452 Final Report v2

8/2/2019 452 Final Report v2

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UNIVERSITY OF MICHIGAN

Final Report: ME 452Design for

ManufacturabilityRedesign of a Hand-held Vacuum Cleaner

Daniel Cheng, Hrushit Dave, Rosanna Zhang and Adithya Varadarajan

12/14/2009

Fall 2009

Instructional Staff:

Professor Donald Malen

GSI Josh Bishop-Moser


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1. Executive Summaryi. Background and motivation: Black and Decker CHV7202 hand held vacuum cleanerwas selected as our product to be re-designed because of its many flaws. Based on online

customer reviews and personal use we determined the main complaints of the vacuumcleaner were that it lacked suction power, directed dirty air in users face and had poorbattery life which motivated us to provide an improved product.

Mission statement: Create a hand held vacuum cleaner which has increased suctionpower and increased battery life at a reduced product cost through better

manufacturability

ii. Design methods and tools employed to improve the designPreliminary design methods included making a containing system map and Kano

questionnaire methods to assess the main requirements. Competitive and Lateral

benchmarking were used to determine the product design specification. Additional

requirements were determined based on requirements of the secondary customers. A

QFD was created to transform user demands into design quality, to deploy the functionsforming quality, and to deploy methods for achieving the design quality into related

subsystems. Multiple concepts were generated by selecting seven primary principles,

creating various concepts for each principle and then selecting the best combination of

the concepts selected. Modular designs were created to address the specific needs of

different target markets and to specify which parts would be different for each product.

Design for assembly methods including using the Boothroyd-Dewhurst charts were used

to make minor changes to the design to reduce cost and improve assembly time.

iii. Resulting improvements in quality, cost and value to the customer and themanufacturer.

The above tools and methods helped us develop an improved hand held vacuum cleaner

having increased suction power. The increased suction power and the reduced number of

sweeps required to clean are mainly facilitated by a better motor and a newly designed

rotating brush at the mouth of the vacuum cleaner. A telescopic handle with a tactile

rubberized grip has replaced the original handle to improve the handling and the user

experience. Additional features include guide light, battery charge signal and a new

switch with high or low power options to improve the efficiency of the vacuum cleaner.

The battery pack is now made to snap fit in order to make it easily replaceable if required


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2. PICTORIAL SUMMARYORIGINAL PRODUCT

RE-DESIGNED PRODUCT


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3.PRELIMINARY WORK

Preliminary work included the identification of parts and their required materials. This was followed by

creating a function diagram to determine the main working principles and the interacting components of

our product.

3.1 Product Dissection and Material List

An exploded view of the disassembled product can be seen in figure 2 below followed by Table 1 (next

page) detailing part name, material, function and method of manufacture.

Figure 1: Exploded view of Black & Decker CHV7202

Index:

Part Number Part Name Part Number Part Name

1.1 Main Housing Right 7 Filter Mount

1 2 Main Housing Left 8 Button


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3.1.1 Part details- Materials and Manufacturing methodsPartNumber Part Name Materials Method OfManufacture Function

1.1 Main HousingRight

High Impact Polystyrene Mold casted Device handle & Coverinternal parts

1.2 Main HousingLeft

High Impact Polystyrene Mold casted Device handle & Coverinternal parts

2.1 BatteryHousing Left

Polypropylene Injection Molding Provide cover forbattery unit

2.2 BatteryHousing Right

Polypropylene Injection Molding Provide cover forbattery unit

3 Foam Filter low-density polyetherFoam

Chemical processingof cellulose

Filter exhaust air

4 Charger Rubber, Polypropylene,Copper

Injection molding Charge the batteries

5 ChargingStand

Polypropylene Injection molding Charging dock wherecharger and Dustbusterconnect

6 Nozzle Polypropylene Injection molding Collects dust anddirects air

7 Filter Mount Polypropylene Injection molding Redirects dust intoNozzle(7) & Holds theFilter(2)

8 Button Polyoxymethylene Injection molding Helps toggle switch

9 SqueegeeAttachment

Low density Polyethylene& Rubber

Injection molding Assists in cleaningliquid spills

10 CreviceAttachment

High Impact Polystyrene Injection molding Assists in cleaningnarrow openings

11 Motor Copper, Steel Ready-Made Provide suction power

12 Batteries Nickel, Cadmium Ready-Made Provide energy tomotor

13 Switch Polypropylene & Copper Extrusion Turns device on/off

14 BatterySupport

Polystyrene Stamping Provide support toBattery


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3.2 Function DiagramWe chose the hierarchical function diagram because our process was not sequential in nature. There wereseveral independent functions that were happening or needed to happen simultaneously. This diagram is

more suited to showing how our components come together and what functions each one serves at

present.


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4. DEVELOPMENT OF DESIGN REQUIREMENTSOur mission statement was developed based on a Kano questionnaire. The main questions for the Kano

method were developed based on the primary complaints we generated based on personal use and onlinecustomer reviews. Target product design specification were created based on results obtained from

competitive benchmarking.

4.1 Customer Complaints

4.1.1Complete List of Complaints

A list of complaints was generated based on personal use and available data on online shopping websites(Please refer to Appendix A):

Air is released through the side vents while vacuuming directly into users face Air released through the side vents has foul odor Hard handle end does not provide a good grip Handle end not big enough Insufficient suction and does not provide 100% results in cleaning Charging dock is flimsy and hard to use with a bulky adapter No Battery indicator or charging status indicator Battery cannot be replaced and does not last over a year Dirt gets stuck to the foam in the dust storage which means that the foam needs to be manually

cleaned after using the vacuum

Hard to clean as dirt is lodged in the nose Too much noise for the size and power generated Not earth friendly High repair costs Stores dirt up in the sides of the nozzle so dirt falls out if tilted wrong Thick nose hard to get between crevice even after using attachment Poor reach- Need to bend down to access corners, floor Not effective as a wet vac Performance degrades as battery is used Charging time is hugely disproportionate to charge duration

4.1.2 Primary Complaints

Air is released through the side vents while vacuuming directly into users face Charging dock is flimsy and hard to use with a bulky adapter Insufficient suction and does not provide 100% results in cleaning Charging does not last long


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4.2Containing System MapA containing system map was created to help visualize the main requirements of our product and all the

elements which affect the product.

