The Glue Pen: A Safer, Easier Hot Gluing Solution by Delaney Rua

A Safer, Easier Hot Gluing Solution

Team 1

Delaney Rua

Gabe Weider

ME215C: Analytical Product Design Spring 2019

McKinley McQuaide Harry Schwartz Matt Mills

The all-new Glue Pen All the utility of the average glue gun – none of the drawbacks. BRAND STATEMENT Many people know the phrase, “The pen is mightier than the sword,” and in our modern times, it turns out the pen is mightier than the gun as well! PRODUCT OVERVIEW This product is a hot glue applicator that is held in the hand like a pen. A fully internal automatic motor extrudes the glue at a constant speed, without having to apply any pressure with your hand! This automation not only makes the gluing more consistent, it also makes a glue gun accessible for older people with arthritis, or children who don’t have the hand strength to use traditional glue guns. The Glue Pen is battery operated, which means no need to struggle with a cord, look for an outlet, or worry about storing it. The Glue Pen’s battery pack heats the metal tip of the product, and powers a 12 Volt motor in the back. This motor turns a worm gear, which translates the motor’s force down the shaft of the product. The teeth in the worm gear then catch the teeth in our specially made glue sticks to push the glue at a consistent rate through the heating mechanism. All of these steps occur at the push of a button! This product is simple to manufacture: ● Outer casing molded from high-density thermoplastic with snap closures for easy repairs ● All electronic components internal, reducing the risk of cut cords, etc. ● Metals and covers that meet safety requirements which are extremely important for this product To test to ensure our product works the way it’s supposed to, we: ● Found the ideal temperatures to optimize heating and cooling before pivoting ● Used force gauges to find the desired pressure from the worm gear ● Calculated the amount of energy the motor needed to apply to the worm gear ● Created a testing apparatus to find ideal speeds of glue extrusion, minimizing necking and globbing Based on our analysis of profitability, this product is much more desirable than a normal glue gun most dominantly because of the lack of hand force required. This opens up a new market of crafters on either end of the spectrum, young and old. Because of this, and with a conservative estimated penetration rate, our calculations give us a market size of roughly 13 million, from a total available market of 24 million. We then surveyed our potential customers, and using their CBC questions were able to calculate an ideal optimization of price for our product. After taking into account the cost of making the product which would be $9.08 initially, the profit model priced our product at $30. While this price does drop market share to 82%, it is the price that we hypothesize will make a profit of $951,152,941 over five years. The Glue Pen diverges widely from anything else on the market, and we have faith (and testing to show) that consumers will be able to see these clear advantages. All we need now is starting capital for manufacturing costs and any connections with suppliers to stores that you may be willing to help us with. We are already on the road, and our next step will be reaching out to manufacturers to see which ones are best to create our product. Then, it’s off to the stores!

Final Render: Form Prototype

Chapter 1 Introduction – Base Product Selection

Fig. 1. The Surebonder 120V Dual Temperature Glue Gun, our initial base product choice

As shown in Fig. 1, our team selected the Surebonder 120V Dual Temperature Glue Gun, purchased from Michael’s. We chose this product in part because of its minimalism – the mechanical and thermal components were simplistic and could be extended in novel ways. We also chose this because it is a device that most Product Design students have access to. The stakes are high to improve this product, and we aim to improve it in such a way that using a hot glue gun becomes a significantly more enjoyable experience. We also considered several other products which we did not end up pursuing. Some of these favorites were kids toys with light/sound components, a pul and go

submarine, an automatic wine corkscrew, a toaster oven, water filtering devices, and curling wands for styling hair. To settle on the hot glue gun, our team visited several stores (Home Depot, Target, Fry’s Electronics, Michael’s), allowing us to brainstorm an initial list of product candidates. From this list, we narrowed products down based on their adherence to a certain set of criteria. The product couldn’t be dangerous, i.e. include blades or open flames, it must have at least two critical “components” (mechanical and thermal, two mechanical, etc), and it had to be common enough that our final rendition would be useful to a large, relatively non-niche market. From this pared-down list, we felt confident in the success of any product we chose, so we decided on our final choice by voting for our top 3 picks from this list. The hot glue gun, of course, received the greatest number of votes from the team.

Fig 2. Pictured (from right to left) McKinley, Matt (on facetime), Harry, Gabe, and Delaney. Team Milk found the perfect hot glue to purchase for the project.

Fig. 3 Gabe talks to a potential customer about her needs for a glue gun that is safe, reliable, and easy to use

Delaney’s Persona Letter Dear Purchasing Agent, My name is Delaney, I’m a First Grade Teacher in Palo Alto, and I am looking to purchase a few hot glue guns to use in my classroom. In order for this glue gun to be suitable for my students, I need to find one that has some more substantial safety measures. It would be nice if I didn’t have to remind my students to turn the glue gun off when they’re done. Also, the barrel tends to heat up significantly and I worry that my students will burn their hands if they touch parts other than the handle. It would also be nice if you could find one that’s cordless, so that I don’t need every student to sit by the wall outlets. The last feature that would be nice is the ability to maximize every glue stick’s life, so that I don’t have to show the students how to replace the glue sticks as often. Thank you!

-Delaney

McKinley’s Persona Letter Dear Purchasing Agent, I don’t want anything fancy, I just need to be able to get through my high school art class. I have Cerebral Palsy, so I need something I will be able to grip easily without a lot of hand dexterity, and something where I don’t need a lot of hand strength in order to release glue. My biggest worry is that I will not be able to hold onto it well enough and I will burn myself and make a scene. I really don’t want to need help to use this, I already need assistance on other components of this class and just want to be able to do this on my own without hurting myself. I do have some trouble keeping the line steady and strait when me hand is free, and when it gets stringy and I can’t get it off of myself as gracefully as others, so anything that would help me with that would be great. Thanks! McKinley

Harry’s Persona Letter Dear Purchasing Agent, My name is Harry and I am a college freshman at Stanford looking to buy a glue gun for a class called ME101. I will be using my glue gun a lot this quarter because we do a lot of rapid prototyping with foam core. It would be ideal if my glue gun was easy to transport because we tend to work in groups that meet all over campus. It would be great if it heated up quickly because I am a busy college student that doesn’t want to waste valuable homework time waiting for my hot glue gun to be ready to use. I also would love one that doesn’t drip a lot because I have to clean up after

myself. If the hot glue gun was sold along with an extensive pack of glue, I would definitely be more inclined to buy that one because I don’t want to have to find time to go back to the store to get more glue and I will probably need a lot of it. Safety isn’t as much of a concern for me as much as efficiency and ability to get the job done. I definitely don’t want to spend a lot of money because I do not have any source of income yet, but I do need something that will be good enough to create neatly and sturdily glued projects considering that the quality of the gluing is part of my grade. I hope we can find a balanced price point. Best, Harry

Gabe’s Persona Letter Dear Purchasing Agent, My name is Gabe, I have just moved to the city and bought my own apartment after graduating college. I have just started to get settled in, and have been getting very into the new DIY trends on facebook and instagram. I have realized that most of these videos require the use of a glue gun or some sort of glue attachments in order to fix things in a stable way. The plan is to use this to make some furniture pieces and knick knacks that will hopefully stand up to the wear and tear of everyday life. So the glue definitely has to be strong, but also the purpose of doing this DIY stuff is to not spend as much money as I would otherwise, which means that hopefully this glue gun will not break the bank. That includes the refillable glue, because if I have to shell out tons of money for every glue stick then that defeats the purpose (A value pack of glue with it might be best). I am also not looking for anything fancy, but for heating up it should come with a stand so it won’t burn whatever is underneath it. Ideally this glue gun will heat up quickly, get the job done, be easy to use and squeeze, and easy to clean up after. My last request would be to keep it pretty small and cute. I don’t have a lot of room in my apartment and I want things to look nice, and one of those big industrial glue

guns with a huge extension cord is not exactly what I’m looking for. In essence, I want a small, cheap, easy to use glue gun that holds pretty durable glue. Thanks, Gabe

Matt’s Persona Letter Dear Purchasing Agent- My name is Marcia and I am looking to buy some kind of device to help with my projects. I am a retired teacher and spend my free time working on arts and crafts daily. Lately, I have struggled with connecting pieces together and need help. Ideally, I would like a device that could glue two materials together with a strong bond. I have heard you guys offer a variety of glueing devices, including hot glue guns (which I am not very familiar with yet). Some of my biggest needs are: I have arthritis in my hands and have limited grip strength, I have read about people getting burned b the hot tip and am quite worried I may do the same, I need something that is reliable and will last me until the day I die because I do not want to have to search for another device again. Thank you for your time and I hope that with your help, I will be able to find the perfect model for me to help me with my projects. Best, Marcia

1.1 Pricing Visual Display

Fig. 4 Fortnite “Inventory” shows the differences between the 3 hot glue guns. Glue guns were compared based on attributes listed.

