although the blades rotate in a viscous fluid. The third category, Magnetic, can really be spilt into two groups: Electric and Fixed Magnet.

Electromagnetic trainers operate on a similar principle to electric generators with the applied motion being converted into electrical energy and usually dispersed in the form of heat. Fixed Magnet type trainers use a basic eddy current principle to apply a resistive force to a rotor.

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Wind

Fluid

Electric

Magnetic

Resistance Adjustability

Fixed Resistance

Adjustable from Low to High range

Remote Control

No

Yes

Yes

Yes

Electric Power

Not Required

Not Required

Required

Not Required

Price

Inexpensive

Expensive

Expensive

Inexpensive

Benefits and disadvantages

Low Cost, Noisy

Flexible, Susceptible to leakage

Quiet operation, Expensive

Adjustable from Adjustable from No resistance to Low to High Locked ranges

Quiet Operation, flexible

Table 5. Comparative Evaluation of Principles

Figure 3a. Commercial Indoor Trainer

Figure 3b. Trainer with Bike Fitted

The trainer may involve several subassemblies. Each one of these main assemblies performs a specific function, with the most important unit being the Main Drive Unit.

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3.4.

Construct a three-stage Duncker diagram for the following problem statement: “Finding time for sports is becoming difficult.” (Figure 4) PS – Finding time for sports is difficult

DS – Finding time for sports is easy

Achieve Desired State – Make finding time for sports easy

Provide more incentive

Participate in health program at work

Make participatin g in sports more convenient

Make it OK if we do not find time for sports.

GENERAL

Reduce nonsports activities

Set up minigym at work

Work fewer hours

Increase available quantity/ locations of sports activities

Eliminate a nonsports hobby

FUNCTIONAL

SPECIFIC

Incorporate exercise into other daily

Take stairs instead of elevator

Park farther away from office

Exercise on own in convenient location / time

Eat healthier

Join gym close to work that is open during time sports not normally available

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Eat less (Reduce calorie intake)

Eat lower calorie foods

3.5.

Select a hearing aid with styles varying from behind the ear to implantable, compatibility with blue tooth, automated volume control and a variety of maintenance tools. Construct a morphological chart and function diagrams for it.

Table 6. Morphological Chart of Hearing Aid Features Power Supply Styles Compatibility Controls Peripherals Directionality

Material Maintenance tools

Lithium-Ion Battery Behind the Ear FM receiver Volume Control Frequency Transposition OmniDirectional Epoxy Resin Wax guards

Means Cadmium Plug-in Battery In the Ear In the Canal IR Blue-tooth Program TelecoilButton Switch Noise Auto T-Coil Reduction Directional Cardioid response Pattern Polycarbonate Polyethylene Dri-aid Kit Cleaning Brush

Inertial Generator Open fit Induction Sensitivity Control Data logging Hyper cardioid

Vent Whisker

The reasons to pick the features from the above morphological chart are as follows: Lithium-Ion Batteries have the highest power capacity to weight ratio and they are rechargeable.

Behind the Ear allows for the options to be incorporated. It also accommodates for the largest range of hearing losses.

Blue-tooth is a technology that is currently popular and seems to be gaining even more favorability: this allows the product to be integrated with other technologies.

Telecoil-Switch delivers the induction signal from conventional phones directly to hearing aids, allowing the signal to be amplified according to the user’s hearing loss.

Data-logging allows the audiologist to analyze the listening environments of the patient as well as the hearing aid’s features that are in use in those environments.

Omni-directional allows the hearing aid to take in and amplify sounds from all directions.

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Polyethylene can be cast in a mold, and the material is rugged and resistant to moisture and corrosive liquids.

Wax guards prevent ear-wax from getting into the hearing aid, resulting in less need for cleaning as well as a smaller likelihood that the hearing aid will be hindered in its sound amplification.

3.6.

TRIZ methodology can help designers to formulate design solutions. Explain the commonality and differences between TRIZ and lateral thinking.

Lateral thinking follows the procedures of creative problem solving. It involves developing new ideas by brain storming approaches such as the following triggering techniques: • • • • • • • • • •

Can we use the product for other uses? As it is? If modified?

Adapt? Is there anything else like this? What does this tell you? Is the past comparable?

Modify? Give it a new angle? Alter the color, sound, meaning, motion, and shape?

Magnify? Can anything be added, time, frequency, height, length, strength? Can it be duplicated, multiplied, or exaggerated?

Minify? Can anything be taken away? Made smaller? Lowered? Shortened?

Lightened? Omitted? Broken up?

Substitute? Different ingredients used? Other materials? Other processes? Other place? Other approach? Other tone of voice? Someone else?

Rearrange? Swap components? Alter the pattern, sequence, or layout? Change the pace or schedule? Transpose cause and effect?

Reverse? Opposites? Backwards? Reverse roles? Change shoes? Turn tables?

Turn other cheek? Transpose ‘+/-‘?

Combine? Combine units, purposes, appeals or ideas? A blend, alloy, or an ensemble?

Futuring. Imagine a situation in the future and project your design to the future.

Idea generation using TRIZ methodology TRIZ procedures are based on patterns and rules that are created on the basis of large numbers of patents and procedures. It is a structured creative problem technique that helps designers to narrow down an idea along a practical path based on previous experience.

Example: Design a new structural material for Bullet Proof Garment.

Statement: Bullet proof vests should be strong, but not heavy.

Step 1 - Identify the contradiction(s).

41

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Strength (improves) versus Weight (worsens) Step 2 - Look at the list of features and identify those important to your contradiction.

Strength - #14 Weight - #2 Step 3 - Identify which are improving features and which are worsening features.

Strength (#14) improves and Weight (#2) worsens Step 4 - Refer to the TRIZ Contradiction Matrix to learn which of Altshuller's Principles may be useful for this problem.

Row 14 (Strength) and Column 2 (Weight) of the Contradiction Matrix indicate the following rinciples may be useful: 40, 26, 27, and 1.

We now look at the Principles list to learn that these numbers correspond to 40: Composite materials 26: Copying 27: Cheap short-living 1: Segmentation Next we brainstorm how we could use these four Principles to solve our problem.

A. 40. Composite materials The explanation of this Principle from the TRIZ website is: •

Change from uniform to composite (multiple) materials such as reinforced polymers.

Suggestions: For lighter-weight, stronger vests, the use of composites is an active area of research. Polymers (Kevlar) reinforced with carbon nanofibers are currently being investigated as a strong lightweight alternative to steel for structural materials.

B. 26. Copying The explanation of this Principle from the TRIZ website is: •

Instead of an unavailable, expensive, fragile object, use simpler and inexpensive copies.

42

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• •

Replace an object, or process with optical copies.

If visible optical copies are already used, move to infrared or ultraviolet copies.

Suggestions: We could copy the design of abbreviated scuba diving wet suits for use as a bullet proof garment.

C. 27. Cheap short-living objects The explanation of this Principle from the TRIZ website is: •

Replace an inexpensive object with a multiple of inexpensive objects, comprising certain qualities (such as service life, for instance).

Suggestions: This Principle does not appear to be readily applicable to this problem.

This is not necessarily unusual, because these Principles are only general suggestions to help focus our thinking in areas that have proven fruitful in previous problems.

D. 1. Segmentation The explanation of this Principle from the TRIZ website is: • • •

Divide an object into independent parts.

Make an object easy to disassemble (Replace worn or damaged parts).

Increase the degree of fragmentation or segmentation.

Suggestions: One could consider several different coverings for different parts of the body (pants, vest, etc.) rather than a one-piece suit. In addition, ideas considered would involve different materials to cover the critical areas such as the chest and head, each taking advantage of specific properties that would be customized for their differing applications. By identifying problem contradictions, the elements of TRIZ can be used to help reach a solution. Using the TRIZ method, additional ideas are generated.

3.7.

Patients suffering from cerebral palsy, traumatic brain injury, and muscle diseases benefit greatly by the availability of improved design tools. Identify how the customer requirements in each situation could be a part of a new product design process.

Cerebral Palsy (CP) is an umbrella term denoting a group of non-progressive, non-contagious motor conditions that cause physical disability in human development, chiefly in the various areas of body movement. Scientific consensus still holds that CP is neither genetic nor a disease, and it is also understood that the vast majority of cases are congenital, coming at or about the time of birth, 43

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and/or are diagnosed at a very young age rather than during adolescence or adulthood. It can be defined as a central motor dysfunction affecting muscle tone, posture, and movement resulting from a permanent, non-progressive defect or lesion of the immature brain. CP is the most common motor disability during childhood. Population-based studies from around the world report prevalence estimates of CP ranging from 1.5 to more than 4 per 1,000 live births or children of a defined age range. The average prevalence of CP is approximately 3.3 per 1,000 or 1 in 303 in 8-year-old children in the United States.

Spastic CP was the most common type of CP, found among approximately 80% of children with CP. 56% of children with CP were able to walk independently, while 33% had limited or no walking ability. Another study found that 41% of children with CP were limited in their ability to crawl, walk, run, or play, and 31% needed to use special equipment such as walkers or wheelchairs. The achievement of independent walking is a major focus of rehabilitation for children with cerebral palsy. Even when mobility could be achieved more easily through the use of assistive technologies such as wheelchairs, independent walking is typically pursued as a major rehabilitation goal and other forms of mobility are often discouraged. Despite these efforts, it is well established that many children with CP do not achieve or maintain functional walking, and will increasingly rely on wheelchairs for some or all of their mobility needs as they age. Published research materials support the physiological benefits, including maintenance of muscle length, bone density, and cardiovascular fitness.

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Need for Gait Rehabilitation Devices: Gait rehabilitation methods in patients with neurologic impairments have relied on technological devices which drive the patient’s gait in a body-weight support condition and emphasize the beneficial role of repetitive practice. Research investigation results suggest that children with CP benefit from robotic-assisted gait training in improving functional gait parameters. Repetitive locomotors training with an electromechanical gait trainer may improve gait velocity, endurance, spatiotemporal, and kinematic gait parameters in patients with cerebral palsy. Exoskeleton is defined as external wearable mechanism for assistance of gait to patients who do not have enough muscle power due to any injury or neurodisorder. Initially, these devices were developed for assisting the natural skeleton of the user in the performance of usual tasks like moving or carrying weights.

These devices can also be used in the rehabilitation of children with locomotion disorders.

Requirements: “To design a pediatric exoskeleton for the rehabilitation of the gait assistance caused by CP” 45 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

Specification of the users were obtained from a preliminary study of the target populations. In order to use an exoskeleton for the purpose of helping an individual with CP learn to walk, there are a couple of specialized needs that will need to be addressed.

Figure 5. Exoskeleton Device 1. The first and most basic difference between existing exoskeletons and one that could be used for CP patients learning to walk is sizing. The current exoskeletons are all designed around an adult stature. They have some ability to adjust to fit a small range of users, but not enough to accommodate an individual very far outside the range of an average adult.

2. Bio-mechanic investigations of gait of CP kids and normal populations for identifying the design parameters of wearable gait assistive devices. Mechanical design and analysis of anthropometric wearable gait assistive devices.

3. Mechatronics integration using sensor modules and bio-signals. Real time adaptive control strategy will be developed to address the variable gait requirement in different environments.

4. Feasibility analysis for the use of brain mapping activity with application of functional electrical stimulation system for “as per demand” based control of gait assistive devices.

Research on gait rehabilitation for CP kids would require close interaction and participations from engineers and physicians. The engineering fields can vary from miniaturized sensor, biocompatible materials, and real-time control 46 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

algorithms. The goal of developing low cost mobility rehabilitation aids would require the integration of the latest MEMS technology, miniaturized actuation devices, and high information processing control.

3.8.

Assistive technology products for elderly people present challenges to product designers who need to understand the general assessment process and issues connected with the basic customer needs. Identify a product that improves quality of life for elderly people, and generate concepts for the product architecture.

Wheelchair utilizing spring and damper system working principle and simulation.

Figure 6a. The photo of the wheelchair that is assembled system with spring & damper used on both front wheels

Figure 6b. A closer look into the spring and damper system mounted above the front wheel to achieve smooth riding experience

‫ݔ‬

݇

‫ܯ‬

Figure 7. Virtual prototype of a wheelchair with a spring and the moment, where the front wheels in the air (right figure) are shown above.

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1. In the first case, the wheelchair is about to go down to the lower ground and the time and acceleration for this case is given below as well as the constants and known elements. ‫ܯ‬: Mass = 0.5kg ݇: Spring constant: 500N/m ݈: Free length = 0.15m ܽ: Acceleration ‫ݔ‬: Displacement ‫ݔ‬ଵ : Initial position = 0.05m ‫ݔ‬ଶ : Desired position = 0.15m

‫ܯ‬.

ௗమ

‫ݔ‬ሺ‫ݐ‬ሻ + ݇‫ݔ‬ሺ‫ݐ‬ሻ = ∑‫ܨ‬

ௗ௧ మ ௗ௫ሺ௧ሻ

ௗమ

‫ݔ‬ሶ = , ‫ݔ‬ሷ = మ ‫ݔ‬ሺ‫ݐ‬ሻ ௗ௧ ௗ௧ at ‫ = ݐ‬0 , ‫ ݔ‬ሺ0ሻ = 0.5݉ ‫ ݃ܯ‬+ ݇. ‫ ݔ‬ሺ0ሻ = ∑‫ܨ‬ 0.5݇݃ ∗ 9.81݉/‫ ܿ݁ݏ‬ଶ + 500ܰ/݉ ∗ 0.05݉ = ∑‫ܨ‬ ∑‫ = ܨ‬29.9ܰ

Calculation to decide the descending time: From the total force, we get the acceleration; ∑‫ܽ ∗ ܯ = ܨ‬ 29.9ܰ = 0.5݇݃ ∗ ܽ ଽ.଼ଵ௞௚.

೘ ೞ೐೎మ

଴.ହ௞௚

= ܽ

ܽ = 60݉/‫ ܿ݁ݏ‬ଶ For the time which the front wheel reaches t ground, we use the following formula where we assume the initial velocity (‫ )݋ݒ‬is zero: ଵ ‫ ݐ ∗ ݋ݒ = ݔ‬+ ଶ ܽ ‫ ݐ‬ଶ ‫ = ݐ‬ඥ2 ∗ ‫ݔ‬/ܽ

= ඥ2 ∗ .1/60 ‫ = ݐ‬0.05777‫ܿ݁ݏ‬

‫ܯ‬

‫ݔ‬

݇

ܿ

Figure 8. Both wheels of the chair have reached the ground (left figure), and the spring is back to its original displacement (right figure) with the damper.

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2. The second case is where the wheel of the chair hits the ground and retraction takes place after full extension. In the realization of the system, we need to introduce the damper which plays a key role for retraction. Below are the known elements and constants as well as the equation of motion and solution for the differential equation.

M: Mass = 65 kg C: Damping coefficient = 400 N sec/m k: Spring constant = 500 N/m l: Free length = 0.15 m x: Displacement xଵ : Initial position = 0.15 m xଶ : Desired position = 0.05 m The equation of motion and its solution is given below: ① mxሷ = −kx − cxሶ ② mxሷ + cxሶ + kx = 0 ୡ ୩ ③ xሷ + xሶ + x = 0 ୫

୫

Figure 9. Simulation The Simulink diagram of the wheelchair with a spring and damper system built into its front wheel. Results of the Simulink realization of spring and damper system in the wheelchair: The cases below prove the best combination of spring stiffness “k” and damping coefficient “c” is chosen. Figure shows that the retraction takes 2 seconds with a damping coefficient of 400 Nsec/m and spring stiffness of 500 N/m.

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Figure 10. Simulation

With K = 400 and C = 100, time from full extension to retract is too long, which is 5 seconds.

Simulation through Working model 2D: Working model provides the capability of easily designing these systems with regard to geometric, kinematic and kinetic parameters. These parameters can be easily modified within the software to explore a wide variety of design choices.

Working model 2D provides a wide array of realistic tools to develop innovative virtual prototypes of mechanical systems. These systems can also be set in motion by appropriate forces or torques as may be applicable to the system.

• • • • • • • • • • • • •

Test multiple versions of your design Fast “run-analyze-refine” cycle helps to optimize designs before building physical prototypes Reduce physical prototyping You are in total control of the simulation environment Quickly build, run, and refine simulations with pre-defined objects and constraints Run, stop, reset, single step, or pause the simulation at any time Analyze your latest design by measuring force, torque, acceleration, etc., acting on any object View output as vectors or in numbers and graphs in English or metric units Input values from equations, sliders and DDE links to MATLAB and Excel Simulate non-linear or user events using a built-in formula language Design linkages with pin joints, slots, motors, springs, and dampers Create bodies and specify its mass properties, initial velocity, electrostatic charge, etc.

Simulate contact, collisions, and friction 50

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• • • •

Analyze structures with flexible beams and shear and bending moment diagrams Run or edit scripts to optimize simulations, document models, and more Record simulation data and create graphs Create visually appealing presentations by attaching pictures Wheelchair utilizing spring and damper system design and simulation: The working model simulation is realized to illustrate the Simulink simulation of the system more succinctly. The working model is more virtual and illustrative than Simulink; therefore the working principle of the spring and damper system can be seen and analyzed for any audience without having knowledge of complex theory and programming. Besides the analytical results of MATLAB/Simulink, the working model software provides the results mechanically and physically. The simulation captures are shown in the following figure.

Figure 11. Simulation by Working Model When the front wheels touch the lower ground, there is no oscillation to disturb the person; the wheelchair is kept straight since the back wheels are still on the higher ground. The spring is at full extraction and the wheelchair is straight. The figure captures the real video of the wheelchair going down the step. At this moment, the front wheels are not in the air yet and the spring and damper is at full retract position.

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Figure 12. Closer view of the attachment This capture of the real video shows the system at full extraction where the front wheels touch the lower ground fast enough that the person is not leaning forward, causing an unsafe situation. The straightness of the wheelchair ensures the smooth ride.

3.9.

A new product must be defined based on customer needs. The customer need is for a device (a) that recognizes that an automobile is locked from a distance, and (b) that can send a signal to lock the automobile if it is unlocked. Examine the above scenario and generate a problem statement for a new product.

Customer Requirements: Most of the modern day automobiles have an electronic remote key system with which the person driving the car can lock and unlock their automobiles.

Frequently, the drivers may inadvertently forget to lock their cars. At times, they do not hear the beep that the car key system emits when it is locked. Quite often it is observed that they leave the car parked, but are not able to remember if they have locked the car or not. They walk the distance to the car and have to check if it is locked.

This new product is of a remote key system that provides visual and/or auditory feedback to the owner confirming that the door has actually been locked. Unlike regular remote keys that issue the command to close the door but have no capacity to confirm that the door has been actually locked, this key activates the door lock via a remote command. The actual door locking process triggers another system embedded within the door and connected to the lock which instantly sends a signal back to the key confirming the locked status of the activated door. Upon receiving the feedback the key emits an audible response and/or vibrates and/or shows the locked state via a red light or a color change or any other feedback

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process/mechanism. That signal remains visible in the key until the driver activates the unlock command in the key.

Using this new product, the car driver and other occupants of the car, having parked the car exited the area of the parked car, can confidently test that the car is locked. Some car manufacturers have addressed the problem by devising a system where the vehicle head lights and tail lights come on when the remote key is pressed. Still there are systems that sound an alarm and audible sound when the vehicle remote is pressed. Most of these audio systems are difficult to distinguish from one another. From the search of the previous work, it is desirable to have a remote key system that addresses above problem. It is desirable to have a system that following engagement of the locking mechanism sends an electronic signal back to the key that it is indeed locked.

Design Features: Previous work by Devdas Shetty and Avital Fast consists of a remote key system called “Secure Key” that addresses the above problem and closes the loop.

Design Requirements: •

• • •

Once the car has received the key signal to lock it, following engagement of the locking mechanism, it sends an electronic signal back to the key that it is indeed locked.

The product has the inherent capacity to retain the message and signal to the driver that the car is locked.

The biofeedback consists of a signal such as vibration, LED light or color change and remains visible in the key.

A remote vehicular key system with locking confirmation assures the driver that the car is indeed locked.

Design Procedure: The product consists of two radio frequency devices. One is referred as hand control and the other is referred to as remote device and is located in the automobile linked to the door closing mechanism.

Each control device is embedded with a radio frequency receiver and transmitter operating on different frequencies.

The output transmission signal of hand control matches and is compatible with the frequency of the remote device. Similarly, the transmission signal of the remote device matches with the hand control device.

The dual transmitters and receivers enable the hand control to receive and identify feedback emanating from the vehicle installed remote device.

This information will provide the status of locking or unlocking in the automobile.

53

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Many vehicles are equipped with travel computers that provide preprogrammed instruction to vehicle drivers on fuel consumption, trip distance, etc.

There will be two receiver devices: one receiver confirms that the door is in the locked position, and the second receiver sends a trigger to the personal computer.

The personal computer has access to long distance communication network, such as a cellular network whereby a communication link is established between the Secure-Key and second communication unit. This way we can do a long distance monitoring of the status of locking of vehicle doors.

Previous Literature: 1. Previous work by Witte, Markus Valter (patent application 20020107010) titled, “Communication system for use with a vehicle” relates to a communication system for use with a vehicle. The system comprises a first communication unit positioned within a vehicle, and a second portable communication unit. Both the communication units have a memory circuit. The transceivers are arranged to establish a short-distance wireless communication link between said first and second communication units. If the communication units are within a communication range from each other, it helps two-way communication between the units.

2. Casey; Stephen J.; Dutcher; Alan P.; Kantor; Sidney; Hnosko; Erick; have a patent application, 20080150680 entitled, “Remote Portable Access System.”

This is a remotely controlled access system for a plurality of containers consisting of access mechanisms for locking the containers, the access mechanisms configured in a network to facilitate communication with a central command node.

3. The patent by David Erik Klein “Audio Signal System for vehicle remote locking mechanism” deals with an audio signal system for a vehicle remote locking mechanism and sends out an audio signal which has multiple sounds and digital audio source with amplification.

Electronic Interface: The system consists of two radio frequency devices, one being the hand control (HC) and the other remote device (RT) that behaves as a testing device with 12V input. Each device contains an RF receiver and transmitter operating on different frequencies. The transmission of HC matches with the frequency of RT. Alternately the transmission in RT matches with the HC. The dual transmitters and receivers enable the HC to receive feedback information from the RT transmitter after its receiver is activated by the HC unit. The transmitter and receiver in either the HC or RT units cannot be on at the same time because they would overdrive their respective receiver input causing the system to be unstable.

Now let’s examine the HC and RT in detail. The transmitter and receiver used are low cost FCC approved radio controllers. The device is designed to send an electronic signal back to the key that it is indeed locked.

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Push And Release

Push And Hold

1N5226

Reciever

9 Volt Battery

Transmitter

Hand Control ( HC )

Vibrating Motor

Figure 13. Schematic of Hand Control Device 3.10.

In establishing the necessity for rehabilitation technology products, clients’ immediate and anticipated medical and functional needs are always considered. Some rehabilitation-related devices include individually configured manual and powered wheelchair systems that have adaptive seating and alternative positioning and require evaluation, fitting, configuration, and adjustment. Using the axiomatic approach and TRIZ, develop concepts and design parameters for an intelligent wheel chair.

Product Selected: Developing a “Voice-Commandable Robotic wheelchair” This will be the Smart Wheelchair of the Future. New engineering developments offer opportunities to develop smart wheelchair assistive technology that can improve the lives of many people who use wheelchairs. This example looks at developing a voice-commandable intelligent wheelchair that is aware of its surroundings so that it can assist its user in a variety of tasks. The goal of this smart wheelchair project is to enhance an ordinary powered wheelchair using sensors to perceive the wheelchair's surroundings, a speech interface to interpret commands, a wireless device for room-level location determination, and motorcontrol software to affect the wheelchair's motion.

