meng 491w senior design project - university of san...

MENG 491W Senior Design Project

Silverware WrapperA Proposal Submitted by:

Alex Moskos, Jarrod Pitts, Mike Spillner, John Tinsley

MENG 491W Silverware Wrapper Fall 2008

ContentsList of Figures...............................................................................................................................................5

List of Tables................................................................................................................................................5

1. Context....................................................................................................................................................6

1.1. Background.......................................................................................................................................6

1.2. Customer Need Statement...............................................................................................................7

1.3. Literature Review.............................................................................................................................7

1.3.1. Prior Work.................................................................................................................................7

1.3.2. Patents.......................................................................................................................................8

1.3.3. Codes and Standards.................................................................................................................8

2. Problem Definition..................................................................................................................................9

2.1. Customer Requirements...................................................................................................................9

2.1.1. Form..........................................................................................................................................9

2.1.1. Fit...............................................................................................................................................9

2.1.2. Function.....................................................................................................................................9

2.2. Assumptions.....................................................................................................................................9

2.3. Constraints......................................................................................................................................10

2.4. Customer Requirements Schematic................................................................................................10

2.5. Test/Evaluation Plan for all Requirements and Constraints............................................................10

3. Concept Development...........................................................................................................................11

3.1. Overview.........................................................................................................................................11

3.1.1. Creative Strategies...................................................................................................................11

3.1.2. Governing Principles................................................................................................................12

3.2. Synthesis and Analysis of Overall Concept......................................................................................12

3.2.1. Overall Concept 1....................................................................................................................12

3.2.2. Overall Concept 2....................................................................................................................12

3.2.3. Overall Concept 3....................................................................................................................13

3.2.4. Overall Concept 4....................................................................................................................14

3.2.5. Overall Concept 5....................................................................................................................14

3.2.6. Overall Concept 6....................................................................................................................15

3.3. Evaluation.......................................................................................................................................15

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3.3.1. Platform Analysis.....................................................................................................................16

3.3.2. Vacuum Analysis......................................................................................................................16

3.3.3. Electromagnet Analysis............................................................................................................16

3.3.4. Cable and Pulley Analysis.........................................................................................................16

3.3.5. Linear Actuator Analysis..........................................................................................................17

3.3.6. Spring Hinges Analysis.............................................................................................................17

3.4. Refinements....................................................................................................................................18

3.5. Selection.........................................................................................................................................19

4. Design Specifications.............................................................................................................................19

4.1. Design Overview.............................................................................................................................19

4.1.1. Description..............................................................................................................................19

4.1.2. Design Schematics...................................................................................................................20

4.2. Functional Specifications................................................................................................................21

4.2.1. Engineering Design Features...................................................................................................21

4.2.2 Functional Specifications..........................................................................................................22

4.3. Physical Specifications....................................................................................................................22

4.4. Product QFD...................................................................................................................................24

4.5. Subsystems.....................................................................................................................................25

4.5.1. Spring-Loaded Napkin Dispenser.............................................................................................25

4.5.2. Vacuum Napkin Placement System.........................................................................................26

4.5.3. Electromagnetic Silverware Placement/Napkin Rolling System..............................................27

4.5.4. Napkin Folding Platform..........................................................................................................27

4.6. Design Deliverables........................................................................................................................29

5. Project Plan............................................................................................................................................29

5.1. Research.........................................................................................................................................29

5.2. Critical Function Prototypes............................................................................................................30

5.3. Design.............................................................................................................................................30

5.3.1. Subsystem I: Spring-Loaded Napkin Dispenser........................................................................30

5.3.2. Subsystem II: Vacuum Napkin Placement System...................................................................31

5.3.3. Subsystem III: Electromagnetic Silverware Placement/Napkin Rolling System.......................32

5.3.4. Subsystem IV: Napkin Folding Platform...................................................................................32

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5.3.5. Subsystem VI: Logic Control.....................................................................................................33

5.4. Construction...................................................................................................................................34

5.5. Testing............................................................................................................................................35

5.6. Project Deliverables........................................................................................................................35

5.7. Schedule.........................................................................................................................................36

5.8. Budget............................................................................................................................................37

6. References.............................................................................................................................................39

7. Appendices............................................................................................................................................39

7.1. Team Member Resumes.................................................................................................................39

7.2. Component Specification Sheets....................................................................................................44

7.2.1 Electromagnet..........................................................................................................................44

7.2.2 Vacuum Compressor.................................................................................................................45

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List of FiguresFigure 1: Customer Requirements Schematic............................................................................................10

Figure 2: Overall Concept 1 Top View Figure 3: Overall Concept 1 Side View.............................12

Figure 4: Overall Concept 2 Side View.......................................................................................................13

Figure 5: Overall Concept 3.......................................................................................................................14

Figure 6: Overall Concept 4 Top View Figure 7: Overall Concept 4 Side View....................................14

Figure 8: Overall Concept 5 Top View Figure 9: Overall Concept 5 Side View......................................15

Figure 10: Overall Concept 6 Top View Figure 11: Overall Concept 7 Side View...........................15

Figure 12: Platform Analysis......................................................................................................................16

Figure 13: Electromagnet Analysis.............................................................................................................16

Figure 14: Cable and Pulley Analysis..........................................................................................................16

Figure 15: Linear Actuator Analysis...........................................................................................................17

Figure 16: Spring Hinges Analysis..............................................................................................................17

Figure 17: Feature Schematic for Silverware Wrapper..............................................................................20

Figure 18: Function Schematic for Silverware Wrapper............................................................................21

Figure 19: Package Drawing for Silverware Wrapper................................................................................23

Figure 20: Napkin Dispenser Wireframe Schematic..................................................................................25

Figure 21: Vacuum Placement System......................................................................................................26

Figure 22: Electromagnet Silverware Placement System...........................................................................27

Figure 23: Napkin Folding Process.............................................................................................................28

Figure 24: Napkin Folding Platform Top View............................................................................................28

Figure 25: Napkin Folding Platform Bottom View......................................................................................29

Figure 26: Project Schedule.......................................................................................................................36

Figure 27: Personnel Diagram...................................................................................................................38

Figure 28: Magnetool Electromagnet Specifications.................................................................................44

Figure 29: Thomas Compressors Specifications.........................................................................................45

List of TablesTable 1: Decision Matrix................................................................................Error! Bookmark not defined.