4.3Mission Statement based on Kano methods

4.3.1 Kano Questionnaire and Results

Functions corresponding to complaints and their Kano Questions (Note : question a is negative and bis positive)


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b. How would you feel if the vacuum cleaner had a simple charger wire?Like

c)

Increased Suction Powera. How would you feel if the vacuum cleaner had sufficient suction to pick up small bitsof paper?Dont Care

b. How would you feel if the vacuum cleaner had sufficient suction to completelyremove the dust/dirt from surfaces?Like

d) Increased Battery Lifea. How would you feel if the vacuum cleaner had a battery life of 20 minutes?

Normalb. How would you feel if the vacuum cleaner had a battery life of 60 minutes?

Like

Kano Method Table

Negative Question Answers

Like Normal Dont Care Dont Like

Positive

QuestionAnswers

Like D C B

NormalDont Care A

Dont Like

Key Delighted , Normal , Expected

Our Kano Method Analysis Survey was carried out by the team as a whole assuming the consumermindset. Based on the results in the table above you can see that our analysis gave us 1 expected function,two normal functions and two delighting functions.

4.3.2 Mission Statement

Create a hand held vacuum cleaner which has increased suction power and increased battery life at

a reduced product cost through better manufacturability.

4.4 Requirements Based on Industry Status

It was determined that the product lies within the static industry and customers

are more attracted by style, brand and quality. (Please refer to Appendix B to see

the questionnaires). A typical rate of improvement for a static product like ours is

a maximum of 10%/year. Since, the product is already being manufactured; new

specifications should be possible to be implemented via current manufacturing


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4.5Requirements based on Primary and Secondary Marketsa. Typical secondary customer: A young couple with a baby: Age: 25-35

A young couple with a baby or a toddler might find this product useful cleaning up food mess andspills. They would want a vacuum that is easy to hold, powerful and efficient, able to pick up both dryand wet spills. They would also want something thats quiet, so it wont disturb their baby. Its importantfor the vacuum to be easy to clean regardless of the kind of garbage it had picked up.

b. Difference between primary and secondary customer needs.

A primary customer is a single male/female in their 20s, who expects the vacuum to be easy touse and durable. They need the vacuum to clean their apartments, so the vacuum has to be efficientpicking up dirt and small trash. The vacuum should be able to reach in narrow space and tight corners.The secondary customer as described in part a would mainly focus on the kind of trash the vacuum is ableto pick up, and how easy it is for them to later clean the vacuum. Its also important for the vacuum to bequiet and attractive since it would be used in a typical home environment.

Single male/female

18-30 yr

Young couple with

baby/toddler

Normal & Expectedfunctions

Easy to useDurableReach in cornersApartment cleaning

PowerfulQuietPicks up dry and wetfood spillsEasy to clean

Delighting functions InexpensiveEasy to storeattractive

AttractiveSeveral settings fordifferent types of trash

4.6Competitive & Lateral BenchmarkingCompetitive benchmarking helped us understand how our product compared with that of our

competitors. It was concluded that some of the competitors provided additional features such as a

rotating bristled brush, better filtration system, LED charging indicator and many more which are

summarized in the tables below.

a) Table a: Competitive benchmarking with products at the same price levelb) Table b: Competitive benchmarking with products at different price levelsc) Table c: Lateral benchmarking with (Appendix C for patents)


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4.6.1 Competitive Benchmarking : Table A: Same Prices

Product Name Black & Decker CHV7202 7.2-

Volt Cordless Wet/Dry

Dustbuster

OUR SELECTED PRODUCT

Eureka 79B The Boss

Cordless Rechargeable

Handheld Vacuum Cleaner

BISSELL 33A1 Pet Hair

Eraser Corded Handheld

Vacuum Cleaner

Hoover S1120 Hand Held

Wet/Dry Hand Vacuum

Cleaner

Product Image

Specifications 7.2-volt handheld vacuumcleaner for both wet and dry

messes sleek rechargeable cordless

design

6-ounce removable binempties easily

17 air watts wet/dry filter wall-mountable charging

base

Includes squeegee attachmentand crevice tool for tightspots

Price $29.99

3.6 V powerClean Air System helps

protect the motorOn-board crevice toolEasy-to-empty dustbin2-1/2-inch-wide cleaning

path

Lightweight designFingertip on/off control

switch

Wall-mountable chargingbase included

Dry VacPrice $29.99

Washable hepa media filterand filter screen

Interchangeable hard nozzleand flexible rubber contournozzle

4-inch-wide cleaning pathEasy-grip handleLightweight DesignFingertip-access on/off

switch

1 Year Warranty

16-foot power cord with acord-wrap system

Price $29.99

Cleans both wet and drymesses

7-1/5 volts of cordlesspower

Push-button power switch 3-inch-wide nozzle Easy-empty dirt cup;

washable

Reusable filter Rechargeable battery; Wall-mountable charging

stand included 1-year limited warranty Price:$29.99


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4.6.2 Competitive Benchmarking: Table B: Different Prices