Chapter 2 From Customer Requirements to Features and Metrics 2.1 List of Customer Requirements School Teacher I need it to be safe to use for kids I would want it to automatically shut off I don’t want to have to plug it in I want the glue to last as long as possible I need the hot parts to be very clearly marked I want multiple High School Student with CP I need it to be easy to hold I need it to require little grip strength I need it to protect me from getting burnt I want it to help me make an even, strain glue line I want it to avoid having strings of glue I would love if it was easy to refill ME101 Student I want it to be light I need it to be easily transportable I would love it to heat up quickly I want to buy a pack of glue with it I need it to be cheap I want it to be easily cleaned up DIY Millennial I want it to look good

I need it to be compact I need the glue to be strong I would like a stand for it to heat up I would love an easy way to store it I need it to be easy to squeeze with one hand ARTS & CRAFTS GRANDMA I need the glue bond to be dependent I need it to be easy to squeeze I want it to be safe to use and not burn me I would love if it cooled down quickly after use I need it to last for years and years

2.2 Define Metrics and Features

Fig 4. This table shows customer requirements for purchasing when it comes to glue guns. We found safety, heating time, and price to be important attributes of the gun.

2.3 Summary of the highlights of a and b In our report it can be seen that, if the glue guns are wireless, they have more trouble heating up quickly unless they are larger in size. We also found that many of the safety precautions were only prevalent on the mini or child versions of glue guns. There also seemed to be a correlation between size, price, and temperature. Also, there was no clear correlation between which glue guns were sold with extra glue guns and which were not. We also found that all of the glue guns were designed with the same type of grip. All of this opens up the area of safety precautions in terms of the design of the glue gun, and maybe an auto shut off valve. It also brings to mind a possible redesign of the trigger function to be more ergonomic. Finally, there is also a possibility of choosing different materials that conduct differently for the tip of the nozzle since heating and cooling are clearly very important for this process.

Chapter 3 Reverse Engineering the Base Product 3.1 Disassembly of Base Product

Step 0: Base Product fully assembled, glue stick inserted

Step 1: Removing screws (x5) and glue stick, unclipping stand from barrel base

Step 2a: Opening plastic casing to reveal inner

Step 2b: Identify electrical and mechanical

electrical/mechanical components

components for removal

Step 3: Remove mechanical trigger mechanism

Step 4: Unclip leads from barrel and pull out from

(on left, white)) and spring, thermal barrel and tip,

socket beneath thermal barrel (only one was

and wiring with temp switch

removable without breaking)

The most interesting parts in the glue gun are the heating element and trigger mechanism. We didn’t realized how big the chamber was inside the gun and how much glue can get melted at once. We found the trigger mechanism to be simplistic yet very effective.

3.2 Bill of Materials

Fig. 5 Layout of all parts inside the glue gun once disassembled.

Bill of Materials Table Part Part Name

Material

# 0

Manufacturing

Sub-Function

Method Gluestick

Glue

Extrusion

For melting and extruding

Left side of

Heat-resistant

casing

Plastic

Injection molding

Encasing electronics & trigger

Right side of

Heat-resistant

casing

Plastic

Trigger

Plastic

Injection molding

trigger Injection molding

mechanism 2b

Trigger

Removable

Metal

Wire coiling

Provide resistance & push trigger back out

Metal

Wire bending

stand 4

Pushing glue into barrel to be heated

spring 3

Encasing electronics &

Propping barrel up when not in use

Thermal

Conductive

barrel with

metal

Metal milling

Heating up glue stick to gel consistency

tip 5

Glue stick

Malleable

insertion

plastic

Injection molding

between glue stick and

sleeve 6

Retaining

Reducing friction plastic slot

Metal

Wire coiling

spring

Keep glue stick sleeve attached to thermal barrel

Tip washer

Ceramic

Additive

Separate thermal tip

manufacturing

from plastic casing

(injection?) 8

Lead clip

Metal

Sheet metal

Keep leads from

bending

moving around/ripping out

Electrical lead 1

Insulated wire

Wire drawing,

Transmitting power to

annealing, extrusion thermal barrel of cable jacketing

converter

Electrical

Insulated wire

lead 2

Wire drawing,

Transmitting power to

annealing, extrusion thermal barrel

Plastic lead

Reflective

covers

plastic

of cable jacketing

converter

Film extrusion (?)

Thermally protecting leads from barrel

sheeting 11

Electrical

Vinyl &

Extrusion &

Keep wire leads

tape

adhesive

adhesion application together, organize the internal components

Temp switch

Plastic & metal Injection molding,

Changing the

sheet metal bending temperature between high and low (Voltage?) 13

Phillips head

Metal

screws (6x)

Straightening &

Connecting the two

tapping

sides of the external casing

Power cord

Insulating

Wire drawing,

plastic & wire

annealing, extrusion barrel with electricity to of cable jacketing

Providing the thermal heat up

Table 1. Breakdown of all parts, materials, and functions.

3.3 Design Discussion Poorly Designed Features: ● The two lead wires are the only components that are placed in an otherwise wide handle ● Heating element is exposed to the environment ● A lot of unused space inside the plastic casing

● Trigger is difficult to push and then clicks, causing uneven flow of glue ● Cord is clunky and doesn’t store easily Well-designed Features: ● Trigger mechanism seems robust and simple, parts are over-engineered to the extent that they won’t break easily ● Handle is wide enough to be ergonomic for a wide range of users ● Internal components are not overly complicated and the number of components reduces the chances of something breaking ● Overall the design is intuitive and minimal ● Trigger mechanism requires no fasteners Potential Failure Modes: ● Internal leads could pull out of heating mechanism if the cord is pulled too hard ● Overheating plastic if plugged in for too long ● User burning themselves ● If the wrong sized glue stick is inserted, glue melts on internal components and becomes nonfunctional ● Switch is fragile and could break ● Tip could ignite environment or melt its own insulated wire if it comes into contact with the cord ● Weakest parts of the gun are the trigger mechanism and attachments of cords from switch to heating element.

Chapter 4 Concept Generation

4.1 Design Directions Concept #1: Precision/Body Redesign for Higher-Fidelity Gluing Advantages Ability to glue in unique shapes

Disadvantages Additional parts increases the risk of broken/malfunctioning components

Ability to reach hard areas in more

Unfamiliarity with a redesigned body raises the

complicated geometries

learning curve, even for experienced glue gun users

Decreased need for precision hand

Glue guns with more specific functions/glue design

control, caters to users with less use

abilities decreases general usability of the glue gun

of their hands Simplification of the gluing process

Over-simplification could create a less versatile glue gun overall

Decreased need for hand strength

May cause glue to be extruded too much or too quickly if the force required for extrusion is too low

Increased fidelity of the final product due to better gluing ability

Concept #2: Increased Safety for Kids Advantages

Disadvantages

Reduces the chances of a child

May seem “childish” to advanced hot glue gun

burning themselves on the hot glue

users

gun barrel

Insulated barrel reduces the amount

May reduce the agility with which a user can wield

of heat dispersed by the glue gun

the hot glue gun, especially in tight spaces

barrel (not just the tip) Reduces the chances of materials in

Reducing overall temp/heat dispersion might make

the environment melting onto the

it more difficult to extrude the glue

barrel/tip of the gun Cordless feature reduces the chances

Having to charge/replace batteries, or increases

of tangling/tripping over cord

heating-up time

Concept #3: Control Over Glue and Fly-aways Advantages

Disadvantages

Control over fly-aways keeps project

May over-complicate the nozzle and lead to a

clean and more aesthetic

higher chance of broken parts

Reduction of fly-aways reduces the

Fly-aways are often a product of high temperature,

chances of burning fingers on excess

which, if lowered, would make glue harder to

glue strands

extrude

Control over glue extrusion reduces

Control ≠ Precision, and a decrease in the flow of

the need to fix hot glue with

the glue may reduce the ability to be precise and

fingers/other tools

move the glue before it sets

These concepts fit with the course due to the variables we can manipulate with. The three concepts are all different in their own ways but are all issues that can be easily modified to help the performance of the product.