Table 2: Modified Decision Matrix.............................................................................................................19

Table 3: Product QFD Matrix for Silverware Wrapper...............................................................................24

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Table 4: Expenses......................................................................................................................................37

1. Context

1.1. BackgroundThe primary customers of this project are mid-level quality restaurants, with their employees and patrons as secondary customers. The goal of our team was to come up with a machine for these restaurants that would cut costs, increase profit, increase efficiency of the work place, and allow the restaurant to use their employees to their full potential. Our team intends to design and construct a machine that will accomplish these things with regards to one specific task.

At a standard mid-level quality restaurant, servers are required to roll silverware into a napkin. This is a necessary but time consuming and tedious task ultimately leading to greater costs for the restaurant and fewer tips for the servers. Both the primary and secondary customers have a need for this product so that they can both increase their revenue. Our machine will perform this task with virtually no human interaction. In order for our machine to perform properly, we must meet the needs of the secondary customers. Those needs include user friendly technology for the employees and then cleanliness and neatness for the customers of the restaurant. Silverware rolled in a napkin shows the customer of the restaurant that the restaurant takes time out of their day to make sure things are clean, neat, and also shows good presentation. A customer’s satisfaction is a business’s top priority and by presenting them with this product means that they have one less thing to worry about when trying to satisfy their customer.

The idea of having a machine perform this task is not new to the restaurant industry. After researching the idea and speaking to restaurant managers, they have already been approached with the idea but have yet to see a product that meets all of their requirements; which is the ultimate goal. Some of the ideas they were approached with were simply drawings and some of them actually took physical form. The ones that were in physical form are ones this project must rival and ultimately overcome to ensure our customer’s satisfaction. One of the ideas that have been tried was a mechanism that simply aided the employees in folding a napkin opposed to doing it for them; this product was ultimately not an efficient enough product for the restaurant industry. Other companies are coming out with machines similar to ours but have still cannot overcome some of the obstacles that this task presents which is why restaurants still have yet to buy one of the these products on the market.

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1.2. Customer Need StatementThe restaurant industry constantly has a need to cut costs and improve certain aspects of their business. There is always room to improve aspects of a restaurant such as décor, food quality, and the level of quality of employees. Making improvements to these aspects would increase customer satisfaction but in order to accomplish these things, a restaurant must forfeit a certain amount of money to do so. Cutting the costs that restaurant owners pay employees to roll silverware in a napkin would allow them to increase the amount of money spent on other aspects of their restaurant such as those listed above. A customer of ours has been quoted saying that he requires four servers a night to roll silverware for a minimum of two hours 365 days a year. This equates to a minimum of $28,000 a year spent on employees rolling silverware. Spending any amount of money under $28,000 to buy a machine that accomplishes this task would meet the need of our primary customer and would allow them to take the money they save, and put it back into their business.

1.3. Literature Review

1.3.1. Prior WorkPrevious attempts and ideas regard this task have been tried but few have been successful. Everything from concepts, basic ideas, and drawings will be taking into account when analyzing the levels of success for this product in the past. Our team knows we are not the first engineers to think of this idea. Every piece of prior work that has been done to try to build this type of machine will be taken into account. Almost every drawing that is seen on the internet tries to use rollers to guide the napkins to one position or to wrap the silverware into the napkin. This design was considered for our product but will not be implemented due to many concerns and to history proving to us this idea isn’t concrete enough to follow through with.

Our research has recently led us to prior and present work that has been done that accomplishes the same task we have set out to accomplish. Certain flaws in these machines have been realized and will be corrected in our machine. The most common flaw is that of simplicity. The two machines that are on the market have been developed in the past five years and are not as efficient as we believe they can be. This allows our team to believe that there is still room for much improvement just as there is with any machine.

The reason this problem is hard to solve is due to the number of variables that are questionable. Examples of these variables include being able to separate one piece of silverware or one napkin from the rest. If you have a stack of a 100 napkins, how can you take just one away from all the others and then be placed in the exact position for the silverware to be wrapped in? How do you separate one fork from the rest knowing that it has a very odd and original shape to it? How do you get a machine to do that on its own? These are all questions that may or may not have been solved in the two products already on the market. In order to come up with a successful design, we need some abstract thinking that others may not have possibly due to lack of creative, knowledge, or a combination of the two.

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1.3.2. PatentsThere are a number of patents for products that deal with this exact problem. Research has been done to evaluate existing patents for this product and has led us to very few relative ones. Some of the following patents need to seriously be accounted for and looked at as to not infringe on them but others are so vague that they need not much consideration.

-Autowraptec is one of the two companies with a product on the market that performs the same task we have set out to accomplish. They have patented “the concept” of their product, this is open for interpretation and will be delt with if needed.

http://www.autowraptec.com/who_is_autowraptec.html

-Google/patent is a part of Google that includes a database of all existing patents for different ideas and machines. This is one of the many for silverware rolling devices that our team has found. This one is incomplete and not actually feasible in our opinion.

http://www.google.com/patents?id=gsgMAAAAEBAJ&dq=silverware+wrapper

-The US Patent and Trademark Office has this silverware rolling device in their database. The ideas used here were taken into consideration and thought about carefully when trying to design our own concepts as to not infringe on their ideas.

http://patft.uspto.gov/netacgi/nphParser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=7404279.PN.&OS=PN/7404279&RS=PN/7404279

These are three of the many patents out there for this type of product. They all include drawings, concepts, ideas, or products that we have looked at and taken into consideration when designing our product. Though our team has seen these ideas, we do not intend to use any of them for our own design because we have identified certain flaws in them which we do not want our machine to include.

