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Product Design for Mold and Die Saneh Boonrampai RMUTI

Saneh Boonrampai RMUTI


Chapter 1: The Product Design Process The Four C’s of Design A Simplified Approach A Problem Solving Methodology Consideration of A Good Design Saneh Boonrampai RMUTI


The Four C’s of Design Creativity

 Requires creation of something that has not existed before or not existed in the designer’s mind before Complexity

 Requires decisions on many variables and parameters Choice

 Requires making choices between many possible solutions at all levels, from basic concepts to smallest detail of shapes Compromise

 Requires balancing multiple and sometimes conflicting requirements Saneh Boonrampai RMUTI


What is Design? Design establishes and defines solutions to and pertinent structures for problems not solved before, or new solutions to problems which have previously been solved in a different way

ď‚´ Difference between Design and Discovery: Discovery is getting the first sight of something but design is the product of planning and work

ď‚´ Good design requires both analysis and synthesis (Analysis is to breakdown complex problems to

manageable parts and synthesis involves the identification of the design elements that will compromise the product and the combination of the part solutions into a total workable system)

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The Design Process- A Simplified Approach General information

Specific information

Design Operation

Outcome

NO Feedback loop

Evaluation

yes

Go to the next step

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Scientific Method vs Design Method State of the art

Scientific curiosity Hypothesis Logical analysis

Proof Scientific Method Saneh Boonrampai RMUTI

Identification of need Acceptance

Communication

Existing knowledge

Conceptualization Feasibility analysis

Production Design Method


Consideration of Good Design 

Design Requirements 

Functional performance (F, σ, power, deflection)

Complementary performance (life of design, robustness, reliability, ease, economy, safety of maintenance)

Total Life Cycle Material selection, productivity, durability

Regulatory and Social Issues ASTM, ASME standards, codes of ethics, EPA requirements

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Design Process I. Conceptual Design II. Embodiment Design III. Detail Design IV. Planning for Manufacture V. Planning for Distribution VI. Planning for use VII. Planning for Retirement of the Product Saneh Boonrampai RMUTI


I. Conceptual Design  Identification of customer needs  Problem definition

 Gathering information  Conceptualization  Concept selection  Refinement of product design specification

 Design review

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II. Embodiment Design ď‚´ Product architecture ď‚´ Configuration design of parts and components (feature present like holes, ribs, splines, and curves are configured). Modeling and simulation may be performed. The generation of physical model of the part with rapid prototyping processes may be appropriate) ď‚´ Parametric design of parts and components (exact dimensions and tolerances, materials and processes, robustness)

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III. Detail Design ď‚´ In this phase the design is brought to the stage of a complete engineering description of a tested and producible product.

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IV. Planning for Manufacture  Designing specialized tools and fixtures  Specifying the production plant that will be used  Planning the work schedules and inventory controls  Planning the quality assurance systems  Establishing the standard time and labor costs for each operation  Establishing the system of information flow necessary to control the manufacturing operation Saneh Boonrampai RMUTI


V. Planning for Distribution  Shelf life consideration  System of warehouses for distribution of the product needs to be designed  Marketing efforts on advertising and news media techniques must be selected  For technical activities specialized sale brochures and performance test data must be generated.

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VI. Planning for use ď‚´ Ease of maintenance, reliability, product safety, convenience in use (human factors engineering), aesthetic appeal, economy of operation, and duration of service are some of the questions to be answered in a consumer oriented product. ď‚´ Acquisition of reliable data on failure, service lives, and consumer complaint and attitudes to provide a basis for product improvement in the next design is an important phase VI activity. Saneh Boonrampai RMUTI


VII. Planning for Retirement of the Product  The final step in the design process is the disposal of the product when it has reached the end of its useful life.  Useful life may be determined by actual deterioration and wear or it may be determined by technological obsolescence.  Industrial ecology considerations dictate a plan for either disposal of the product in an environmentally safe way or, better, the recycling of its materials, or remanufacture or reuse of product components. Saneh Boonrampai RMUTI