Product Name Black & Decker CHV7202 7.2-Volt

Cordless Wet/Dry Dustbuster


Black & Decker PHV1800CD 18V

Pivoting-Nose Cordless Energy-Star

Handheld Vacuum Cleaner

Shark SV736K 15.6-Volt Cordless

Handheld Vacuum Cleaner with

Motorized Brush

Product Image

Specifications 7.2-volt handheld vacuum cleaner forboth wet and dry messes

sleek rechargeable cordless design 6-ounce removable bin empties easily 17 air watts wet/dry filter wall-mountable charging base Includes squeegee attachment and

crevice tool for tight spots

Price $29.99

Cordless 2-speed handheld vacuumcleaner with 10-position pivoting

nozzleCyclonic action and EZ Clean Wheel

system help maintain suction power

3-stage filtrationEnergy Star approved meets EPA

energy efficiency guidelines

Easy-empty systemFolds in half for storing

Includes upholstery brush, smallcrevice tool, and wall-mountablecharging base

Price $69.99

Cordless handheld vacuum cleanerwith Twister Cyclonic technology

Detachable motorized brushremoves pet hair and dirt fromupholstery and carpet

Crevice tool for hard-to-reach spotsWashable filterConvenient dust cupLED charging and low-battery

indicator

Powerful 15.6 Volt motor

Price $39.99


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4.6.3 Lateral Benchmarking: 3 Products Selected (Please See Appendix C for Patents)

Product

Name

Black & Decker CHV7202 7.2-

Volt Cordless Wet/Dry

Dustbuster


Above ground pool cleaner:

Hayward 500 Aqua Bug

Above-Ground Automatic

Pool Cleaner

Shop vac:

925-23-10 Industrial 10-

Gallon, 6.5-HP Wet/Dry

Vacuum

Medical Suction Device:

Devilbiss Stationary

Suction Machine

Product

Image

Specifications 7.2-volt handheld vacuumcleaner for both wet and drymesses

sleek rechargeable cordlessdesign

6-ounce removable binempties easily

17 air watts wet/dry filter wall-mountable charging base Includes squeegee attachment

and crevice tool for tightspots

Price $29.99

SmartDrive programmedsteering system

Bottom of the pool is cleanedquickly and completely

Installs in less than 10minutes, without tools

Unique turbine systemprovides constant balancedflow assuring quiet operation

and gentle movement acrossthe pool bottom

Advanced, contoured headdesign allows the AquaBug tocomplete the steering patternin minimal time

Price:$129.00

8" x 1.25" LockOn HoseHand Grip & Airflow

Control 10" wet/Dry Nozzle

Crevice ToolRound Brush, Gulper

Nozzle, Dual SurfaceSelector Nozzle

Tool Basket, Cartridge FilterHigh Efficiency Disposable

Filter Bag1 Year WarrantyPrice:$245.95

Device for removingliquids or gases by suctionfrom the body cavities

High performancecapabilities

Runs on rechargeablebatteries

Vacuum adjustments allowfor 80-550 mm Hgfree flow

of 27 liters/minuteSmallest and strongestportable suction unit of itskind.

Price:$190.00


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4.7 Product Design Specifications

Product design specifications were created based on data available from competitive and lateral benchmarking. These specifications helped us

determine target values for our end product and incorporate these requirements in our final design.

Specification Units competitive product current product targetPrimarymarket world class Interactingsystem ConstraintorNeed Kanocategoryelectricpower volts 110 110 110 110/220 USpowersupply Constraint

ChargingTime Minutes 40 60 40 40 Consumer/Batterys uppl ie r Const rai nt Delightful

UseableTime Minutes 30 20 60 30 Consumer Constraint Normal

Sweepstoclean Times 2or3 3or4 1 1 Consumer Need N/A

AttachmentHolder Yes/no yes no yes yes Consumer Need N/A

CreviceAttachment Yes/no yes yes no yes Consumer Need N/A

Warranty Years 1yr 1yr 2yr 2yr Manufacturer Need N/A

DustBinCapacity in^2 5 6 6 6 Consumer Need N/A

EaseofCharging Simple/Difficult Simple Difficult Simple Simple Consumer Need Normal

PlacementofAirVents Away/Toward AwayfromUser TowardUser AwayfromUser AwayfromUser Consumer Need Expected

ParticleSizepickedup Dust/dirt/small dust/dirt dust/dirt dust/dirt/smallpaperbits dust/dirt/smallpaperbits Consumer Need Delightful

BatteryChargeIndicator Yes/no no no yes yes Consumer Need N/A

TelescopicHandlewithTactileGrip Yes/no no no yes yes Consumer Need N/A

RemovalofDustfromFilter Simple/Difficult Simple Difficult Simple Simple Consumer Need N/A

Replaceable Battery Yes/no no no yes yes Consumer Need N/A

AbilitytoPickUpwater Yes/no no yes no yes Consumer Need N/A

Weight Pounds 2

lbs 3

lbs 2

lbs

2lbs Consumer Constraint

N/AOperationNoise dB 85 85 85 75 Consumer Need N/A


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5. QUALITY FUNCTIONAL DEPLOYMENT

5.1 Quality Function Deployment Main System

A main QFD was created to transform user demands into design quality, to deploy the functions forming

quality, and to deploy methods for achieving the design quality into subsystems and component parts, and

ultimately to specific elements of the manufacturing process.


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5.2 Part Deployment QFD Matrix

Part Deployment QFD matrices were created to help determine the main characteristics required in the

redesigned parts. For our project we concentrated on redesigning the handle for the vacuum cleaner and

designing a rolling bristled shaft for increasing the suction of the vacuum cleaner. Both the QFDs helped

us determine constraints for the design of individual parts. The QFDs also helped us seek the right

materials by researching materials with properties having maximum weightage in the part deployment

QFD

5.2.1 Part Deployment QFD for handle

5.2.2 Part Deployment QFD for rolling Bristled brush


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6. CONCEPT GENERATION AND SELECTION

Based on the function diagram seven main working principles were determined to be redesigned and also

the components these working principles were related to were identified.