1.3.3. Codes and StandardsThough we have not identified specific codes, standards, and regulations for a product such as ours, thought has been put into it. Codes with regards to public health and safety as administered by the FDA will need to be considered seeing as our product will be in a restaurant and handle silverware which people will use directly after our product touches it. Other codes that may need to be attended to and looked at include regulations about mechanical equipment in a kitchen. There are generally not too many mechanically moving parts in a restaurant kitchen; it usually just includes oven, refrigerators, people, etc. Now with our product, that list will include a device that mechanical carries out a system of operations. The last code that will need to be dealt with is that of electrical codes and regulation. Any piece of electrical equipment is subject to standards, our product is no different. Those regulations must be taken into account when designing our product.

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http://www.google.com/patents?id=gsgMAAAAEBAJ&dq=silverware+wrapper

http://www.autowraptec.com/who_is_autowraptec.html


Standards in the restaurant industry that our product must consider are that of the standard size of a knife, fork, and napkin. We need to know this so that our product can accommodate them. If ignored, our product would be virtually useless and pose no purpose or benefit to the restaurant industry.

2. Problem Definition

2.1. Customer RequirementsThe final machine should coincide with requirements that directly relate to the customer. The form, fit, and function requirements are as follows:

2.1.1. Form1. Must be less than 36 in tall.(M)2. Must be less than 30 in wide.(M)3. Must be less than 50 in long.(H) 4. Encasement should protect against outside factors (Spills, physical forces).(M)5. Napkin Wrapper must be aesthetically pleasing.(M)

2.1.1. Fit1. Must accommodate a napkin that is 19 inches in length and width.(H) 2. Must accommodate a Fork and knife that are 7in by 1in in length and width.(H) 3. Must accommodate 100 napkins.(H)4. Easily assembled and disassembled for convenient transport and set up.(M)5. Must operate on 110 V.(H)

2.1.2. Function1. Roll two sets of silverware and napkin in one minute.(H)2. Operate for 8 hours continuously. (H)3. Dispense and transfer one napkin to the wrapping platform.(H)4. Must be user friendly to the customer.(H)5. Easy access to all critical parts for easy maintenance.(H)

2.2. AssumptionsIn order to simplify the problem, certain conditions need to be assumed. These conditions are realistic and practical.

1. Silverware will be placed by hand on the napkin.2. Silverware will be magnetic.3. Silverware will be dry.4. Napkins will be placed in a neat stack into the container.5. Device will be used inside (ie. not outdoors).

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6. User will be trained to use the machine.

2.3. ConstraintsThe constraints of this project regulate size, safety, cost and testing. These constraints are not adjustable, and must be followed exactly. During the design and manufacturing of the silverware rapper, the following constraints will be followed…

Size

1. Must fit on worktable in Loma 5 when unassembled.2. Must fit through Doorways, 32in, when unassembled.

Safety

1. No exposed moving parts (knives, forks, electromagnets).2. No exposed pinch points (springs, folding platforms).3. No high energy compressed springs.4. No voltages higher than 120V.

Cost

1. Prototype manufacturing cost should not exceed $1500.

Testing

1. Capable of being tested in Loma Hall.

2.4. Customer Requirements Schematic

Power Supply (110V) Stack silverware set neatly in Napkins (19X19) containerForks Silverware wrapped in napkinKnives

Noise Heat

Figure 1: Customer Requirements Schematic

2.5. Test/Evaluation Plan for all Requirements and ConstraintsThe two most important function requirements are the need for the machine to work for 8 hours per day, and produce one set per minute. The testing procedures for these two function

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requirements will be very simple. At least one person will be present while the machine is on for eight hours. The person will ensure that the machine consistently wraps at a speed no slower than two sets per minute. The person will also be there to observe and troubleshoot any malfunctions. This test will be administered no less than 5 times.

Initial critical function tests should also be administered. The ability to separate and transfer on napkin from a stack is crucial to the design of the wrapping machine. Using a household vacuum and different orifice sizes, we will test to ensure that the machine can repeatedly transfer one and only one napkin to the folding platform.

Another critical function is the rolling apparatus. It should be tested to ensure a neat and repeatable roll every time. In order to test this function, the napkin and silverware will be prepared by hand to the appropriate step. From this point on, the rolling apparatus will complete the process.

3. Concept Development

3.1. Overview

3.1.1. Creative StrategiesOur primary creative strategy was brainstorming. We provided a large quantity of ideas putting forth even the wildest of ideas providing for a solid foundation of solutions for our project.

Functional decomposition was a useful creative strategy for our group. We broke our machine into the following functional subsections:

Napkin bin Napkin placement Silverware placement Napkin folding Rolling Napkin Logic Control

This technique allowed us to concentrate on solving specific tasks greatly increasing our ability to solve problems.

Analogies were another helpful creative strategy. We drew an analogy between our tracking system and an arcade machine. We drew an analogy between separating napkins and a paper printer.

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Motor #1

Folding Platform

Motor

Motor #3 Motor #2

Electromagnet

Electromagnet & Motor Motor #1

Folding PlatformMotor #3

Motor #2


3.1.2. Governing PrinciplesThe functions of all designs are governed by certain principles, from Engineering, Physics, Chemistry, Ergonomics, Mathematics, etc. The following governing principles are used in our design:

1. fluid dynamics (vacuum), 2. heat transfer (cooling electromagnet)3. kinematics/dynamics (folding platform, vacuum track, platform track)4. solid mechanics/FEM (component stresses)5. tribology (bearings and lubrication) 6. robotics (motors, rotating arms)7. electromagnetics8. software (programmable logic controller)

3.2. Synthesis and Analysis of Overall Concept

3.2.1. Overall Concept 1Through brainstorming, this was the first feasible design that our group conceived. This design consists of a folding platform that rotates on three hinges. Each hinge is controlled by a motor that rotates the platform folding the napkin. There is an electromagnet that when magnetized attract the silverware. The electromagnet is controlled by a motor that rotates, wrapping the silverware within the napkin. The advantage of this design is its simplicity. The disadvantages of this design are that it requires 3 motors to fold the napkin and the electromagnet motor requires 2 degrees of freedom to wrap the napkin. This design is neither original nor elegant.