The robotic wheelchair learns the layout of its environment (hospital, rehabilitation center, home, etc.) through a narrated, guided tour given by the user or the user's caregivers. Subsequently, the wheelchair can move to any 55

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previously-named location under voice command (e.g., "Take me to the cafeteria"). This technology is appropriate for people who have lost mobility due to brain injury or the loss of limbs, but who retain speech. The technology can also enhance safety for users who use ordinary joystick-controlled powered wheelchairs by preventing collisions with walls, fixed objects, furniture, and other people.

Such a voice-commandable wheelchair could improve the quality of life and safety of tens of thousands of users. Moreover, considerable health improvements and cost savings could accrue through the reduction or elimination of collisioninduced injuries such as wounds and broken limbs. Such a product should be tested in a specialized-care residence for adults with multiple sclerosis and other progressive neurological conditions. The efforts in developing this intelligent wheelchair span multiple domains, including robotics, artificial intelligence, machine learning, human computer interaction and user interface design, speech recognition systems, and the role of technology for people with disabilities and people who are getting older.

Using axiomatic thinking procedures, a relationship between functional requirements and design parameters can be established. TRIZ and creative problem techniques will provide ideas and possible alternatives for solutions.

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Chapter 4 Exercises 4.1.

What are the key factors in identifying customer needs?

Key factors in identifying customer needs are: a) Identify who are the real customers for a product b) Possess a deep understanding about the requirements of the customer for a specific product c) Identify real needs as opposed to the general perception about a product d) Gather customer needs through interviews, observations, focus groups, internet surveys, and marketing calls and surveys e) Identify the primary, secondary, and tertiary customer requirements f) Collect early information on customer reactions on cost, maintenance, and the timing of a product g) Recognize how customers would react to a new product launch

4.2.

Consider an example of a consumer product whose function diagram can identify the aspects of a recycling and environmentally appropriate product. Identify the design approach to the product you have chosen.

Function Diagram A function diagram provides a clear picture of the objectives of the product. It is a loosely structured methodology derived from previous ideas. It is based on customerderived functions rather than engineering conceived forms. It translates the customer functions into product functions, evaluates manufacturability through analysis, and creates alternate products. The function analysis methodology has several major steps in the product design process. They are: • • • • • • •

Determine the needs and views of the customer Establish the product function from the perspective of the customer Translate the needs, desires, and views of the customer into design ideas Use creative thinking techniques to generate new concepts based on function Develop a symbolic image of the product by constructing a function family tree Perform design for assembly analysis to identify manufacturability difficulties Select a product design based on function and form, using the concept selection process

The function of the overall product is first defined and then followed by the definition of the sub-functional group of parts. This is followed by the detailed functional view of each part. Parts may work together to perform a function even though they are not assembled together into the same subassembly. Subassemblies indicate only the order in which parts are joined together on the assembly line, not the functional relationships between parts.

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Approach The Function Family Tree (FFT) is a block diagram indicating only the functional relationship between the product and its environment or between various segments of the product. The FFT is particularly important in the product concept phase because it allows us to break major products into smaller, more manageable design problems. As an example, a function diagram of a flashlight that can identify the recycling and disposal aspect of its components is shown in Figure 1. The diagram especially addresses the portion on recycling and disposal. Flashlights contain batteries, and the FFT can identify the recycling and disposal aspect of the batteries used in the flashlight.

Example: Highlighting Disposability and Recyclability - Flashlight Convert electricity to

Open/close circuit

light Provide light

Illuminate

Facilitate Holding

Send current

Form circuit

Hold Bulb

Store elec. energy

Protect Bulb Reflect light

Light Facilitate Disposal

Retain Beauty

Identify recycling schedule

Battery for disposal

Bulb for disposal

Figure 1. Example of Function Tree battery disposals in Flashlight The function tree can be further extended to detail out how the bulbs and batteries are disposed of by adding additional blocks on the right side 4.3.

Assuming that you are creating a new supermarket cart, generate three concepts and a concept selection chart. Identify the concept screening data based on these criteria: (1) ease of handling, (2) portability, (3) weight of material that can be carried, and (4) durability.

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New Supermarket Shopping Cart To demonstrate its process for innovation, a new shopping cart is created considering issues such as ease of handling, maneuverability, weight, and durability. The procedure consists of setting up a multidisciplinary team, brainstorm sessions, research, prototyping, and gathering user feedback on a design.

Ease of handling: The new design ideas will consist of redesigning the steel frame and redesigning the accessories from the point of handling. A. The steel frame is redesigned to be nestable so that it can be reduced in size by telescoping parts that slide into each other. The nestable steel frame holds removable plastic baskets to increase shopper flexibility. B. A dual child seat uses a swing-up tray for a play surface, and a hole provides a secure spot for a cup of coffee or a bunch of carnations.

Weight: The use of carbon fiber material decreases the overall weight and provides a means to promote brand awareness. Telescoping steel frames will also contribute to weight reduction.

Maneuverability: One of the unique features of the cart is the design of its steerable back wheels. Normally fixed straight for stability and familiarity, an easy sideways effort allows the wheels to turn left or right. Pushing the cart forward puts the wheels straight again.

Durability: Steerable back wheels allows easy forward, backward, and sideways motion.

They also reduce the need for frequent maintenance. New generation of carbon fibers will provide more durability to the product.

Read more at https://www.ideo.com/work/shopping-cartconcept#pZUQ1ro0iUgXD7eC.99 In a formal concept selection chart, several concepts are listed in a tabular form. They are all evaluated and rated against the criteria such as ease of handling, maneuverability, weight, and durability.

4.4.

Assume that you are designing a mountain bike for optimal safety and ease of maintenance. Develop an FFT structure.

The bicycle industry is a hi-tech, multi-million dollar industry that touches virtually every household in one way or another. The industry spans a wide range of market segments. A segment of the bicycle market revolves around two main groups: road bikes and mountain bikes. The design of the bikes in these categories has evolved dramatically over the last few years - to such an extent that several specific categories have developed (Figure 2).

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Figure 2. Bicycle Types The demand for such a wide range of categories arises from the riders and in particular from the competition which is inevitable with such sports. Manufactures often sponsor athletes in a range of categories in order to display and test their new products in a high stress environment - with the technology eventually filtering down to the public.

Competition has led to the development of lightweight bicycles with revolutionary features such as carbon fiber frames, disc brakes, and front and rear suspension. These are often designed using cutting edge materials and computer software to accurately simulate the forces a bike frame is subjected to - allowing the designer to reduce the weight of the bike without compromising its overall strength. A Morphological Chart (Table 1) for a mountain bike will identify the key features and means to achieve these.

Key Area:

Means:

Resistance

Magnetic

Electric

Fluid

Wind

Drive

Tire

Rim

Drive Train

Pedals

Energy

Flywheel

Spring

Electrical

Bicycle Mount

On both Front wheels Wheel Table 1. Morphological Chart

Rear Wheel

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A mountain bike or mountain bicycle is a bicycle designed for off-road cycling.

Mountain bikes are typically ridden on mountain trails, fire roads, logging roads, single tracks, and other unpaved environments. These types of terrain commonly include rocks, washouts, ruts, loose sand, loose gravel, roots, and steep grades (both inclines and declines). Mountain bikes are built to handle this terrain and the obstacles that are found in them like logs, vertical drop offs, and smaller boulders.

Considerations for a mountain bike for safety and ease of maintenance: Mountain bikes share similarities with other bikes, but incorporate features designed to enhance durability and performance in rough terrain. These typically include • suspension on the frame and fork, • large knobby tires, • more durable heavy duty wheels, • more powerful brakes, and • lower gear ratios needed for steep grades with poor traction.

While designing a mountain bike from the viewpoint of optimal safety and ease of maintenance, additional considerations are taken. They are listed below.

• • •

•

Rigid: A bicycle with neither front nor rear suspension; a hardtail with a rigid fork.

Hard tail: A bicycle equipped with a suspension fork and a rigid frame.

Soft tail: A bicycle having neither front nor rear suspension. The frames and occasionally front forks of these bicycles include some built-in flexibility to absorb small bumps.

These designs are much more common in road bikes than mountain bikes.

Dual or full suspension: A bicycle equipped with both front and rear suspension. The front suspension is usually handled by a telescopic fork similar to that of a motorcycle, and the rear by a mechanical linkage driving a telescopic shock absorber. Front suspension is often implemented using a telescopic fork. The specifics of the suspension depend on the type of mountain biking the fork is designed for and is generally categorized by the amount of travel. For instance, manufacturers produce different forks for cross-country, downhill, free-ride, and endurance riding, which all have different demands for amount of travel, weight, durability, structural strength, and handling characteristics.

Suspension fork design has advanced in recent years with suspension forks becoming increasingly sophisticated. The amount of travel available has typically increased. When suspension forks were introduced, 80–100 mm of travel was deemed sufficient for a downhill mountain bike. This amount of travel is now common for cross-country disciplines, whereas downhill forks typically offer 200 mm of travel for handling the most extreme terrain.

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Full Suspension

Material

Design for down hill

Telescopic fork

Linkage for rear

80mm travel

Bike Rigidity

Rear

Seat

Transmission

Figure 3. Typical FFT Showing Rigidity in Mountain Bikes 4.5.

Assume that you are working on a new generation of X-ray CT scanner that contributes to patients’ well-being by minimizing radiation and providing improved image recognition. Determine the overall function that needs to be accomplished, and create subfunction descriptions and a concept selection chart.

X Ray CT Scanner Medical imaging is the most common application of X-ray CT. Its cross-sectional images are used for diagnostic and therapeutic purposes in various medical disciplines. A CT scan makes use of computer-processed combinations of X-ray images taken from different angles to produce cross-sectional (tomographic) images (virtual "slices") of specific areas of a scanned object, allowing the user to see inside the object without cutting. Digital geometry processing is used to generate a three-dimensional image of the inside of the object from a large series of two-dimensional radiographic images taken around a single axis of rotation. The majority of CT systems use X-ray tubes, although tomography can also be done using a synchrotron or gamma-ray emitter as a monochromatic X-ray source. Important tube characteristics are the target material and peak X-ray energy, which determine the X-ray spectrum that is generated; current, which determines X-ray intensity; and the focal spot size, which impacts spatial resolution.

Most CT X-ray detectors utilize scintillators. Important parameters are scintillator material, size and geometry, and the means by which scintillation events are detected and counted. In general, smaller detectors provide better image resolution but reduced count rates because of their reduced area compared to larger ones. Strengths X–ray CT Scanners lie on non-destructive 3D imaging with little or no sample preparation required.

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Some observed limitations of X-ray CT Scanners: • Resolution limited to about 1000-2000x the object cross-section diameter; high resolution requires small objects • Finite resolution causes some blurring of material boundaries • Calibration of gray levels to attenuation coefficients complicated by polychromatic Xrays • Large geological specimens cannot be penetrated by low-energy X-rays, reducing resolving capability • Not all features have sufficiently large attenuation contrasts • Large data volumes require considerable computer resources for visualization and analysis New generation of X ray scanners will need improvement and redesign in the following areas: • Resolution • Performance improvement • Faster scan • Maintenance free X-ray source • Automatic sample changer and micro-positioning stage • Email link • Exportability to iPhone/iPad

Resolution

New Xray CT scanner

Micro Positioning

Phase contrast enhance

Resolution 14500X14500

Detectors

New Material for Scintillation detectors

Automatic sample changer Scan ability

Email link Software for mobile platform

Reduce X ray spectrum spot size.

Samples under tension/Compr ession iPhone/iPad interface

Figure 4. Function Diagram showing improvement in resolution, positioning, and external communication

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A new generation machine will be a high-resolution micro-CT. The system can nondestructively visualize up to 209 Megapixel (14450x14450 pixels) virtual slices through objects, more than 2600 such slices after a single scan. The system includes a built-in precision micro-positioning stage and can scan samples during compression, tension, cooling, or heating. A 16-position automatic sample changer allows the adding/removing/replacing of samples without interrupting a live scanning process. At the end of the scan the system can send you an e-mail with a direct link to the scanning results, which can be opened across a network. Reconstruction results can be sent to an iPod. Special software for mobile platform performs volume rendering and virtual cut of objects with touch screen gesture controls.

4.6.

Electric toothbrushes are being used in the jewelry industry for polishing. However, the continuous use of the electric toothbrush causes electric motors to burn out.

Develop a step-by-step product architecture for a handheld electric polishing device for jewelry that can be operated 8 hours per day.

Figure 5. Commercial toothbrushes in the market Electric tooth brushes are widely used in jewelry cleaning. The function of the jewelry cleaner should be such that it is portable and does proper cleaning without damaging the jewelry. The handheld instrument should be robust enough to withstand 8 hours of continuous use each day. Figure 6 shows the functional diagram of an electric jewelry cleaner. It shows sensors for overload protection so that the motor does not get burnt out.

Soap water gets injected to the brush as it rotates. The rotation stops if the installed sensor detects overload in the motors. It also has newly researched and developed portable lithium ion batteries that will last 8 hrs.

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Input Energy

Output Energy

Liquid water

Rotating electric brush

Signal senor for overload

Energy

Soap

Overload trip

Convert energy to rotational

Portable External storage, Lithium ion 8- hr. battery

Storage of soap water

Apply soap water on actuation

Sense

Trigger stop signal

Trip rotation

Soap water

Motor torque

Apply rotational energy to brush

Figure 6. Electric Jewelry Polisher 4.7.

How do ethical issues impact product architecture? Identify three major technological innovations in the past 20 years. For each, list any ethical issues they pose for engineers and scientists. Comment on how they can be rectified by product redesign.

Engineering designs sometimes fail because of the unethical behaviors of those who are responsible for development and implementation. Engineers and designers have to be familiar with the ethical, social, and economic and safety considerations in engineering practice.

Unethical actions may lead to the loss of a designer’s professional reputation. Engineers should be encouraged to the accepted standards of the profession, provide guidelines about these standards to design groups, and encourage professional societies to monitor ethical issues.

Three examples selected are: 1. General Motors (GM) ignition switch 2. Connecticut Nuclear Power plant 65 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

3. Acoustic gun General Motors Ignition Switch Case During 2015/2016, there was a high profile case involving ignition switches in General Motors (GM) cars. In some cases involving GM models, the ignition switch would accidentally rotate and make the engine stall, causing the car to stop. This has caused several accidents on highways.

The original design had identified these faults at the design and development stage. The design solution was changing the design to mount the key cylinder in a higher position and lengthening the detent plunger in the ignition switch. It was rejected due to cost concerns.

GM considered altering the fob from a slot opening for the key ring to a smaller hole opening.

Even though this fix wouldn’t directly address the ignition switch problem, engineers believed it could prevent a keychain attached to a driver’s key fob from dangling as low, thus reducing the chances of a key getting knocked into the off position. But that option, as well, was rejected as too expensive. (The piece required to change the opening from a slot to a hole would have cost 57 cents per part.). This case resulted in several deaths and millions of court damage to GM. Action: The redesigned ignition switches are being used in the current GM cars.

Connecticut Nuclear Power plant The owner of the Millstone Nuclear Power Station in eastern Connecticut admitted in 1996 that it had falsified environmental records and deliberately promoted unqualified plant operators. The owner, Northeast Nuclear Energy Company, pleaded guilty to 23 Federal felonies and agreed to pay $10 million in fines, the largest penalty ever for a nuclear plant in this country. The violations took place from 1994 to 1996. NU admitted that hydrazine, a toxic chemical used to reduce the corrosion of pipes, had gushed into Long Island Sound at a rate of one gallon an hour during 1996 and that testers at the company had diluted their samples with ocean water to hide the problem from Federal regulators.

Problems with the training program at Millstone came to light in 1996 when six of seven candidates for control-room operator licenses failed Federal exams, prosecutors said. The three reactors in Waterford, Conn., were shut down under orders from the Nuclear Regulatory Commission because of problems with design, safety, and paperwork. One of the three reactors is being decommissioned, while the other two have been restarted and are producing energy.

Action: Northeast Utilities has made major investments in operator training and has shut down the plant for a long period.

Acoustic Gun Acoustic guns have been a cause of ethical concerns for many. This example examines the use of acoustic guns for fish deterrence and passage by acoustic pressure 66 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

There are numerous reasons to evaluate the effects of anthropogenic sound in aquatic ecosystems. This includes determining safe operational levels for seismic technologies on native organisms, as well as using sound technology to divert native fish away from hydropower intakes or toward fish ladders. Underwater sound provides many challenges for industry and the natural resource agencies, as significant gaps exist in our understanding of the effects of sound on fishery resources. Pulse pressure and continuous low frequency acoustics have the ability to physiologically interact with aquatic organisms and alter behavior.

Specific effects of sound are dependent on the species, life stage, size, frequency of application, the environment it is applied in, and how loud the sound is emitted. Each technology can be operated in a static or mobile application, deployable as small or large-scale operations, making it a viable option for numerous applications. Water guns provide three mechanisms for deterrence: 1) the use of sound at frequencies fish can hear, 2) a pressure wave, and 3) high velocity water jets.

Presently, acoustic water guns and low frequency acoustics offer a method for deterring aquatic species using underwater sound energy. Both options operate as low frequency sources that can function at low or high operating pressure levels. The acoustic pressure emitted by these technologies quickly dissipates, making this a chemical free, low impact option.

Figure 7. Acoustic water gun principles Action: There is a lot of environmental concern regarding the use of acoustic guns. More studies need to be done before the wide scale introduction of acoustic water guns.

4.8.

Generate a design concept for securing a coffee cup near the driver’s seat of a vehicle. The device should prevent the cup from spilling and not interfere with the vehicle’s proper operation. It should be universally adaptable to a wide variety of vehicles.

1.

2.

3.

4.

Establish need.

Design objectives.

Set constraints.

Set evaluation criteria.

67

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5. Specify the needed information to be gathered.

6. Define the problem.

1. Establish Need: • Coffee cup holder for car (near the driver seat) • Locking system to prevent the cup from spilling • It does not interfere with the proper operation of the car • Adaptable to a wide variety of vehicles • Detachable (designed to be unfastened or disconnected without damage) • Easy to use • Durable material for various temperatures • No need to modify car interior • Cost does not exceed $10 • Flexibility of coffee cup size 2. Design Objectives: • The device should detachable • Plug and play, no interior modification needed 3. Design Constraints: • Spilling free • Does not interfere with the driver • Size max 200 x 150 x 150 mm (HxWxL) • Weight does not exceed 0.5 kg • Cost does not exceed $10 • 2 years lifetime 4. Evaluation Criteria: • Simplicity • Easy to install and dispatch • No harm to the interior • Low cost • Durability 5. Needed Information to gather: • Average amount of coffee in cup • Average coffee cup size and weight • Coffee cup material • General car interior layout/design • Temperature inside the car (max/min) • Available relevant holder design in the market

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Final Problem Definition: Design a simple device for securing a coffee cup near the driver’s seat of an automobile that prevents the cup from spilling, doesn’t interfere with the proper operation of the car, and adapts to a wide variety of vehicle and coffee cup size. The device should be detachable, have no interior modification needed, and does not harm the interior. The max size is 200 x 150 x 150 mm. It should weigh less than 0.5 kg, have a 2 year lifetime, and cost no more than $10. It also should have a simple design, be easy to install, and be durable.

4.9.

Develop the product architecture of a device that will allow the inside and outside surfaces of windows to be cleaned from the inside only.

A window cleaner has three surface brushes on the outside of the window and a permanent magnet with a handle on the inside to control the motion of the brush. The brush will have three sides: a brush side, a squeegee side, and a sponge side to moisten the surface. The brush part will have steel chords so that the magnets on the handle can hold onto them while in use. A safety wire will be attached so that the part will not land on the unsuspecting pedestrians if it ever falls off.

Plastic

Hold squeegee, sponge, and brush on three sides

Steel chord

Magnets on the handle can hold them in use

Aluminum Rods

Handle

Magnets

Two separate pieces attached to a window

Velcro

Tie

Brush

Scrubbing

Squeegee

Dry

Sponge

Moistening

Figure 8. Function Diagram of Window Cleaner 4.10.

According to a survey by the Department of Transportation’s National Highway Traffic Safety Administration (NHTSA), only about 14% of drivers in the United States know how to find their tire pressure and maintain it properly. Consider creating a new product that would be a smart air pump station for automobile tires.

This system should contain the car manufacturer’s recommended tire pressure in an internal database without requiring more input from the customer than a basic knowledge of the vehicle’s make, model, and year.

69

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Product Need A smart air station’s system runs automatically for most vehicle drivers. In this innovative system, the drivers do not have to possess any knowledge about their vehicle’s tires pressure value while pumping. This is because the smart air pump station’s system keeps many vehicles’ manufacturer recommended tire pressure within its database. Any drivers who want to inflate or deflate their tires can find their vehicle’s name, model, and year from the touchscreen display.

After pushing the start button, the system inflates or deflates tires depending on how much pressure is in the tire. When the tires reach the recommended pressure value, the smart air pump station automatically stops the airflow.

Case Study of a Smart Pump The purpose of this project is to create and design a “Smart Air Pump Station” for filling automobile tires. This system will contain the exact car manufacturer’s recommended tire pressure in an internal database without requiring more input from the customer than a basic knowledge of their car’s make, model, and year. There will be little possibility of inflating tires to the wrong pounds per square inch (PSI), and it even accounts for temperature conditions. For example, with a manual air station, the customer may inflate their tires to the pressure listed on the sidewall of the tire as opposed to the listing in the doorframe or owner’s manual, and this is assuming they know how to properly read a tire gage to begin with. Inflating to the pressure listed on the sidewall of a tire is incorrect and potentially dangerous, as that is the maximum pressure the tire could be when it is 70 degrees Fahrenheit outside.

Tire Pressure Standards The NHTSA has also developed a Federal Motor Vehicle Safety Standard that requires the installation of tire pressure monitoring systems (TPMS) that warn the driver when a tire is significantly (25% or more) underinflated. This standard applies to passenger cars, trucks, multipurpose passenger vehicles, and buses with a gross vehicle weight rating of 10,000 pounds or less, except those vehicles with dual wheels on an axle. Their goals are safety and reducing fuel use nationwide. Unfortunately, having a warning indicator within the car to tell you that a tire is 25% underinflated does not educate someone on what to do about it. It is entirely possible that an incompetent user could fill the tire to be 24% underinflated (at which point the light would go out) and call it a job well done. The far more common case would likely be the same fate as the check engine and check oil lights: something you get around to when you have time for it, say next month. Additionally, TPMS’s would not take ambient temperature into account, and as such may cause erroneous warning lights when the pressure is correct for the circumstances.

Benefits of Properly Inflating Tires There are many benefits to having all the tires on a vehicle correctly inflated. First and foremost, having improperly inflated tires decreases gas mileage. A vehicle’s performance in miles per gallon decreases by about 0.4% per PSI that the tires are underinflated. The U.S. Government

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Accountability Office estimates that 1.2 billion gallons of fuel are wasted annually due to underinflated tires.

Extended Life Another advantage of having properly inflated tires is found in extending tire life. Properly inflated tires exert much less stress on the sidewalls of the tires, which were never intended to take the extra load. With over-inflated tires, the load concentrates on the center treads, causing them to wear out at an accelerated rate relative to the rest of the tire. In the under-inflated case, the center concaves inward, while the lower portions of the sidewalls bow out, causing the sidewall to be under considerably more stress while driving. In addition to the obvious safety hazard, this also causes accelerated wear on the tire, which in turn decreases the lifespan.