6.1.1 Concepts created for various Working Principles

1. Working Principle Creation We considered the following list of working principles and basedon the best combinations of these working principles we generated a variety of concepts for our

design.

1. Pick up Dirt The below were the options considered as ways to pick up dirt. Basedon our understanding of practicality and feasibility we decided that the lint roller, the

piston pump and the static charge attraction methods are not as good as the motor

suction and the rolling bristled brush options.

a. Static Charge Attractionb. Motor Suctionc. Piston Pump Suctiond. Rolling Bristled Brush to pick up larger wastee. Lint Roller type system

2. Filter Picked up Waste The below options were considered as ways of filteringthe waste that passes through the system. The electrostatic precipitation option is the

most unfeasible while the water filter is impractical in a handheld vacuum cleaner

even if it is effective.

a.

Mesh Filterb. Foam Filterc. Water Filter for Dustd. Double filter for larger and finer particles (filter tape)e. Electrostatic Precipitation processf Replaceable filters like coffee filters

PickUpDirt

Motor

FilterPickedUpWaste

Dust

Filter+Holder

StoreWaste

Dust

Container

StoreElectricPower

Battery

RechargeBattery

Charger+Dock

TurnOn/Off

Switch

HoldSystem

handle


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d. Dust container built into handlee. Collapsible Dust bag storage system

4.

Store Electric Power The below options were considered as ways to store thepower in the system. The most practical options will be the batteries which are most

readily available while the most impractical option will be the use of a spring.

a. Standard Batteryb. Lithium Ion Batteryc. Store as Mechanical Energy in a springd. Capacitors to store chargee. Compressed Air to create a vacuum

5. Recharge Battery The below options were considered as ways to recharge theinternal power storage device. We determined that the use of a wireless charging pad

and solar recharging would both be highly inefficient and would not help us achieve

our goal for a quick charging time.

a. Electric Power from Outletb. Solar Rechargingc. Dynamo Recharging (convert mechanical into electrical energy)d. Recharge from USBe. Wireless charging pad (use induction)

6. Turn On/Off We evaluated the options for controlling the system (On/Off) usingthe Pugh chart given in the next section.

a. Switchb. Rotating Control that controls speed as well (like a fan regulator)c. Biometric on/off slide thumb to turn on and turn off powerd. Spring Loaded stays on as long as you hold it downe. Slider with high/low power optionsf. Voice Control System

7. Hold System These were the ways that we felt the system could be held duringoperation. All of these options are feasible and we decided to determine the best one

based on its compatibility with the overall best design system.

a. Standard Handleb. Telescopic Handlec. Folding Suitcase Handled. Wraparound Strap to attach to arm/foote. Tactile/Rubberized Gripf. Thumb Grip (refer to sketch)


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6.1.2 Pugh Chart used to rank various ideas created for Working Principle No.6- Switch On/Off

From the above Pugh chart we concluded that a slider with power options is definitely the bestoption for switching the vacuum cleaner on/off

6.2 Created final concepts

The first chart on the large A3 sheet shows all the concepts created for working principles withsketches. The second chart shows the 5 concepts created. This was followed by a Pugh chartranking the 5 concepts following which we selected our best design concept.


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6.2.1 Sketch of Various Working Principles created and highlighted in blue features working principles selected for final concept. Explanation for that is provided on the next page.


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6.2.2 Generated Concepts

Based on the sketches and working principles shown on previous page we selected 5 combinations which would make our 5 conceptsfor the redesigned vacuum cleaner. Some initial sketches based on these concepts are shown on the next page.


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6.2.2.1 Generated Concept 1


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6.2.2.2 Generated Concept 2


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6.3 Final Concept Selection

6.3.1 Pugh Chart Comparing Various Concepts

The System Pugh chart shown on the next page helped us determine the best concept for ourfinal design. This chart is shown on the next page and we determined that design 5 is the bestconcept we generated. All future steps such as a final sketch, architecture strategy and DFAmethods were employed based on this final design

Pugh Chart comparing all our designs based on the given design criteria

6.3.2 Final Selected Concept


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7. ARCHITECTURE STRATEGY

We used the decision making matrix to decide what components we should platform and whatcomponents are better made brand specific. From the matrix we decided to platform the motor, batteryand switch because the costs to offer variety in these components are high but not helping appreciably indifferentiating our product. We decided to offer brand-specific modules for handle, charger and dock,dust container and dust filter because the cost to produce these modules are low and helps greatly indifferentiating our product.

Decision making Matrix

CosttoOfferVariety

hig

h

Platform it Analyze to DecideMotor

Batteryswitch

Does not matter Offer brand-specific

Handle

low

Charger+dock

Dust Container

Dust filterlow high

Importance to Overall Profit through Brand differentiation

After deciding which components to platform and which ones to make brand specific, we use themodularity matrix to decide which module is included in our modules. We decided to have two brands,basic and pro, with the premium modules in the pro brand.

Modularity Matrix

Brands: Basic Pro

Motor platform (all the same)

Dust filter Double filterDouble filter (replaceable)

Dust Containerhandle dust container(platform)

battery Li-ion (platform)


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8. DESIGN FOR ASSEMBLY METHODS

The methods we employed for DFA helped us understand the assembly efficiency of the productand to help improve it by combining or redesigning a few parts which would help reduce the costof assembly.

8.1 Summary

Using the Boothroyd and Dewhurst (B-D) (Please see Appendix D) charts for manual handling andmanual insertion, we performed DFA analysis on the existing design of our product and estimated theassembly efficiency.

In our initial design, the total manufacturing time is 190.5 seconds which cost 76.20 cents with a designefficiency of 29.9%.

After our redesign, the total manufacturing time is improved to 138.05 seconds and cost 55.22 cents(20.98 cent savings) and increased design efficiency up to 52.2%.