Figure 2: Overall Concept 1 Top View Figure 3: Overall Concept 1 Side View

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Napkin

Vertically Moving Platform

Stationary Wall

Folding Mechanism #1



Motor

Stationary Wall

MotorElectromagnet


3.2.2. Overall Concept 2This concept came as we brainstormed ways to reduce the amount of motors required to fold the napkin. This design consists of a folding platform that moves vertically on a slide controlled by a motor. As the platform moves downward a set of three levers are pulled causing the platform to rotate about spring loaded hinges, folding the napkin. The platform then returns to its starting position where an electromagnet that when magnetized is attracted to the silverware. The electromagnet is controlled by a motor that rotates, wrapping the silverware within the napkin. The advantage of this design is that it accomplishes the task of folding the napkin using one motor. Another advantage of this design is that it reduces the degrees of freedom required by the electromagnet motor down to one. The disadvantage of this design is that it increases the size (height) of this machine and uses linear motion reciprocating.

Figure 4: Overall Concept 2 Side View

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Compressor

Vacuum Head

Napkin Stack

Vacuum Track

Motor #3 Motor #2

Motor #1

Folding Platform

Motor Electromagnet

Claw (x3)

Folding PlatformMotor #3

Motor #1 Motor #2Electromagnet, Motor & Claws


3.2.3. Overall Concept 3 This design concept came as we brainstormed ideas to reduce the subfunctions required to wrap silverware. This concept also came in an effort to reduce the size of our machine. This design consists of an overhead vacuum that operates in three degrees of freedom on top of the napkin stack. The vacuum attaches to the corner of a single napkin dragging the napkin to create the desired fold. The advantage of this design is that it reduces the size of the machine and the subfunctions required to perform this task. The main disadvantage of this design is there will be irregularity in the fold and robotics are needed to move the vacuum head.

Figure 5: Overall Concept 3

3.2.4. Overall Concept 4Similar to Concept 1, this design uses a folding platform with 3 hinges, each controlled by a motor. A claw clasps the silverware and napkin and then rotates to fold the napkin. A guide rail helps keep a tight and secure fold. This design still requires 3 motors to fold the napkin and repeatability of the clasping is a concern. This design is neither original nor elegant. The advantage of this design is it is simple.


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3.2.5. Overall Concept 5This concept came in an attempt to reduce the size of Overall Concept 2 This design consists of a stationary folding platform. A motor rotates an arm that actuates levers that allow the spring loaded hinges to fold the platform and napkin. The electromagnet is controlled by a motor that rotates, wrapping the silverware within the napkin. The advantage of this design is that it accomplishes the task of folding the napkin using one motor and reduces the size (vertically) of the machine. The disadvantage of this design is that the rotating arm places unwanted forces along the lever arms and spring loaded hinges.


3.2.6. Overall Concept 6This concept came as we brainstormed ways to improve upon Concept 5 This design consists of a stationary folding platform. A motor rotates an arm that actuates cables drawn through pulleys allowing the spring loaded hinges to fold the platform and napkin. The electromagnet is controlled by a motor that rotates, wrapping the silverware within the napkin. The advantage of this design is that it accomplishes the task of folding the napkin using one motor, reduces the size (vertically) of the machine and best directs the force required to rotate the folding platform. A possible disadvantage of this design is the cable slipping from the pulley.

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Folding Platform

Folding Platform

Motor

Rotating Arm Lever

Folding Platform

Folding Platform

Motor

Rotating Arm

Pulley

CablePlatform Lever

Mspring

W

L1

hingeplatform

Fcable

L2

Fork & Knife

Napkin

Electromagnet

T2

x

x

z

T1

PulleyCable

Platform Lever



3.3. EvaluationIn this section analysis is performed on the major functions (refer to sections 3.3.1 – 3.3.6) required in our design concepts. Secondly, a decision matrix based on analysis is provided to help determine the best design.

3.3.1. Platform Analysis

∑M=Iα=(Fcable ) (L2 )−Mspring+(W )(L2)

3.3.2. Vacuum AnalysisSee Section 5.2 Critical Function Prototypes

3.3.3. Electromagnet Analysis

See Section 5.2 Critical Function Prototypes

3.3.4. Cable and Pulley Analysis

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Figure 12: Platform Analysis

Figure 13: Electromagnet Analysis

Lfold1

Lfold2

Lfold3


Solve for the Tension (T) in the cables using:

∑Fx=ma

∑Fy=ma

∑Fz=ma

Solve for the distance (x) by analysis of the rotating arm motion

3.3.5. Linear Actuator Analysis

Lfold = distance required to create fold

∑L = Total Stroke of Linear Actuator

∑L=Lfold1+Lfold 2+Lfold3

∑L = 28 in

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Lfold1 = 14.5 in

Lfold1 = 6.75 in

Lfold1 = 6.75 in

Figure 15: Linear Actuator Analysis

MW

Lhinge

platform


3.3.6. Spring Hinges Analysis

∑M=0=M−WL

Table 1: Decision Matrix

Meet Codes

110 Volt Compat.

Machine Size Weight Cost Reliability

Overall Score

Design 1 Go Go 6 4 5 4 19Design 2 Go Go 4 3 4 3 14Design 3 Go Go 9 8 2 2 21Design 4 Go Go 6 4 5 4 19Design 5 Go Go 7 6 8 5 26Design 6 Go Go 8 7 8 7 30

3.4. RefinementsIn this section, refinement of the critical functions will be discussed. Machine size, weight, cost, simplicity and reliability were important factors in the refinement process.

Napkin folding is a critical function with considerable improvement. The original design (Design Concept 1) consisted of 3 motors rotating the platform about hinges. Reducing the number of motors from 3 to 1, Design Concept 2 provided refinement in our design. Design Concept 2, however, required greater size of our machine. Design Concept 5 and 6 allowed us to reduce the motors required to create the folds while maintaining an optimal machine size. Design Concept 6 came as a refinement to Design Concept 5 as force alignment and fatigue concerns were addressed.