Safety Aspects Perhaps the most important aspect of properly inflated tires is safety. Over-inflated tires are prone to blow-outs when driving over large bumps, primarily because they cause a spike in pressure on already stressed elements. Over-inflation also creates a potentially unpleasant ride due to the fact that rigid tires cannot absorb the impact of small holes or bumps. Under-inflation may also cause a blowout because the sidewall can bulge outwards and the increased friction heats up that portion of the tire, leading to potentially permanent damage in the form of fatigue cracking or an outright catastrophic failure. Outside of these obvious and abrupt safety hazards, handling in a vehicle with under-inflated tires degrades rapidly in proportion to the severity of the inflation deficit. The reason for this is that the load of the tire in contact with the road is concentrated on the treads just under the sidewall, as opposed to being evenly spread across the full width of the tire. As the tire rolls, the sidewall flexes in compression, and as a result the steering feels “mushy” compared to optimally inflated tires. In addition, the chances of hydroplaning increases with under-inflated tires due to the potential amount of water that can get between the tire and the road.

Design of Smart Air Station A smart air station is designed for motor vehicle users. It is possible to use many kinds of locations, such as gas stations, new generation cars’ charging stations (electric vehicle charging station), outdoor-indoor and university parking lots, etc. In this paper, we will see the difference between a regular air station that is located at gas stations today and new generation smart air station in the future.

Product Scope Features The following features will be incorporated into the commercial design and were designated by the sponsor. Note that the prototype only contains the features denoted due to cost constraints.

• 15 inch LCD (liquid crystal display) touchscreen monitor (4:3) for easy viewing to display user instructions, fees, and ads.

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•

• • • •

• • •

Desktop computer located inside housing for programming and database of recommended tires’ pressure values. It is faster than many kinds of devices and it presents more practical solutions.

Features ergonomic “easy grip” shape for user comfort.

Automatically inflates or deflates tires to the car-maker recommended tire pressure and shuts off once the desired pressure is reached.

Recognizes outside temperature (hot or cold) in order to determine the proper adjusted tire pressure. ½ inches thickness plywood housing with white color vinyl siding covering and ventilation channels for air compressor and desktop computer fan. With the advantage of vinyl siding, the smart air station is protected from weather conditions.

Retractable air hose.

Attractive and unique aesthetic look.

Audio and visual interactive cues.

Comparison with Other Examples in the Market Manual Pumping System This system is operated entirely by hand and the pressure value is measured with a manual pressure gauge. Before drivers pump the air in to their vehicle’s tires, they have to know how much pressure is needed to inflate the tires to the proper values. While pumping the tires, the drivers have to check pressure gauge step by step to reach the recommended pressure. When they reach the recommended value, they stop the inflation and the process is completed.

Figure 9. Manual Air Station Model

Semi-Automatic System This system is similar to a manual pumping system, but there is only one specific detail that the pressure value controlled by a counter. To use a semi-automatic pumping system, drivers have to know their tires’ recommended pressure value. While pumping the tires, the drivers have to adjust the recommended pressure value at the analog or digital counters.

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Figure 10. Digital or Analog Semi-Automatic Air Stations At the end of the inflation, the system automatically stops the airflow and reaches the recommended value of the tires.

Smart Air Station A smart air station’s system runs automatically for most vehicle drivers. In this innovative system, the drivers do not have to possess any knowledge about their vehicle’ tire pressure values while pumping. This is because the smart air pump station’s system keeps many vehicles’ manufacturer recommended tire pressure values within its database. Any drivers who want to inflate or deflate their tires can find their vehicle’s name, model, and year from the touchscreen display. After pushing the start button, the system inflates or deflates tires depending on how much pressure is in the tire. When the tires reach the recommended pressure value, the smart air pump station automatically stops the airflow.

Figure 11. Fully Automatic Smart Air Station With the help of two solenoid valves, a smart air pump station runs reversible as described above and reaches the desired pressure. The smart air station is a completely new product that could be used in the future. All similar products that we use at gas stations can only operate for inflating process, but smart air stations can potentially be used for deflating as well.

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74 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

Chapter 5 Exercises 5.1

List three reasons why reducing the number of parts in a product might reduce production costs. Also list reasons that costs might increase.

It is generally understood that with fewer parts, there is less material to buy and less inventory to control. This leads to savings in procurement and inventory control. Since there are fewer parts to be assembled, the labor to assemble the product is normally reduced. In addition, with fewer parts there are fewer parts to fail so that warranty costs should also decrease. If the part reduction process is conducted systematically, reducing the number of parts normally helps to reduce the production costs. This is primarily due to the labor savings involved throughout the process.

However, reducing parts can sometimes cause costs to increase. For example, if a part is designed to be more complex or the part has multiple features representing combination to reduce the total part count, the fabrication costs of the new part may increase. This is due to the added complexity and increased manufacturing processing needed. It is also possible that the new part might require additional time to install in the final assembly, which would increase labor costs. These are the issues that must be examined, and decisions have to be made to provide the most desirable solution for the customer.

Reducing the number of parts in an assembly reduces production costs: • By requiring less time to put the assembly together • By requiring less tooling to attach the different components • By requiring less hardware to fasten the different components in the assembly Costs might increase, however, because: • By reducing the parts count the smaller number of parts that are left are going to be more complicated and require more time to fabricate • The more complicated parts are going to require more tooling to fabricate • Replacing a non-conforming part also becomes more expensive

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5.2

Consider the following 10 “design rules” for electromechanical products. Do these seem to be reasonable guidelines? Under what circumstances could one rule conflict with the other one? How should such a trade-off be settled? a. b. c. d. e. f. g. h. i. j.

Minimize part count Use modular assembly Stack assemblies Eliminate adjustments Eliminate cables Use self-fastening parts Use self-locating parts Eliminate reorientation Facilitate parts handling Specify standard parts

The following summary of the above “design rules” explains the intent of several of the rules and how they can be beneficial tools during the design process and ultimately the end product. a. Minimize part count: Reducing part count generally reduces cost by reducing the labor required for assembly, minimizing the amount of material that must be procured, and reducing the inventory that must be controlled. b. Use modular assembly c. Stack assemblies d. Eliminate adjustments: Eliminating adjustments helps to reduce assembly and set-up time. Done properly, it also reduces product variation, making the product more repeatable. Repeatability and reduced variation generally lead to a more robust and reliable product. e. Eliminate cables f. Use self-fastening parts g. Use self-locating parts: Self-locating parts help to reduce labor by reducing the amount of time the assembler spends trying to align mating parts during assembly. It also helps to reduce the need for special fixturing, thus saving money in equipment costs. h. Eliminate reorientation: Eliminating reorientation of parts helps to reduce costs by minimizing part handling time, thus shortening assembly time and increasing production rates. This holds true for both manual and automated assembly operations.

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i. Facilitate parts handling j. Specify standard parts: By specifying standard parts, the designer can take advantage of another company’s high volume production advantages. The parts are readily available, with short lead times and lower costs than a custom part. There are often competitive products from different manufacturers which further drive down prices. Standard parts are also beneficial for customer service, because they are normally available off the shelf. It may not be necessary to hold service stock in order to support the customers, thus saving more money.

In general, all of the above “design rules” are good and reasonable guidelines to be used, but not every rule can be applied in all situations. In fact, the rules can be contradictory at times. For example, standard parts might not be selflocating because the manufacturer has tried to make the parts more universal to cover as many applications as possible. Another example can occur when eliminating adjustments or reducing the part count results in the part becoming difficult or impossible to assemble.

In these cases, compromises must be made. The compromises must be decided based on what is the overall best solution, taking into consideration cost, ease of assembly, reliability, serviceability, and most importantly the customer requirements. In the case of the standard part vs. the self-locating part, the standard part would be the rule to follow in most situations based on cost advantages unless the issues that it creates are too difficult or costly to overcome. However, in the case of eliminating adjustments or reducing part counts, the ease of assembly would normally dictate the solution.

5.3

Is it practical to design a product with 100% efficiency (DFA index = 1.0)?

What conditions must be met to achieve this efficiency? Can you think of any products with very high (>75%) assembly efficiency?

100% efficiency is possible. A part which has a high design efficiency index will be constructed almost entirely of essential parts and will be quick to assemble.

Design efficiency is determined by using the appropriate formula. The manual assembly design efficiency is obtained by using the following equation: Em =

3N m Tm

Where, Em is the manual design efficiency Nm is the theoretical minimum number of parts Tm the total assembly time

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Research has shown that a part which is both easy to handle and easy to insert can be assembled in the ideal time of 3 seconds. The ideal assembly time and the theoretical minimum number of parts may never really be achieved. From the above equation, one can see that if the assembly is constructed of 4 essential parts and can be put together in 12 seconds, then it will have a design efficiency index of 1.

The automatic assembly design efficiency can be determined by using the formula Ef =

.09 N m CA

Where, Ef is the automatic design efficiency Nm is the theoretical minimum number of parts CA is the total assembly time cost A product with high design efficiency will have fewer parts and a reduced assembly time. The cost of manufacture and assembly is largely determined at the design stage. The designer should be aware of the nature of the assembly process.

There should always be sound reasons for requiring separate parts, which create higher assembly costs.

5.4

What are the major characteristics of each of the following three assembly analysis methods: Boothroyd-Dewhurst (BDM), Lucas, and Hitachi?

Hitachi, BDM, and Lucas Methods are supported by computer software systems which provide step-by-step instructions. BDM and Lucas Methods distinguish manual from automatic assembly, while Hitachi Method does not. The most complete calculation of design efficiency is provided by BDM. The BDM Method determines the design efficiency, taking into account part reduction and handling and insertion improvement. The Hitachi Method calculates the design efficiency based on the insertion process only, while the Lucas Method is focused on reducing the number of parts. The Hitachi technique gives a process overview of the assembling sequence and insertion operations. There is no explicit criterion for minimum parts count. The Hitachi method does not offer direct analysis for parts feeding and orientation. For this reason, the design for automated assembly is not an option, with the argument being that assessment of product design for automated assembling is sensitive to part configuration and difficult to handle precisely at the early design stages. These aspects should be dealt with at later design stages.

The Lucas Method is based on a symbolic logic programming paradigm. The advantage of this is that it is easier to encode and derive the DFA rules embodied in the method and provide the user with generalized suggestions for possible design changes as the evaluation proceeds. The Lucas Method adopts aspects of 78

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both Hitachi and BDM by dealing with handling and insertion with some consideration of automation and some emphasis on the fitting (insertion) processes. The design efficiency of the Lucas Method is based solely on the scope for reducing the number of parts in the product design, and it is not as comprehensive as the BDM.

5.5

The following five rules represent ideas for efficient design for manufacturing. Explain these ideas with an example of your own. a. Facilitate easy handling and orientation b. Standardize parts c. Reduce part count d. Eliminate assembly adjustments e. Use self-locating screws

a. Facilitate easy handling and orientation Design parts for easy handling so that components can be handled with minimum difficulty and time. Minimize non-value added manual effort in orienting and merging parts.

• • • • •

Parts must be designed to consistently orient themselves when fed into a process.

Design must avoid parts which can become tangled, wedged, or disoriented.

Incorporate symmetry in the components, low centers of gravity, easily identifiable features, guide surfaces, and tools for pick-up and handling.

Ensure that parts can be separated from bulk.

Ensure that parts can be automatically transported.

Choose the type of design that will allow the use of automation in parts handling and assembly such as vibratory bowls, tubes, magazines, pick and place robots, or vision systems. When components are purchased, look for components that are already oriented in magazines, bonds, tape, or strips.

b. Standardize parts Group technology can be used to guide the selection and development of manufacturing cells for common parts or product families. Common parts will result in lower inventories, reduced costs, and higher quality.

• •

Standardize and use common parts and materials to facilitate design activities.

Minimize the amount of inventory in the system, and standardize handling and assembly operations.

79

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Operator learning is simplified and there is a greater opportunity for automation as a result of higher production volumes and operation standardization. Limit unique components because suppliers are less likely to compete on quality or cost for these components.

c. Reduce part count: The designer should go through the assembly process part by part and evaluate whether the part can be eliminated, combined with another part, or if its function can be performed in another way. To determine the theoretical minimum number of parts, ask the following: • • •

Does the part move relative to all other moving parts?

Must the part absolutely be of a different material from the other parts?

Must the part be different to allow possible disassembly?

d. Eliminate assembly adjustments: The cost of manufacture and assembly is largely determined at the design stage.

The designer should be aware of the nature of assembly processes and should always have good reasons for requiring separate parts. Design the product for ease of assembly by utilizing simple patterns of movement and minimizing the axes of assembly. Avoid complex orientation and assembly movements in various directions during assembly.

• •

• • •

• • •

Part features should be provided such as chamfers and tapers.

The product’s design should enable assembly to begin with a base component with a large relative mass and a low center of gravity upon which other parts are added.

Avoid unnecessarily high tolerances that are beyond the natural capability of the manufacturing processes.

Avoid tight tolerances on multiple, interconnected parts. Tolerances on multiple assembled parts can stack up undesirably.

Provide mistake-proof assembly so that the assembly process is unambiguous. Components should be designed so that they can only be assembled in one way; they cannot be reversed. Notches, asymmetrical holes, and steps can be used to mistake-proof the assembly process.

As far as possible, products should be designed to avoid post assembly adjustments.

Incorporate design verifiability into the product and its components.

Assembly should proceed vertically with other parts added on top and positioned with the aid of gravity. This will minimize the need to re-orient the assembly and reduce the need for temporary fastenings and more complex fixturing. A product that is easy to assemble manually will 80

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normally be easily assembled with automation. Automated assembly will be more uniform, more reliable, and of a higher quality.

e. Use self-locating screws The use of self-locating screws facilitates the assembly process and reduces the assembly time. Use standardization and minimize variety while using fasteners.

Some of these rules may present some conflicting situations: Using self-locating screws may facilitate the assembly process. However, the elimination of screws and fasteners and the replacement of them with snap-fits can provide further advantages. Threaded fasteners (screws, bolts, nuts, and washers) are time consuming to assemble and difficult to automate. Consider the use of snap-on fits to replace welded joints.

While creating parts for easy part-handling and orientation, it may be difficult to use a standardized component. The part may have to be uniquely designed.

The rule of simplification and part reduction is followed because for each part, there is an opportunity for a defective part and an assembly error. The probability of a perfect product goes down exponentially as the number of parts increases. As the number of parts goes up, the cost of fabricating and assembling the product also rises. As the number of parts gets reduced, the cost of inventory and purchasing gets reduced.

5.6

With the following information for a cartwheel assembly, perform a design for assembly analysis.

The cartwheel assembly has seven parts. The design for assembly analysis considers the part dimensions, geometry, features, handling, and assembly time.

Figure 1. Cartwheel Assembly 81 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

Comp. Name

Comp. Type

Dimensions (in mm)

Qty

Axle

Part

170 length, 15 diameter

1

Tire

Part

250 diameter, 60 thick.

1

Front Spring Plate

Part

60 diameter, 5 thick.

1

Front Spring

Part

135 length, 50 diameter

1

Hex Bolt

Part

25 length, 18 diameter

4

Front Pillar

Part

290 length, 120 diameter

1

Wheel Bracket

Part

310 x 220 x 140

1

The components are re-organized according to the nature of the assembly.

No. Item Name Type

Repeat Min. Parts Tool Item Count Acquisition Handling/ Time (sec) Acquisition Time (sec)

Item Total Oper. Total Oper. Description Insertion Time (sec) Cost @ Time $30/hr (sec)

1 Part

Wheel Bracket

1

1

0.00

1.95

1.50

3.45

$0.03 add

2 Part

Tire

1

1

0.00

1.13

4.80

5.93

$0.05 add

3 Part

Axle

1

0

0.00

1.13

5.00

6.13

$0.05 add & interference fit

4 Part

Front Pillar

1

0

0.00

1.80

2.60

4.40

$0.04 add

5 Part

Hex Bolt

4

0

2.90

1.50

5.70

31.70

$0.26 add & thread

6 Part

Spring

1

1

0.00

1.84

1.50

3.34

$0.03 add

7 Part

Spring plate

1

0

0.00

1.13

1.50

2.63

$0.02 add

TOTALS:

10

3

2.90

10.48

22.60

57.58

$0.48

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Cart Wheel Analysis DFA efficiency Total assembly Total labor cost Number of different parts or sub-assemblies Number of parts and sub-assemblies assembled (including repeats) Number of reorientations and standard or user ops. (Including repeats) Theoretical minimum number of parts or unanalyzed subassemblies Hourly labor rate ($/hr)

15.01% 57.58 sec 0.48 10.00 10.00 0.00 3.00 30.00

The design for assembly index is 15.01. One way of improving this index is by reducing the assembly time. Suggestions for redesign: the designer might consider reducing the number of parts. Reducing or eliminating the fasteners is a starting point. The front pillar and bracket can be combined into one part.

5.7

Select a product with less than 15 parts; estimate the total product cost.

What types of products are more suitable for direct marketing immediately after the design phase rather than after the conventional customer test with prototypes of products?

The cost of product development is roughly proportional to the number of people on the project team and the duration of the project. Many companies have realized that very few products can be developed in less than one year. In addition to the expenses for development effort, a company will almost always have to make investments in tooling and the required equipment for production. This cost could be as much as the product development cost itself. Most companies consider these expenses as fixed costs of production. The product design steps would consist of the following: background research analysis, concept generation, product design specification, consideration of alternatives, detailed design, cost valuation, and prototype construction.

Product costs in managerial accounting are those that are necessary to manufacture a product. Product costs equal the sum of your direct materials costs, direct labor costs, and manufacturing overhead costs. Using the actual costing method, you can determine your small business’s overall product costs and product costs per unit based on the actual costs you incurred during a period.

Material Cost: Direct materials are the materials a company uses to manufacture a product that you can trace directly to the product, such as the bicycle tires on a specific bicycle. Add together the costs of the direct materials you used over a particular period, such as one month, to determine your total direct materials costs. For example, assume you make bicycles. If you used $5,000 in bicycle tires

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and $3,000 in other bicycle parts during a month, you get $8,000 in total direct materials costs.

Direct Labor: Direct labor costs are the total costs you incur to employ the workers that directly assemble or manufacture your products. These costs include wages, payroll taxes, pension contributions, and contributions for life, health, and worker’s compensation insurance. Add together the costs you incurred for the month to determine your total direct labor costs. For example, if you paid $1,000 in wages, $100 in payroll taxes, and $500 toward pensions and insurance, you get $1,600 in total direct labor costs.

Overhead Cost: Manufacturing overhead costs are costs necessary to make a product, but that cannot be traced directly to a specific product. Examples include indirect materials, such as masking tape, and indirect labor costs, such as the costs to employ a maintenance worker. Examples of other overhead costs are property taxes, rent, and utilities. Add together each manufacturing overhead cost you incurred during the month to determine total manufacturing overhead costs. For example, assume your small business had $3,000 in total manufacturing overhead costs during the month.

Product Cost per Unit: Add together your total direct materials costs, your total direct labor costs, and your total manufacturing overhead costs that you incurred during the period to determine your total product costs. Divide your result by the number of products you manufactured during the period to determine your product cost per unit. Using the numbers from the previous examples, add together $8,000, $1,600 and $3,000 to get $12,600 in total product costs. Assume you manufactured 100 bicycles during the same period. Divide $12,600 by 100 to get a product cost per unit of $126.

Products suitable for direct marketing are products that can be assembled by the customers. These could be toys or products that are sold as kits. Hobby products such as quad-copters or miniature drones can be sold through direct marketing.

5.8

Briefly describe interrelationships, if any, among product architecture and its material selection, manufacturing-process selection, and life cycle maintenance and reliability. Give examples of products for which only one or two of the factors are dominant.

The product architecture is governed by the satisfaction of many different factors. Variation in some factor may influence another factor. Let us consider the example of an automobile.

Let us take the example of a vehicle that has to withstand the 5 mile/hour bump test. The impact resistance is dependent on the material type, primarily its thickness and the frame structure. A weaker, plastic type of material would need higher thickness than a stronger, high carbon steel. The choice of the material has a bearing on the cost. Another important factor to be considered is repair cost.

For example, repairing a bumper made of a plastic material that was hit might mean replacing the entire bumper, while a steel bumper hit at 5 mph might need 84

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only minimum repair or polishing. A metallic bumper would be more expensive to repair. The steel bumper would also require maintenance to prevent rust and maintain reflectivity. A plastic bumper would be maintenance–free in most cases.

If the plastic bumpers are painted, they may need some amount of maintenance.

Plastic bumpers generally have a longer life cycle if they do not get damaged and are properly maintained. A metallic bumper may have to be replaced because of rust and corrosion after a few years.

5.9

List five items that must be considered when designing a machined part to ensure efficient manufacturing and easy assembly. What are the considerations when designing a section for extrusion (a metal-forming operation)? What three questions form the criteria for eliminating a part from the assembly or for combining it?

While designing a machined part, some of the considerations are as follows: 1. Recognize the specific function of each part and the specific feature of a part that enables it to perform that function. Select a material on the basis of ease of fabrication as well as function and original cost.

2. Use the simplest configuration and specify standard sizes whenever possible. Try to use the configuration that requires the least number of separate operations. In addition, try to use configurations attainable with efficient manufacturing.

3. Provide clamping, locating, and measuring surfaces. In addition, specify tolerances and surface finish with consideration of the functional requirements and processes.

4. Design for ease of fabrication: •

There should be an optimum combination of material and production processes to minimize manufacturing costs.

•

Use net shape for molded and forged parts to minimize machining and processing effort.

•

Avoid unnecessarily high tolerances that are beyond the natural capability of the manufacturing processes.

•

Avoid tight tolerances on multiple, interconnected parts. Tolerances on multiple assembled parts can stack up undesirably.

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5.

Design for ease of assembly: •

• •

•

Design for ease of assembly by utilizing simple patterns of movement and minimizing the axes of assembly. Avoid complex orientation and assembly movements in various directions during assembly.

Part features should be provided such as chamfers and tapers.

The product’s design should enable assembly to begin with a base component with a large relative mass and a low center of gravity upon which other parts are added.

Assembly should proceed vertically with other parts added on top and positioned with the aid of gravity. This will minimize the need to re-orient the assembly and reduce the need for temporary fastenings and more complex fixturing. A product that is easy to assemble manually will normally be easily assembled with automation. Automated assembly will be more uniform, more reliable, and of a higher quality.

Manufacturing Process and extrusion related design rules

The considerations that must be taken into account when designing a section for extrusion:

Guideline

Poor

Better

Impact-extruded parts should be symmetrical.

Avoid sharp changes in cross section, sharp edges, and fillets.

Avoid tapers and almost equal diameters.

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Avoid hollows and maintain uniform wall profiles.

Provide rotationally symmetrical parts without material protrusions.

The three questions that form the criteria for eliminating a part from the assembly or combining it are: • Does the part move relative to all other moving parts?

• Must the part absolutely be of a different material from the other parts?

• Must the part be different to allow possible disassembly?

5.10

Consider the assembly of a product. a. Why is standardization important? b. What suggestion should be offered if the designer cannot make the part exactly symmetrical? c. Can screws be considered an essential part of a product? d. What design attributes of LEGO blocks make them popular? e. Select a product from the following list and offer a proposal for its design by outlining a step-by-step design procedure.

• Food processor • Wheelbarrow • Quadcopter • Steerable knee walker as an alternative to crutches a. Standard components are less expensive than customized components.

Common parts will result in lower inventories, reduced costs, and higher quality.

• Standardize and use common parts and materials to facilitate design activities.

• Minimize the amount of inventory in the system, and standardize handling and assembly operations.