4.2 Concept Generation

Figure 1: Brainstorm ideas starting with one

Figure 2: Brainstorm ideas starting with

partner by trading off drawings and adding to

other partner, by trading off drawings and

them, similar to the 6-3-5 concept.

adding to them, similar to the 6-3-5 concept.

Figure 3: Fidelity Analogy Map

Figure 4: Idea for better grip for a more ergonomic way to squeeze the glue out.

Figure 5: Idea for an easier clicking motion on

Figure 6: Idea for dispensing glue with a

button to dispense glue

click-pen grip pushing the glue through a heating element

Figure 7: Idea for a better tip that allows for

Figure 8: Idea for a slimmer squeeze tip that

precision as well as a dispensing button near

has a two sided grip to dispense the glue

it.

Figure 9: Fidelity Analogy Map

Figure 10: Idea for a button that adds glue in a Figure 11: Idea for a tip that has bearings in precise dot.

order to increase precision.

Figure 12: Safety Analogy Map

Figure 13: Idea for a retractable tip to cover heated elements and easier to refill

Figure 14: Idea for a finger cover to protect from heating elements.

4.3 Decision Preparation MAUT Matrix 1 Metrics and Features

Attribute Importance Weight

Removable bottom Fig 1

Glue Wiper Fig 2

Glue dot heater Fig 10

Two sided Click squeezer “pen” Fig 4 design Fig 5

Precision roller Fig 11

Hand Force

Product Weight

Nozzle Size

Glue precision

Cleanliness

Affordability

Handle Ergonomics

Barrel Diameter

Glue Extrusion Mechanism

Usability Learning Curve

Aesthetics

Comfortable casing material

TOTAL

Figure 15: MAUT Matrix of Design Sketch Directions PUGH Matrix 1

Figure 16a: Pugh Matrix 1

PUGH Matrix 2

Figure 16b: Pugh Matrix 2

4.4 Summary of Results The results of our Pugh Matrix showed a strong tie between the Precision roller and the Two Sided Squeezer. This demonstrated that these two designs had the most improvements from their competitor while minimizing any new detrimental features. The Multi-Attribute Utility Theory takes into account how highly we value each of the key features and metrics we are comparing. These assigned weights led to different results, and were used to decide between the two tied frontrunners from the Pugh Matrix.

4.5 Final Decision In order to decide on our design for our final direction, we wanted do consider the results of both the Pugh matrix and MAUT. Our results differed between the two tests because of how we distributed our weights, valuing things like precision abilities and hand force more than barrel diameter and nozzle size. We considered safety as a product of our designs usability because as we talked with more people, we found that most burns occur from either poorly designed stands, or the inability to place glue cleanly in the correct locations, causing users to touch the hot glue to move it. Our focus on precision was informed by this finding. Optimizing the ability to press the trigger easily was a priority for many of our user groups and both an accessibility consideration, and a comfort one. We found that the Precision Roller best fit these needs, supported by its dominance in our Pugh Matrix, and high ranking in our MAUT.

Figure 17: Glue Pen Storyboard

Figure 18: Updated Customer Requirements, Metrics, Features

Chapter 5 Function Trees and Design Concept Selection 5.1: Moving from Function trees to a Design Concept 5.1.1 Function Trees Diagram and Explanation

Fig. 1. Function Tree Diagram showing how the main tasks and subtasks involved when glueing things together using a hot glue gun.

For the primary function of Gluing Things Together we found that there were three main subfunctions: heat up, dispense glue and cool down.

The heat up function of the glue gun is pretty straight forward. You plug the glue gun into an outlet and it heats up. The only sub-sub function we saw that could really improve the product is providing feedback. Most people wait an unprescribed amount of time to check if the glue gun is ready and the way they check is to put their hand near the tip which is not the safest method.

The dispense glue function of the glue gun has a lot of room for improvement. There are three sub-sub functions of dispensing which are to dispense fast, neatly and accurately. There is not a lot of control over how fast your glue gun dispenses your glue or the amount it dispenses. All of the control is in how hard you pull the trigger which we compare to steering a car that has a manual steering wheel, outdated. Instead, we could take the stress off of your finger and automate it into the glue gun. Everybody who has used a glue gun is familiar with the strings of glue and the excess mess that always builds up around the workstation. This can definitely be improved. We also felt that glue guns can be improved through providing better guidance and stability.

The cool down function of the glue gun is again very straight forward. Typically, people inconveniently have to wait another unprescribed amount of time for the tip to be cool enough to store away. We could improve this process, but also the problem that always comes from having a long cord.

5.1.2: Idea Generation via Metaphor Maps

Figure 2: Brainstorming how to provide

Figure 3: Ideating how to dispense glue

visual/audible feedback to user to signal

neatly onto workpiece

whether glue gun is hot or cool.

Figure 4: Mind map used to figure out how

Figure 5: Brainstorming different ideas of

to dispense glue accurately onto workpiece.

how to cool down the hot glue gun.

5.1.3: Design Concept Generation via Permutations of Sub-Functions Figures 6, 7, 8, and 9 illustrate design concepts generated by combining sub-functions:

Figure 6: Green, red, and blue indicators provide

Figure 7: The cool down stand allows the

the user with visual feedback to determine the

user to place the hot glue gun into a safe

temperature of the glue gun.

location after glueing, preventing the user from grabbing the hot gun

Figure 8: The “glue pen” provides the user with

Figure 9: Laser guides allow the user to

an effective, accurate glue gun to precisely place

determine the path of the glue gun as

their glue to the workpiece.

they move along their glue.

5.1.4: Design Concept Decision via PUGH Matrix, Final Sketch

Figure 10: Pugh matrix shows the 4 different concepts (heat/cool indicator, cool down stand, glue pen design, laser guide) we generated compared to the benchmark Surebonder glue gun. The matrix shows how the different designs rate compared to the metrics/ features on the left. NOTE: a score of 1 means the concept is better than the benchmark.

Figure 11: High-fidelity sketch shown above demonstrates our glue pen design. Features to note are the light indicator at the top signaling whether the gun is either red (hot) or blue, (cooled down), the button to release glue which decreases the amount of force required to advance the glue stick, and the disk-shaped top at the tip which keeps the hot tip off of the surface when the gun is set down and also helps the user precisely place the glue.

Chapter 6 Function Block Models

6.2: Function Block Models 6.2.1: Function Block Model and Preliminary Equations

Figure 12: Function block model shows the flow of using the glue gun

and the equations related to each task.

6.2.2: Discussion of Insights The key functions within our block model are the heat up process, the precise distribution of glue, and the cool down process. Our model shows a strong association within the heat up/application process and glue control/fidelity, which is particularly dependent on viscoelasticity. Initially, we predicted this relationship may exist between fidelity and viscosity, but upon further research and calculations, we found that viscoelasticity is what will determine the ease of applying and spreading the glue. Our equation demonstrates the inverted parabolic relationship we predict between precision and viscoelasticity, having a peak consistency, before which its thickness and firmness requires excess force and allows little time for adjustments before solidifying, and after which it becomes difficult to control again. Beyond our key customer requirement of control, we saw a relationship within the cool down and resting stage and the safety requirement. We consider excess glue one of the primary contributors to safety risk, based on our customer interviews. Our flow diagram shows a relationship between the resting angle of the glue gun and glue dripping out. We developed an equation for this based on the Melt Flow Index of the glue which indicates how much glue flows out of the tip based on a certain tested force. We assumed the impact of the force to be linear and thus set up a proportion to scale down to the force experienced at rest based on the propped angle.

6.3: Key Engineering Variable Tests 6.3.1a: Test 1: Prop Angle and Excess Drip

Figure 13: Prop set at 0 degrees. No

Figure 14: Prop set at 45 degrees

glue dripped out of collected at rim.

(standard propping angle). Glue collects on rim and begins spilling to surface.

Figure 15: Collection of excess glue after glue gun propped at 45 degrees for 10 minutes.

6.3.1b: Test 2: Glue Viscoelasticity and Precision In this test, we heated the glue gun until glue was able to be extruded (which took 2:08 minutes) and tested whether there was a relationship between the viscoelasticity of the glue, the temperature at which it reached these viscoelastic values, and the precision afforded by the glue’s viscoelasticity. We found that viscoelasticity increases as a function of temperature and time, and temperature is linearly related to the time that the hot glue gun has been plugged in. This helped us ensure that our equations regarding a user’s ability to make precise lines with the hot glue increases up to a certain degree of glue viscoelasticity.