Napkin wrapping is a critical function with significant development. The original design (Design Concept 4) required robotic arms/claws to wrap the silverware. The concept of an electromagnet to attract silverware and wrap the napkin provided great refinement to our project.

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Figure 16: Spring Hinges Analysis


Napkin placement is a critical function with refinement. Using theory from Design Concept 3 a vacuum will be used to place the napkin onto the folding platform. Section 5.2 describes the critical function test conducted to verify this function will work.

3.5. SelectionTable 2: Modified Decision Matrix

Meet Codes

110 Volt Compat.

Machine Size Weight Cost Reliability

Product Quality Programming

Overall Score

Design 1 Go Go 6 4 5 4 6 3 28Design 2 Go Go 4 3 4 3 6 6 26Design 3 Go Go 9 8 2 2 2 5 28Design 4 Go Go 6 4 5 4 8 2 29Design 5 Go Go 7 6 8 5 6 8 40Design 6 Go Go 8 7 8 7 6 8 44

Our team has selected Design Concept 6 for this project. Based upon analysis, refinements and a modified decision matrix this design became the obvious decision.

4. Design Specifications

4.1. Design Overview

4.1.1. DescriptionOur design rolls a napkin around a knife and fork using a simple chain of operations:

1. A vacuum device removes a napkin from a spring-loaded stack and transports it to a platform with an arm capable of rotary motion.

2. After the napkin is in place an electromagnet transports a knife and fork onto the napkin on the platform.

3. An arm swings under the platform contacting a series of spring-loaded hinges, which fold the napkin around the silverware.

4. An electromagnetic device grips the napkin and silverware and spins producing a rolled combination of napkin and silverware.

5. The electromagnet transports the rolled silverware into a removable holding bin.

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We intend to have this device roll a minimum of two compact silverware sets per minute. The process should be repeatable with rare customer interaction. The system has four main subsystems:

1. Spring-loaded Napkin Dispenser2. Vacuum Napkin Placement System3. Electromagnetic Silverware Placement/Napkin Rolling4. Napkin Folding Platform

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4.1.2. Design Schematics

Figure 17: Feature Schematic for Silverware Wrapper

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Vacuum Napkin Placement SystemSilverware Placement and Napkin Rolling System

Rolled Silverware Bin

Compressor and Electronics Storage

Napkin Folding Platform

Napkin Dispenser

Silverware Platform


Figure 18: Function Schematic for Silverware Wrapper

4.2. Functional SpecificationsThe functional specifications of the silverware wrapper are as follows:

4.2.1. Engineering Design Features

4.2.1.1. Spring-Loaded Napkin Dispenser Spring-loading system maintains constant height of top napkin Compressor and Electronics mount below the apparatus

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110 V Power

Rolled SilverwareKnives andForks Start

Napkins

Heat, Noise


4.2.1.2. Vacuum Napkin Placement System Compressor capable of producing approximately 450 air watts of suction at

approximately 20 kPa of pressure Vacuum platform disperses vacuum equally to lift a napkin from the dispenser Six bar rotating transportation system Transports napkin from dispenser to platform and returns to start position in 6

seconds

4.2.1.3. Electromagnetic Silverware Roller/Silverware Transport Electromagnet with 30 lbs of lifting power Horizontal rotation from start position to silverware platform, to folding platform,

and return to start position in 6 seconds Vertical motion to pick up and drop of silverware Radial rolling of napkin around silverware in 5 seconds Transport of rolled silverware from platform to bin in 7 seconds

4.2.1.4. Napkin Folding Platform Arm travels one rotation of 360 degrees in 7 seconds Contacts cable mechanism resulting in three folds of platform Platform folds spring back to avoid interference with further folds

4.2.2 Functional SpecificationsThe functional specifications of the silverware wrapper are as follows:

1. Silverware rolling speed of two silverware sets per minute2. Produce a tight rolled set of silverware (less than 1.25” in diameter)3. Supported silverware sized 7” by 1” and magnetic4. Supported napkins sized 19” by 19”5. Napkin handling: 100-napkin input container6. Extensive safety guards to prevent user injury

4.3. Physical Specifications Outer dimensions 60”x30”x30” or less 19”x19”x10” topless napkin dispenser 19”x19” folding platform Weight of less than 100 lbs

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Figure 19: Package Drawing for Silverware Wrapper

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4.4. Product QFD

Table 3: Product QFD Matrix for Silverware Wrapper

Design Specifications Physical FunctionalCustomer Requirements and Constraints

Priority Manageable Size

Supported Napkins

Supported Silverware

Napkin Container Capacity

Rolling Speed

Quality Rolled

Silverware

CR1: Consistent Speed

4 5

CR2: Reliability 5

CR3: Interface easily with existing restaurants

3 3 5 5 3 4

CR4: User Friendly 5 3 5 4

C1: Safety 5 3

Target Values 60”x30”x30” 19”x19” 7”x1” Mag. 100+ 2/min d<1.25”Technical Difficulty 1 1 1 2 3 5

Importance Rating 39 15 15 34 20 32

Each of the individual customer requirements and constraints are accounted for by at least one of the design specifications. Though safety is only accounted for by one physical design specification, it’s design will not be problematic as simple encasing guards can prevent user injury.

For the most part, each part of the project with a high importance rating has a low difficulty. Items such as size and napkin container capacity do not hold a high difficulty whatsoever. Creating a product within our design specifications in these two regions will occur without effort. Producing a high quality of rolled silverware is both a difficult and important task, and will be accounted for by focusing the design and construction process on creating an appealing finished product.

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4.5. Subsystems

4.5.1. Spring-Loaded Napkin DispenserThis system is made up of a spring-loading system, which maintains constant height of the top napkin of the stack. This container will be topless with dimensions of 19”x19” and a depth capable of holding approximately 100 napkins. Open space will exist under this system, in which the vacuum compressor, microcontrollers, and any other necessary electronics will be housed.