Because of standardization, the operator learning is simplified and there is a greater opportunity for automation as the result of higher production volumes and operation standardization. Standardization results in limiting unique 87

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components because suppliers are less likely to compete on quality or cost for these components. Group technology can be used to guide the selection and development of manufacturing cells for common parts or product families. b. If the designer cannot make the part symmetrical, the part should be redesigned to exaggerate unavoidable asymmetries. This will facilitate easy part recognition and improve assembly efficiency. c. The screws are normally not considered as essential parts, as they can be replaced by snap-fits or press-fits which are more efficient for assembly purposes. (However, there may be unique design situations requiring the use of screws for mounting or disassembly purposes). d. The design attributes of LEGO blocks are: • They are interchangeable (sets can work with other sets) • Parts can be connected in multiple ways. They snap-fit together • Easy to assemble and dissemble • Self-locating • Resistance to nesting/tangling • 90 degrees beta symmetry • Safe for children (no sharp edges) • Durable • Visually appealing e.

Select a product from the following list and offer a proposal for its design by outlining a step-by-step design procedure.

• Food processor • Wheelbarrow • Quadcopter • Steerable knee walker as an alternative to crutches

The selected product is a Food Processor. Let us identify the components and evaluate design efficiency.

The Food Processor shown below is a juice extractor. This product requires assembly and disassembly before and after each use. The parts identified and the assembly view is shown below. The following chart shows assembly analysis. (Please note that items 1 and 6 are not considered a part of the assembly process.)

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Juice Extractor Comp. # 1 2 3 4 5 6 7

Comp. Name

Comp. Type

Dimensions

Qty

Food Pusher Cover Cutter/Strainer Separator Pulp Bin Juice Container Safety Latches

Part Part Part Part Part Part Part

105 length, 72 dia 215x170x140 60 Length, 130 dia 100 length, 150 dia 110x80x230 60x80x150 30x4x130

1 1 1 1 1 1 2

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Assembly Analysis 1

2

No Part

Description

4 3 5 2 7

Separator Cutter/Strainer Pulp Bin Cover Safety Latches

5

6

7

8

Number of α + β Manual Identical Symmetry Handling Operations Code

Manual Handling Time

Manual Insertion Code

Manual Insertion Time

Total Assembly Theoretical Time Minimum (2)x[(5)+(7)]=TM Number of Parts

1 1 1 1 2 6

1.95 1.5 1.95 1.95 1.13

0 0 0 0 0

1.5 2.5 1.5 2.5 3.5

3.45 4 3.45 4.45 4.63 19.98

Design Efficiency: E

3

4

720 360 720 720 0

3 1 3 3 0

9

1 1 1 1 1

= 3N/T = 3*6/19.98 = 90%

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Chapter 6 Exercises 6.1.

Explain the importance of incorporating DFD guidelines during an original design.

List a few benefits that are achieved by doing that.

What is Design for Disassembly (DFD)?

Design for Disassembly (DFD) is a design philosophy that requires consideration to be given for a product or a part even after it is in service. The inclusion of procedures for design for disassembly, recyclability, and re-manufacture will save resources by prolonging the useful life of the product. Design for Disassembly is a necessary condition in order for products to be economically recycled. It improves components and material reuse and remanufacturing processes, thus extending the service life of the products.

During product evaluation, the designer is required to assess component functionality, form, manufacturing processes, and assembly characteristics using certain data previously obtained. The designer is able to quantify the suitability of the design using certain predetermined assessment tools.

Employing DFD When employing the procedures of DFD, one should look at the life-cycle phases of development, production, distribution, usage, and disposal from the conceptual product design stage. This mandates certain procedures be established for disposal, recycling, and occupational health. These requirements are not only for new products, but also for other types of products, especially ones that are already in the marketplace.

DFD techniques vastly reduce waste in the manufacturing and recovery processes and allow for greater flexibility during product development, shorter development time scales, and reduced development costs at the end of life. These lower costs even prolong the life of products by allowing for changes. Most of the products are not designed for easy dismantling or disassembly. Implementing DFD into a design specification enables the product and its components to be better suited for re-use or recycling. DFD is a good strategy that helps reduce environmental impact in the application phase. If a product is easy to disassemble, it will be possible to repair it more easily, resulting in an increase in its service life.

The automobile industry has used the DFD principles for some time, as demonstrated by the presence of automobile junkyards and the availability of a wide range of rebuilt automotive components. Automobiles are one of the most highly recycled products. In terms of weight, about 75% of an automobile is recovered and recycled, including most of the metal components. Three primary operations in automobile-recycling are: • Dismantling of the automobile • Shredding and separating the iron components • Separating the non-ferrous components

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DFD is most effectively applied at the beginning of a design, as it can reduce the amount of time and materials used.

Benefits of incorporating DFD in early design As manufacturers are becoming more responsible for their products when they reach the end of their operational lives, the dismantling of products has emerged as one of the most serious part of this exercise. In situations involving integrated design principles, certain assembly procedures or joining techniques can make it very difficult to disassemble a product and separate materials into non-contaminated groups. A good strategy is to include DFD guidelines in the current product design processes.

Benefits of DFD: • Facilitates maintenance and repairs, thereby reducing costs.

• Facilitates part/component re-use, thereby recovering materials and reducing costs.

• Assists material recycling, thereby avoiding the disposal and handling of waste.

• Assists product testing and failure-mode/end-of-life analysis.

• Facilitates product take-back and extended producer responsibility, thereby reducing liability and assisting in regulatory compliance.

6.2.

Write briefly about any similarities or differences that you see between DFA and DFD guidelines. Explain the interaction between the guidelines. (Do they supplement or contradict each other?)

Similarities between DFD and DFA include minimizing part counts and handling times.

At times, using common materials allows for multiple parts to be integrated into a single part. It can also allow for disassembly to be simplified, even if the parts are not integrated into a single part. This simplification occurs because the parts can remain assembled and be recycled as one piece.

DFD and DFA differences do arise, especially when simplifying the securing of parts in an assembly. Many of the preferred DFA methods such as snap fits and press fits can make it more difficult to disassemble components. In these cases, alternative methods or other compromises should be considered in attempting to optimize both the assembly and disassembly methods.

There are places where DFA is at odds with DFD, and other places where they can complement each other. Conflict occurs in places where parts are never intended to come apart. For example, a multi-part plastic housing for a heater fan in the dashboard of a car is an item that should never be accessed for the life of the car. As such, parts can be snapped, glued, or ultrasonically welded (whichever is easiest). DFA and DFD can also be at odds over the fastening method selected. On the opposite side are parts or

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assemblies that are subject to routine maintenance. Making the system easy to access and reassemble can greatly reduce the cost of ownership for the end user.

6.3.

Practice making a design for disassembly evaluation chart using the spreadsheets.

(The rating factors method and Kroll’s disassembly evaluation chart can be developed and compared).

6.3.1

DFD Using Rating Chart Method

Example: Escalator Escalator systems play an important role in transporting passengers safely between underground and station platforms. However, due to the complex working conditions (such as uneven load, extreme weather, etc.) of escalator systems, maintenance is constantly needed and unexpected failure frequently occurs. The escalators used in train/subway/metro stations are exposed to extreme operating conditions such as extreme weather/temperature, uneven loads and shock, etc., which can greatly shorten their life span. The increase to labor and maintenance costs impedes the escalator’s ability to efficiently serve its riders and effects its overall stability. The failure and repair of the escalator systems result in high costs, significant amounts of labor, and customer dissatisfaction. For evaluating the design of the escalator housing, the Rating Chart method and Kroll methods are used. This case study presents the results of a comparison of rating scores for original and new designs of bearing housing.

The following is a list of constraints that limit the design choices that are available or impact the escalator housing redesign: • Thermal Environment of a minimum 90°C ambient temperature • Interoperability with client/manufacturer fabrication capabilities • Limited accessibility • Minimum modifications to existing structure and parts Tables 1 and 2 present the results of rating scores for two different designs. The columns numbered 1 to 7 in the tables represent task/damage, reuse, removal, recyclability, disassembly time access, and tooling rates. The rating score was calculated by adding the ratings from the columns numbered 1 to 7, dividing by the sum of the maximum rating of each column (i.e., 9 + 9 + 9 + 9 + 9 + 9 + 9 = 63), and multiplying the result by the weighting of each part (i.e., number of parts of each component in the assembly divided by the total number of components in the assembly).

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Figure 1. Assembly diagram for original design of escalator housing

Table 1. DFD Analysis of Original Design using Rating Chart Method Parts name Stub Shaft Bearing Bearing Housing Handrail Drive Pulley Double Sprocket Total parts

# of Parts 1

1

2

3

4

5

6

7

9

9

9

9

3

0

6

Rating Score 14.29

1 1

9 9

9 9

9 9

6 9

1 3

0 3

3 3

11.75 14.29

1

9

9

9

9

4

6

6

16.51

1

9

9

9

9

4

6

6

16.51

Total Score

73.33

5

Figure 2. Assembly diagram for new design of escalator housing

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Table 2. DFD Analysis of New Design using Rating Chart Method Parts name Stub ShaftAdditional Boring holes bearing bearing housing Handrail drive pulley Double Sprocket Total Parts

# of parts 1

1

2

3

4

5

6

7

9

9

9

9

8

9

9

Rating Score 19.68

1 1

9 9

9 9

9 9

6 9

8 9

9 9

3 9

16.83 20.00

1

9

9

9

9

9

9

6

19.05

1

9

9

9

9

9

9

6

19.05

Total Score

94.60

5

PERFORMANCE EVALUATION

Through this practice, a special case of an evaluation of escalator housing using the DFD method has been examined. The main changes made in the new design based on the new rating chart method are: (1) new bearing is used which is easy to assemble and disassemble. It can sustain larger loads; (2) new bearing housing is open at two ends so that the bearing can be easily accessed and replaced if needed. It also has a boring hole, which can be used to support the housing during assembly/disassembly of the bearing without the need of additional tools; and (3) new stub-shaft with boring holes can support the bearing housing during the assembly/disassembly of the bearing without additional tools.

These changes affect the design for the disassembly rating score. Referring to Tables 1 and 2, the disassembly rating score has increased from 73.33 to 94.60, increasing the ease of disassembly. After examining different types of failure modes and defects that occur in the major components of escalator drive systems, the bearings/lubrication system that is in adjunct with the bearing shaft assembly has been redesigned using the DFD method. The normal maintenance and repair of these sub systems is time consuming as shown by the Rating Chart method. However, comparing them with the DFD analysis of new design shows how the DFD method can greatly improve efficiency in comparing the new design to the original design. These improvements will save on the cost of labor during maintenance for the firm in the future.

The new parts also work with existing infrastructure and are easy to manufacture.

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DFD Using Rating Chart Method and Kroll Method 6.3.2 Example - Twin Size Dorm room “Bed”

Component

Description

Type

Dimensions (inches)

Quantity

1

Bed Header

Part

36 length x 18 x 1

1

2

Bed Footer

Part

36 length x 12 x 1

1

3

Header Uprights

Part

30 length x 3 x 2

2

4

Footer Uprights

Part

24 length x 3 x 2

2

5

Header, Footer, Upright bolt

Part

1/2 - 20 x 3 length

12

6

Aesthetic Caps Big

Part

3 x 3 diameter

4

7

Aesthetic Caps Small

Part

1 x 1 diameter

14

8

Inner leg (Height Adjustment)

Part

24 length x 2.75 x 1.75

4

9

Inner leg Locking bolt and nut

Part

3/8 - 16 x 2.5 length

8

10

Leg Stabilizers

Part

1.5 x 3 diameter

4

11

Leg Stabilizer bolts

Part

3/8 - 16 x 2 length

4

12

Mattress Frame

Part

81 length x 41 x2

1

13

Mattress Support

Part

39 length x 1 diameter

38

14

Mattress support bolts

Part

3/8 - 16 x 1.5 length

76

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An evaluation chart using the Kroll Method is shown below in Table 3. This analysis shows that the same product could have been achieved by better design such that components are made as one part instead of multiple components.

Table 3. Kroll Evaluation Chart Number Minimum of Part number Repetitive number of parts Tasks 1 1 1 2 1 1 3 0 2 4 0 2 5 0 12 6 0 4 7 0 14 8 0 4 9 0 8 10 0 4 11 0 4 12 1 1 13 0 38 14 0 76 Total Assembly time

Tool Type P P G G U F F R U P U W W U

Task Direction Z Z Y Y Z Z Y Y Y Y Y X Z Z

Tool Required I I I I III I I II III I III II I III

Tool Accessibility 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Position 1 1 2 2 1 1 1 2 1 2 2 1 1 1

Force 2 2 3 3 2 1 1 3 2 2 2 2 2 2

Time (minutes) 1 1 1.5 1.5 1.5 0.5 0.5 1.5 1.5 1 1 3 2 1

Special 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Subtotal 6 6 8.5 8.5 6.5 4.5 4.5 8.5 6.5 7 7 8 7 6

Total 6 6 17 17 78 18 63 34 52 28 28 8 266 456 1077

Tool type

Task direction

Tools

Accessibility

Position

Force

Special

F – Flip G – Grip P – Push/ pull R – Remove U – Unscrew W – Pry out

X – Front Y – Top Z – Side

I – Single grip II – Double Grip III – Allen Key

1 – readily

1 – Standing 2 – On Knees

1 – minor 2 – lower moderate 3 – upper moderate

1 – None

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6.4.

How can the use of self-aligning and self-locating features facilitate automatic assembly?

For automatic assembly to be efficient, it is necessary that the parts are designed for ease of handing during assembly operations. Designing parts for self-aligning and selflocating assists the process of handling the part.

Designing Parts for Ease of Part Handling The manual handling process involves the transportation and orientation of parts or subassemblies before they are inserted into or added to the work fixture or partially built up assembly. Some guidelines for design for ease of part handling are: • Avoid parts that tangle or nest • Avoid parts that interconnect • Design parts to prevent nesting A subassembly is considered a part if it is added during assembly. Time spent on assembly increases if the part requires holding down. Holding down is required if the part is unstable after placement, insertion, or during subsequent operations. A part may require gripping, realignment, or holding down before it is finally secured. Holding down also refers to a situation that maintains the position and orientation of a part already in place.

Parts can present handling difficulties if they nest or tangle, stick together because of magnetic forces or grease coatings, are slippery, require careful handling, etc. Parts that nest or tangle are those that interlock when in bulk, but that can be separated by one simple manipulation of a single part. Examples of this concept include paper cups, closed end helical springs, and circlips (ring washers). Parts that are slippery are those that easily slip from ringers or standard grasping tools because of their shape and/or surface conditions. Parts that require careful handling are those that are fragile or delicate, have sharp corners or edges, or present other hazards to the operator. Flexible parts are those that substantially deform during manipulation and also require the use of two hands.

Examples of such parts are paper or felt gaskets, rubber bands, and belts.

The design for manufacturing guidelines on self-aligning and self-locating features are useful in manual and automated assembly sequencing. The proper use of self-aligning parts assists the assembly sequence. Self-aligning and self-locating features facilitate automation of the assembly process, as there is less need for human intervention. Since the features are self-locating, automation also requires a lesser degree of freedom.

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6.5.

In what way does the method of fastening and joining a component to a product affect the feasibility of recycling?

Through the proper selection of fastening methods, including replacing fasteners and screws with Snap-Ons and other similar kinds of fastening mechanisms, disassembly can be made easier. If parts of similar material composition are substituted by one part, segregating parts for recycling becomes easier.

6.6.

What is the role of (a) alpha, (b) beta, and (c) preproduction prototypes in evaluating new products? (a) Alpha prototype - first comprehensive prototype.

The role of alpha prototypes is to determine whether or not the product will work as designed and whether or not the product satisfies the key customer needs. (b) Beta prototype - second comprehensive prototype (for “customer debugging”).

The role of beta prototypes is to answer questions about the performance and reliability in order to identify necessary changes for the final product. (c) Preproduction prototype - final prototype prior to launch.

Preproduction prototypes are made in small numbers on the production line to test processes and check assembly capabilities.

6.7.

With a flow chart, explain what the term design for manufacturing methodology means.

Design for Manufacturing is the process of designing a product so that it is easy to manufacture at the lowest possible price. DFM is primarily concerned with reducing overall part production cost and minimizing the complexity of manufacturing operations.

It aims to reduce material, overhead, and labor costs; shorten the product development cycle; and focus on standards to reduce cost. The key rules of DFM are part count reduction; standardization; ease of fabrication, robustness, and orientation; minimal flexible parts; ease of assembly; and efficient joining and fastening. The ability of designers to apply these rules is a key factor in design for manufacturing.

A flow chart explaining the design for manufacturing methodology is shown in Figure 3.

The method consists of examining three major factors. They are (a) reduction of cost of components, (b) reduction of cost of assembly, and (c) reduction of cost of supporting production. (a) Reduction of cost of components: Since the number of components influences the cost, keeping the number at an optimum level is important. The procedure involves identifying the criticality of each component in relation to its functionality. Factors such as the possibility of merging one or more components into a single component are of major concern.

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(b) Reduction of cost of assembly: Focuses on reducing cost by redesigning the components, specifically the geometry of and handling method of the component so that the time involved in the assembly is reduced. The reduction in assembly time, in addition to the reduction of components used, will contribute to reducing the cost of assembly. (c) Reduction of cost of supporting production: The redesign of the component and the assembly process will simplify the process of handling and disassembly. This procedure assists the designer by comparing two situations so the designer can assess the type of supporting production equipment, tools needed, number of Jigs and fixtures used in the production, and the cost of the production process. The designer can also compare the cost of initial design and the cost of redesign. At this stage the designer can review alternate designs and examine the product from the viewpoint of cost, quality, performance, and visual appeal. Factors such as additional investment needed to support the new design and return on revenue are also major considerations. The designer can then calculate the cost of redesign and its impact on sales and other institutional factors.

Proposed Design

Estimate the Manufacutring Costs

Reduce the Costs of Components

Reduce the Costs of Assembly

Reduce the Costs of Supporting Production

Consider the Impact of DFM Decisions on Other Factors

Recompute the Manufacturing Costs

N

Good enough ?

Y

Acceptable Design

Figure 3. DFM process (Ref: Ulrich and Eppinger (2012))

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Chapter 7 Exercises 7.1

Examine two products with the same function but made by different manufacturers.

Suggested products are food grinder, food blender, electric can opener, hair dryer, coffee grinder, electric knife sharpener, electric razor, small electric fan, electric toothbrush, and electric tools such as a screwdriver and hand drill. Do the following: a. List what you think the functional requirements should be. b. Identify the performance attributes you would like it to have. c. Identify the features you would like it to have.

One of the products selected is Hair Straightener. One product under the category of Hair Straightener is also known as a Hair tong. It is used for making frizzy hair smooth and shiny. Alternatively, this instrument is also useful if one wishes to make curls or create waves for a new look. Hair Straighteners are used to heat the hair using two conductive surfaces hinged together which are compressed between hairs and then pulled down the length of the hair. Special attention is paid to the plate material while choosing the Hair Straightener. This determines the evenness in heat distribution. The quality of the coating material determines the final results. In the current market, the most popular flat irons are coated with tourmaline or ceramic. In order to control the temperature, most Hair Straighteners offer a thermos-regulator with a few heating options.

Hair straighteners have become an extremely popular means to transform wavy or curly hair into straight locks as well as creating waves and curls for people with naturally straight hair.

General Requirements of the product can be listed as: a. General Functional Requirements: • Variable Heat Settings • Floating Plates • Long Swivel Cord • Fast Recovery Time • Auto Shut Off • Dual Voltage b. The performance attributes • Easy to handle • Safe to use • Quick heating • Durable • Efficiency 101 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

• Affordable price c. The features • Efficient heating speed • Able to straighten wet or steam hair • Variable temperature settings with digital display for accuracy • Worldwide voltage • Electric shock protection Two different kinds of Hair Straighteners are selected for comparison Hair Straightener Model 1 HSI Professional Ceramic Tourmaline Ionic Flat Iron, with Travel Size Worldwide Dual Voltage 110v-220v

Figure 1. HSI Professional Ceramic Tourmaline Ionic Flat Iron Special Hair Straightener features of Model 1 • • •

•

Titanium infused ceramic plates 3 Preset Temperatures from 220 to 350oF; Heat time 40 secs Due to preset modes with button control, one can choose the best option for the type of hair. The set buttons are situated internally near the plates. This stylish straightener will create shiny, long-lasting hairstyles Special features: Ceramic G2 Digital Titanium Flat Iron

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Hair Straightener Model 2 Apalus Brush Hair Straightener, with Travel Size Worldwide Dual Voltage 110v-220v Special Hair Straightener features of Model 2 • • • • •

Ceramic-coated bristles heat up to gently relax hair as you brush 60-minute auto shut off; LCD display Adjustable temperature control, easy on/off This straightener creates shiny hairstyles for all hair types, heats up to 450 degrees 6-ft. swivel cord

Figure 2. Apalus Brush Hair Straightener Specifications: Product Name Heat material Display Temperature Display Temperature Variation Power Adapter Product Size Net weight Package Dimensions Certification Power Output Voltage Color Accessories

Brush Hair Straightener PTC (ceramic) LCD Celsius & Fahrenheit exchangeable 150°C(302°F) ~ 230°C(450°F) US/EU/UK/AU Plug 27 x 7 x 4 cm 0.5 Kg 0.65 Kg CE, FCC, Rohs 30W 110V-240V Pink, black, or customized color User Manual

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7.2.

In Figure 7.1E (replicated as Figure 3 below), identify the better design and provide the rationale for your decision.

Design A Design B

Rationale Improved design is _____ because Improved design is A because it has ribs while the other one has locking angles. The parts should be designed to prevent nesting.

Improved design is _____ because Improved design is B because it is symmetrical.

Improved design is _____ because Improved design is B because the bigger hole eliminates the need for tight tolerances and results in a higher quality assemble.

Improved design is _____ because Improved design is B because the bigger hole eliminates the need for tight tolerances and results in a higher quality assemble.

Figure 3.

7.3.

Assume that a company decides to produce a new model of cellular telephones on a manual assembly line. The objective is to design its manual assembly line. This product has an annual demand of 100,000 units. The line will operate 50 weeks per year, five shifts per week, and 7.5 hours per shift. Work units will be attached to a continuously moving conveyor. Total work content time will be 42.0 minutes.

Assume the line efficiency is 0.97, the balancing efficiency is 0.92, and the repositioning time is 6 seconds. Find the following: a. The hourly production rate to meet the demand b. The number of workers required

Useful Equations to calculate the workstation requirements: Let us assume that the cellphone assembly line is of the manual assembly type. Equations can be developed to determine the required number of workstations on a production line. If we are 104 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

designing a single model line to satisfy the annual demand for a product, the required hourly rate of the line will be

RP =

Da 50 SH

Where, RP = the actual average production rate, (units/hr.) assuming 50 work weeks/year S = number of shifts/week H = hours/shift Da = the demand rate per week The average production time TP is shown as, 60 RP (a) Calculation of hourly production rate to meet the demand: TP =

Da = 100,000 units over a 50-week period S = 5 shifts/week H = 7.5 hours/shift

RP =

100,000 = 53.3 ≅ 53 Units/hour 50 × 5 × 7.5

(b) To calculate the number of workers required: Work content time C = 42.0 minutes Balancing efficiency E = 0.92 Average production time, TP, is shown as, 60 60 = = 1.13min /unit RP 53 Repositioning time, Tv = 6 secs (0.1 min) TP =

Service time, Ts = 1.13 – 0.1 = 1.03 minutes.

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Operators required to operate the line:

W =

7.4.

CE 42 × 0.92 = = 37.51 ≈ 38 Ts 1.03

See Figure 7.2E (replicated as Figure 4 below) for the sectional view of two rectangular boxes that are enclosed on four sides. The boxes are made by injection molding. Assuming that their wall thickness is the same, compare the two designs.