The major changes (listed below) made in the design were to achieve ease of assembly by minimizing the

number of parts and applying the DFA rules are summarized below.

1) Connecting shaft for rotating bristled brush at the open end using motor/battery power wasReplaced with a much simpler wheel gear purely mechanical system:

a. It would avoid excessive assembly steps by reducing the number of partsb. The rotating shaft can be rotated by implementing a high gear ratio between wheels at the

front end and the shaft.c. Avoids using motor/battery power thus increasing efficiency

2) Connection of Individual parts to the battery (switch,signal light,guide light and power inlet) wasreplaced with a wire module which is connected to each of these parts and is connected to thebattery

a. It avoids the different wires from tangling or nestingb. It increases speed and ease of assembly as only one connection is made to the battery

3) Rolling Bristled brush nozzle is no longer detachable but the shaft is directly snap fitted in thedust container

a. Decreases number of parts and cost4) Redesigned rolling bristled brush: Modified the spiral design which increases rotation via airflow

and has inbuilt bristle-like characteristicsa. Reduced number of parts

5) Combination of signal light and guide light- The guide light will be programmed to serve as asignal light during charging thus combining two different lights into one


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8.2 Assembly efficiency Table of initial Design


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8.3Assembly efficiency Table after redesign


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9. DESIGN FOR SNAP FITS

Some main areas were identified to include snap fits which would help increase the assembly efficiency

and reduce the number of parts in our redesigned product.

9.1 Methods and Equations used

After examining the assembly efficiency tables, we identified the parts that could be redesign into snapfits either for eliminating fasters or simply for assembly time reduction.The 2 snap fits design we chose to add into our design are:

1) Snap fit between the two halves of the interior housing for the motor which can be seen inattached figure2) Snap fit between dust container(subassembly1) with main housing (subassembly2) which can beseen in the attached figure

Assumptions:1) Based on existing product and material selection in previous homeworks we select

Polypropylene (PP) as the appropriate material for both the snap fit parts2) The interior housing snap fit is permanent and would not have to be separated while there would

be frequent separation and joining in the dust container snap fit3) Calculations are for each cantilever beam in the snap fit4) It was assumed that we would need an assembly force of 25N5) Appropriate assumptions were made for thickness, width and height for each snap fit

Equations used:

1) /180 - to convert degrees to radians for bending angle2) Finding Deflection force---Where: b=width, h=thickness, E= Secant Modulus, = strain, l=length

3) Finding Assembly Force---Where: P = Deflection force, = coefficient of friction, = assemblyangle

4) Finding Required Beam Deflection---- Where = permissible strain, l=length, h=thickness, y=beam deflection


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9.2 Calculation of Snap fits

9.2.1 Calculations for Interior Housing Snap fit

1) Interior HousingMaterial Properties

Material coeff of friction () strain E (Gpa)

Polypropylene 0.450 0.056 1.22

Dimensions (m) Angles

b (width) h (thickness) length alpha 40 0.698 rad

0.008 0.002 0.030 beta 65.8 1.148 rad

Calculated Results

Engagement Force P 12.15 N

Assembly

Force F 25.16 N Deflection y 0.0168 m

Below is our final concept designing a snap fit for our vacuum motor. This snap fit helps our assembly

efficiency by eliminating fastener therefore increasing assembly efficiency and reduce cost.


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9.2.2 Calculation for Snap fit for dust container

2) Dust ContainerMaterial Properties

Material coeff of friction () strain E (Gpa)

Polypropylene 0.450 0.0336 1.22

Dimensions (m) Angles

b (width) h (thickness) length alpha 40 0.698 rad

0.008 0.002 0.040 beta 65.8 1.148 rad

Calculated Results

Engagement Force P 5.47 N

Assembly

Force F 11.32 N Deflection y 0.0179 m

Below is our snap fit design for our dust container and body of the vacuum. This snap fit is designed for

repeated assembly and disassembly of the user for ease in emptying dust in the container.


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10. MATERIAL AND PROCESS SELECTION

This section covers our detailed material and process selection procedure that was used to determine the

materials and manufacturing processes for our vacuum cleaner redesign. The focus is on two primarycomponents that were redesigned and these are the HANDLE and the ROLLING BRISTLED BRUSH.

10.1HandleWe have redesigned the handle with certain additional features such as tactile grip, telescopic

functionality and the switch located on the handle. However, for the sake of the homework we focus on

the main cylindrical shaft of the handle.

10.1.1 Primary and Secondary Functions1. Primary Function -- STRENGTH

a. Bear Axial Loads This is important because the handle should be able to withstand theload of the system when used.

b. Bear Torsional Loads This is important as the handle should not be flimsy and twistduring operation

c. Impact Resistance This is important to ensure that the handle does not break whendropped.2. Secondary Functions

a. Lightweight The majority of system weight arises from the core components of themotor and batteries. The handle shouldnt add to that excessively as the system needs tobe handheld thus the need to be lightweight.

b. Durability (Wear Resistance) This is necessary as the handle will be the most usedinterface between the user and the vacuum cleaner system and this needs to be able towithstand wear over time.

c. Insulate Heat/Electricity There will be heat generated by the rotation of the motor andthere will also be electricity in the system when charging, in order to prevent the userfrom coming into contact with either of these it is necessary that the handle be aninsulator.

d. Low Cost The majority of system cost arises from the core components of the motorand batteries and the handle needs to be low cost in order to keep the total system withina reasonable price.

10.1.2 Function Objective Constraints-----Property Limits, Material Indices

Component Handle

Function Grip for entire system Objective Minimize Cost

Constraint m


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10.1.2.1 Justification of Property Limits

1. Mass The primary mass of the vacuum cleaner comes from the motor. It defeats the purpose ofa handheld vacuum cleaner if the handle weighs more than 500 grams.