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Figure 20: Napkin Dispenser Wireframe Schematic

4.5.2. Vacuum Napkin Placement SystemA vacuum compressor capable of producing approximately 450 air watts of suction is suspended above the vacuum system. This vacuum compressor connects to the vacuum cart via a flexible plastic hose. This hose will be connected to a 19”x19”x1” hollow platform. Holes in the bottom of the platform will distribute the vacuum force evenly over the area of the napkin. The apparatus will be suspended from four parallel bars, one of which is connected to a motor that can rotate the bars approximately 160o. With the apparatus in contact with the top of the napkin stack, the vacuum turns on creating suction between the pressurized platform and the top napkin. Once the napkin adheres to the platform, the arms rotate vertically 160 o to the napkin folding platform. The vacuum turns off placing the napkin on the platform, and the system returns to the start position above the napkin dispenser.

Figure 21: Vacuum Placement System

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4.5.3. Electromagnetic Silverware Placement/Napkin Rolling SystemThe electromagnet silverware roller consists of a flat rectangular electromagnet connected to three motors, which allow it horizontal radial, stationary rotational, and vertical motion. This system initially transports the silverware from the silverware platform(located to the side of the folding platform) to the folding platform. The electromagnet system swings via motor to a position above a knife, turns on, picking up the knife, swings back to a location above the center of the napkin, and turns off placing the knife onto the center of the napkin. This process repeats for a fork. Once knife and fork are in place, the magnet rotates to make way for the folding process.

After the platform folds the napkin, the electromagnet mechanism swings back above the folded napkin. It descends to make contact with the napkin and silverware and turns on. The system rotates rolling the napkin around the electromagnet. The entire system then swings and dispenses the silverware set onto a ramp, down which it slides neatly into the storage bin.

Figure 22: Electromagnet Silverware Placement System

4.5.4. Napkin Folding PlatformThe folding platform is made of a square of plastic with three torsion-spring hinges. The platform is divided into four sections, three triangular and one pentagonal, with the torsion springs allowing for the rotation the three triangular sections. It has a small indentation in the center, which serves as a receptacle for the silverware during rolling. Attached below the platform is a motor-propelled arm, which swings 360 degrees. As the arm swings it trips folding systems on each of the platform sections. The sections swing upward as the arm passes, folding the napkin and then returning to the flat position. The three napkin folds take place in the following manner:

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First Fold Second Fold Third Fold


Figure 23: Napkin Folding Process

A slide-out bin with an open top will sit below the folding platform. This will serve as a receptacle for the rolled napkins. This system will allow for complete removal of the bin in order to store rolled napkins elsewhere in the restaurant.

Figure 24: Napkin Folding Platform Top View

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Figure 25: Napkin Folding Platform Bottom View

4.6. Design Deliverables The design deliverables for the silverware wrapper are as follows:

Preliminary Design Report with associated modeling and analyses Full set of engineering drawings: separate drawings of each subsystem and subsystem

component Detailed plan for order of building operation Outline of specific testing procedures Bill of Materials Cost estimates

5. Project Plan

5.1. ResearchResearch that still needs to be completed in order for the project to succeed includes research of the critical function subsystems in the project. This includes different types of motors, servo vs. stepper. The project may require positional analysis to determine if the mechanisms are in the correct place so that they can perform their task. This would require a motor with position feedback so that the machine can work correctly. These motors also need to be able to perform with the loads applied on them. We need to do some torque analysis and research of the different motors as well. Another area that needs to be researched is the air flow of a

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compressor so that the machine can be efficient, too much air flow being pulled by the compressor means more power which may not be needed. The last major area that must be researched is the electromagnet. We must research lifting force of magnets because surface dependency is usually pretty high. The project requires an electromagnet to be able to pick up two pieces of silverware through a napkin which been folded over itself three times, and then spin which creates a centripetal force causing the magnet to be even more inefficient, research must be completed to determine if an electromagnet of our specific size is feasible.

5.2. Critical Function PrototypesOne critical function prototype that has already been constructed and tested was the vacuum which picks up a single napkin from a stack. The use of a simple house hold vacuum and custom made valve (to regulate air flow) was connected to hoses which were then applied to different areas of the napkin to see if it was able to pick it up without picking up multiple napkins. The prototype was cheap, a success, and gave us knowledge and confidence in that aspect of the design. The only other critical functions in the project that needs to be tested is our electromagnet. We know that the shape of magnet that we are proposing would roll the silverware into the napkin neatly but we are not sure that the shape of the magnet allows for the proper amount of force needed to pick up the silverware. We know that the silverware is magnetic and can be picked up via an electromagnet but we cannot build a simple prototype to test the exact conditions of our project. Therefore we need to test out the actual magnet our project will require. We have ordered the magnet from a manufacture who has a 30 day return policy which will allow us the time to test its function.

5.3. DesignThe process of our design begins after a stack of napkins is loaded into the tray as well as the silverware being placed in the proper position. From this point, a number of subsystems will begin, critical functions will be carried out, and our project will be on its way to a successful chain of operations.

5.3.1. Subsystem I: Spring-Loaded Napkin DispenserA stack of approximately 100 napkins will be placed into a tray much like that of a stack of paper in a printer. The napkins that our machine is being designed for are 19 in x 19 in. The size and shape of our tray must be design accordingly. At the bottom of the tray, a combination of springs must be used to push the stack up to a certain position in order for the rest of the project to work. Hooke’s Law will be used to design the specific measurements of our springs.

Using this, we will be able to figure out what we need our spring constant to be with regards to the weight of our stack at any given time during operation. This subsystem will push the top

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napkin of the stack to a certain position every time so that Subsystem II can be performed. Things to consider in Subsystem I are the fatigue rates of spring constants and materials when subjected to this type of constant compression. We also want the inside of the tray to be as clean as possible so that the outside edges of the napkins do not get dirty easily when in the tray.