Chapter 2 : Product Design for Manufacturing

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Outline DESIGN PROCESS  Strategies for New-Product Introduction  New-Product Development Process  Cross-Functional Product Design  Supply Chain Collaboration

DESIGN TOOLS  Quality Function Deployment  Design for Manufacturing  Value Analysis  Modular Design

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Product Design: Why Does Operations Care?  In the old days, “over the wall”  Now:  must be able to make it (process)  technology  availability of resources

 must have the capacity  must deliver a quality product or service  must decide inventory policies

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Strategies for New-Product Introduction  Market Pull (“We

Make What We Can Sell”)

 food industry

 Technology Push (“We

Sell What We Can Make”)

 electronics

 Interfunctional View  personal computers

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Chapter 3 : New Product Development Process  Concept Development  Idea generation and evaluation of alternative ideas

 Product Design  Design of the physical product

 Design of the production process

 Pilot Production/Testing  Testing production prototypes  Finalize the ‘information package’ Saneh Boonrampai RMUTI

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New Product Design Process (Figure 3.2)

Concept development

Product design

Preliminary process design

Pilot production/testing

Final process design

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3.1 Cross Functional Product Design  Traditionally, individual functional areas (engineering, operations, marketing) operate without consulting each other. This is the sequential or ‘over the wall’ approach.

 Often results in misalignment.  Concurrent approach requires the various functional areas to cooperate and work together in the same time frame.

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Cross Functional Product Design (Figure 3.3)

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3.2 Quality Function Deployment (QFD)  Also known as “House of Quality”

 Developed in Japan in 1972  Tool for concurrent design of products  Customer Attributes (“Voice of the Customer”)  Engineering Characteristics (“Voice of the Engineer”)  Tradeoffs  Competitors’ Comparison

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3.3 HOUSE OF QUALITY (QFD)

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HOUSE OF QUALITY (QFD)

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HOUSE OF QUALITY (QFD)

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Chapter 4 : Manufacturing Process

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What is Manufacturing? It is defined as, the process of converting raw materials into products. The word manufacturing is derived from the Latin word manu factus meaning made by hand.

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Manufacturing is a complex activity that involves a variety of resources and activities:            

Product Design Machinery and Tooling Process Planning Materials Purchasing Manufacturing Production Control Support Services Marketing Sales Shipping Customer Service

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Manufacturing Steps and Components of a Light Bulb

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4.1 DFMA Design for Manufacture, Assembly, Disassembly, and Service

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4.2 Design for Manufacturing (DFM) Value Analysis (or engineering) Simplification of products and processes

Modular Design Multiple products using common parts, processes, and modules Saneh Boonrampai RMUTI

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What is DFM?  Design for Manufacture – integrates the design process with materials, maufacturing methods, process planning, assembly, testing and quality assurance.

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4.3 Value Analysis

 Terms in Value Analysis:  Objective: primary purpose of the product  Basic Function: Makes the objective possible  Secondary Function: How to perform the basic function

 Value analysis seeks to improve the secondary function, e.g., how to open a can or make a tool box. Saneh Boonrampai RMUTI

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Objectives of Value Analysis  Enhance the design of a good or service to provide higher quality at the same price, or the same quality at a lower price.  Modify the design of production process to lower the cost of a product or service while maintaining or improving quality.  In other words, improve the ratio of usefulness (quality) to cost. Saneh Boonrampai RMUTI

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DFM: An Example (a) The original design

(b) Revised design

(c) Final design

Assembly using common fasteners

One-piece base & elimination of fasteners

Design for push-and-snap assembly

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Summary DESIGN PROCESS  Strategies for New-Product Introduction  New-Product Development Process  Cross-Functional Product Design  Supply Chain Collaboration

DESIGN TOOLS  Quality Function Deployment  Design for Manufacturing  Value Analysis  Modular Design

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Considerations Characteristics, capabilities, and limitations of materials Manufacturing process Machinery Equipment Saneh Boonrampai RMUTI

 Machine performance  Dimensional accuracy  Surface finish  Processing time  Effects of processing method on part quality


4.4 Design for Assembly (DFA)  Requires consideration of ease, speed, and cost of putting all the parts together.  Disassembly must also be possible for good design.  Easy assembly = easy disassembly Saneh Boonrampai RMUTI


Benefits of DFA  Easy disassembly makes for easy service of parts.  Software is available to expedite the process and minimize cost.