Identify the design that is less costly to produce. Explain the rationale behind your decision.

Figure 4.

The rectangular boxes enclosed are made by the injection modelling process. Injection molding is particularly advisable when a large number of intricate parts are produced.

The major advantage of injection molding is that one part can replace what would be otherwise an assembly of many components. Injection processing becomes economical when the components are mass produced. As the modeling process gets completed, the parts have to be designed for easy ejection. When the parts are mass produced, the savings made in terms of manufacturing time also impact the cost of the product.

When thermoplastics are used for injection molding, they exhibit shrinkage upon cooling and solidification. Certain design recommendations are followed to take care of the effects of gate and ejector pin locations in addition to shrinkage and surfaced finish.

Thermoset molded parts must be designed so that they may be easily removed from the mold.

The “ribs,” as shown in Figure 4, should be perpendicular to the parting line to permit removal of a part from the mold. If external undercuts are essential, straight draw is not possible, and side-activated split-molds or removable mold sections are required. This results in increased mold and piece part cost. Also inevitable is the additional parting line 106 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

or flash line, which may require additional finishing operations for removal. Both designs as shown above have some advantages and disadvantages.

The first design (left side) does not have external projection features. However, the internal design can still present problems. Internal undercuts in a part are almost impossible to mold and be avoided. The right side design is comparatively less costly to produce.

7.5.

How can the use of self-aligning and self-locating features facilitate automatic assembly? In what way does the method of fastening and joining the component of a product affect the feasibility of recycling?

Self-aligning and self-locating features facilitate in automation of the assembly process, as there is less need for human intervention or requirement of vision. Also, since they are self-locating, the automation requires less degree of freedom.

By proper selection of fastening methods, like replacing fasteners and screws with snapon and other similar kinds of fastening mechanisms, disassembly can be made easier. If parts of similar material compositions are substituted by one part, segregating of parts for recycling becomes easy.

7.6.

Figure 7.3E (replicated as Figure 5 below) shows the sectional view of two proposed alternative designs for an injection-molded box-shaped part that is enclosed on four sides. Assume that the wall thickness is the same in both designs. According to their tooling costs, which of the two designs is the least expensive?

Figure 5.

Just as described in Exercise 7.4, the injection molding process is used in mass production requiring a large number of intricate parts. The benefit of injection molding is that one part can replace what would be otherwise an assembly of many components.

As the modeling process is completed, the parts have to be designed for easy ejection.

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Certain design recommendations are followed to take care of the effects of gate and ejector pin locations in addition to shrinkage and surfaced finish. Thermoset molded parts must be designed so that they may be easily removed from the mold.

In the first design (left figure), the direction of mold is parallel to recess with the parting plane so the mold can be opened and the part can be ejected. In the second design (right figure), undercuts caused by the location of the parting require special moving parts in order to allow the parts to be ejected. The first design (left figure) is least expensive.

7.7.

As a product designer, create a product that has intricate parts that must be extruded. Identify a different way to fabricate the part without using a die.

Illustrate your procedure.

Figure 6.

Metal Extrusion When designing a metal extrusion process, the geometric profile of the extruded section is an important factor affecting the forces involved, metal flow, die wear, and part quality. Some cross sections, when extruded, will produce undesirable force distributions and metal flow. It is important to consider design features of the parts well in advance of any manufacturing process. These factors are crucial in extrusion processes, because of the possibility of manufacturing constraints.

Design for Extrusion This section will discuss the effect of different features of a profile and how to optimize the cross section for metal extrusion manufacture. First, it is important to understand that the nature of the forces involved in metal extrusion are fundamentally different than those of other forming processes. For example, in a process such as metal forging, the forces acting on the operation will vary throughout the process, as stress will change as the forging stroke progresses. With extrusion, (although in direct extrusion there is somewhat of a decrease in the necessary force, as the operation progresses, due to decreasing friction with billet length), the forces acting are generally consistent throughout the bulk of the operation.

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Some components need to have a very specific geometry and must be manufactured that way. However, if manufactured products may be geometrically altered in such a way as to ease in their manufacture, without changing their ability to perform their desired function, then they should be redesigned for manufacture. Symmetry is generally preferred in extruded metal cross sections, particularly with regard to open areas of the cross section. Open areas in an extrusion's cross section will complicate the process by changing the forces involved.

Die wear and breakage are primary considerations of a manufacturing process designer when designing a metal extrusion operation. Controlling material flow is essential in metal forming manufacture. In addition, the stresses applied to the die, as a result of this metal flow, must be calculated and the mold must be designed to handle these forces. Some areas of the die may be subject to greater stresses than others, while some areas of a die may not be able to handle as much stress as others. The geometry of the mold must be considered carefully with respect to the forces created as the part is being extruded.

Extrusion Guidelines Excessive stresses in places that cannot handle them can cause rapid wear and die breakage.

Extrusion die tongues cause a weaker area in the die's geometry. The location of die tongues and the forces they are subject to are an important factor in die design. a. Improving the design of an extrusion by balancing die tongues.

Figure 7.

• •

Symmetry provides for more balanced forces and helps avoid overstressing areas of the extruding die.

Hollow areas within the cross section, in particular, should be balanced.

b. More symmetrical hollow sections are preferred.

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Figure 8.

Usually, larger hollow areas cause more difficulties during the metal extrusion operation.

Reducing the area of hollow sections, if possible, may ease the manufacturing operation.

If hollow sections can be eliminated completely in favor of a single solid extrusion, it would be a better design for manufacture. c. If possible, eliminate hollow spaces in favor of a solid cross section.

Figure 9.

Thin walled metal extrusions are often produced in the manufacturing industry. However, there are limits to the minimum wall thickness. The minimum wall thickness of an extrusion depends largely on the type of extruded metal. The minimum wall thickness for aluminum extrusions is usually about .040 inches. A common type of extruded steel may have a minimum wall thickness of three times that of aluminum. Standard wall thickness throughout the profile is desirable, if not, the wall thickness should be as balanced as possible. d. If possible, design the extrusion’s profile with a standard wall thickness.

Figure 10.

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One way to improve the design of a metal extrusion process that requires a cross section of walls of different thickness is to smooth the transition between thick to thin walls with a large radius. e. When extrusion design with a standard wall thickness is not possible, a large radius can provide a smoother transition between sections of different thickness.

Figure 11.

The manufacturing designer should avoid sharp corners in a metal extrusion's profile, if at all possible. f. Sharp edges in an extruded profile should be avoided if possible.

Figure 12.

As mentioned earlier, die tongues are critical areas for mold wear and breakage.

Rounding certain corners of a metal extrusion can strengthen die tongues. g. Extrusion design for manufacture: Rounded edges strengthen die tongue.

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Figure 13.

Alternate ways of fabricating this part without a die: 1. Additive manufacturing 2. Fabrication of different parts shown in Figure 6 and welding the parts 1. Additive manufacturing Additive manufacturing is of a recent origin. Additive Manufacturing (AM) is an appropriate name to describe the technologies that build 3D objects by adding layer-upon-layer of material, whether the material is plastic, metal, concrete, or human tissue. Common to AM technologies is the use of a computer, 3D modeling software (Computer Aided Design or CAD), machine equipment, and layering material. Once a CAD sketch is produced, the AM equipment reads in data from the CAD file and lays downs or adds successive layers of liquid, powder, or sheet material in a layer-upon-layer fashion to fabricate a 3D object.

The term AM encompasses many technologies including subsets like 3D Printing, Rapid Prototyping (RP), Direct Digital Manufacturing (DDM), layered manufacturing, and additive fabrication. AM application is limitless. Early use of AM in the form of Rapid Prototyping focused on preproduction visualization models. More recently, AM is being used to fabricate end-use products in aircraft, dental restorations, medical implants, automobiles, and even fashion products. While the adding of layer-upon-layer approach is simple, there are many applications of AM technology with degrees of sophistication to meet diverse needs.

2. Fabrication of different parts of the drawing shown in Fig. 6 and welding the parts: The fabrication consists of the creation of a central component shown in the figure by regular machining. The connecting ribs are fabricated separately. There are four different ribs. All the ribs are joined to the central component. Different joining processes can be used to connect the ribs to the main component. The most popular joining processes are welding, joining by laser welding, and joining by electron beam welding.

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7.8.

See Figure 7.4E (replicated as Figure 14 below) for two design possibilities.

Assuming that the wall thickness is the same in both designs and that the part is to be injection molded, which of the two designs is less expensive produce and why?

Figure 14.

The first design (left figure) has two external undercuts which require special provisions for ejection of parts from the mold cavity. In the second design (right figure), there are no external undercuts. As such, the first design adds tooling complexity and cost. Hence the second design (right figure) is less expensive.

7.9.

A decision must be made on the layout for the production of a new product that involves a critical bearing mounting for a new escalator system. Identify the uniqueness of the three possibilities: (a) conventional layout, (b) process-based layout, and (c) cellular layout using group technology.

The bearing mount chosen is shown in the following figure. Depending on the type of Escalator system, there could be many variations of the mounts. Most of the mounts are supported by flanges.

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Figure 15 (a and b).

The mountings can be produced by any of the manufacturing layouts proposed here.

Raw Material

A

D

C Machines/resources are grouped according to the process they perform such as Drilling, Machining, and Assembly.

Components travel from one area to another depending on the design.

Assembly

Figure 16. Schematic of a Conventional Manufacturing System Raw Material

D B

C

D

E

A

B

D

F

F

E

D

G

Machines/resources are grouped and layout is structured according to the manufacturing process needed for a common product. If the process needs are Drilling, Machining, and Assembly operations, the layout is designed accordingly.

Ready Part

Figure 17. Schematic of Process based layout © Cellular Manufacturing layout 114 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

In the Cellular Manufacturing type of layout, the fabrication takes place in a confined cell where tools, machines, and handling devices such as robots are brought together in a sequenced and optimal fashion.

Raw Material

B

A

F

D

Ready Part

Figure 18. Schematic of a Cellular Manufacturing System 7.10.

Describe the interrelationships among product architecture, material selection, manufacturing process assembly, maintainability, and reliability. A 1-liter jug is manufactured in large numbers as a consumer product. Identify the design alternatives for fabrication using (a) plastic and (b) metal.

The product architecture is governed by the satisfaction of many different factors.

Variation in some factors may influence other factors. The trade-off and inter-relationship among factors like material, thickness, cost, and impact resistance against customer repair cost needs to be satisfied at the design stage.

Let us consider the example of an automobile.

The vehicle is to withstand the 5 mile/hour bump test. The impact resistance is dependent on the material type, its thickness, and the frame structure. A weaker and plastic type of material would need higher thickness than a stronger high carbon steel. The choice of the material has a bearing on the cost. Another important factor to be considered is repair cost.

For example, repairing a bumper made of plastic material that was hit at 5 mph might mean replacing the entire bumper, while a steel bumper hit at 5 mph might need 115

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minimum repair or polishing. A metallic bumper would be more expensive to repair. The steel bumper would also require maintenance to prevent rust and maintain reflectivity. A plastic bumper would be maintenance–free in most cases. If the plastic bumpers are painted, they may need some amount of maintenance. Plastic bumpers have a longer life cycle if they do not get damaged and are properly maintained. A metallic bumper may have to be replaced because of rust and corrosion after a few years.

For example, during the design of a commonly used product such as a bearing, one faces two dominant factors such as material cost and repair cost under warranty. The designer has to consider the interrelationships among product architecture, material selection, manufacturing process assembly, maintainability, and reliability The design differences in plastic and metallic jugs: i) Handle: In the case of a plastic jug, the handle can be integrally molded, whereas in the case of a metal one, the handle is separately formed and welded or riveted to the jug. The basic shape is formed by spin forming or drawing. ii) Rim Design: While the plastic rim is of the same section as the body, the rim of the metal jug is curled up to prevent sharp edges. iii) Material Thickness: Injection molded plastic jugs should be at least 2 to 3 mm for mold ability and strength characteristics. Metal jug thickness can be as small as 0.8 mm. iv) Jug Shape: For the plastic jug, a change side with a draft angle is necessary for extraction of the mold. Lip for metal jug can be provided with curls. Metal jugs can be fabricated with diverse shapes and comparatively low wall thickness.

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Chapter 8 Exercises 8.1

Consider a popular product such as hand soap dispensers currently used in the market. Assuming you will improve the quality, identify how you would go about redesigning the product. Indicate how you would develop robust design methodology to create the best product.

In light of the fact that computers are used everywhere, we chose a product, “Computer Keyboard”. Let us examine a typical keyboard and identify its major design features. The function diagram and morphological charts provide ideas for product creation and performance. Let us also examine different components and design features of the components from the view point of assembly. The design efficiency is calculated after considering the benefits of design for manufacturing (DFM). Following this, a redesign of the keyboard is performed and the new design features are analyzed.

Product: IBM keyboard 104 KB 8923 PS2 History: The product identified is IBM keyboard 104 KB 8923 PS2, Manufacturer IBM. This product was made at a manufacturing location in Thailand. While reviewing the developments of the product, it was found that the earliest PC was introduced in the early 1980s. The keyboard PC/XT had 83keys. Some of the keyboard problems were corrected in the 1984 version PC/AT. In 1986, the keyboard was enhanced to include 101 keys. In 1995, the 104-keyboard was introduced, which has specific functions for Windows application.

Figure 1. Keyboard Models All 104 keys in the keyboard have moving parts. The keys are inserted into the keyhole, and motion of the keys is supported by membrane frame. In addition, the 2 keyboard bottom supports pose relative movement too. The same applies to the 8 keys that require 117 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

spring balance supports, such as left shift key, right shift key, etc. The function diagram, as shown in Figure 2, identifies major features and components that are needed.

Morphological charts identify alternate pathways to obtain the results.

Function Diagram for a Keyboard

Input

Output Keyboard

Words that communicates order

Motion of hands

Power supply +5 Voltage DC

Signals that represent graphics or Text on computer

Keyboard Switch Apply translation signals Matrix Circuits Column Signals Row Signals

Key Code Scan Code Singe-byte Code

Figure 2. Function Diagram of Initial Design

Feature Keyboard switch Material Looks Mounting Key Caps Mounting Case Power supply

Means Mechanical Wood Flat Screws

Membrane Hard plastic Rounded Snaps

Screws Store

Snaps Adhesives XT-style System AT-style System

Capacitive Silicon Obtrusive Eliminates

Table 1. Morphological Chart of Initial Design

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Figure 3. Part Analysis of Initial Design

IBM KB-8923 keyboard has 39 different groups of parts, and the total number of parts is 139. There are seven groups of keys that are not identical and there are 8 unique single keys such as left shift, right shift, etc. (Each of these keys contains a spring for balance support, as the key length is long).

The actuation of the key and the design of keycap plays a major role in Keyboard design.

The key actuation can be done in several ways. Some of the popular methods are listed in Figure 4. The principles shown in the figure are mechanical, foam element type, membrane type, and capacitive type.

Mechanical

Foam Element

Membrane type

Capacitive type

Figure 4. Major design features of the Keyboard 119 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

IBMKB-8923Keyboard Part Number

Part Description Number of identical parts Material 1 BaseCover 1 Plastic 2 PS2Cable 1 Plactic andmetal 3 Film1 1 Paper 4 Film2 1 Paper 5 Metal Frame 1 Steel 6 PrintedCircuit Layer 1 1 Paper 7 Circuit ConnectionLayer 1 Paper 8 PrintedCircuit Layer 2 1 Paper 9 MembraneFrame 1 Soft plastic 10 Circuit Board 1 Plastic andmetal 11 PS2screw 2 Metal 12 TopCover 1 Plastic 13 Front Cover Screws 4 Metal 14 BottomCover Screws 8 Metal 15 BottomCover Support 2 Metal 16 R1Key 18 Plastic 17 R2Key 14 Plastic 18 R3Key 18 Plastic 19 R4Key 36 Plastic 20 SSKey 5 Plastic 21 AKey 2 Plastic 22 CKey 1 Plastic 23 TKey 2 Plastic 24 Shift Lkey 1 Plastic 25 Shift LKey BalanceSupport 1 metal 26 Shift Rkey 1 Plastic 27 Shift RKey BalanceSupport 1 metal 28 Enter Key 1 Plastic 29 Enter Key BalanceSupport 1 metal 30 BackSpaceKey 1 Plastic 31 BackSpaceKey BalanceSupport 1 metal 32 Spacebar 1 Plastic 33 Spacebar BalanceSupport 1 metal 34 0NumKey 1 Plastic 35 0NumKey BalanceSupport 1 metal 36 + NumKey 1 Plastic 37 + NumKey BalanceSupport 1 metal 38 Enter NumKey 1 Plastic 39 Enter NumKey BalanceSupport 1 metal

Size 170mm*455mm*30mm 2209.8mmlength, 5mmdia 227mm*42mm*1mm 90mm*100*1mm 133mm*437mm*4mm 125mm*437mm*1mm 125mm*437mm*1mm 125mm*437mm*1mm 125mm*437mm*5mm 50mm*88mm*6mm 7mmlength, 6mmdia 175mm*455mm*24mm 11mmlength, 6mmdia 12mmlength, 6mmdia 29mm*43mm*10mm 18mm*18mm*17mm 18mm*18mm*16mm 18mm*18mm*15mm 18mm*18mm*17mm 19mm*23mm*17mm 18mm*22mm*17mm 18mm*34mm*15mm 18mm*28mm*15mm 18mm*42mm*18mm 12mm*34mm*2mm 18mm*52mm*18mm 12mm*43mm*2mm 18mm*42mm*11mm 12mm*32mm*2mm 18mm*37mm*18mm 12mm*34mm*2mm 18mm*118mm*15mm 12mm*76mm*2mm 18mm*37mm*16mm 12mm*32mm*2mm 18mm*37mm*15mm 12mm*33mm*2mm 17mm*37mm*17mm 12mm*32mm*2mm

* Key descriptions(I.eR1, R27), pleaserefer tohanddrawingafter thispage

Table 2. Component Breakdown (initial design) Design Analysis (Design for Assembly and Design for Disassembly) The design for assembly analysis is carried out using the standard method, such as the Boothroyd Dewhurst procedures. The following results were observed after conducting DFMA analysis (Manual assembly with $30 labor rate/hour): • Design Efficiency – 53.3% • Total Assembly Time – 615.6 seconds • Theoretical Minimum Number of Parts – 114 The Fishbone diagram (shown in Figure 5) gives an idea of the strength design for disassembly.

Parts scores, time scores, and rating scores were identified using the “Rating Score” method.

Using this, the overall design score for the initial design was calculated.

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Figure 5. Reverse Fish Bone Analysis of the Keyboard Actual Time 74.71 70.18 72.50 72.5%

Rating Score Time Score Parts Score Overall Design Score

Est. Time 74.71 54.05 70.27 66.3%

Table 3. Design for Disassembly Analysis IBM Keyboard - Overall Rating Work Parts, Time, then Rating

100.00% 90.00% 80.00% 70.00% 60.00% 50.00% 40.00% 30.00% 20.00% 10.00% 0.00% Rating Value

Rating Score

Time Score

Parts Score

74.71%

70.18%

72.50%

Figure 6. Rating Score Method 121 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

New Keyboard Design Redesigned Keyboard There is a major change in design, as with the introduction of membrane technology, the number of parts is drastically reduced. There is only one moving part, which is the top frame with keys; this is because all keys and the silicon frame are made in one piece. In this keyboard design, no membrane frame is found. However, the membrane structure is built in with the top silicon frame.

The morphological charts are shown in Figure 8. The new redesigned keyboard has 7 different groups of parts, and the total number of parts is 7.

Morphological Chart

Figure 7. Morphological Chart of the Keyboard (New Design)

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Key Key Rod

Key Hole

Membrane Frame

Elastic Membrane Frame Collapse, but it will back up when key is retract

Printed Circuit Layer2 Insulation layer Printed Circuit Layer1

Figure 8. Redesigned Key Actuation Principles

Figure 9. Redesigned Key Principles

Parts

Sizes

Thermoplastic Elastomer Flippable Frame 450mm*140mm*20mm Membrane Frame 440mm*128mm*4mm Printed Circuit Layer 2 with PCB 440mm*128mm*1mm Spacer 440mm*128mm*1mm Printed Circuit Layer 1 460mm*128mm*5mm U-Shaped Fitting Feature 520mm*150mm*40mm

Materials Thermoplastic Elastomer Natural Rubber Sub-assembly item PCB Thermoset Sub-assembly item PCB Thermoplastic Elastomer

Table 4a. Material Choice for Parts (Redesigned)

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Part No.

Part Description

1 2 3 4

Base Silicon frame Printed Circuit layer 1 Circuit Connection layer Printed Circuit layer 2 with circuit board PS2 cable

5 6 7

No. of Identical Parts 1 1 1 1 1

Material

Size

Silicon Metal & Plastic Paper Paper, Metal, Plastic Metal & Plastic

493x138x7 mm 128x444x1 mm 128x444x1 mm 128x494x5

Indication plate 1 Plastic Top silicon frame 1 Silicon Table 4b. Part Description (Redesigned)

7 mm length, 6 mm diameter 40x117x2 mm 495x138x1 mm

DFMA analysis of new design indicates (Manual assembly with $30 labor rate/hour): • Design Efficiency – 76.2% • Total Assembly Time – 22.7 seconds • Theoretical Minimum Number of Parts – 6

Figure 10. Reverse Fish Bone Analysis of the Redesigned Keyboard

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Actual Time Rating Score 77.78 Time Score 85.71 Parts Score 100 Overall Design Score 87.8% Table 5. Design for Disassembly Analysis

Est. Time 77.78 75.00 100 84.3%

Figure 11. Rating Score Method IBM Keyboard

Redesigned Keyboard

53.30%

76.20%

615.6 seconds

22.7 seconds

114/138

6/6

Rating Score

74.71%

77.78%

Time Score

70.18%

85.71%

Part Score

72.50%

100.00%

Design Efficiency DFMA Analysis

DFD Analysis

Total Assembly Time Theoretical Minimum Number of Parts

Table 12. Comparison of DFA and DFD analysis for IBM Keyboard and Redesigned Keyboard The redesigned keyboard has just seven parts. The number of parts are drastically reduced. There is also improvement in assembly time, and overall design efficiency in the new design.

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8.2

Regarding learning curve analysis, a. Under what circumstances is it most applicable? b. What determines the degree of slope for a given learning curve? c. A company producing defensive missiles spent 125,000 hours to complete the first unit. The second and third units were produced with an 86% learning factor. Assuming the same learning factor and the rate of $40 per hour, what would be the cost of the fourth unit? a. Under the following circumstances, the learning curve is most applicable: i.

A high proportion of manual labor ii.

Uninterrupted production iii. Production of complex items iv. No major technological change v.

Continuous pressure to improve b. The rate of improvement is called the slope of the learning curve. Each time the production quantity doubles, the average cost is reduced by a constant percentage that determines the slope for a given learning curve. c.

Basic equations: Y = Ki

b

P = 86% b=

log 0.86 = −0.2176 log 2

Y = 125000 ∗ i −0.2176 For the fourth unit, i = 4

Y = 125000 ∗ 4 −0.2176 = 472800 Cost = $40 ∗ 472800 = $18,912,000

8.3

In response to a consumer inquiry, a manufacturing industry is estimating the cost of a new product, which is similar to the one it has now. It is estimated that 400 labor hours will be required to produce the first unit. Draw graphs of labor requirements for units 1 through 25 for 80% and 90% learning curves.

126 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

Basic Equation: Y = Kib From Table 8.11 from the Textbook, the values of exponent (b) for 80% and 90% are -0.322 and -0.074, respectively.