Estimated time of completion: 2-3 weeks

5.3.2. Subsystem II: Vacuum Napkin Placement SystemOur second subsystem is the vacuum apparatus. A vacuum, as well as other subsystem parts will be stored directly below the stack of napkins in a compartment for easy access and maintenance. As mentioned in section 4, a hose will be run from the vacuum up to an apparatus that will be the size of our napkin. The apparatus that the hose runs into will be a box shape with the dimensions 19in x 19in x 1in with 20 holes in the bottom of it so that it can pick up a napkin neatly when pressed down to the top of the napkin stack. The apparatus will be suspended from four parallel bars, one of which is connected to a motor that can rotate the bars approximately 160º when a 5 lb-ft force is applied to it. Once the apparatus hits the top of the napkin stack, the vacuum turns on and suction is created between it and the top napkin. The motor that is connected to the parallel bars rotates the apparatus and napkin 160º over to a platform where our next subsystem will be carried out. The vacuum turns off, allows the napkin to be supported solely by a square shaped platform, and then the motor rotates the vacuum apparatus back to its original position.

Certain things to consider for this subsystem are permeability of a cloth napkin and air flow through a certain size hole. An inexpensive compressor can be used if simple prototyping and math is completed to determine the least amount of air flow that can be used to pick up a napkin. The parallel bars which will have to be strong enough to support the vacuum apparatus that weighs approximately 5 pounds. The parallel bars will be approximately 14 inches long so that it can rotate the vacuum apparatus over to the platform where the napkin will be folded. The motor must be powerful enough and have enough torque so that it can rotate the apparatus at a reasonable speed. This means we need a motor with approximately 5 lb-ft of torque opposed to a more expensive one that might have 20 lb-ft of torque when it’s not needed. The motor must also have position control so that we can determine where it is with relation to the rest of our machine. Other things that need to be kept in mind when designing this subsystem is material of the parallel bars, strength vs. weight, and the friction between those bars when rotated.


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5.3.3. Subsystem III: Electromagnetic Silverware Placement/Napkin Rolling SystemIn this subsystem, we must take one knife and place it in the middle of the napkin and then repeat the step for a fork as well. For this system, we will be using an electromagnet. This magnet will be 6in long, ½ in thick, and 1½ in wide and have 114 lbs of pulling force. That magnet is then connected to a motor and will be able rotate horizontally 200º. The silverware will be placed off to the side of the platform that the napkin is on. The magnet will rotate over via a motor to where the silverware is. This motor will have the force of a magnet (1 lb) and the force of silverware (approx. 1 lb) acting on its drive shaft in the perpendicular direction. To counteract this force, our design will include support structures that hang from above which are connected to the back end of the magnet. This way our motor is not damaged due to weight. Another motor that is on a nut and bolt system will turn and will allow the magnet to travel vertically up and down. To pick up the silverware, we will rotate the bolt it so that the magnet lowers 1 inch so that it is in contact with the knife. The magnet turns on and is then connected to the knife. The nut and bolt system then raises the magnet back to its original position. The horizontally rotating motor will then rotate the magnet over to the center of the napkin, the magnet will turn off and the knife will drop into the middle of the napkin. This process will be repeated the same way for a fork. Once the knife and fork are stacked on top of each other in the middle of the napkin, the magnet will rotate over so that it is no longer over the napkin.

This is the first function of this subsystem; the second function of this subsection is rolling the silverware in the napkin. After our napkin is folded over our silverware, which is described in subsystem IV, our magnet will need to perform another function. The horizontal motor will rotate the magnet back of the silverware which is in the middle of the napkin now, the nut and bolt system will lower 1½ inch so that it is pressing down on the napkin and silverware. The magnet is turned on and the magnet will raise up 1 inch. The dimensions and specifications of our magnet are now being put to use. Another motor which is placed at the top of the other two is also connected to the magnet. This one must have 2 lb-ft torque so that the magnet, silverware, and napkin can rotate in a stationary position for approximately 2-3 seconds. The motor turns on and rolls the napkin over the silverware, as well as the magnet so that it is trapped inside the rolled napkin with the silverware. A separate subsystem will separate the two. Things to consider for this subsection are cleanliness of the magnet. We need the magnet to be able to stay clean for a long period of time, as well as to be able to travel into the proper position so that cleaning can occur. Also the force of an electromagnet must be calculated, especially without the use of surface dependancy in order for this subsection to work correctly.


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5.3.4. Subsystem IV: Napkin Folding PlatformOnce our napkin is in place and our silverware is in the middle of the napkin, our napkin must be folded three times before it can be rolled. As demonstrated in section 4, one fold must fold half of the napkin over the other half so that from an overhead view the napkin goes from a square shape to a triangle. This part of the platform will have a triangle shape with a base of 26 inchs long, and a hieght of 13 inches and will rotate about the base. The second and third folds must fold the corners of the napkin that are closest to the head and the end of the silverware. The shape of these parts of the platform will also be triangle shaped with the dimensions 8in x 8 inch x 11.3in where it will be rotating about one of the 8 inch sides. Each hinge will be pushed and rotated over so that it can accomplish the fold which is initiated from a lever and pulley system located beneath the platform. The exact geometry and combination of levers and pulleys have not been decided on at this time but the general idea is feasible and will be employed. The goal is to translate rotational motion in the horizontal direction to rotational motion in the vertical direction. We feel that the best way to redirect motion is a cable looped through a hook or rig systems. The part of the platform that folds the napkin will spring back into its original position due to a torsion spring in place at the hinge. The second and third fold will repeat this same step in a timely fashion as to not get in the way of the other folds. The material required for this platform will mostly like be a light weight type of plastic, there is no real wear and tear on the platform so durability isn’t an issue. The lighter the material, the easier it is for the motor to spin and rotate the combination of levers for each fold. This cuts down on costs for material and for the motor needed because it requires less force than if the platform was made of a heavier material.


5.3.5. Subsystem VI: Logic ControlThis completes the design for our machine and concludes that our machine will require the use of subsystems that consist of:

1 spring system 4 motors 1 electromagnet 3 spring hinges

Other aspects of our design include material selection and geometrical design which will be taken into account when making specific decisions about each subsystem.