Fig. 16. Our test set-up for the precision/viscoelasticity test. In this test, we tested a user’s ability to follow precise line patterns with the hot glue gun at various temperatures, and thus various viscoelasticity values of the glue.

Chapter 7 Engineering Model Preparation 7.4: Preliminary Engineering Model and Model Madlibs 7.4.1: Customer Requirement Selection and Relations To choose the three Customer Requirements that were most important to our design, we consulted our list from last week, and decided among ourselves which requirements we felt were most integral: ● Can be used with one hand ● It needs to be safe ** ● Must heat up quickly ● Must be easily refillable * ● Has to be easily transportable ● Needs to come with glue ● Glue must come out quickly ● It needs to last many uses ** ● Must be cheap ● Can't take up too much space ● Needs to cool down quickly ** ● Needs to be cordless ● Glue bond must be strong ** ● Handle needs to be ergonomic ** ● Must have a stable resting position ** ● Must be easy to squeeze **

Our three most important Customer Requirements from our previous design analysis were that the glue gun: ● Must be safe - looking at temperature of the body ● Must be able to last many uses (be durable) - look at RPMS of motor (if it runs at high RPM’s, motor will eventually burn out ● Must have an ergonomic, easy-to-control handle - we can look at force required to extrude glue We chose these Customer Requirements out of our larger list because we felt that they best exemplified the design direction that we were pursuing. Our goal is to create a hot glue gun that has improved safety, durability, and ergonomic features. In our storyboard from last week, we illustrated that our ideal customer would be a grandmother seeking a hot glue gun with improved usability features in the categories described above. Moving forward, we used these requirements to guide the metrics and features that we would use to determine success in whatever our re-design would be. 7.4.2: Maximizing/Minimizing Key Engineering Metrics From the three Customer Requirements chosen earlier, we cross-referenced our list of engineering metrics to determine which would be most relevant to our analysis. From our engineering metrics list, we decided that the following metrics were important to further discuss: ● Product dimensions ● Hand force required to dispense glue ● Product weight ● Time to reach max temp ● Time to cool down To test the limits of our design framework, we wanted to see what potential our product had if we took the following two metrics to their maximum or minimum:

1. Hand force required to dispense glue – MINIMIZED a. If we were to minimize the force required to dispense glue to its smallest possible value, we would increase the chances that users of all abilities would have the opportunity to use our product. 2. Glue volume extruded per trigger compression – MAXIMIZED a. Ideally, we would maximize the amount of glue extruded per trigger compression to a certain degree, such that glue is still easy to control but the amount of force required to extrude the glue is still low. However, this might be difficult to achieve given that the current glue gun settings require a high amount of force to extrude glue per degree of trigger compression, especially at lower temperatures. 7.4.3: Model Madlibs For the Precision Gluer’s customer, it would be best to minimize the hand force required to extrude one inch of glue in a straight line. For the Precision Gluer’s customer, it would be best to maximize the glue extruded with each trigger pull, in order to increase the economy of each movement/trigger pull motion. For the Precision Gluer’s customer, it would be best to minimize the cool-down time to less than 5 minutes, in order to improve safety and be able to pack up the glue gun quickly after finishing a project. 7.4.4: Graphing Relationships Among Engineering Variables and Cost/Market “As the time to cool down decreases, the hot glue gun must be made of different metals, be more insulated, and perhaps have other features that dissipate heat. The manufacturing cost would then depend more heavily on the materials being used than on the manufacturing processes”

Engineering variable: Time to cool down Manufacturing cost: Considerations for cost:

● Materials being used ● Metal with a low specific heat ● Very insulated plastic for barrel ● Insulated cover/cap to dissipate heat from tip ● Manufacturing processes ● Injection molding ● Metal fabrication ● Milling/turning ● Electronic components ● Assembly line

Fig. 17. Graph of relationship between hand force necessary to extrude 1 inch of glue (in kg) and overall qualitative market response

Fig. 18. Graph of the relationship between manufacturing cost (in overall magnitude compared to our benchmark) and time to cool (in mins)

Chapter 8 Building the Engineering Model

8.2 Mathematical Model of Key Functions

Table 1. Our theoretical model shown above illustrates an idealistic model using assumptions for certain variables and parameters. We used Solver to determine correct values for the maximum temperature reached and the cool down time, given assumed values for the room temperature and final cool-down temp of the hot glue gun.

8.3 Identifying the Model’s Objective Function Model Madlib “For the Precision Gluer’s customer, it would be best to minimize the cool-down time to less than 5 minutes, in order to improve safety and be able to pack up the glue gun quickly after finishing a project.” Objectives Minimize energy used to heat up aluminum/glue to minimize cool down time Constraints Specific Heat of Glue, Specific Heat of Aluminum, Initial Temperature, Mass of Aluminum, Radius of Hole, Melting Point of Glue, Surface Area of Heating, Element Contact, Material Cooling Constant, Peak Precision Parameters Electrical Power, Time to Heat, Peak Viscoelasticity, Precision, Human Force Variables Human Force, Max Temperature Formal Optimization Statement Our goal is to minimize the amount of time required to cool down the hot glue gun to a temperature that is reasonable to both handle and pack the glue gun away. Originally we aimed to minimize the energy used to heat up the glue gun in order to reduce the time required for the glue gun to cool down, but realized that the Newton Cooling Constant, k, is dependent on final and initial temperatures, and is a property of the material itself. In order to reduce the cool-down time we focused more on the glue gun’s material properties, i.e. the aluminum cooling constant vs. other metals, rather than the power input. Our ultimate goal is to minimize the glue gun cool down time to under 20 minutes without sacrificing the maximum temperature reachable, as this determines the heated glue’s viscosity and ultimately the precision of the hot glue gun application.

8.4 Optimization Using Solver

Table 2. Our theoretical model with values calculated via Solver in Excel. We were able to calculate values for the maximum temperature reached and the cooling time.

8.5 Model Manipulation Looking at our information and playing around with it, one of the key things that we learned is that looking at the heat transfer as a parameter can really change the values that we were trying to optimize. Originally, we had assumed that heat transfer was close to 100% as we assumed most of the heat would go directly from the aluminum to the glue. Then as seen in our testing, the glue and the aluminum have different temperatures and we calculated with different ∆Ts that it was roughly 80%. While playing around with that number, we realized that if we can get that transfer to be more efficient, then it will greatly reduce heating and cooling times. We also played with changing the size of the nozzle and surface area and its effects on how long it took the glue gun to cool down, given the more surface area, although we did end up putting them as constants since we were not trying to optimize the tip in our design process.

Chapter 9 Moving from Theoretical to Empirical 9.1 Experimental Prototype Scoping As we moved from our theoretical model to our empirical model, we incorporated certain changes that allowed us to more accurately model the hot glue gun in accordance with our real-world observations. Our original objective in creating the theoretical model was to reduce the amount of time it takes for the hot glue gun to cool down to a certain allowable “cooled-down” temperature, T(t) (see Appendix 1 for nomenclature explanations). In doing so, it was important that we test or hold constant certain equations, variables, and assumptions from our theoretical model to create a more robust and accurate empirical model. We decided to input real values from our tests for the maximum temperature reached by the glue gun, as well as a real-world value for the cool down time (45 minutes). These parameters allowed us to calculate a realistic value for k, Newton’s cooling constant – given that we had already determined reasonable values for the room temperature and the temperature at which we deemed the hot glue gun “cool”. We will focus on two main variables from our theoretical model in our experimental prototype, in order to optimize the cool down time. These variables were taken from our list of customer requirements, and are the temperature at different parts of the hot glue gun (the tip, middle, and back of the gun as well as the glue temperature), and the time that each component took to reach its maximum temperature. We also tested the time it took for each component to reach a cool-down temperature of 27ºC. Our experimental prototype will test the relationship between the component material/location and its heat up/cool down time.

9.2 Mock Testing Results In preparation for building a strong empirical engineering model of our modified hot glue gun, we ran a few mock tests to understand the relationship between the heat up/cool down time of various components and their temperatures over time. By heating up a real, disassembled hot glue gun, we measured the temperature of the tip, middle, back, and the glue itself every 30 seconds for approx. 45 minutes. The results of this mock test are shown below as both a plot over time and a table of the raw data. This mock test allowed us to identify a few important parameters that we could then hold constant in our empirical model: cool-down time, room temperature, and maximum temperature achieved by the hot glue gun heating element.