2. Conductivity No part of the vacuum cleaner should be conductive as it should insulate andprotect the user from electric shock. Thus, the conductivity has to be approximately around that

of air. (Good insulator)

3. Axial force Assuming that the remainder of the vacuum cleaner weighs approximately 1kg, thehandle should be able to withstand the weight of the cleaner without deforming/breaking during

operation

4.

Cost It has to be low cost in order to keep the price of the system low.5. Inert material the material shouldnt react with various things in the environment in order to

remain robust.

10.1.2.2 Material Index -- Strength limited, outer radius specified -- Maximize

/

10.1.3Material Selection First Stage Property Limits


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10.1.4List of materials from first stage of material selection

Handle Suitable Justification Applications

Acrylonitrile

butadiene styrene

(ABS)

Yes Meets all requirements, tough,weather resistant, Cost effectiveand lightweight

Housings, luggage shells, toys

Natural rubber (NR) No Although it meets all therequirements it is highlyflammable and cannot be recycled

NA

Polyethylene (PE) Yes Low density, price and meets allrequirements including yieldstrength and insulation

Milk containers

Polypropylene (PP) Yes Fire retardant, widely used,Lowdensity, price and meets allrequirements including yieldstrength and insulation

Pipes, pipe fittings, beer bottles, airducts

Polystyrene (PS) Yes Low density, price and meets allrequirements including yieldstrength and insulation

Electronic housing, householdappliances

Polyvinylchloride

(tpPVC)

Yes Low density, price and meets all

requirements including yieldstrength and insulation

boat fenders, pipe fittings, medical

tubes

10.1.5Material Selection Second Stage Application of Material Index

Application of Material Index in CES (Red Arrows indicate direction of increasing index)

Slo e=3/2


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Final material selected is Polypropylene because:

- Good insulator, meets density & cost requirements and has high yield strength

-Lowest density and Lowest cost combination as compared to other candidate materials

-Already being used in current product

- Maximizes Material Index as seen in figure on previous page

10.2Rolling Bristled BrushIn order to increase the suction of the vacuum cleaner we have added a rolling bristled brush. However,for the sake of material selection and process selection for the homework we focus on the main rotating

shaft which holds the bristles but we do not focus on the bristles in the homework

10.2.1 Primary and Secondary Functions1. Primary Function DURABILITY

a. Resist Wear over extended and repeated use This component will constantly come incontact with the surface that needs to be cleaned and will also be in constant rotation

during operation and it should withstand this.b. Resistant to Water Since the vacuum cleaner will continue to have wet/dry operation,

this shaft needs to be resistant to water.c. Resists Torsional Deformation While cleaning, the rotating brush will encounter

torsional forces that oppose the direction of rotation and it should be able to withstandthis.

d. Resists Thermal Deformation The repeated rotation at high speeds is bound togenerate heat due to friction with the surface that needs to be cleaned. The shaft material

needs to be able to withstand this heat generation without deforming.2. Secondary Functionsa. Light Weight This is important as the motor needs to drive this rotating shaft and if it

is heavy it will cause the motor to be inefficient, less powerful and will affect the batterylife.

b. Shouldnt Absorb Odors This is important as the smell of the picked up wastematerial shouldnt stay on the rotating shaft and cause an inconvenience to users

c. Low Cost The majority of system cost arises from the core components of the motorand batteries and the shaft needs to be low cost in order to keep the total system within a

reasonable price.

10.2.2 Function Objective Constraints-----Property Limits, Material Indices

Component Handle


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10.2.2.1 Justification of Property Limits

1. Mass The primary mass of the vacuum cleaner comes from the motor. It defeats the purpose ofa handheld vacuum cleaner if the bristle brush weighs more than 150 grams.

2. Fatigue Strength This part will undergo repeated rotations over its life time and will probablyencounter the most forces over the product life time. So fatigue strength is important to have a

durable product.

3. Cost It has to be low cost in order to keep the price of the system low.4. Inert material the material shouldnt react with various things in the environment in order to

remain robust.

10.2.2.2 Material Index -- Strength limited, outer radius specified -- Maximize

/

10.2.3Material Selection First Stage Property Limits


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10.2.4List of materials from first stage of material selection

Rolling Bristled Brush Suitable Justification Applications

Acrylonitrile

butadiene styrene

(ABS)

Yes Meets all requirements, tough,weather resistant, Cost effectiveand lightweight

Housings, luggage shells, toys

Natural rubber (NR) No Although it meets all therequirements it is highlyflammable and cannot be recycled

NA

Polyethylene (PE) Yes Low density, price and meets allrequirements including yield

strength and insulation

Milk containers

Polypropylene (PP) Yes Fire retardant, widely used,Lowdensity, price and meets allrequirements including yieldstrength and insulation

Pipes, pipe fittings, beer bottles, airducts

Polystyrene (PS) Yes Low density, price and meets allrequirements including yieldstrength and insulation

Electronic housing, householdappliances

Polyvinylchloride

(tpPVC)

Yes Low density, price and meets all

requirements including yieldstrength and insulation

boat fenders, pipe fittings, medical

tubes

10.2.5Material Selection Second Stage Application of Material Index

Application of Material Index in CES (Red Arrows indicate direction of increasing index)

Slo e=3/2


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Final material selected is Polypropylene because:- Meets weight, fatigue strength, yield strength and cost requirements-Lowest density and Lowest cost combination as compared to other candidate materials

-Already being used in current product- Maximizes Material Index as seen in figure above

10.3 PROCESS SELECTION

Since polypropylene was the identified best material for our two redesigned parts we combined our

process selection process into one section. The batch sizes remain the same for both the parts with other

comparable aspects as well. Process selection was done by comparing the attached process matrices and

also by plugging in values into the CES program for both the handle and the rolling bristled brush shaft

Manufacturing methods are based on the following seven properties: material, shape, mass, section size,

tolerance, roughness, economic batch size. The engineering requirements we require for the redesign of

handle and shaft of brush head are summarized in Table 1.