 The end result is Design for Manufacture and Assembly (DFMA)

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Methods of Assembly

ď‚´Fasteners or adhesives ď‚´Welding, soldering, brazing

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Methods of Assembly (cont.)

Hand/Machine assembly? # of parts Amount of care/protection required Cost of labor Saneh Boonrampai RMUTI


Chapter 5 : Selecting Materials

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Types of Material Ferrous metals Nonferrous metals Plastics (Polymers) Ceramics, glass, diamond

Composites Wood

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General Manufacturing Characteristics of Various Alloys

Alloy

Castability

Weldability

Machinability

*Aluminum

E

F

E-G

G-F

F

G-F

*Copper *Gray cast iron *White cast iron *Nickel

E

D

G

G

VP

VP

F

F

F

*Steel

F

E

F

*Zinc

E

D

E

SanehE, Boonrampai RMUTI G, good; F, fair; D, difficult; VP, Very Poor Note: excellent;


Chapter 6 : Product design for Mold

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Outline  Equipment and process steps  Design for Part  Design for manufacturing, tooling and defects

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THERMOPLASTIC, THERMOSET: •Thermoplastics are resins that can be reground after molding, and molded again. •Thermoplastic are often compared to Wax.

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•Thermosets can be molded once only; they tend to be denser materials for special purposes , thermosets are often compared to an egg; once the egg is hard boiled it can't be returned to a liquid and recooked as sunny side up.


Plastics Processing: Injection Molding

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Mold Structure: Parting line A dividing line between a cavity plate and a core plate of a mold. - Make a parting line on a flat or simple-curved surface so that flash cannot be generated. - Venting gas or air.

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Two plate mold

One parting line

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Three plate mold

Two parting lines

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Melt Delivery

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Gate -Delivers the flow of molten plastics. -Quickly cools and solidifies to avoid backflow after molten plastics has filled up in the cavity. -Easy cutting from a runner

-Location is important to balance flow and orientation and to avoid defects.

L = 0.5-0.75 mm h(thickness) = n.t W= n30A1/2

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Runner cross section

Runner cross section that minimizes liquid resistance and temperature reduction when molten plastics flows into the cavity. - Too big - Longer cooling time, more material, cost - Too small - short shot, sink mark, bad quality - Too long - pressure drop, waste, cooling

Hot runner, runnerless mold

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Runner balancing

Balanced

Not balanced

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Defects Molding defects are caused by related and complicated reasons as follows:

* Malfunctions of molding machine * Inappropriate molding conditions * Flaws in product and mold design * Improper Selection of molding material

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Weldline This is a phenomenon where a thin line is created when different flows of molten plastics in a mold cavity meet and remain undissolved. It is a boundary between flows caused by incomplete dissolution of molten plastics. It often develops around the far edge of the gate.

Cause Low temperature of the mold causes incomplete dissolution of the molten plastics. Solution Increase injection speed and raise the mold temperature. Lower the molten plastics temperature and increase the injection pressure. Change the gate position and the flow of molten plastics. Change the gate position to prevent development of weldline.

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Flashes Flashes develop at the mold parting line or ejector pin installation point. It is a phenomenon where molten polymer smears out and sticks to the gap. Cause Poor quality of the mold. The molten polymer has too low viscosity. Injection pressure is too high, or clamping force is too weak. Solution Avoiding excessive difference in thickness is most effective. Slow down the injection speed. Apply well-balanced pressure to the mold to get consistent clamping force, or increase the clamping force. Enhance the surface quality of the parting lines, ejector pins and holes.