Figure 1. A plot of the heating rate of the hot glue gun heating mechanism, split by component type/location. This graph shows the relationship between the time it took a component to heat up and its ultimate temperature.

Time (s)

Temperature (℃)

Tip

Middle

Back

Glue

22.3

25.7

24.7

23.5

22.4

27.3

25.6

22.3

31.4

22.3

30.5

40.87

32.6

22.6

32.2

39.3

32.7

22.6

35.7

45.2

32.9

22.8

37.9

47.1

105

22.6

40.4

50.2

120

23.1

38.2

53.1

135

23.1

60.6

50.8

150

23.4

45.3

60.5

165

43.9

180

23.3

48.4

67.7

195

51.3

210

23.5

225

24.9

65.8

240

25.1

67.5

255

25.3

55.6

270

24.5

53.2

70.6

Table 3. A table illustrating the raw data from our mock prototype testing. This prototype allowed us to determine the max cool-down time and reasonable maximum temperatures.

9.3 Empirical Engineering Model

Table 4. Our empirical model prior to optimization via solver. The difference between this table and that of our theoretical model was that this table incorporated values for heating up/cool down time and maximum temperature determined via our mock prototype testing.

9.4 Empirical Model Optimization using Solver

Table 5. This table shows the optimization via Solver of our empirical engineering model. This table illustrates the time to cool down as a function of the k (material cooling constant) and the maximum temperature of the hot glue gun.

Chapter 10 Two Cardboard Prototypes 10.1 Rough and Useless Form Prototype

Figure 2: The pen design shown above fits

Figure 3: Pressing down the button at your

perfectly into the hands of the user, with the

pointer finger easily dispenses glue,

button to dispense glue conveniently at your

decreasing the amount of force from pulling

pointer finger.

a trigger.

Figure 4: The pen design measures 17 cm in

Figure 5: The cap at the end comes off and

length. It can fit up to 13 cm of glue in the

can be placed over the hot tip to collect

chamber. The blue light at the top signals to

excess glue and prevent injuries from

the user that the pen is cool enough to

touching the hot metal.

touch. When the pen is hot, the light will turn red.

Our aim with this form prototype was to communicate four key design features. The first is the overall pen-like shape designed for precision and ergonomics, as well as

decreasing wasted space. The second key design feature was the trigger mechanism. The form prototype allows us to observe with different users the comfortable range of motion of the active fingers in this position. The third key design feature represented in our form prototype is the temperature indicator at the back of the device which shines blue when safe to touch, and red when hot. Not only does this allow for a safer way of knowing when the device is ready to use, it also allows user to begin use as soon as it is ready as opposed to guessing. This feature is represented by a blue strip at this point, but allows us to observe the visibility at its current location within the design. The final key feature is the cap which rests at the distal end of the device when the glue pen is in use, and covers the hot tip during cool down and storage. This allows for a decrease in time spent waiting for cool down and storage as it enables earlier storage.

10.2 Rough and Useless Experimental Prototype

Figure 6: This design is our new idea for

Figure 7: The new heating chamber is

the heating mechanism. A smaller piece

placed at the tip of pen, below the

of metal both heats and slows quicker

button, preventing the user from

and can also melt the same volume of

touching the warm casing of the pen.

glue. The coils run along the walls of the chamber, hence evenly heating the glue from all sides. Our experimental prototype capitalizes on the experimentally supported assumption that the heat transfer from the aluminum heating element to the glue is highly efficient. This showed that the heating element size could be decreased, decreasing heat up and cool down time, while also improving space efficiency. Our new heating element design is approximately half the length of the currently 83.5 mm heating mechanism, reducing it down to 45 mm, with heating could surrounding it. Figure 6 demonstrates its approximate location within the device, which would be just below (in the proximal direction) where external hand placement is intended. The inner volume of the new heating mechanism allows for the volume of a full glue stick to be stored within it (represented in figure 7) but it’s decreased size aims to optimize safety and efficiency of space and time. Note it is modeled slightly larger than actual intended size (approximately 1.4x) to enable the inclusion of the inner details we explored, but in practice is sized to rest inside the plastic body represented in figures 2-5.

Chapter 11 Experimental Prototype Design Plans 11.1 Testing Plan Our goal is to find combinations of Vpaper and Fhand that create ideal diameters of glue streams.

Pretest 1. Attach paper to fishing reel mechanism.

2. Attach Heating Mechanism so that it is face down in the middle of the vice leaving a little bit of room between the paper and the tip. *new 3. Plug in heating mechanism. 4. Place force gauge to end of glue stick. 5. Once heating mechanism/tip are hot, push glue through at a constant force while pulling paper in a straight line at a constant velocity. 6. Visually inspect either necking, build up, or an ideal diameter. 7. Repeat for multiple combinations of Vpaper and Fhand

Velocity of the Paper Pull (Vpaper)

Force of Glue Pushed into Heating Element (Fhand)

F1V1

F1V2

F1V3

F2V1

F2V2

F2V3

F3V1

F3V2

F3V3

Table 1: Green cells indicate which force/velocity pairs we will test in our preliminary test

Experimental Prototype 1. Attach our motorized constant force mechanism. 2. Conduct same process with our mechanism at different constant velocities. The speeds of the motor at which we get ideal diameters will tell us what speeds conduct what force because we already know which Fglues match specific Vhands.

11.2:

Drawings

Figure 1: Full assembly of Lego worm gear box

Figure 2: Engineering drawing of gear for worm gear mechanism

Figure 3: Engineering drawing for lego axle

Â Figure 4: Engineering drawing for Lego worm for the worm gear mechanismÂ

Â Figure 5: Engineering drawing of lego box that encloses the worm gear mechanismÂ

Â Figure 6: Engineering drawing of second Lego axle for worm gear mechanismÂ

Figure 7: Engineering drawing for glue stick. Knoches are .15in which align with the tooth thickness of the gear.

11.3 Bill of Materials

Table 1: Bill of Materials: raw and purchased materials, and parts reclaimed, donated, fabricated and purchased.

11.4 Fabrication Plan Step 1: 3D Print Mold Tools Required: 3D Printer Time Required: 3 Hours (Do it overnight) Materials Required: PLA Part Numbers: n/a, 3D printer. No parts used yet. Person Responsible: Delaney We will create a CAD model of a two-part mold to prepare for our modified glue stick molding process. This mold will be cylindrical with a rack pattern on one side. Teeth holes need to be within tolerance because incorrect tolerances will lead to an incorrect final assembly. Step 2: Mold Glue Stick Tools Required: Hot Glue Gun, Mold

Time Required: 1 Hour Materials Required: Glue Stick, Heating Element, Non-Stick Powder Part Numbers: 6 Person Responsible: McKinley Melt hot glue down in a bowl in a microwave. Apply non-stick powder in the mold. Pour fluid glue into the mold. Close mold. Wait until glue dries and then remove mold. Step 3: Assemble Constant Force Mechanism Tools Required: N/A (Hands) Time Required: 15 mins Materials Required: Lego Worm Screw Gears, Motor Part Numbers: 1-6 Person Responsible: Matt Attach motor to worm gear mechanism. Step 4: Align Propelling Mechanism with Heating Mechanism and Attach to a Stand Above Paper Tools Required: Vise Grip Time Required: 5 minutes Materials Required: Heating Mechanism, Glue Stick, Worm Screw Mechanism Part Numbers: 1-3 Person Responsible: Harry Secure the glue gun within the vise grip.

Chapter 12 Create a Manufacturing Cost Model for Your Final Design

Fig. 1. Drawings of Final Design of the Glue Gun, showing the interior mechanism used to advance and extrude glue

12.1 Manufacturing Cost Model

Table 1. Manufacturing Model of our Glue Pen final design

Increasing the functionality would cause the cost of the pen to go up due to an increase in volume of plastic from injection molding. Also, to improve functionality we would have to install a worm gear mechanism which also adds cost.