Table 1: Engineering Requirements

Specification Handle Shaft

Material Thermoplastic Thermoplastic

shape Circular

prismatic/3d

Hollow

Circular

prismatic/3d Hollow

Mass (kg) 0.34 < 0.1

section thickness (mm) 3 4

tolerance (mm) 0.5 0.5

roughness (um) < 2 < 2

batch size (units) 100,000-1,000,000 100,000-1,000,000

After going through the seven category selection (Appendix G) we have identified Injection Molding,

Blow Molding and Resin Transfer Molding as the most appropriate processes that fits our engineering

requirements. These were determined by carrying forward our part characteristics through the various

process matrices. This process has been summarized in the table below.


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Selection

Criteria

Thermo

plastic

Shape Mass Section

thickness

Tolerance Roughness Batchsize

Selected

Processes

Injection

Molding

Injection

Molding

Injection

Molding

Injection

Molding

Injection

Molding

Injection

Molding

Injection

Molding

Convention

Machining

Convention

Machining

Convention

Machining

Convention

Machining

Convention

Machining

Convention

Machining

Blow

Molding

Blowmolding polymer

casting

polymer

casting

Blow

Molding

Blow

Molding

Blow

Molding

Resin

Transfer

Molding

compression

molding

Blow

Molding

Blow

Molding

Rotational

Molding

Resin

Transfer

Molding

Resin

Transfer

Molding

rotational

molding

Rotational

Molding

Rotational

Molding

Resin

Transfer

Molding

thermo

forming

Resin

Transfer

Molding

Resin

Transfer

Molding

ResinTransfer

Molding

On comparing these results with CES we determined that injection molding is our best option. CES

results are shown in Appendix E. The alternative method based appropriate for manufacturing our part

with the seven categories of selection is conventional machining, blow molding and Resin transfer

molding. If we were to have lower batch sizes, conventional machining would be more economical for

our needs.

10.4 IT GRADES

10.4.1 HANDLE

The critical dimension selected was the Handle Diameter. We selected this dimension as it is extremely

important to have a comfortable grip during operation of the device. Our selection was based on the

optimum anthropometric hand grip diameter as obtained from the paper Optimal cylindrical handlediameter for grip force tasks by Yong Ku-Kong and Brian D. Lowe in 2004 for the National Institute of

Occupational Safety and Health. According to this paper, the most comfortable grip sizes range from 30

to 40mm and our team selected 30mm in order for the handle to be usable by the larger population. This

selection arose from the anthropometric design philosophy that determines that designing a grip for

ll h d i ll k i bl b l h d b h h d


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Calculation of Tolerance Grade

10

0.45

0.001

Using a Tolerance Value of 0.5 mm = 500 microns and the selected X value of 30mm we obtained

13.72

13

Injection Molding IT Grades = 9-14 (Achieves required IT grade, (Appendix F))

10.4.2 ROTATING BRISTLE BRUSH SHAFT

The critical dimension selected is the length of the rotating bristle brush shaft. This is important because it

has to fit perfectly in the mouth of the vacuum cleaner while allowing a smooth rolling operation with

minimum friction.

The dimensional tolerance of the length of the rotating bristle brush shaft is important because it must be

able to fit inside the head of the nozzle head.

Calculation of Tolerance Grade

10

0.45 0.001

Using a Tolerance Value of 0.5 mm = 500 microns and the selected X value of 100mm we obtained

12.79

12

Injection Molding IT Grades = 9-14 (Achieves required IT grade,(Appendix F))

10.5 SUMMARY OF MATERIAL AND PROCESS SELECTION

10.5.1 Material:

Base on the CES material selection tool, we have identified Polypropylene as the ideal material for both

the handle and the bristle brush shaft. Polypropylene is ideal for the handle because it meets our weight,

fatigue strength, yield strength and cost requirements. In addition, Polypropylene is better than other

materials because it has the lowest density at lowest cost and is already proven to be effective on the


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10.5.2 Primary Manufacturing Process:

Based on CES results and answers to question 5 we have decided that Injection Molding is the most

suitable manufacturing method to produce both our Handle and the shaft for the rolling bristled brush. Itmeets all our requirements based on material, shape, mass, thickness, tolerance, roughness and economic

batch size characteristics. Secondary process that can be used include conventional machining, blow

molding and resin transfer molding based on CES results and process capability matrices.


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11. DRAWING AND KEY PARTS WITH DIMENSIONS

11.1 Final Concept Perspective Drawing

Sketch below shows the perspective view and the side view of the product exterior. The diagram to the bottom right shows how the

telescopic handle feature we proposed would extend and collapse during use. All the redesigned parts are labeled on the sketch.


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43

11.2 Exploded View of the Product Interior

The exploded diagram shows the relationship between all the main parts. A cross section of the interior of the product main body shows

the major components such as the battery, motor, and the double filtration system.


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12. DESIGN FOR ROBUSTNESS

12. 1 SNR Calculation

In order to fine tune some of the engineering characteristics, we have to conduct a series

of experiments to obtain the optimal configurations of the product. To demonstrate this process,

we have selected Air Watts as our example engineering characteristic. Air watts are obtained by

the measurement of suction and airflow at vacuum cleaner inlet. This is also an important

customer attribute because suction power was one of the delighting functions rated by the

customers. In this case, our optimizing target is bigger the Air Watts value, the better the

suction, which means we need to use the corresponding Signal to Noise Ratio equation tocalculate the SNR value and Loss value.