Estimated time of completion for entire design: 16 weeks

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5.4. ConstructionThe silverware wrapping apparatus will be separated into two main sections - napkin folding and napkin placement. The napkin folding section includes the following subsections: folding platform, rotating arm and cables, and the electromagnet arm. The napkin stacking section includes the following subsections: spring system, vacuum apparatus, and four bar mechanism.

The folding platform will be made from plastic. The laser cutter will be used to cut out the skeletal background for each of the four panels. A cloth-like material will be stretched over the skeletal structure to provide a flat, smooth surface. Holes will be drilled in each platform where they will be connected using spring hinges.

The rotating arm will be made out of a light metal. The rotating arm will be machined into a rectangle using the mill. A hole will be drilled and tapped in the bottom of the arm at one end where it will be attached to the threaded shaft of the driving motor. The motor, pulleys, and hinges will be bolted onto a platform that is placed a few inches lower than the folding platform. The pulleys and cables will be purchased.

The electromagnet arm will consist of a linear actuator and two motors. We will purchase the linear actuator and fasten it to the base of the entire machine. A motor will be bolted onto the top of the actuator. The drive shaft of this motor will be vertical and attached to a platform made from a light metal. This platform will be machined using a mill, and a hole will be drilled and tapped in the middle to attach to the motor shaft. Four holes will also be drilled into it so the rolling motor can be bolted onto the top of it. This motor shaft will be attached to the electromagnet.

The spring system for the napkin dispenser will consist of a square container that is a little larger than the dimensions of a napkin. The container will be purchased. A platform will be cut to the size of the napkins and will sit inside the container. A telescoping support system under the platform will be made using different size pipes that will be cut to size using the band saw. A compression spring will be inside of the telescoping support system to provide a force up on the platform and napkins.

The four bar mechanism used to transfer the napkins will be made of plastic. Each link will be cut to size using the laser cutter. The motor driving the system will be placed on the same platform where the rotating arm and lever subsystem is on. The links will be attached to each other using bolts. The two driving linkages will be bolted to a shaft driven by the motor.

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The vacuum apparatus will be made of plastic. The laser cutter will be used to cut the six sides of the apparatus and the six sides will be glued together to create a rectangular box. The bottom piece will have holes cut out to allow air flow and create suction.

5.5. Testing Each subsection and the machine in its entirety will need to be tested. The four bar mechanism will be tested to ensure that it can transfer one napkin to the folding platform and return to its original position in under 6 seconds. The electromagnet will be tested to confirm that it can deliver one fork and one knife to the folding platform within 6 seconds. The folding platform will be tested to ensure that it can complete the three folds in 7 seconds.

The electromagnet arm and platform will be tested to make sure it can move vertically 1’ and rotate 360 degrees. It will also be tested to make sure it can roll the fork and knife inside the napkin within 5 seconds. The electromagnet will then be tested to ensure that it can dispose of the set into the bin under the platform and return to its original position in 7 seconds.

After each subsection has been tested, the entire machine will be tested as a whole. The machine needs to be able to complete all tasks in 30 seconds. The machine has to be able to work for 8 hours on a daily basis. We will need to test the machine for one week straight for 8 hours a day to make sure it will function properly.

5.6. Project Deliverables Final Design Report including test results A working prototype that meets customer requirements Analysis of any failed components Brief user instructions

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5.7. Schedule

Pre-Proposal

Formal Proposal

Proposal Presentations

Critical Function Testing

Preliminary Design Review

Bill of Material

Order Components

Receive Components

Critical Design Review

Christmas Break

Manufacturing

Final Design Review

Testing

9/1/08 11/1/08 1/1/09 3/3/09 5/3/09 7/3/09

Start DateCompleted

Figure 26: Project Schedule

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5.8. BudgetTable 4: Expenses

Description Qty. Unit PriceExtended Price

Nap

kin

Bin Sheet Metal 1 $50.00 $50.00

Metal Springs 4 $20.00 $80.00

Nap

kin

Plac

emen

t Compressor 1 $150.00 $150.00

Metal Bars 1 $25.00 $25.00

Ducting 1 $50.00 $50.00

Motor 1 $50.00 $50.00

Silv

erw

are

Plac

emen

t

Electromagnet 1 $80.00 $80.00

Metal 1 $20.00 $20.00

Motor 2 $50.00 $100.00

Nap

kin

Fold

ing Plastic Sheet 1 $75.00 $75.00

Hinges 3 $20.00 $60.00

Motor 1 $75.00 $75.00

Metal Bars 1 $25.00 $25.00

Cable Wire 1 $30.00 $30.00

Oth

er Programmable Logic Controller 1 $400.00 $400.00 Building Materials ( nuts, bolts, springs, hinges, etc.) 1 $300.00 $300.00

Subtotal $1,620.00

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Figure 27: Personnel Diagram

40

Silverware

Wrapper

Transfer/Storage of m

aterials

FoldingRolling

Nap

kinSet

PlatformArm

s/Levers

Electromag

netElectrom

agnet Arm

Programm

ing

4 Bar M

echanism

Vacuum

Napkin

DiscarderSoftw

areHardw

are (m

otors, controllers)

Spring System

5.9. Personnel


6. ReferencesThomas: Standard Product Catalog. Retrieved 10 October, 2008 from the World Wide Web: http://www.magnetoolinc.com/

Magnetool Inc: Low Profile Electromagnets. Retrieved 6 October, 2008 from the World Wide Web: http://www.combinedfluidproducts.com/pdfs/ThomasPumps&Compressors.pdf

Cheesecake Factory Liaison: Nate Urbassik

7. Appendices

7.1. Team Member Resumes

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42


43


44


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7.2. Component Specification Sheets

7.2.1 Electromagnet

Figure 28: Magnetool Electromagnet Specifications

http://www.magnetoolinc.com

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7.2.2 Vacuum Compressor

Figure 29: Thomas Compressors Specifications

http://www.combinedfluidproducts.com/pdfs/ThomasPumps&Compressors.pdf

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meng 491w senior design project - university of san...

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