12.2 Fixed Cost Model and Business Approach Our product will be available both in stores and online. The main stores we will be targeting include craft stores and large retail stores like Target and Walmart. Through selling in stores, we hope for customers to see the Glue Pen next to the old fashioned Glue Gun and see first hand how it will be better than what they are used to. Our big fixed costs for us at the beginning of our company is advertising and R&D. The Glue Pen is the first of its kind and we need to spread the word about our innovative product. We will buy ads in local craft stores, create online ads that are directed at parents with young kids in school, and send our sales reps to talk to demonstrate our product at stores across the

country. We believe that the best way for our product to explode is to have people see it with their own eyes and be able to feel it in their hand. R&D is a huge part of our company in our beginning years. We are developing a new product that is unlike any other. We need to create injection molds which have a large overhead cost, but once they are made can produce thousands (hopefully millions) of parts for us. We hope that the R&D team will find ways to make our pen design not only better for the user, but also cheaper to make in the coming years. As far as salaries go, for the first year, the 5 of us will only take in a very small salary. We plan to put our own money into the company for the first year or two to get the ball rolling and once we start profiting more and more, we will increase our salaries.

12.3 Error and Uncertainty The biggest uncertainty for us is the assembly portion of the product. We love our design but we think that when manufactured at a large scale, assembly time may become an issue and cost us more than we thought. In our cost estimates, we allocated a large portion of money towards R&D, which we hope can develop an assembly method for our manufacturing process. What our group can do between now and then is put some of the assembly process into the users hands. For example, maybe the user opens the package to three parts (motor, body, heating element) and there is a simple 3-step process on how to attach it. There are many products on the market that have the user assembly them (i.e. vacuum, kids toys, etc.

12.4 Linking Manufacturing Model and Engineering Model

Table 2. Glue Gun Engineering Model, edited to reflect changes made to our engineering/customer objectives from the previous design pivot

Chapter 13 Potential Market Size and Growth Trajectory 13.1 Total Potential Size of the U.S. Market We were unable to find data using Passport and Euromonitor for hot melt adhesives, Surebonder, and rival companies such as Black and Decker and 3M. Therefore, we chose to estimate the size of the hot melt adhesive market (including hot glue guns and related products) by first consulting Statista to determine quantitative values for the crafting market. To determine who the actual market for our glue pen would be, we employed a top-down approach to market sizing. Our estimate proceeds as follows:

Market 1: Population of the U.S. [3] Source: United States Census Bureau, 2018 Reasoning: The largest American market we could capture within the constraints of this assignment was the entire population of the U.S. We used this value as a benchmark for the rest of our calculations. Value: 327,167,434 Market 2: Population of U.S. between 18 and 64 [3] Source: United States Census Bureau, 2018 Reasoning: The changes made for our hot glue pen vs a traditional hot glue gun are changes targeted towards the adult age range, focusing more on the precision and accuracy of glue application than child safety features, for example. Value: 55.7% of the total US pop. = 182,232,260 people Market 3: Percent of US adults who self-reported crafting/sewing in 2018 [ 1] Source: Statista Survey

Reasoning: Our hot glue pen is intended to be used in hobby and crafting situations – thus, we chose to single-out the percentage of the US adult population who self-reported crafting or sewing in 2018. Value: 45.26% of the US adult population = 82,478,320

Fig. 2. Statista data on percent of Americans who sew/craft, broken down by age

Market 4: Adults who craft/sew for specific reasons (kid’s crafts, paper crafts, decor) Source: Statista Survey Reasoning: Of the subset of US adults who craft, it’s important to narrow down the type of crafting being done. We determined that kid’s crafts, paper crafts, and home decor were the three major subsets of crafting that employed hot glue guns the most.

Value: Avg. percentage of crafters in these 3 categories: 29% = 23,918,713 people

Fig. 3. Statista survey data illustrating the breakdown of craft types done by crafting adults in the US

Our final estimate of the total hot glue gun market size was 23,918,713 individuals. However, it is unlikely that our product would be able to capture a market this large. To create a more conservative market size estimate, we formulated a penetration rate of 55% – targeting the 25% of the market immediately above age 18 and the 30% of the market immediately below age 64. This gives us an overall market estimate of 13,155,292 people.

13.2 Assumptions In creating the spreadsheet of our Marketing Model, we made a few important assumptions: ● Our total market size was the percentage of the US population between the ages of 18 and 65 who reported that they craft/sew, in particular those who engage in Kid’s Crafts, Paper Crafts, or Household Crafts. ● We estimated that the most important attribute configurations (pulled from our Engineering Model) were extrusion rate (in cm/sec), handle diameter (in cm), and price (in USD) ● The proportion of consumers that would buy the Glue Pen at an ideal extrusion rate of 1.27 cm/sec has a value of 0.05 ● The proportion of consumers that would buy the Glue Pen at a conservative price of $15 has a value of 0.05 ● We adjusted the choice share by incorporating the proportion captured/lost per 1 sec added to the glue extrusion rate ● We also adjusted the choice share by incorporating the proportion captured with a price increase/decrease from $15 13.3: Projected 5 Year Growth To determine our projected 5 year growth, we started with a baseline of our estimated market size of 13,155,292 people. Over the course of the following 5 years, this number should fluctuate depending on a number of factors – in particular, the current growth/decline rate of the hot melt adhesive market. We consulted Stanford SearchWorks to determine this growth rate, which was estimated at 6% annually between 2017 and 2024. Given that this growth rate is over a longer time frame than our 5 year timeframe, we chose a 5% annual growth rate. According to the report, global demand for hot melt adhesives was valued at approximately USD 6 billion in 2014 and is expected to generate revenue of USD 7.5 billion in 2020, expanding at a CAGR of around 6% between 2015 and 2020. In terms of volume, the global hot melt adhesives market stood at around 1,500 kilo tons in 2014

13.4 Linking Marketing Model and Engineering Variable

Table 3. Marketing Model of our Glue Pen assuming market size increases by 150%/year resulting in a $23.9 million market size in year 5

Chapter 14 Building a Profit/Loss Model for the Glue Pen 14.5 Investigate Profitability Yearly Profits: 1 - $5,179,034 2 - $8,042,744 3 - $12,336,616 4 - $18,697,423 5 - $28,133,635 Sum NPV Yearly Profits: $63,809,963 Assumptions that make an impact on this projected profit: ● the market size and capture rate of the most relevant portion of the market ● the proportion of customers that would purchase the Glue Pen based on the weighted constraints placed on the final product ● a profit margin of approx. $6/unit Our NPV Yearly Profits were surprisingly high, which we believe to be most heavily dependent on the market size estimation we made at the beginning of this section. If we had determined a more conservative estimate for the market size, while maintaining a stable profit margin and units sold, our Sum NPV Yearly Profits would likely have been much more reasonable (within the range of a few dozen million USD). Our profit model is as follows:

Table 4: Profitability Model

Chapter 15 Consumer Survey Design 15.1 Link to Survey (Appendix 1) https://bit.ly/2ERej5f To design this survey, we chose questions that we felt would most accurately reflect the attributes of our product that were critical to its market success. These were chosen from our engineering model, and the wording was altered to make the phrasing easier to understand. We chose to include questions that assessed the user’s demographics, glue gun use frequency, and preferred glue gun attributes. We decided to make each CBC question have four levels rather than three – the speeds at which glue was extruded were nuanced enough that three levels weren’t able to fully capture the range of speeds. After sending out the survey prior to publishing, we sent our survey to a few close friends and asked them to edit wording to make the questions easy to understand for those who are unfamiliar with the terminology we used.

Chapter 16 Fabrication Document 16.1 Fabrication Plan

Step 1: 3D Print Mold Tools Required: 3D Printer Time Required: 3 Hours (Do it overnight) Materials Required: PLA Part Numbers: Person Responsible: Delaney We will create a CAD model of a two-part mold to prepare for our modified glue stick molding process. This mold will be cylindrical with a rack pattern on one side. Teeth holes need to be within tolerance because incorrect tolerances will lead to an incorrect final assembly. Step 2: Mold Glue Stick Tools Required: Hot Glue Gun, Mold Time Required: 1 Hour Materials Required: Glue Stick, Heating Element, Non-Stick Powder Part Numbers: 6, 7 Person Responsible: McKinley Melt hot glue down in a bowl in a microwave. Apply non-stick powder in the mold. Pour fluid glue into the mold. Close mold. Wait until glue dries and then remove mold. Step 3: Assemble Constant Force Mechanism

Tools Required: N/A (Hands) Time Required: 15 mins Materials Required: Lego Worm Screw Gears, Motor Part Numbers: 1-5,9 Person Responsible: Matt Attach motor to worm gear mechanism. Step 4: Align Propelling Mechanism with Heating Mechanism and Attach to a Stand Above Paper Tools Required: Vise Grip Time Required: 5 minutes Materials Required: Heating Mechanism, Glue Stick, Worm Screw Mechanism Part Numbers: 1-7 Person Responsible: Harry Secure the glue gun within the vise grip

16.1 Updated Engineering Drawings

Figure 2: Full assembly of Lego worm gear box

Figure 3: Engineering drawing of gear for worm gear mechanism

Figure 4: Engineering drawing for lego axle

Figure 5: Engineering drawing for Lego worm for the worm gear mechanism

Figure 6: Engineering drawing of lego box that encloses the worm gear mechanism

Figure 7: Engineering drawing of second Lego axle for worm gear mechanism

Figure 8: Engineering drawing for glue stick. Knoches are .15in which align with the tooth thickness of the gear.