Labor hours required to produce the first unit K = 400 For P = 80% , Y = 400i − 0.322 For P = 90% , Y = 400i

− 0.074

Using Matlab, the following plot has been created for Labor requirements for units 1 through 25 for 80% and 90% learning curves.

Matlab Code: % Exerxise 8.3 % Plot of labor requirenments for unit 1 through 25 for 80% % and 90% learning curves i=[1:1:25]; y1=400*i.^(-0.322); y2=400*i.^(-0.074); plot(i,y1,i,y2,'linewidth', 2); title('Learning Curves for 80% and 90%') xlabel('Cummulative Units') ylabel('Labor Hours (Production Units)') legend('y1 = 400*i^{-0.322}','y2 = 400*i^{-0.074}') 127 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

8.4

A department in a small manufacturing organization produces two types of parts, A and B. Assume that it produces y1 units of type A and y2 units of type B. Each part is manufactured using a two-step process involving two robots, M and N. The manufacturing times for y1 units of A on robots M and N are 4 hours and 6 hours, respectively. Similarly, the manufacturing times for y2 units of B on robots M and N are 8 hours and 4 hours, respectively. For a three-week period, the availability of robot M is 120 hours and of robot N is 100 hours. The estimated profit generated per unit by type A is $40 and by type B is $30. The department can sell the parts as soon as they are manufactured. Estimate graphically how many units of each part type should be manufactured to maximize profit. (Suggestion: In this case, the objective function is the profit function expressed as Z = 40y1 + 30y2, where Z is the total profit. The availability time constraints for robots M and N, respectively, are 4y1 + 8y2 ≤ 120 6y1 + 4y2 ≤ 100 Let us assume y1 to be the units of type A and y2 to be the units of type B. Constraint Equations: 4 y1 + 8 y2 ≤ 120 6 y1 + 4 y2 ≤ 100 y1 , y 2 ≥ 0 Total profit ( Z ) = 40 y1 + 30 y 2

128 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

Looking for a graphical solution: g1 = 4 y1 + 8 y 2 − 120 g 2 = 6 y1 + 4 y 2 − 100

g 3 = − y1 g 4 = − y2 Z = 40 y1 + 30 y2

Four constraint equations are graphically represented. The objective function Z = 40 y1 + 30 y 2 is drawn for different values of y1 and y2 to determine the maximum value of profit (Z). Optimum values of y1 and y2 are found for the maximum value of Z. y1 = 10 , y 2 = 10 , and Z = $700 .

Matlab code: %Create a grid from ?1 to 25 with an increment of 0.5 for the variables x1 and x2 [y1,y2]=meshgrid(-1:0.5:40,-1:0.5:40); %Enter functions for the profit maximization problem f=40*y1+30*y2; 129 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

g1=4*y1+8*y2-120; g2=6*y1+4*y2-100; g3=-y1; g4=-y2; %Initialization statements; these need not end with a semicolon cla reset axis auto %Minimum and maximum values for axes are determined automatically xlabel('y1'),ylabel('y2') %Specifies labels for x- and y-axes title ('Profit Maximization') %Displays a title for the problem hold on %retains the current plot and axes properties for all subsequent plots %Use the “contour” command to plot constraint and cost functions cv1=[0:0.01:0.1]; %Specifies two contour values, 0 and .3 const1=contour(y1,y2,g1,cv1,'g','LineWidth',2); %Plots two specified contours of g1; k=black color text(15,8.4,'g1') %Writes g1 at the location (15, 8.4) cv2=[0:0.01:0.01]; const2=contour(y1,y2,g2,cv2,'r','LineWidth',2); text(7,15.2,'g2') cv3=[0:0.01:0.1]; const3=contour(y1,y2,g3,cv3,'m'); text(.25,30,'g3') const4=contour(y1,y2,g4,cv3,'k'); text(33,1,'g4') text(3,5,'Feasible Region') hold off For optimization z = [-40; -30]; %coeff for objective (negative for maximization) A = [4 8; %coeff for constraints 6 4]; b = [120; 100]; %RHS for constraints lb = zeros(2,1); %lower bounds for x (QM, QA) %options = optimoptions('linprog','Algorithm','simplex') [x,fval,exitflag,output] = linprog(z,A,b,[],[],lb,[],[]) %,options) %optimization

130 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

8.5

A manufacturing firm has the capability to produce three different products in its factory. Fabricating each product requires several manufacturing operations. See Table 8.1E for the time required for each operation, the maximum operation capacity per day, and the unit profit for each operation. Set up the relevant constraint equations to select the appropriate product mix to maximize profit.

Operation

Product 1 Time/Unit (minutes)

Machining Welding Casting Profit/Unit ($)

1 3 1 3

Product 2 Time/Unit (minutes)

Product 3 Time/Unit (minutes)

2 1 0 2 4 0 2 5 Table 8.1E Time Vs. Operation

Operation Capacity (minutes)

430 460 420

Let x = Units of product 1 Let y = Units of product 2 Let z = Units of product 3

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x + 2 y + z ≤ 430 3 x + 2 z ≤ 460 x + 4 y ≤ 420 x, y , z ≥ 0 Total Profit "U " = 3 x + 2 y + 5 z Solution to the problem is obtained by converting the inequality constraints to equation form by adding three slack variables s1,s2,s3 ≥ 0 . x + 2 y + z + s1 = 430 − − − −(1) 3 x + 2 y + s 2 = 460 − − − − − (2) x + 4 y + s 3 = 420 − − − − − −(3) The problem is solved using the simplex method algorithm. It is an iterative process. For each iteration, the following steps are used.

Steps: 1. The three variables to be solved using equations (1-3) are called the basis variables.

For the first iteration, we choose the initial basis variables to be those variables that appear in only one constraint equation and whose coefficients in these equations are unity. For the subsequent iterations, we chose variables from step 5 and 8 of the previous iteration.

2. Solve constraint equations for values of the selected basis variables.

3. Evaluate U for this iteration.

4. Begin search for improved solution by expressing U in terms of nonbasis variables, using constraint equations as necessary to eliminate basis variables from U. 5. Select as incoming basis variable that variable for which a unit increase has the greatest effect on increasing U. 6. Express constraint equations in terms of current basis variables and incoming basis variable.

7. Select as outgoing variable the current variable that imposes the most severe constraint on the incoming variable.

8. With new basis variables selected, set the nonbasis variables to zero and start the next iteration.

STEP ITERATION 1 1 Basis: s1,s2,s3 x=y=z=0 2 s1=430 s2=460 s3=420 3 U=0

ITERATION 2 Basis: z,s1, ,s3 x=y= s2=0 Z=230 from (2) s1=200 from (1) s3=420 from (3) U=1150

ITERATION 3 Basis: y,z,s3 x= s1= s2=0 Z=230 from (2) y=100 from (1) s3=20 from (3) U=1350

132 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

4

U=3x+2y+5z

Using (2) to eliminate z, U=3x+2y+5(230-3/2x-1/2s2) U=1150-9/2x+2y-5/2s2

5

z is the incoming basis variable

y is the incoming basis variable

6

z+s1=430----(a) 2z+s2=460---(b) s3=420--------(c) from(a ), s1 , requires, z ≤ 430

2y+z+s1=430----(a) 2z=460---(b) 4y+s3=420--------(c) From (b), z does not limit y from (c), s 3 , requires , y ≤ 105 using (b) to eliminate z from (a) shows that s1 requires y ≤ ( 430 − 230 ) / 2 s1 is outgoing variable x= s1=s2=0

7

from(b), s 2 , requires, z ≤ 230 From(c), s3 does not limit z s2 is outgoing variable 8

y=s2=0

Eliminate z from (1) and (2), then solve for y in terms of x,s1,s2 U=1150-9/2x5/2s2 +2(100+1/4x1/2s1+1/4s2) U=1350-4x-s1-2s2 No further increase in U is possible.

The optimum product mix ratio is to make 100 units of product 2 and 230 units of product 3.

8.6

Briefly explain what a product’s robust design implies. Construct an orthogonal array for a robust design experiment on a newly designed surface roughness instrument. Roughness is measured in gray scale values by using a laser- and microcomputer-based vision system. Control parameters provided for the surface roughness instrument are: Laser distance Ambient light Laser power

10 Present 500 miliwatt

15 Not present 1000 miliwatt

Gray-scale setting

190

200

Genichi Taguchi proposed a new philosophy for solving quality problems. He developed the foundation of Robust design. Taguchi developed a relatively easy-to-understand method to design a fractional factorial experiment that helps to make products/processes "robust" and with less variation. Robust design uses ideas from statistical experiment design and addresses two major concerns:

133 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

• •

How to economically reduce the variation of a product's function to the customer environment How to ensure that decisions found optimum during laboratory experiments will prove to be so in manufacturing and customer environments.

The answer provided by robust design methodology to the two concerns listed above make it a valuable tool for improving productivity.

Robust Design using Taguchi’s approach: • • •

Design quality into the product. Do not use inspection to sort out the poor-quality products.

Set a target. The cost of quality is the deviation from the target values.

Make the product insensitive to uncontrollable external factors.

This is achieved by optimizing the product and process designs to make the performance minimally sensitive to the various causes of variation. This is called parameter design.

However, parameter design alone does not always lead to sufficiently high quality.

Further improvement can be obtained by controlling the causes of variation where it is economically justifiable, typically by using more expensive equipment, higher grade components, and better environmental controls, all of which lead to higher product cost, operating cost, or both. The benefits of improved quality must justify the added product cost.

Let us consider an example where tolerance specification is given as 0.50 ± 0.02. In this case, it would be immaterial whether the actual figure is 0.48, 0.50, or 0.52; the specifications would be equally satisfied. Taguchi defines quality as product uniformity around a target value. Here the target value is 0.50, and the actual values achieved closer to the set target value would be better than the values further away from the target. To summarize the basic principle, there are two steps involved in the robust design approach to enhance quality of the design: • •

Optimizing the design of the product/process Making the design insensitive to the influence of uncontrollable factors (robustness)

The first step in conducting a robust design experiment is to identify the factors that influence the process. There are two factors that influence a process: noise and control factors. The number of control factors are determined depending on the complexity of the process. After both factors have been determined, the ‘parameter’ settings for all factors are selected. Then an orthogonal array (explained in the next section) is constructed using 134 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

all the factors and levels for each factor that have been predetermined earlier. The experiment is performed according to the parameter settings of each row in the orthogonal array with or without replications. Taguchi focused on robust design and he identified critical factors whose variation and tolerance could be controlled to ensure product performance under service conditions that obtain optimum cost quality by utilizing maximum tolerance.

Robust Design Technique applied to Surface Roughness Analyzer Instrument This instrument works with a new non-contact optical method based on light diffraction principles. When applied to engineering surfaces, it rapidly provides precise surface roughness data on engineering and machined surfaces. The roughness measurement conventionally involves the use of a stylus device, which is drawn over the sample in order to detect and record variations in surface irregularities. Compared to the contact stylus method of inspection, the optical technique is very much preferred. Roughness measurements are made by utilizing a laser and microcomputer based vision system by measuring the intensity of the collimated, monochromatic light source diffracted in the spectral direction and captured by a video system that provides an analog signal to a digitizing system for conversion to digital information. This information is subsequently modified to display the surface roughness value. The method further includes a microcomputer based procedure which provides the operator interaction in the form of menu driven steps which guide the operator through the requirements of each phase of the process; the calibration, measurement, and analysis phases.

Camera

Screen

Laser

Mirror

θ Workpiece

Schematic of the Laser based roughness analyzer Experiment Using Robust Design The objective of a robust design study is to find the optimum recommended factor setting for the surface roughness analyzer to minimize the variability in the readings. This instrument relies on the spread of the laser light on the work piece to determine the surface roughness; therefore, the reliability of the analyzer depends mostly on everything 135 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

that involves the laser and its path. As an example, four parameters setting each at two levels were introduced into the experiment in the form of orthogonal arrays.

The parameters are 1.

2.

3.

4.

Laser angle Background Distance from the Laser to workpiece Background lighting.

The parameter setting for the new experiment is shown in the table below Parameter Abr Level 1 Level 2 •

Laser Angle

La

20°

30°

•

Background Surface

Bs

Glossy

NonGlossy

•

Distance from Laser to Workpiece Background Lighting

Dt

4.5 in

5.5 in

Bl

Off

On

•

Parameter settings for surface analyzer

Parameter Optimization Experiments are done to minimize the effects of the laser angle and the distance from the laser to the workpiece and also the interactions between them. The parameter setting for this experiment is identified. The following table shows the optimal setting of the parameters achieved after robust design analysis.

Parameter

Condition

Laser Angle

25°

Distance of laser to work piece

4.5 in

Background paper

non-glossy

Optimal settings for the instrument In many industry situations, the robust design method is successfully used to determine the optimum setting of the system. The application of the method in electronics, automotive products, photography, and many other industries has been an important 136 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

factor in rapid industrial growth. It proves to be useful and easy to implement in the design process. Furthermore, the nature of the method allows the designer to investigate every possible variable and its effects in this application. In addition, it also reduces the time required to complete the experiments.

8.7

One of a company’s production shops makes two products, each of which requires three manufacturing operations. The company can sell all it can make of both. In fact, it is considering to increase its production capacity. See Table 8.2E for the operation’s constraints and other data.

Product

1 2 Hours available

Production Time Required per Unit (hour/unit) Operator Operator 2 Operator 3 1 1.2 2.3 4.5 2.3 6.8 1.9 24.0

32.0

Cost ($)

Selling Price ($)

$80 110

$95 130

24.0

Table 8.2E Operation’s constraints a.

Determine the product mix that maximizes profit. b.

If production capacity were to be increased, to which operation should the additional capacity be allocated?

Let us assume x1 to be product 1, and x2 to be product 2.

Constraint Equations: 1.2 x1 + 2.3 x2 ≤ 24 2.3 x1 + 6.8 x2 ≤ 32 4.5 x1 + 1.9 x2 ≤ 24 x1 , x2 ≥ 0 Total profit = (95 − 80) x1 + (130 − 110) x2 f = 15 x1 + 20 x2

137 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

Looking for a graphical solution: g1 = 1.2 x1 + 2.3 x2 − 24 g 2 = 2.3 x1 + 6.8 x2 − 32

g 3 = 4.5 x1 + 1.9 x2 − 24 g 4 = − x1

g 5 = − x2 f = 15 x1 + 20 x2

Five constraint equations are graphically represented. The objective function f = 15 x1 + 20 x2 is drawn for different values of x1 and x2 to determine the maximum value of profit (f). Optimum values of x1 and x 2 are found for the maximum value of f. x1 =3.904, x 2 = 3.385, f = $126.26 .

Using Matlab for Graphical Solution Mfile for Graphical solution %Create a grid from ?1 to 25 with an increment of 0.5 for the variables x1 and x2 [x1,x2]=meshgrid(-1:0.5:25,-1:0.5:20); %Enter functions for the profit maximization problem f=15*x1+20*x2;

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g1=1.2*x1+2.3*x2-24; g2=2.3*x1+6.8*x2-32; g3=4.5*x1+1.9*x2-24; g4=-x1; g5=-x2; %Initialization statements; these need not end with a semicolon cla reset axis auto %Minimum and maximum values for axes are determined automatically xlabel('x1'),ylabel('x2') %Specifies labels for x- and y-axes title ('Profit Maximization') %Displays a title for the problem hold on %retains the current plot and axes properties for all subsequent plots %Use the “contour” command to plot constraint and cost functions cv1=[0:0.01:0.1]; %Specifies two contour values, 0 and .3 const1=contour(x1,x2,g1,cv1,'g','LineWidth',2); %Plots two specified contours of g1; k=black color text(14,3,'g1') %Writes g1 at the location (14, 3) cv2=[0:0.01:0.01]; const2=contour(x1,x2,g2,cv2,'r','LineWidth',3); text(10,1.5,'g2') const3=contour(x1,x2,g3,cv2,'b','LineWidth',3); text(0.5,12,'g3') cv3=[0:0.01:0.1]; const4=contour(x1,x2,g4,cv3,'m'); text(.25,18,'g4') const5=contour(x1,x2,g5,cv3,'k'); text(23,.4,'g5') text(1,2,'Feasible Region') hold off

For optimization Using Matlab Mfile z = [-15; -20]; %coeff for objective (negative for maximization) A = [1.2 2.3; %coeff for constraints 2.3 6.8; 4.5 1.9]; b = [24; 32; 24]; %RHS for constraints lb = zeros(2,1); %lower bounds for x %options = optimoptions('linprog','Algorithm','simplex') [x,fval,exitflag,output] = linprog(z,A,b,[],[],lb,[],[]) %,options) %optimization

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8.8

Automatic cameras can have a number of associated variables, for example, film speed, flash, and focus. Each independent variable affects the dependent variable, which is the picture quality. The levels of these variables follow: Film speed, A Flash, B Focus, C

400 ASA On In

100 ASA Off Out

a. Construct a suitable orthogonal array and substitute appropriate control variable values. b. Will 100% interchangeability or statistical interchangeability generate wider tolerances?

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The given condition has two levels and three factors, as outlined in the following tables.

Taguchi orthogonal array Trial 1 2 3 4

1 1 1 2 2

2 1 2 1 2

3 1 2 2 1

Value substitution for the Taguchi orthogonal array Trial 1 2 3 4 8.9

1 100 100 400 400

2 OFF ON OFF ON

3 OUT IN IN OUT

The Taguchi quadratic loss function for a part in a snow blowing equipment is ࡸሺ࢟ሻ = ૝૙૙૙ሺ࢟ − ࢓ሻ૛ , where y = actual value of critical dimension and m is the nominal value. If m = 100.00 mm, determine the value of loss function for tolerances (a) ±0.15 mm and (b) ± 0.10 mm. ‫ܮ‬ሺ‫ݕ‬ሻ = 4000ሺ‫ ݕ‬− ݉ሻଶ (a)

‫ ݕ‬− ݉ = 0.15 ‫ܮ‬ሺ‫ݕ‬ሻ = 4000ሺ0.15ሻଶ = $90 (b)

‫ ݕ‬− ݉ = 0.10 ‫ܮ‬ሺ‫ݕ‬ሻ = 4000ሺ0.10ሻଶ = $40 8.10

What role does research play in product design? Indicate four sources of research and the desired information that could be expected from each source. Using webbased research, identify five corporations and their product lines. In what way do these products support the corporate strategy?

Research is the key factor in the design and successful market launch of the product. The companies that spend a higher percentage of revenue on research have a good possibility of keeping up with the market forces worldwide.

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Four sources of research are: 1. Internet 3. Patents

2. Reference books, journals, Standards and trade catalogs 4. Use of simulation tools

1. Internet: This relatively new-research tool has proven to be very effective. The Internet can facilitate and provide information on a range of competitive products and research publications. The Internet facilitates companies to conduct research and release new designs much faster. With the Internet connection becoming available in more and more countries, the Internet based technology provides new opportunity. For market research on new products, the resources available from the Internet are unlimited. The technology can help the product to get to the market as quickly as possible and explore the best possible alternatives. The advances in software and hardware have made it possible to animate prototypes and create design alternatives, adding a whole new dimension of utility to the practice. The Internet can be utilized to contact suppliers, vendors, and contractors. The Internet provides an extremely inexpensive and widely distributed format for distributing and soliciting product information and feedback. Distributing Internet based models via local networks, wide-area networks, or the Internet is very easy.

If the research is focused on customers, the use of Internet tools in early focus-group sessions can yield effective feedback from potential customers, leading to higher market acceptance for the ultimate product. Traditional communication and collaboration often result in significant expenses from travel, personnel relocations, and telecommunications.

Internet communication addresses most of these needs by enabling real-time linking of multiple sites in one virtual product; the result is a far more efficient use of time than traditional meetings. Access via the World Wide Web is simple and intuitive with the help of standard browsers available today.

Search Tools The most popular search tools for finding information on the Internet include Web search engines, meta search engines, Web directories, and specialty search services. A Web search engine uses software known as a Web crawler to follow the hyperlinks connecting the pages on the World Wide Web. The information on these Web pages is indexed and stored by the search engine. To access this information, a user enters keywords in a search form and the search engine queries its algorithms, which take into consideration the location and frequency of keywords on a Web page, along with the quality and number of external hyperlinks pointing at the Web page.

A Meta search engine enables users to enter a search query once and it runs against multiple search engines simultaneously, creating a list of aggregated search results. Since no single search engine covers the entire web, a meta search engine can produce a more comprehensive search of the web. Most meta search engines automatically eliminate 142 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

duplicate search results. However, meta search engines have a significant limitation because the most popular search engines, such as Google, are not included because of legal restrictions.

A Web directory organizes subjects in a hierarchical fashion that lets users investigate the breadth of a specific topic and drill down to find relevant links and content. Web directories can be assembled automatically by algorithms or handcrafted. Human-edited Web directories have the distinct advantage of higher quality and reliability, while those produced by algorithms can offer more comprehensive coverage. The scope of Web directories is generally broad, such as DOZ, Yahoo!, and The WWW Virtual Library, covering a wide range of subjects, while others focus on specific topics.

Specialty search tools enable users to find information that conventional search engines and meta search engines cannot access because the content is stored in databases. In fact, the vast majority of information on the web is stored in databases that require users to go to a specific site and access it through a search form. Often, the content is generated dynamically. As a consequence, Web crawlers are unable to index this information. In a sense, this content is "hidden" from search engines, leading to the term invisible or deep Web. Specialty search tools have evolved to provide users with the means to quickly and easily find deep Web content. These specialty tools rely on advanced bot and intelligent agent technologies to search the deep Web and automatically generate specialty Web directories, such as the Virtual Private Library.

Advantage of using the Internet for product related research: •

Shortening of the product definition phase involving the customer, marketing, and design engineering.

•

Provides instantaneous access to knowledge and experience from different locations and disciplines during the design and development stage to achieve high quality results quickly.

•

Exploring and building on ideas in the product implementation stage involving trade-off decisions between manufacturing, tooling, and design engineering.

•

Improved design coordination with remote and non-remote partners.

Disadvantages: •

Internet security

•

Bandwidth

•

Exposed proprietary information

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There are other research search mechanisms such as Google including Research at Google; Google Research Blog; Think with Google; Google Research Programs; Google Scholar; Google Research on Twitter; and Google Research Scientist.

2. Reference books, journals, Standards and trade catalogs: In the early stages of research, many reference books will be useful as they provide analytical techniques and abstract ideas. Published literature includes scientific journals, conference proceedings, trade magazines, government reports, and new product reports.

The state of the art information is available from scientific journals. Many good ideas are published in trade journals, which are usually oriented towards a specific discipline.

However, there are some trade journals that are targeted at product designers. Handbooks cataloging technical information can also be very useful as research tools. Examples of reference standards are: SME Handbook of product design, Standards Handbook of Mechanical Engineers, etc.

Electronic database searches are another research tool to gather information from the published literature. The database can be accessed through online sources or in the form of CD-ROM storage devices.

3. Patents: The patent literature is a good source of information. Patents are readily available sources of information that contain drawings and explanations of how many products work. The patents are also useful to check what concepts are already protected and must be avoided for a certain period. Since there are millions of patents, a patent search narrows the area of interest. A patent search on a specific topic is done in three steps.

1. Identify the class and/or subclass of the area of interest.

2. Find the numbers of the specific patents that have been filed in the specific class that has been identified.

3. For a specific patent number, the information is available from the patent itself or from the official gazette announcement.

4. Use of simulation tools: Interactive product simulation can assist the product designers in conducting more efficient research. Use of Interactive product simulation procedures assists the research and development of a department’s efforts. They can provide earlier access to prototypes, faster updates than with physical models, and enterprise distributions of information in an easy-to-understand format. They can support existing processes and provide long-term value that extends beyond the finalization of product designs. In the design and detailing phase of product development, during which the primary need is to conduct frequent design reviews, Internet based simulation tools provide a means of integrating work from many different people and processes for group review and feedback. Instant online model 144 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

changes on 3D models allow design optimization and lower manufacturing costs through immediate understanding of impact and implications of design alternatives.