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Short shot This is the phenomenon where molten plastics does not fill the mold cavity completely. and the portion of parts becomes incomplete shape. Cause The shot volume or injection pressure is not sufficient.

Injection speed is so slow that the molten plastics becomes solid before it flows to the end of the mold. Solution Apply higher injection pressure. Install air vent or degassing device. Change the shape of the mold or gate position for better flow of the plastics.

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Warpage This deformation appears when the part is removed from the mold and pressure is released. Cause Uneven shrinkage due to the mold temperature difference (surface temperature difference at cavity and core), and the thickness difference in the part. Injection pressure was too low and insufficient packing. Solution Take a longer cooling time and lower the ejection speed. Adjust the ejector pin position or enlarge the draft angle. Examine the part thickness or dimension. Balance cooling lines. Increase packing pressure.

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Sink marks

ts ts < t t -Equal cooling from the surface -Secondary flow -Collapsed surface

â&#x2020;&#x2019;Sink Mark Saneh Boonrampai RMUTI


CAE (computer aided engineering) Process simulation Material data base CAD

MOLDFLOW C-Flow

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Considerations in design of injection molded parts Guideline (3)

gate location determines weld lines

weld lines

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* Source: http://www.idsa-mp.org/proc/plastic/injection/injection_design_7.htm


Injection Molding: molds with moving cores and side-action cams - If the geometry of the part has undercuts [definition ?]

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Mold Structure: Undercut, Slide core

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Designing injection molds: typical features

[source: www.idsa-mp.org]

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Designing injection molds: typical features

(a) Shut-off hole: no side action required

(b) Latch: no side action required

(c) Angled Latch: Side action cam required

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Design Steps

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1. Plastic’s Type- Shrinkage

 Ex. ABS=0.5%, PP=1-3%

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2. Parting line

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3.

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Core Saneh Boonrampai RMUTI

Cavity


3. Number of Cavity

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Ejector system

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Cooling System

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Chapter 7 : Press Operations & Types of Dies

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Press Working ď&#x201A;´ Use of mechanical and hydraulic presses for forging and extrusion has been mentioned earlier. Knuckle type mechanical presses are used widely for sheet metal work. These presses are usually of vertical configuration. These presses are provided with a heavy flywheel driven by an electric motor. A ram moves up and down the guide ways provided in the frame of the press, when the ram is connected to the flywheel through a connecting rod and a crank mechanism. The clutch for transferring the motion from the flywheel to the ram is operated by a foot operated treadle. The arrangement is somewhat similar to the mechanism of a reciprocating engine. Such presses are very useful for providing short powerful strokes.

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These presses are available in two configurations: (i) Open frame type, and (ii) Closed frame type.

ď&#x201A;´ Open frame type presses are less robust as compared to closed frame type, but provide greater access for loading material as they are open in front as well as sides. Due to their appearance, they are also referred to as C-frame or gap presses as well. ď&#x201A;´ Closed frame type presses are used for heavier work. The capacity of the press is indicated by the force (or tonnage), the press is capable of exerting.

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OPERATIONS PERFORMED WITH PRESSES Apart from punching and blanking, several other useful operations are performed with the help of mechanical presses: Some of these are listed below: (i) Bending, (ii) Deep drawing, (iii) Coining, and

(iv) Embossing. These operations are described briefly.

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BENDING Bending means deforming a flat sheet along a straight line to form the required angle. Various sections like angles, channels etc., are formed by bending, which may then be used for fabrication of steel structures.

Three common methods of bending are illustrated in Fig.

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DEEP DRAWING In deep drawing process, we start with a flat metal plate or sheet and convert it into cup shape by pressing the sheet in the center with a circular punch fitting into a cup shaped die. In household kitchen, we use many vessels like deep saucepans (or BHAGONA), which are made by deep drawing process. If the depth of cup is more than half its diameter, the process is termed as deep drawing and with a lesser depth to diameter ratio, it is called shallow drawing. Parts of various geometries and shape are made by drawing process. The deep drawing process is illustrated in Fig.

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