Table 1. Bill of Materials did not change from Assignment 7.

16.2 Learning Process

While building the prototype, we learned a lot about the planning of each step. While our process was fairly straight forward, typing up a fabrication plan helped us efficiently test our mechanism. Creating the mold was a tricky step that we didn’t think would take as long as it did. But once we got the design all drawn up in CAD, it was quite straight forward 3D printing it and pouring in the liquid glue. Now once we have the mold for future tests, we can focus our time and energy on the glue pen itself.

Chapter 17 Test Reporting 17.1 Testing Documentation

Revised Testing Plan Our goal is to find combinations of Vpaper and Fhand that create ideal diameters of glue streams Pretest 1. Attach paper to fishing reel mechanism.

2. Attach Heating Mechanism so that it is face down in the middle of the vice leaving a little bit of room between the paper and the tip. (NEW) 3. Plug in heating mechanism. 4. Place force gauge to end of glue stick. 5. Once heating mechanism/tip are hot, push glue through at a constant force while pulling paper in a straight line at a constant velocity. 6. Visually inspect either necking, build up, or an ideal diameter. 7. Repeat for multiple combinations of Vpaper and Fhand

Velocity of the Paper Pull (Vpaper)

Force of Glue Pushed into Heating Element (Fhand)

F1V1

F1V2

F1V3

F2V1

F2V2

F2V3

F3V1

F3V2

F3V3

Table 2: Green cells indicate which force/velocity pairs we will test in our preliminary test

Experimental Prototype 1. Attach our motorized constant force mechanism to the lego scaffolding (NEW). 2. Conduct same process with our mechanism at different constant velocities

based on different voltages fed to the motor (NEW). The speeds of the motor at which we get ideal diameters will tell us what speeds conduct what force because we already know which Fglues match specific Vhands.

Link to Video of Prototype in Action https://drive.google.com/a/stanford.edu/file/d/1aKTGQGWdhBJUktfuF1sVkOOEG_cDpWNv/ view?usp=sharing

17.2 Analysis of Testing Results

Fig 1. Results of the pull test

Fig. 2 Visual representation looking at speed vs force vs extrusion.

Measure Error significantly affected our testing results. As you can see from our video, our mechanism that pulled the paper at a constant velocity was turned by hand which automatically instills human error. Also, our judgment of ideal vs. build up vs. necking was completely based on the consistency of the diameter. This measurement was done visually because it was pretty easy to tell the difference between the different results however that is another place for human error. We created equations in our empirical model to calculate at what speed is the optimal speed for glue extrusion.

Chapter 18 Engineering Model Update and Final Design Update 18.1 Engineering Model Update

18.2 Proposed Design Revisions As soon as we started testing we realized that the velocity of the paper needed to be on the slower side to get better results for perfect diameters. However, once we put 20+ lbs of force we saw that there was more buildup happening aka we could’ve

increased the velocity of the paper (which when implemented is the velocity of our glue pen). Our goal for the future is to get the ideal amount of force so that the user can move the glue pen faster. We could either design to have a hotter heating mechanism so that less force is required to push the glue through or we could alter our manufacturing process for our glue molding to allow more precise meshing of gears to glue stick.

Chapter 19 Survey Data Analysis 19.1 Publish Survey and Collect Data To spread the word, we each are going to email our dorm email lists. Harry is going to send the link to the whole football team and ask to spread it amongst their friends. Our published survey is available online via: bit.ly/2ERej5f

19.2 Analysis of Survey Results 19.2.1 Analysis of non-CBC data Our published survey contained eight non-CBC questions, which provided us with valuable feedback on the frequency users used hot glue guns, their preferred improvements to the existing functionality, and their interest in an automated glue pen design. Given that our glue pen design was somewhat finalized in terms of functionality, we decided that only the most critical questions and responses would be analyzed in this section. This will allow us to more clearly draw connections between the recorded responses and our final glue pen design decisions. Our questions were as follows: Q1: How old are you? This was a screening question, and allowed us to collect demographic information on our respondents. Due to the nature of our campus and friend/family circles, we gathered responses from mostly college-aged students. Q2: How often do you use a hot glue gun?

This question assumed that the user had used a hot glue gun, and if we were to recreate this survey we would add a screening question to determine whether the respondent had frequent experience using a hot glue gun before the survey began. “How often do you use a hot glue gun?” 1 – Once a year -> 5 – Daily

Fig. 1. Responses to the question regarding the frequency with which respondents used a hot glue gun. The large percentage of respondents who stated that they hadn’t used a glue gun more frequently than once per year was surprising, and showed us that we should target more niche user groups if we were to re-run this survey. Q3: What do you normally use a hot glue gun for?

The range of applications for hot glue guns was large and the responses disparate, meaning that our audience wasn’t targeted for just one form factor of hot glue gun design.

Fig. 3. Survey responses showing the most common use cases for hot glue guns among our respondents.

Given that a majority of our respondents were college students, it makes sense that the category “School Project” would be the most common use case, followed closely by crafting. We then asked a few questions about the ease of use of a hot glue gun, from the extrusion rate to the force required to pull the trigger. Q4: Compared to regular liquid glue, hot glue is ____? This question assessed the desirability of hot glue over regular glue, however, it didn’t address the reasons behind why someone might choose hot glue over regular liquid glue and vice versa. The breakdown of responses told us little to nothing, since responses were about 30% for each of the three responses (easier to use, the same, or harder to use than regular liquid glue). Q5: What aspect of hot gluing would you most like to get rid of?

Table 1. Responses to the question of which aspect of hot gluing respondents would most like to get rid of.

1 - Globbing of Glue 2 - Stringing/Necking of Glue 3 - Hand force required 4 - Time to heat up 5 - Lack of precision 6 - Price From this table, it is clear that the time to heat up is a pain point for respondents, followed closely by stringing/necking of glue and globbing. It would have been useful to have these survey results at the beginning of our design process – to guide us towards a glue pen design that would optimize the heat up/cool down time as well as the diameter of the glue extruded. Q6: Rate the following statement on a scale of 1 to 7: “Using a hot glue gun hurts my hand” About 27% of respondents (the largest percentage) responded that using a hot glue gun significantly disagreed (6 out of 7) that using a hot glue gun hurt their hand. This was a surprising data point, as it showed us that the pain of using a hot glue gun was not a concern for most infrequent users. However, if we were to re-do this survey with frequent users of hot glue guns, it’s likely that this would change from strongly disagree to moderately or strongly agree (based on our prior user research).

100

Our other two questions were shown at the end of the survey, and asked respondents about their interest in a glue gun that automatically dispensed glue at a constant rate, and whether they wanted to share any memories of using hot glue guns. There was a generally positive response, although we were also able to gauge changes to the design that we wouldn’t have otherwise known without asking respondents directly in an open-ended style. Responses to this question included:

“I think that would be so helpful! I hate getting hand cramps from the

trigger thing”

“I think the manual control is essential for some applications but the automatic is nice for many others”

“I would have to modify how I used it, as I do like how you can use

moderation with a trigger. If you could control how much glue came out with an automatic button, I would like that, as the trigger does hurt to keep

pushing on.”

“I feel like I want the mechanical feel of the manual trigger because I think it would give me more control over the glue.”

“I might need different speeds for different things.”

Overall, it seemed as though our respondents ranged from mildly interested to apathetic about hot gluing in general, which may have been a function of the niche group of respondents we reached out to. Less than 50% of users used a glue gun more frequently than once per year. Of those users, there is a focus on the reliability of the glue extrusion and the heat up/cool down time of the glue gun. It was encouraging to see an interest in reducing the uncontrollable extrusion rate, as that feature has been our main focus for the glue pen design.