As users can add real-time animations to the virtual product and edit them to indicate part paths and sequences as well as check for collision and clearances, cross-disciplinary collaborative design reviews can quickly evaluate individual ideas in the context of overall product assembly, maintenance, and usability. The use of interactive tools in early product research can yield more-effective feedback from potential customers, leading to higher market acceptance for the ultimate product.

Five corporations are • Pratt & Whitney • Jacobs vehicle systems • Wiremold Company • ABB • Trumpf Inc. Pratt & Whitney Pratt & Whitney is a leader in the design, manufacture and support of engines for commercial, military, and general aviation aircraft, space propulsion, and power systems.

Pratt & Whitney is focused on continuously improving products and processes to deliver the performance and reliability the customers expect. It is an ISO9001-certified company.

Commercial Aviation Large Commercial Engines JT8D JT9D PW4000-100" PW4000-112" GP7000 Parts Pratt & Whitney Canada Engines PT6A - Large JT15D PT6B Parts

PT6A - Small PW300 PT6C

Military Aviation F100 F117 PW4000 JT8D-219 Power Systems & Mechanical Drive FT8 ST30 ST6L-72 ST6L-79 ST5 Brush Seals

PW2000 V2500

PW4000-94" PW6000

PW100 PW500 PW200

PW800 PT6T/T400 PW900

F119 Parts

F135

ST6L-90 ST6L-81

ST40 ST18

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Space & Missile Propulsion RL10 RD180 Orbus 21D

MK-72 Booster

Space Shuttle Turbo pumps Booster Separation Motors

THAAD National Missile Defense (NMD) System

Pratt & Whitney is also involved in maintenance services, spare parts, field services, and support systems.

Jacobs’s vehicle systems As the world's leading manufacturer of engine brakes, Jacobs continues to push design, manufacturing, and performance standards beyond accepted limits. As Jacobs pursues incremental improvements, each hurdle represents the next standard. Each achievement becomes the basis of yet another. Quite simply, defying limits is the energy and spirit of Jacobs. No other manufacturer can match our products' track record & proven reliability.

Since 1961, over 2 million Jake Brake retarders have been specified, installed, and proven in over 1 trillion miles of driving.

Their engine brakes are used in Caterpillar C-10, C-12 & 3176/B Engines Caterpillar 3306 Engines, Caterpillar 3406B/C/E Engines Cummins N14 Engines

Wiremold Company The Wiremold Company, founded in 1900 and headquartered in West Hartford, Conn., is a leading manufacturer of wire and cable management systems, power and data quality products, and data/communications connectivity systems. The Wiremold Company has embarked upon an aggressive program of quality improvement and product introduction using the “Kaizen” philosophy.

The Wiremold Company is developing and introducing new products faster than ever before. Strategic acquisitions of companies such as Walker Systems, Interlink Technologies, Brooks Electronics, Shape Electronics, and Sentinel Lighting have added new solutions that meet today’s challenges. This company mainly concentrates on power, data transfer devices, and wiring systems like WallSource Box, Nonmetallic Raceway, Metal Raceway, AnySize Raceway, Aluminum Raceway, Prewired Raceway, and Plugmold.

ABB (Asea Brown Boveri Ltd.) ABB's strategy is to offer more value for customers while building a leaner organization.

ABB is a global leader in power and automation technologies that enable utility and 146 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

industry customers to improve performance while lowering environmental impact. ABB is moving all of its offerings to a common architecture, to deliver Industrial IT-enabled products and services that allow customers to optimize their operations and link up in real time with their suppliers and customers. The result is a leap in efficiency, quality, and competitiveness.

The products are in wide categories like Utilities; Process Industries; Manufacturing and Consumer Industries; Oil, Gas and Petrochemicals; Power Technology Products; Automation Technology Products; and Financial Services.

TRUMPF Inc. TRUMPF Inc. is the North American subsidiary of TRUMPF GmbH +Co. KG. based near Stuttgart, Germany. With more than 566 employees, TRUMPF Inc. is the largest subsidiary within the TRUMPF Group. TRUMPF Inc. is dedicated to serving the fabricating machinery, OEM laser, and laser marking needs of the American, Canadian, and Mexican markets and is the largest manufacturer of fabricating machinery in the United States. The TRUMPF Group of companies has subsidiaries in 23 countries and with about 5,600 employees, generates sales in excess of $1.1 billion. The TRUMPF Group is a world leader in sheet metal fabrication machinery and industrial lasers. The products are: • Machine Tools: TRUMPF offers computer controlled machine tools for flexible sheet metal and material processing.

• Laser Technology: High powered CO2 and solid-state lasers are ideal for cutting, welding, or marking applications in industrial fabrication.

• Electronics: This includes dc power supplies and radio-frequency generators for laser, induction, and vacuum technology.

• Medical Technology: This field includes surgery tables, systems for physical therapy, and systems for high frequency and laser surgery.

• Power Tools: In this field, TRUMPF offers power tools for cutting, fastening, and shaping.

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Chapter 9 Exercises 9.1

Explain how you would select a team to design a product of multicomponent nature.

What strategies would you use to have an effective design as speedily as possible?

How would you use the prototype design process? Describe two rapid prototyping methods, identify the benefits of each, and provide sketches.

Characteristics of the Team for a Multicomponent Product Team Selection The product design process is of a complex and interdisciplinary nature. Carrying out a project on product design requires gathering a team of people with diverse expertise. It is important that the group dynamics of the participants be of the right caliber. The methodology used by the product team would determine the quality of the final product and its innovativeness and competitiveness. A good team leader is essential to coordinate the team members effectively so that the group can remain focused. In selecting a product design team, various factors to be considered are: • Composition of team members • Creation of an environment for design discussions • Management of the team • Methodology and approach Team Quality The team must have clearly defined goals such as identification of budgets, staffing, and overall responsibilities. The team has to develop an atmosphere that is conducive to free thinking. Most importantly, the team must have strong leadership. Teams generally make better decisions than individuals, especially in situations that are relatively broad and farreaching in scope (e.g., strategic planning). Teams should be represented by the disciplines that are related to the product. Because of the diversity in background, experience, and skills of the team members, team members are more likely to consider a wider range of alternatives to solving problems and be more creative in their solutions.

When dealing with sensitive issues, a team has more potential power than any one of the individuals.

Team Members Next to the selection of the project, the single most important task is to choose the right players to serve on the team. As with any type of team, having the right combination of individual skills, attitudes, and leadership will have a dramatic impact on the outcome of a project. It is also very important to have a good understanding of how teams should and can work together in meeting their goals.

Product teams are usually composed of highly motivated individuals from various areas of the company who may never have worked together. Regardless of whether concurrent 149 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

engineering is used to develop a new product or process, or to modify an existing one, some start-up problems must be anticipated. If people in the various functional departments are comfortable with traditional design approaches, the switch to teamwork may be difficult. In the traditional approach, each department has a well-defined piece of action. Each function adds its value as the project is passed from department to department, often with minimal interaction.

Team Leader Leaders of multifunctional or cross-functional teams are faced with the challenge of optimizing team performance. For a successful team, any team project must be preceded by adequate managerial preparation. An underlying foundation in the concept of teamwork must be developed within the organization in advance. Picking the right team leader is absolutely critical to a project’s success. The leader needs to have a combination of knowledge and qualities that will bring out the best in the team. Some of the qualities to look for are listed below: • • • • • • •

Respected technical specialist in one functional area; Encourages change; Strong desires to contribute toward positive change; Willingness to listen to ideas of others and to evaluate those ideas objectively; Good level of creativity; Effective oral communication and persistence; and Willingness and desire to work with others in problem solving.

Depending on the size of the team and the resources available, the team leader should arrange team training. Special training in team dynamics, product economics, and value engineering techniques will improve the probability of the team’s success.

Strategies for Effective designs are possible when the team makes a concentrated effort by approaching the problem from many sides. Activities that include alternate designs, prototyping, and experimentation using additive manufacturing tools must occur concurrently. Analytical prototypes are representations of the product in a mathematical manner with computer simulation. Various useful aspects of the product are analyzed.

Some of the tools used are system equations and analysis, graphics based computer simulation, modeling using visual simulation with hardware in the loop, and computer models of three-dimensional geometry.

The advantages of 3D computer based prototypes include: the ability to easily visualize the three dimensional form of design, the ability to automatically compute physical properties such as mass and volume, and the detection of geometric interference among parts. Using CAD tools for modeling and simulation of the alternate performance scenarios can speed up the design specifications. Automotive industries use simulation

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and modeling in every aspect of automotive design, testing, performance evaluation procurement, productivity, and integrating management functions.

Use of Prototypes: Prototypes are used in product development stages to ensure that components and subsystems of the product work together as expected. Physical prototypes include models that look like the product so that they can be used for the proof of concept, test the idea quickly, and validate the functionality of the product. Physical prototypes are useful as integration tools in product development projects because they require the assembly and physical interconnection of all of the parts and subassemblies that make up a product. A prototype model of the product can be used as the medium through which the marketing, design, and manufacturing functions agree on basic design decisions. Prototypes are used throughout the design process. In the research stage, prototypes yield test information as well as consumer feedback and performance comparisons.

Prototypes by Additive Process: The technique, known as additive manufacturing (because it builds an object by adding ultrathin layers of material one by one), could transform how the company designs and makes many of the complex parts that go into everything from gas turbines to ultrasound machines. Additive manufacturing is a major new development in making rapid prototypes. Aerospace industries, especially the companies involved in jet engines, are making rapid strides in prototyping. Companies such as General Electric, Pratt and Whitney, and Rolls Royce are making a radical departure from the way they have traditionally manufactured things. These companies are preparing to produce a fuel nozzle for a new aircraft engine by printing the part with lasers rather than casting and welding the metal. Jet engine makers chose the additive process for manufacturing the nozzles because it uses less material than conventional techniques. That reduces the company’s production costs and, because it makes the parts lighter, yields significant fuel savings for airlines.

Popular rapid prototyping methods are: • • • • • •

Stereo lithography Selective Laser Sintering Poly Jet 3D Printing Urethane Castings Fused Deposition Modeling Metal Prototyping

Two rapid prototyping methods are: 1. Stereo lithography (SLA) 2. Selective Laser Sintering (SLS)

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Both the methods belong to a family of processes known as solid freeform fabrication (SFF).

Stereo lithography Stereo lithography is a process for fabricating a solid plastic part out of a photosensitive liquid polymer using directed laser beams to solidify the polymer. The general schematic of the equipment can be seen in Figure 1. The parts are fabricated layer by layer, in which one layer is added onto the previous layer to gradually build the desired threedimensional geometry. Initially, the platform elevator is located at a distance from the surface of the liquid equal to the thickness of the first, bottom-most layer. The laser beam scans the surface following the contours of the slice. The laser beam is directed by the data file that has been generated from the CAD solid model of the part geometry. The three dimensional geometry in the CAD file is transformed into a series of layers that approximate the solid geometry of the part. Each layer is about 0.005 to 0.020 in. (0.13 to 0.50 mm). The liquid is a photopolymer that, when exposed to the ultra-violet (uv) laser beam, solidifies or is cured. The result is a solid layer of plastic that adheres to the platform. The platform elevator is moved downwards by a distance equal to the layer thickness and the subsequent layers are produced analogously.

Figure 1. Stereo Lithography Process

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Figure 2. Selective Laser Sintering process Selective Laser Sintering (Figure 2) Selective sintering can be used to develop functional products directly from 3D data.

Products are created by selectively fusing layers of powder material – Selective Laser Sintering – made of materials with wide-ranging properties specially developed for the process. Optionally, the surfaces can be refined by infiltrating color or by coating.

Selective Laser Sintering (SLS) uses an approach similar to stereo lithography. Instead of a liquid polymer, powders of different materials are spread over a platform by a roller. A laser sinters selected areas, causing the particles to melt and then solidify. Processes that behave in this way are generally known as selective laser sintering (SLS) processes.

There are two stages in laser sintering: from solid to fluid and from fluid to solid. Layer by layer, the powders are gradually joined into a solid mass that forms the threedimensional part geometry. The materials being used or investigated include plastics, wax, metals, and coated ceramics. Current materials used in selective laser sintering include, polyvinyl chloride, polycarbonate, and nylon.

9.2

Design communication is an important aspect of product design. How does a design engineer communicate product related ideas with suppliers around the world?

Design engineer communicate product related ideas with suppliers around the world through documenting their work using technical or design reports. Good design engineers must use more than just technical skills; the ability to communicate and sell a design solution to others is also a critical skill. They can use visual materials like graphs, charts, videos, slides, animations, and posters to clearly communicate the solution to a design problem.

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Design Communication In the field of design communications, the medium of communication plays an important contribution. There are many communication mediums practiced by designers. Good communication should be emphasized at several levels of the product design stage, irrespective of the fact that it is a staged presentation to an audience or at the stage of understanding the customer perceptions. Communication could be considered successful when most of that design ideas can demonstrate understanding of the product soon after the presentation. The design ideas can be effectively presented if they are structured in the form of a technical seminar where the information is presented sequentially. This sequencing, necessitated by the fact that communication inherently takes place over time, follows a preset path through the material. The good principles for effective communication applied to design are: • • • • • • • •

Organize the presentation of design in a chronological set of presentations.

Use a constantly evolving attribute of the material to sequence it along a path.

Order the concepts so that earlier concepts facilitate the understanding of later concepts.

Provide a memorable introduction and conclusion.

Use multiple representations, visualizations, and simulation tools.

Use the technology available in digital media to communicate.

Allow for multiple levels of engagement and understanding.

Examine the environmental impact on design.

Communicating Design Ideas: The success of a good product design is influenced by effective communication. Some of the communication mediums range from email, social media like Facebook and Twitter, simulation software, internet design sharing software, phone calls, and even text messages.

Recording and Presenting Design Ideas: The results of the design are recorded in a notebook. George Dieter, author of many text books on Engineering Design, recommends following good practices for keeping a record of good design through notebooks. A good engineering design notebook provides valuable information on product formulation, concepts and shows how it is created.

• • • • • •

The book should have a well-documented index Make entries while performing design work Include favorable and unfavorable results and things not fully understood at the time Include graphs, photographs, and digital information Rough graphs and plots can be created at the time of the design Give complete reference to books, journals, patents, and other sources of information

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Presenting design ideas: • Presentations are like good stories; they get attention with probing questions. One of the well tested methods to keep interest is to challenge ideas, use humor, and resolve conflicts • Summarize key points and remind audiences of key conclusions • Slides should enhance what you say • Use your allocated time wisely; rehearse the timing (standard allocation is 25% intro, 65% body, 10% round-up) Recent Trends in Communication Social Media Social media, such as Facebook, Twitter, Flickr, and YouTube, are free and easy-to-use tools to communicate directly with the target audiences. They provide a great platform for the designer to share photos, updates, and anecdotes about one’s project or program.

Using social media enables one to share information with people who are not regular visitors to one’s website. It also provides a valuable ‘multiplier effect.’ By sharing information such as news about an open call about product launch, people can gain information on the design of the product. For example, when people become fans of a Facebook page, ‘like,’ or comment on a post on the page’s wall, this is shared with their networks.

Social media can also be a way of getting people to visit the designer’s website if they share a link to a news item they have published. Sharing content from the website on social media also increases the designer’s search engine ranking through in-bound links (other websites). Designers can also enable people to share content they read on the website by setting up social media tools on the site. Icons of popular social media appear under a web article/page so visitors can ‘bookmark/share/save’ the content.

Websites: • Setting up Google Analytics for the designer’s page gives valuable information about the website users. One can see who visited the site, how long they stayed on individual pages, what link they followed to reach the design content, and more.

• If one sets up web pages on an existing site about the project, the web designer has to place a visible and easily accessible link or banner on the front page of the website so that people can find the project information. One has to make sure that a link to the website is added.

• The website domain name (the URL address) should be unique so that search engines can distinguish it, but it should also be easy to type/remember. There are many online platforms and solutions for creating simple websites and advice on how to fill the pages with content • Today, people increasingly send wireless transmissions that bounce off satellites.

This allows one to access information or people no matter where you happen to be. Electronic communication takes many forms. Companies’ aggressively marketing products may decide to establish a Facebook® profile or some other medium and send a text message to someone’s phone. Some organizations create 155 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

blogs. Designers have the opportunity to communicate using instant messaging programs or join an online community. YouTube is a site that offers amateur or professional videos that vary from funny to autobiographical sketching.

9.3

Describe the role of integration of information technology in bringing together technological and business aspects of product creation. Give a suitable example, and explain the concept of designing a process for manufacturing integration.

Information technology has a major role in the modern globalized world. The impact of information technology has been felt not only in product design, but also in manufacturing, testing and identification of suppliers, design for supply chain, and the emergence of several tools for the next generation of manufacturing. Modern product manufacturing has seen enormous benefits due to well-planned supply chain efficiency.

Information technology has been addressing the manufacturing challenges in product creation. While creating products globally, supply chain flexibility is a key optimization metric since it allows responses to all of the dynamic parameters of the supply chain, including new global contracts that often mandate rapid changes in assembly sites, tax and tariff penalties, and export control.

The following developments have impacted the integration of information technology in companies.

• • • •

• •

Many high value subsystems and final assemblies are produced by global supply chains.

Supply chain optimization is often a complex function of many variables.

Manufacturing enterprise requirements for the major companies have changed.

To optimize among a number of global sub-system suppliers and final assembly sites, the procedure of optimization needs to consider the capacity and cost fluctuations at contract assembly sites, tax and tariff considerations, and value added taxes.

Fluctuations in currency when you sell in different countries have to be considered for product costing purposes.

Testing replication - both capital and human resource support of testing, costs of transportation and warehousing, and additional contract requirements or incentives for value-added in a country.

The ability to move manufacturing rapidly among multiple worldwide sites can be a distinct advantage of using supply chains. Optimized use of supply chains allows you to craft one set of suppliers with a set of contracts, and at the same time take advantage of the dynamic conditions in the marketplace. Some of the effective networks are: • Employee Network • Design Network • Business and Manufacturing Process Network • Global Enterprise and Planning Network • Knowledge and Information Support Network 156 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

Other advantages of good communication systems are: • Flexible Manufacturing alternatives and selection based on design and manufacturing facilities • Planning procedures to support both business and manufacturing processes • Standards for networking capabilities across the company supply chain for real time responses • Facilities planning & visibility of orders/jobs from business processes to despatch • Estimation of Order Completion dates based on both internal and external processes • Incorporates a dynamic real time approach to enable agility in responding to customer demands 9.4

Simulation and modeling are used in a wide variety of design configurations that examine the capabilities of components and systems. Consider a product such as a food processor and identify CAD/CAM roles for making major components.

Simulation and Modeling play a major role in product design. Simulation and Modeling procedures impact new product creation procedures in many industries, the main amongst them being the automotive and aerospace industries. These industries deploy increasingly sophisticated solutions to streamline and speed up product development as well as to improve overall product quality. With new digital factory layout tools and improved 3D visualizations, manufacturers can digitally design and validate full factories in up to half the time previously required to do the job. Virtual product design procedures involving simulation of complex systems allow designers to develop systems without finalizing the hardware. The simulation procedure can be a “what if” scenario when the hardware doesn’t exist. Trade-offs between simulation speed and the level of accuracy are necessary because of system resource availability.

Interactive modeling is crucial to the design process, and it can occur in a mixed environment where real and virtual objects are combined. The key aspect of the virtual environment is that the visual representation of system partitioning and interaction lends itself to mechatronic applications. They also reduce system complexity from a developer’s standpoint, allowing for concentration on the application details. Virtual simulations enable everyone to work on development before the first prototype is completed. Engineers can validate the entire operating cycle for the machine by driving the simulation with control system logic and timing. With industries leading all-digital design, validation, and commissioning of factory automation devices, virtual commissioning of factory-floor layout is becoming important. Typical Software Tools used are shown below in Figure 3.

Computer based design tools can be used at various phases of design. In the concept phase, a three dimensional computer aided design can be used to generate data for a three dimensional rapid prototyping technology, allowing designers to examine the shape of a 157 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

product even in the early stages. In the design analysis phase, parameters such as stress, vibration, heat, and flow can be integrated by automatically converting data from three dimensional computer aided design (3D-CAD) systems. In the manufacturing phase, CAM systems can be used to generate manufacturing processes data directly from solid models without human intervention. Modern materials-based finite element modeling (FEM) and manufacturing simulation software provide solutions for optimization of metal cutting processes.

Design Concept, Sketch Tools such as Pro E, CAD Systems

Concept Design

Design Mechanism such as ADAMS

Analysis such as COSMOS, ANSYS

Mechanism Analysis

Initial Design

FEA for Design

Solid Modeling

Rapid Prototyping

Manufacture Tool Path

Manufacture FEM

Prototyping such as Stratasys, Alaris

Manufacturing Analysis

such as Thirdwave

Manufacturing simulation such as Pro-Manufacture

Figure 3. CAD/CAM tools for Product Design Simulation software tools enable detailed analyses of such manufacturing processes as milling, turning, and grinding. This allows designers to improve material removal rates, part quality, and tool performance while decreasing the need for physical testing. In the rapid prototyping phase, modern software tools can create precision three-dimensional prototyped parts directly from 3D CAD system. As shown in Figure 3, designers must use different software tools from conception to prototype. By integrating these software tools, they can reduce development costs, shorten development times, and improve reliability. Some of the algorithms and software tools available to designers are: • • • • • • •

Early design phase: AutoCAD, Pro/E, Solid Works Mechanism Analysis: Pro/Mechanica, ADAM Finite Element Analysis: ANSYS, Pro/Mechanica, COSMO Manufacturing Simulation: Pro/Manufacture Manufacturing Finite Element Modeling: Third Wave Rapid Prototyping: Z builder, Alaris 3D, Dimension Assessment of manufacturability: DFM/DFD 158

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A typical Food Processor model and its components are shown in Figure 4.

Figure 4. Typical Food Processor and its components Most of the plastic components are plastic-injection molded. The parts are created using extensive CAD procedures to make a die. The dies are created using CAD/CAM machine tools. The base of the food processor is also created using molds. The metallic components are created by machining. The blades are machined and welded to the central hub. The small holes in the metallic discs are created by punching operation, especially in an industrial type punch press using the multiple punches.

CAD/CAM Roles in Product Creation The basic design represented in the physical world by computer aided design and manufacturing tools (such as Catia, Autodesk, and Solid works) have advanced simulation tools, although they are oriented toward physical construction rather than process control integration. The simulation platform can examine stress under dynamic loading condition. It also addresses nonlinear analysis like deflection and impact with flexible materials such as foam, rubber, and plastic. In many cases, simulation and analysis of physical entities is useful in a design that does not include a computer-based controller. The rendering provision permits visualization of the models in action. When creating large models, the modeling environment can demand significant amounts of computing power. The creation of large models can be a challenge to computing.

Virtual Machine Prototyping Mechanical systems are increasingly controlled by sophisticated electric motor drives that get their digital intelligence from software running on an embedded processor. Getting electromechanical designs right requires multidisciplinary teamwork and superb 159 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

communication among team members. A decision like choosing the characteristics of a lead screw actuator has a ripple effect throughout the design and can impact the performance of other systems. To help facilitate a more integrated design process, we need to add motion simulation capabilities to CAD environments to create a more unified mechatronics workflow. Integrating motion simulation with CAD simplifies design because the simulation uses information that already exists in the CAD model, such as assembly mates, couplings, and material mass properties. Adding a high-level function block language for programming the motion profiles provides easier access to control those assemblies.