10 log

)

1/

12.2 Control and Noise Factors

Before conducting the actual experiments, we need to determine the control factors and

noise factors that influence the Air Watts values. The important control factors and noise factors

along with their levels of control are listed below.

i. Control Factors1. Motor Selection Power rating 7.2v (+1) or 3.6v (-1)2. Power Source Voltage Level 7.2v (+1) or 3.6v (-1)3. Design of Nozzle Difference between inlet and outlet in terms of

cross section area 16 cm2

(+1) or 4 cm2

(-1)

4. Design of Fan Amount of air displaced 3 ft3/s2 (+1) or 1 ft3/s2 (-1)

ii. Noise factors1. Operating Environment Temperature 115F = 46C (+1) vs. 32F =

0C ( 1)


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12.3 P-Diagram

With these important factors determined, we were able to set up a P-Diagram for the engineering

characteristic we intend to optimize. The P-Diagram is shown below.

12.4 Factor interaction

The only interaction that can be found in our list of important factors is an important one.

It is the interaction between the motor selection depending on power rating and the selection of

the power source depending on the voltage level of the motor. If a motor with a higher power

rating is selected then correspondingly a higher voltage level power source needs to be

incorporated. E.g. our existing vacuum cleaner motor has a power rating of 7.2V and the poweris sourced from six 1.2V rechargeable batteries. A linear graph below shows the interaction

between all the control factors.

CONTROL

FACTORS

OperatingEnvironment

Temperature

46C(+1)vs.0C(1)

RelativeHumidity

85%(+1)vs.15%(1)

Motor

Selection7.2v

(+1)or3.6v(1)

PowerSource

7.2v(+1)or

3.6v(1)

Designof

Nozzle

16cm2(+1)or

4cm2(1)

DesignofFan

3ft3/s

2(+1)or

1ft3/s

2(1)

AirWatts

(Largerisbetter)

NOISE

FACTORS

1


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12.5 Taguchi Method

Using the Taguchi method, we could conduct the least numbers of experiments to

determine how the selected control factors and noise factors affect the outcome of Air Watts.Below is our experimentation set up with all the aforementioned factors listed, where theirdefinitions and levels are also noted below. The interaction between Motor Selection and Power

Source is placed in column three. No actual experiments were conducted, and therefore no data

is present in the chart.


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13. CONCLUSIONS

Based on the preliminary and final design methods we have redesigned the Black & DeckerCHV7202 hand-held vacuum cleaner to improve its functionality. We were successful in addressing all

our customers complaints and providing an overall improved system.

We have successfully met our mission statement in the redesign of the B&D vacuum cleaner in

simultaneously increasing suction power and battery life. Through the addition of rotating suction brush

head, we are able to increase the suction power of the unit while still using the original motor. Although

the airflow would inevitably decrease due to the extra loading on the motor, we believe that the rotating

brush would more than compensate for the losses to increase suction performance overall. The addition oflithium ion batteries allows our system to increase duration of use per charge, as it has greater energy

density than the current Ni-Cd batteries. We have redesigned the existing handle to include a telescopic

handle with a tactile rubberized grip which provides better reach and increases user comfort. We have

replaced the existing filter with a double filter to improve the filtration system and reduce the foul odor

emitted by the existing product. The air flow has been redirected away from the users face by relocating

the exhaust air vents. A guiding light has been incorporated into our system to improve visibility in dark

corners, narrow spaces or for usage during night time. An additional signal light will indicate the batterystatus to the user. Finally, we have replaced the existing flimsy and unintuitive charger with a simple

plug-and-play charger.

However, if this design needs to be taken to the next step, there are some issues which need to be

addressed. The additional weight created by the new features needs to be considered as it might hamper

the portability of the product. Another parameter that requires optimization is the available space and

placement of individual components to incorporate all the new features while providing adequate empty

space for thermal dissipation of motor. An in-depth cost analysis needs to be performed to determine theviability of the product after the addition of the new features. The cost analysis would need to concentrate

on the cost benefit ratio of using the lithium ion battery over the original Ni-Cd battery. Prototyping and

further testing would be required to test the percentage increase of suction power and battery life over the

original product. Testing would also be required to compare the new filtration system with the old one.

Minor aesthetic issues such as color scheme, surface smoothness and ergonomic design need to be

addressed.

Given a chance to start over again we would definitely follow same methodology in improving

our product design but would like to incorporate increased detail to technical issues with respect to the

engineering of the product. This would include simulation of air flow in the vacuum cleaner, detailed

engineering CAD which would allow us to build a prototype and compare it with the existing product.


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14. REFERENCES

[1] www.amazon.com

[2] Black & Decker Website[3] ME 452: Lecture Notes and Course Pack[4] Optimal cylindrical handle diameter for grip force tasks by Yong Ku-Kong and Brian D. Lowe in

2004 for the National Institute of Occupational Safety and Health.


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15. APPENDICES

Appendix A: Customer Reviews on Amazon


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AppendixB.1:DeterminationofStatic/DynamicproductAppendix B.1.1: Questionnaire A


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Appendix B.1.2: Questionnaire B


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AppendixC:Patentsusedforlateralbenchmarking

Appendix C.1: Patent for Shop Vac: Industrial Vacuum Cleaner

Appendix C 2: Patent for Medical Suction Device


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Appendix C.2: Patent for Medical Suction Device

Appendix C.3: Patent for Above Ground Swimming Pool Cleaner


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Appendix C.3: Patent for Above Ground Swimming Pool Cleaner

Appendix D: BD Charts used for DFA


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AppendixD:B DChartsusedforDFA

AppendixD.1:HandlingChart

AppendixD.2:InsertionChart


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pp

APPENDIX E -- CES Results for PROCESS SELECTION (section 10.3):


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Appendix E.1:Handle

Appendix E.2: Rolling Bristled brush


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APPENDIX F: IT Grade Charts


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APPENDIX G: Process Capability Charts


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APPENDIX G: Process Capability Charts Continued


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452 Final Report v2

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