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19.2.2. Analysis of Choice-Based Conjoint Data Attribute #1: Speed of Gluing

Table 2. Utility and part-worth of Attribute #1, Gluing Speed. The trendline for this attribute was quadratic.

Attribute #2: Handle Diameter

Table 3. Utility and part-worth of handle diameter, which was Attribute #2. The trendline for this attribute was quadratic.

Attribute #3: Glue Stick Refill Time

Table 4. The overall utility among each option for Attribute #3, glue stick refill time. The trendline for this attribute was polynomial.

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Attribute #4: Price

Table 5. The utility and part-worth of glue pen price, which was Attribute #4. The trendline for this attribute was polynomial.

19.3 Incorporating Utilities into Marketing Model

Table 6. Overall screenshot of our marketing model given the attributes from our CBC questions. Shown are the utilities of each attribute choice, as well as the part-worth values for each attribute.

Part worth for each attribute: Attribute 1 (Glue Speed) – 0.32 … Quadratic trendline Attribute 2 (Handle Diameter) – 0.13 … Quadratic trendline Attribute 3 (Glue Refill Time) – 0.83 … Polynomial trendline Attribute 4 (Price) – $1.91 … Polynomial Trendline

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It is clear that the most important attribute is price, which comes as no surprise to us. The surprising part comes that glue refill time is more important than the glue speed. It then started to make more sense as our open ended question answers included opinions that a very annoying part of using a glue gun is refilling the glue stick. In the future, knowing this, we may want to spend more time thinking about how to maximize that time with longer glue sticks or sacrificing glue speed. Also, it was surprising that the least important aspect of the product is the handle diameter. In actuality, this would really affect the user’s ability to glue and be comfortable, but I think that doing the online survey without the physical item in front of them biased people against weighting it because it is hard to visualize. The total utility and choice share for each attribute is shown in the table above, which we used to optimize the overall utility of our design configuration. Of the attributes’ options, the highest utility among each were as follows: 1.5 cm/s gluing speed 2.5 in handle diameter 30 min refill time $11 price

Table 7: Marketing Model Product Utility and Choice Share Calculations

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Chapter 20 Linked Model Optimization 20.1 Overall Design Optimization

Table 8. Overall design optimization, shown here with Solver

While trying to work solver, we realized that we wanted to maximize profit. Therefore, we created a side variable on this page so that we could use solver effectively, and got the profit from the choice share*total size when multiplied by the price-cost. This actually gave us an interesting finding where the most profitable price for our product was much higher than we originally thought at $49.85, but that obviously came with the drawback of having only 62% of the market share. In order to get these numbers we decided on reasonable ranges for the other variables to lie between. The number of units sold obviously went down, but the bump in price made the profit larger.

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20.2 Competitor Design Optimization

Table 9: Solver Design Optimization with Competitor

When we made this competitor it took 15% of our market share. While using the same constraints as before, we tried to optimize our product. What we realized was that our product must have been already optimized to its full extent because the values did not change. We also think it is because we made our competitor fairly reasonable, in the sense that if we had made our competitor extremely cheap or extra large etc. it might have changed our data in weird ways. Still, even though our price is high, we still have the largest profit (our profit now being calculated from the percent of market share we have with the competition accounted for).

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20.1 and 20.2 UPDATED SOLVERS

Table 10: Updated Solver

Our solvers for 20.1 and 20.2 were done on the wrong sheet but with the correct data, giving us the same answer that this solver gave after working with the TAs. This solver still came out to an ideal price of $49.85, but our team decided to put a limit on the product at $30.00, keeping that as the constraint for price as shown above. This keeps 82% of the market share, and 35% with a competitor which seems much more reasonable than 56% alone and 14% with a competitor.

20.3 Ultimate Redesign We ultimately chose to go with the product configuration that arose from our original optimization sans-competitor. The attributes of this design are as follows: Optimal Glue Pen Attributes: Price - $49.85 Handle Diameter - 2.48” Refill rate - 42 min Extrusion rate - 1.764 cm/s

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We chose this design because of its dominance in the market despite reasonable values for each attribute, and because of its strength against competitors. The only attribute that is out of the ordinary in this design configuration is the price, which was not within the range of our CBC attribute choices. With this product we would sacrifice our market share for making a larger profit, which we believe is a reasonable decision that lots of companies are faced with. In this case, we would rather go with a maximized profit than having a larger market share. We also realize since the price was out of scope, we do not know how accurate the market share calculation would be at extrapolating from the data we have. We would have to do more surveys to understand if our choice is reasonable.

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Appendix 1 Nomenclature Explanations Symbol

Description

Units

Max Temperature

˚C

T(t)

Final cool-down temp

˚C

Cool-down time

sec

Electrical Power

J/sec

Heat-up time

sec

Initial room temperature

˚C

Precision

F-Human

Human Force

SpH

Specific heat of Ethylene-vinyl acetate

J/kg˚C

SpAl

Specific heat of Aluminum

J/kg˚C

Initial room temperature

˚C

mAl

Mass of aluminum

Radius of hole

Melting Point of Glue

˚C

Cooling Constant of Aluminum

Material cooling constant

˚C/min

VGl

Volume of glue heated

cm^3

DGl

Density of Glue

kg/cm^3

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Heat Transfer

Peak Precision

QAl

Heat Aluminum

mGl

Mass of Glue Heated

QGl

Heat Glue

∆T

Change in Temp Glue

˚C

Surface Area of Tip

cm^2

∆t

Time to Cool

Min

LoT

Length of Tip

ORoT

Outer Radius of Tip

SLoT

Slant of Tip

A.1 Customer Survey Question 1 How old are you? a. Under 12 b. 12-18 c. 18-25 d. 25-45 e. 45-60 f.

60 and older

Question 2 How often do you use a hot glue gun:

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Once per year

Every other week

5 Daily

Question 3 What would you normally use a hot glue gun for? a. Crafting b. School Project c. Home Improvements d. Fixing broken objects e. Other: ____________ Question 4 Compared to regular liquid glue, hot glue is _____. a. Easier to use b. Harder to use c. Just as easy to use Question 5 What aspect of using a hot glue gun would you most like to get rid of? Please assign 100 Points among the following: ___ Globbing of the glue (pic) ___ Stringing/necking of the glue (pic) ___ Hand force required ___ Time to heat up ___ Lack of precision ___ Price

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Question 6 Rate the following statement on a scale from 1 to 7: 1 = Strongly Disagree

7 = Strongly Agree

It hurts my hand to use a glue gun. 1

Question 7 CBC Question Question 8 CBC Question Question 9 CBC Question Question 10 How would you feel if a glue gun had an automatic button rather than a trigger to push out the glue? Question 11 Do you have any memories associated with using a hot glue gun? CBC: Choice-Based Conjoint Questions (to understand the relative importance of diff factors for the hot glue pen) Engineering Model Factors: ●

Velocity of Glue Extrusion

●

Handle Diameter of Glue Pen

●

Price

●

How often glue needs to be replaced

“If these were your only options, which would you choose?” (example 1 of 9) 1. Choice 1 a. Velocity of Glue Extrusion i.

2 cm/s

b. Handle Diameter i.

2.5 cm

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c. How often glue needs to be replaced i.

Every 15 mins

d. Price i.

$20

2. Choice 2 a. Velocity of Glue Extrusion i.

1 cm/s

b. Handle Diameter i.

2 cm

c. How often glue needs to be replaced i.

Every 10 mins

d. Price i.

$15

3. Choice 3 a. Velocity of Glue Extrusion i.

1 cm/s

b. Handle Diameter i.

2.5 cm

c. How often glue needs to be replaced i.

Every 30 mins

d. Price i.

$15

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Fig. 1. Sample CBC in Sawtooth Discover, showing the various choice combinations for our Glue Pen’s attributes

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Bibliography 1. Crafts and hobbies: U.S. participation in the last year 2016 | Statistic. (n.d.). Retrieved from https://www.statista.com/statistics/694416/crafts-and-hobbies-us-participation-in -the-last-year/ 2. Share of sewers/craftsmen in the U.S. by age 2018 | Statistic. (n.d.). Retrieved from https://www.statista.com/statistics/227426/number-of-sewing-worker-and-crafts man-usa/ 3. US Census Bureau. (2018, December 20). 2018 National and State Population Estimates. Retrieved from https://www.census.gov/newsroom/press-kits/2018/pop-estimates-national-state .html

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