Figure 5. Simulation verification of torque load This concept is known as "virtual machine prototyping." It brings together motion control software and simulation tools to create a virtual model of an electromechanical machine in operation. Virtual prototyping helps designers reduce risk by locating system-level problems, finding interdependencies, and evaluating performance trade-offs.

Evaluating Trade-off Simulations enable everyone to work on development before the first prototype is completed. Engineers can use force and torque data from simulations for stress and strain analysis to validate whether mechanical components are stiff enough to handle the load during operation. They also can validate the entire operating cycle for the machine by driving the simulation with control system logic and timing. They can calculate a realistic estimate for cycle time performance, which is typically the top performance indicator for a machine design, and compare force and torque data with the realistic limitations of transmission components and motors. This information can help identify flaws and drive design iterations from within the CAD environment. As in the example of Figure 5, simulations also simplify evaluating engineering trade-offs between different conceptual designs.

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Virtual Prototyping Virtual Prototyping (VP), also known as simulation-based-design, refers to the iterative design refinement of a designed product using a computer-based functional physical simulation. VP is rapidly gaining importance as the engineering practice of choice to aid rapid product development and shorten the design cycle.

Virtual product design parallels production design Virtual prototypes with the ability to turn 360 degrees and flip end over end make it possible for you to see the product from every possible angle. Virtual prototyping is one of the most convenient methods of communication between a designer and our customers. It has become apparent that the Supply Chain of an advanced product does and should influence the product design.

9.5

Compile a list of different AM technological machines that are currently on the market today. What are the distinguishing features of each? What different materials can these machines process?

The following are the different AM technological machines that are currently on the market today: a) Stereo lithography (SLA) b) Selective Laser Sintering (SLS) c) Selective laser melting (SLM) d) Digital Light Processing (DLP) e) Fused deposition modeling (FDM) f) Electronic Beam Melting (EBM) g) Laminated object manufacturing (LOM) a)

Stereo lithography (SLA):

Stereo lithography is a process for fabricating a solid plastic part out of a photosensitive liquid polymer using directed laser beams to solidify the polymer. The parts are fabricated layer by layer, in which one layer is added onto the previous layer to gradually build the desired three-dimensional geometry. Initially, the platform elevator is located at a distance from the surface of the liquid equal to the thickness of the first, bottommost layer. The laser beam scans the surface following the contours of the slice. The laser beam is directed by the data file that has been generated from the CAD solid model of the part geometry. The three dimensional geometry in the CAD file is transformed into a series of layers that approximate the solid geometry of the part. Each layer is about 0.005 to 0.020 in. (0.13 to 0.50 mm). The liquid is a photopolymer that, when exposed to the 161 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

ultra-violet (uv) laser beam, solidifies or is cured. The result is a solid layer of plastic that adheres to the platform. The platform elevator is moved downwards by a distance equal to the layer thickness, and the subsequent layers are produced analogously. b)

Selective Laser Sintering (SLS):

Selective sintering can be used to develop functional products directly from 3D data.

Products are created by selectively fusing layers of powder material – Selective Laser Sintering – made of materials with wide-ranging properties specially developed for the process. Optionally, the surfaces can be refined by infiltrating color or by coating.

Selective Laser Sintering (SLS) uses an approach similar to stereo lithography. Instead of a liquid polymer, powders of different materials are spread over a platform by a roller. A laser sinters selected areas, causing the particles to melt and then solidify. Processes that behave in this way are generally known as selective laser sintering (SLS) processes. In Laser sintering, there are two stages: from solid to fluid and from fluid to solid. Layer by layer the powders are gradually joined into a solid mass that forms the three-dimensional part geometry. The materials being used or investigated include plastics, wax, metals, and coated ceramics. Current materials used in selective laser sintering include polyvinyl chloride, polycarbonate, and nylon. c) Selective laser melting (SLM): Selective laser melting (SLM) is a technique that also uses 3D CAD data as a source and forms 3D object by means of a high-power laser beam that fuses and melts metallic powders together.

Figure 6. Selective Laser Melting

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Like other 3d printing methods, the CAD file needs to be processed by special software to slice the CAD file information into 2D layers. The file format used by the printing machine is also a standard.stl file. The fine metal powder is evenly distributed onto a plate, and each slice of 2D layer image is intensively fused by applying high laser energy that is directed to the powdered plate. The energy of the laser is so intense that metal powder melts fully and forms a solid object. After the layer is completed, the process starts over again for the next layer. Metals that can be used for SLM include stainless steel, titanium, cobalt chrome, and aluminum.

This method of printing is widely applied to parts with complex geometries and structures with thin walls and hidden voids or channels. Lots of pioneering SLM projects were dedicated to aerospace application for different lightweight parts. SLM is great for projects that experience problems like tooling and physical access difficulties to surfaces for machining, as well as those that restrict the design of components. The technology is not widely spread among at-home users, but mostly among manufactures of aerospace and medical orthopedics. The whole process of acceptance, certification, and final approval takes some time, which results in long time for development and qualification for this technology. d)

Digital Light Processing (DLP):

Digital Light Processing is a display device based on optical micro-electro-mechanical technology that uses a digital micro mirror device. DLP is similar to SLA that works with photopolymers, but a different source of light is used. The material used for printing is liquid plastic resin.

Figure 7. Digital Light Processing

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The products of such printing are robust and have excellent resolution. A big advantage of DLP over SL is that fewer materials are used for detailed production, resulting in lower costs and less waste. e) Fused Deposition Modeling (FDM): Fused deposition modeling (FDM) technology is the only 3D printing technology that builds parts with production-grade thermoplastics, so things printed are of excellent mechanical, thermal, and chemical qualities.

Figure 8. Fused Deposition Modeling Printing time depends on the size and complexity of the object. Small objects can be completed relatively quickly while bigger or more complex parts require more time.

Compared to stereo lithography, this technique is slower in processing. FDM technology is widely spread nowadays in a variety of industries such as automobile companies like Hyundai and BMW and food companies like Nestle and Dial. FDM is used for new product development, model concept, prototyping, and even manufacturing development.

This technology is considered to be simple-to-use and environment-friendly. With the use of this 3D printing method, it became possible to build objects with complex geometries and cavities.

Different kinds of thermoplastic can be used to print parts. The most common of these are ABS (acrylonitrile butadiene styrene) and PC (polycarbonate) filaments. There are also several types of support materials including water-soluble wax or PPSF (polyphenylsulfone). f) Electronic Beam Melting (EBM): EBM is another type of additive manufacturing for metal parts using an electron beams.

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Figure 9. Electronic Beam Melting The material used in EBM is metal powder that melts and forms a 3D part layer by layer by means of a computer that controls an electron beam in high vacuum. The process is usually conducted under high temperatures up to 1000°C. The materials that are used for EBM are pure Titanium, Inconel 718, and Inconel 625.

The application of EBM is mainly focused on medical implants and aerospace area. g) Laminated Object Manufacturing (LOM): Laminated object manufacturing (LOM) is another method of 3D printing in which layers of plastic or paper are fused — or laminated — together using heat and pressure, and then cut into the desired shape with a computer-controlled laser or blade.

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Figure 10. Laminated Object Manufacturing The LOM process includes several steps. Firstly, a CAD file is transformed to computer format, which are usually STL or 3DS. LOM printers use a continuous sheet coated with an adhesive, which is laid down across substrate with a heated roller. The heated roller that is passed over the material sheet on the substrate melts its adhesive. Then the laser or knife traces the desired dimensions of the part. The laser crosses hatches of any excess material in order to help to remove it easily after the printing is done.

LOM is not the most popular 3D printing method, but it is one of the most affordable and fastest ones. The cost of printing is low due to inexpensive raw materials.

9.6

A manufacturing company introduces rapid prototyping techniques in the creation of biomedical products. What extra considerations might be needed when producing medical models using AM in comparison to conventional manufacturing?

Special Considerations for Biomedical Products in AM The biomedical virtual product is usually coupled with Virtual or Augmented Realty (AR) tools to enhance the ability of medical students and practitioners interacting with real-time deformable models that simulate, sometimes with the integration of haptic capabilities, clinical and pathological conditions. They are used for diagnostic purposes, in particular if diagnoses are concerned to interactive 3D imaging, and represent another important example of VP applications. The use of virtual prototypes and VR techniques represents a new challenging topic for clinical research also in clinical psychology.

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Finally, the use of VP is coupled with VR or AR for telemedicine or tele-surgery purposes.

Virtual Models for Medical Applications A complete virtual engineering prototype is composed by: a 3D solid model, generally a 3D CAD model; a human-product interaction model; and some perspective test related models (i.e., structural analyses, motion analyses, manufacturability evaluation models, etc.).

The use of VP or VR tools is strictly connected to the creation of and the interaction with virtual models. In fact, next to real or physical models, medical researchers have developed different kinds of computer-based models to design and analyze objects or to understand biophysical phenomena. Computer modeling improvements have allowed working in virtual environments for different purposes and in an easier and safer way.

Figure 11. Reconstruction of hip and femur bones from MRI At this point, it is important to distinguish the different types of 3D virtual models used because their adoption is closely connected to the kind of application fields they are used for. Computer-based biomechanical models can be classified as virtual bio-models used for the visualization of biological structures and human organs. Examples include 3D CAD models reconstructed from Computer Tomography (CT) or Magnetic Resonance Imaging (MRI) scans (see Figure 11), and computational bio-models used for performing biomechanical analysis, for example finite element models (FEM) of anatomical structures and joints (knee, hip, mandible, foot, etc.) used for the determination of stress and strain distributions (Figure 12).

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Figure 12. Musculoskeletal full body model Virtual bio models, used for visualization purposes, are represented by different kinds of non-deformable, deformable, or real-time deformable models. It is possible to classify these models by their development method, which can be based on heuristic approaches, continuum mechanics approaches, or hybrid approaches. Generally speaking, deformable models are used in surgery simulation systems to better reproduce the behavior of human organs and tissues, also in real-time. Computational models can be subdivided into static, dynamic, and kinematic. Static models investigate the deformations of the anatomical structures or bones under load and muscle forces. Dynamic models use muscle forces and directions to study the system dynamics. Kinematic models focus more on the analysis of movement.

VP and Simulation Tools for Orthopedics Implant Designs As software and the technologies used to scan the human body have improved, the challenge now is to improve the understanding of healthy motion for joint kinematics to better design prosthetic devices.

Until now, implant companies have made extensive use of physical and rapid prototypes for testing hip joints, shoulder joints, knee replacements, and spinal implants, both for reliability and regulatory approvals. The tendency of orthopedic device manufacturers is to increase investments in VP technologies, in particular in biomechanical simulations and finite element analysis (FEA), in order to conduct full body simulations of the musculoskeletal system.

VP tools allow users to visualize how the product will work in a more realistic way.

Moreover, these technologies may be used by the surgeons for training or surgical procedure planning purposes.

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The traditional product development process for orthopedic devices usually starts with the 3D CAD model generation and moves to the use of FEA software packages to perform stress analyses and determine high strain areas. This design approach requires building 3D models of both the device and the surrounding anatomical structure.

Modeling and simulating activities require a large amount of time and the entire process can take one or several days to complete, but the information obtained is valuable and can be used for further analyses such as strength, durability, and wear of the device. Once the FEA is complete, the design process continues with the generation of a physical prototype for kinematic performance testing. This phase of the process typically takes some months (four to six or more) to complete. It represents a key activity of the whole development process and it may need some iteration until clinical trials begin.

In modern design approaches, VP and test methods are introduced to reduce the number of design iterations by replicating the laboratory tests within a virtual environment, allowing the simulation of real life events (e.g., stair climbing, sitting, standing and jumping movements) to assess the implant performance. These procedures enable engineers looking at the whole kinematic performance, including strength and durability, using biomechanics simulations (multibody dynamics) and FEA to perform virtual system simulations that make the testing process faster. Once validated, the results of these virtual testing activities enable designers to reduce the number of laboratory tests and to reach clinical trials faster.

Traditionally, FEA, which has been the only approach for years, does not give engineers information about the boundary conditions and the loads to apply to the orthopedic device for ensuring its accuracy and its alignment with clinical trials. Hence, today, as a new tendency, many manufacturers use full body simulations for gathering mechanical loads to apply to FEA to understand the device performances more accurately.

Working in a common environment and transferring data effectively between FEA and biomechanics simulation systems represent a great improvement of the process, and it gives engineers accurate results faster than traditional test methods.

9.7

Describe why surface modeling software is not ideal for describing models to be created using AM. What problems might occur when using surface modeling only?

Surface Modeling Surface modeling begins with wire frame models, and later the surfaces which are defined mathematically are added. An improvement over wireframe modeling and surface modeling is the solid modeling approach. A solid model can describe a part completely. The physical attributes of the object consist of solid primitives such as blocks, cylinders, cones, spheres, and edges. These shapes are considered as basic geometrical representations. The primitives are combined through the use of Boolean 169 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

operators of union, difference, and intersection. An object is represented by a tree like data structure that describes how an object is built up from simpler objects. Using these descriptors, the part can be specified as a combination of shapes or features and oriented in a specific way.

Surface modeling is a technique for engineering Freeform Surfaces with a CAD system.

The technology has encompassed two main fields: either creating aesthetic that also perform a function; for example, car bodies and consumer product outer forms, or technical surfaces for components such as gas turbine blades and other fluid dynamic engineering components. CAD software packages use two basic methods for the creation of surfaces. The first begins with the construction curves from which the 3D surface is then swept or meshed through.

Figure 13. Surface being created from curves From these initially created surfaces, other surfaces are constructed using either derived methods such as offset or angled extensions from surfaces or via bridging and blending between groups of surfaces.

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Figure 14. Variable smooth blend between surfaces

Figure 15. Example surface pole map Freeform surface modeling techniques describe the skin of a 3D geometric element.

Freeform surfaces do not have rigid radial dimensions, unlike regular surfaces such as planes, cylinders, and conic surfaces. They are used to describe forms such as turbine blades, car bodies, and boat hulls.

Surface modeling was initially developed for the automotive and aerospace industries, while freeform surfacing is now widely used in all engineering design disciplines from consumer goods products to ships. However, they are of limited use in Additive Manufacturing. Additive Manufacturing methods generate solids and geometrical shapes based on three dimensional modeling. Surface modeling programs create just a surface without any depth.

9.8

Various types of models and prototypes are created before a product is fully configured. These can be models for proof of concepts, mathematical models, physical prototypes, model kinematic models, and virtual models. Describe the way in which these models differ in complexity, cost, and completeness.

Models are used in creating a product. Models represent an ideal situation of a real life problem with the aid of different theoretical and experimental techniques. Models can be classified based on type, function, and working principles.

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Mathematical models represent the theory and application of a particular product, the relationship between input and output in terms of transfer functions, and a representation of output. Primary mathematical models describe the behavior of a product or a system in terms of physical and chemical first principles. Mathematical models can represent the relationship between the product output, efficiency, and the relationship between variables and output. If the dimensions, material properties, and conditions of use of the product are known, a primary mathematical model enables us to determine the performance of the system.

Physical prototypes are created using drawings, mock-ups, dummies, scale models, and 3D printed prototypes. Based on topology descriptions, a physical model is created and describes system properties in system-adapted variables. These models are also known as iconic models from which real experiments can be constructed.

Kinematic models describe the simulated motions, position, and velocity at each of the joints. These models are used to study the movement of links, bars, joints, and the position of robotic joints in a three dimensional space.

Figure 16. Virtual Modeling and Prototyping Virtual models Design management teams have realized that virtual prototyping provides interaction between human–machine and ergonomics for superior product creation. Designing around the full product life cycle encourages engineers to make prudent decisions about component design and materials—choices that can offer payback when it is time to recycle. By integrating pre-developed components, manufacturers can respond quickly to

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market opportunities. Increasing the percentage of designs for a carry-over component that can be reused in another product not only reduces cycle time, but also lowers risk.

Some manufacturers have employed this practice in a full-scale program-development platform that manages each product as a generation within a product family. Skilled integrators also incorporate customer feedback, not just as a one-time exercise, but also as an ongoing, parallel activity. Auto manufacturers use virtual design and prototyping in their design and testing activities that support the development of the vehicles’ physical components. These areas include packaging design and assembly, which require a tradeoff between weight and dimension, layout optimization, and component mounting.

Developers can analyze numerous designs via a computer screen. Simulations of cockpit airflow using virtual smoke, tank refueling sequences, rollover testing, and roll bar activation enable the analysis of designs that is especially important for race cars.

The use of virtual reality for design analysis through simulations includes changing the lateral acceleration for better drivability and varying the car’s steering and longitudinal acceleration. The simulation provides ample data on engine control system integration and four-wheel drive torque distribution. Virtual prototyping technology is useful in evaluating hybrid technology and battery packs for emission reduction. Some companies also use virtual reality simulations for analyzing high-speed braking, studying the relationship between braking-force distribution between the front and rear along the track distance, and testing two- and four-wheel drives at different tracks with varying surface roughness.

Using modeling and simulation, the designer can create a mathematical model for the product under design. Such a model can be of any degree of complexity and completeness, can use any appropriate variables, and can be manipulated quite easily.

9.9.

Why is the interchangeability of parts important in the production of consumer products? How have digital manufacturing and additive manufacturing impacted it?

Interchangeable parts Interchangeable parts are parts (components) that are, for practical purposes, identical.

They are made to specifications that ensure that they are so nearly identical that they will fit into any assembly of the same type. One such part can freely replace another, without any custom fitting (such as filing). This interchangeability allows easy assembly of new devices and easier repair of existing devices while minimizing both the time and skill required of the person doing the assembly or repair.

The concept of interchangeability was crucial to the introduction of the assembly line at the beginning of the 20th century, and it has since become an important element of some modern manufacturing. However, it is not used in every industry.

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Interchangeability of parts was achieved by combining a number of innovations and improvements in machining operations and the invention of several machine tools, such as the slide rest lathe, screw-cutting lathe, turret lathe, milling machine, and metal planer.

Additional innovations included jigs for guiding the machine tools, fixtures for holding the workpiece in the proper position, and blocks and gauges to check the accuracy of the finished parts. Electrification allowed individual machine tools to be powered by electric motors, eliminating line shaft drives from steam engines or water power and allowing higher speeds, making modern large scale manufacturing possible. Modern machine tools often have numerical control (NC) which evolved into CNC (computerized numeric control) when microprocessors became available.

Methods for industrial production of interchangeable parts in the United States were first developed in the nineteenth century. The term American system of manufacturing was sometimes applied to them at the time, to distinguish them from earlier methods. Within a few decades such methods were in use in various countries, so the American system is now a term of historical reference rather than current industrial nomenclature. Before the 18th century, devices such as guns were made one at a time by gunsmiths, and each gun was unique. If one single component of a firearm needed a replacement, the entire firearm either had to be sent to an expert gunsmith for custom repairs, or discarded and replaced by another firearm. During the 18th and early 19th centuries, the idea of replacing these methods with a system of interchangeable manufacture was gradually developed.

Origins of modern concept In the late 18th century, French General Jean-Baptiste Vaquette de Gribeauval promoted standardized weapons in 1765. One of the accomplishments of the system was that solid cast cannons were bored to precise tolerances, which allowed the walls to be thinner than cannons poured with hollow cores. However, because cores were often off center, the wall thickness determined the size of the bore. Standardized boring allowed cannons to be shorter without sacrificing accuracy and range because of the tighter fit of the shells. It also allowed standardization of the shells.

The Congress was captivated and ordered a standard for all United States equipment.

Interchangeable parts removed problems concerning the inability to consistently produce new parts for old equipment without significant hand finishing that had plagued the era of unique firearms and equipment. If one firearm part failed, another could be ordered, meaning that the firearm wouldn't have to be discarded.

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Socioeconomic context The principle of interchangeable parts flourished and developed throughout the 19th century and led to mass production in many industries. It was based on the use of templates and other jigs and fixtures, applied by semi-skilled labor using machine tools to augment (and later largely replace) the traditional hand tools. Throughout this century, there was much development work to be done in creating gauges, measuring tools (such as calipers and micrometers), standards (such as those for screw threads), and processes (such as scientific management), but the principle of interchangeability remained constant.

With the introduction of the assembly line at the beginning of the 20th century, interchangeable parts became ubiquitous elements of manufacturing. Interchangeability relies on a part’s dimensions falling within the tolerance range. The most common mode of assembly is to design and manufacture such that, as long as each part that reaches assembly is within tolerance, the mating of parts can be totally random. This has value for all the reasons already discussed.

Digital Manufacturing and Additive Manufacturing facilitate Interchangeability The area of creation of interchangeable parts has been deeply impacted by digital manufacturing and additive manufacturing techniques. Designers and engineers at General Electric Company have begun looking at ancient objects and prehistoric bird skeletons, and delving anew into topology for inspiration on new forms of design. Their thinking: centuries of making things under the constraints of old methods may have caused their predecessors to discard innovative structures simply because there was no practical way to produce them through milling or casting. But what was impractical in the past may be quite feasible today.

The rise of the 3D printer has coincided with the digitization of the physical world through the use of 3D scanners and, increasingly, two-dimensional photos that can be stitched together digitally using software to create precise 3D renditions of anything made of atoms.

Additive Manufacturing Additive manufacturing enables the creation of materials with multiple parts and moving components without assembly. Because the process is entirely controlled by computers following precise digital instructions, the very first piece that's manufactured is just as good as the last one. The incremental cost of producing a part becomes strictly a function of time and materials.

Digitization of manufacturing compresses everything—from the early design of a product to its final assembly, everyone can now work together simultaneously. The software 175 © 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

makes it possible, and you get much better results than when all of these activities were being done in different silos.

The new nozzle will be 3D printed as a single part rather than assembled from 18 pieces, and it will be up to five times more durable. Some of these components are being used in the next generation of aircraft engines from Pratt and Whitney and General Electric. All these developments have a huge impact on manufacturing.

9.10

Imagine that you must choose between a plastic or a metal for a part you are designing. What are some reasons for selecting plastic? What are some reasons for selecting metal?

The selection of a part, either plastic or metallic, is based on the application of the part, expected life of the part, environmental conditions during use, and any constraints imposed such as cost, weight, and size.

Reasons for Plastic part Plastic parts are normally used in the following situations: • Application requires low temperature usage; the components are not subjected to repetitive heavy external load • Plastic components are chosen if the weight of the part has to be kept low • Plastic components can be easily molded using injection molding • Plastic parts tend to be cheaper if they are produced in large quantities, especially for mass production • Injection molding is used for manufacturing a wide variety of parts, from small components like AAA battery boxes to large components like truck body panels.

Once a component is designed, a mold is made and precision machined to form the features of the desired part. The injection molding takes place when a thermoplastic or thermoset plastic material is fed into a heated barrel, mixed, and forced into the metal mold cavity where it cools and hardens before being removed.

Reasons for Metallic part • Metallic parts are used in situations requiring applications where components are subjected to heavy continuous use with possibility of wear and tear. The parts have to last long and maintain dimensional accuracy when subjected to variations in temperature.

• Mold and die are used to produce plastic parts. Mold and dies are subjected to temperature variation and operate at temperatures where plastic parts melt. Mold and dies are constructed from pre-hardened steel, hardened steel, aluminum, berylliumcopper alloy, and other materials.

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•

•

Metallic parts using hardened steel molds are the most expensive to make, but offer the user a long lifespan. This offsets the cost per part by spreading it over a larger quantity.

The most economical molds are produced out of aluminum. When designed and built using Computer Numerical Control (CNC) machines or Electrical Discharge Machining processes, these molds can economically produce tens of thousands to hundreds of thousands of parts.

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