concept screening

Week 6 – Tuesday

Concept Screening

ME 4054W:SENIOR DESIGN PROJECTS

IDENTOPP

DEFINE PROBLEM

GEN CONCEPTS

GATHER INFO IMPLEMENTSCREEN

CONCEPTS HANDOFF

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Notes

• Mobile App Challenge– Entrepreneurship / Design Challenge– http://z.umn.edu/MobileAppChallenge

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Class Agenda

• Methods of Concept Screening• Concept Screening (Pugh) Matrix• Concept Scoring (Decision) Matrix

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Concept Selection

• You never have enough information

• Use estimation, analysis, and some prototyping

• Look for new concepts during the process

• Weed out bad (vs picking “best”)• Follow structured process

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***Controlled convergence

• While concept generation is easy (and fun), concept selection is difficult (and fun)

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WAYS NOT TO DO SCREENING

• Gut feel• Boss says, “Do it this way”• Single customer decides• One team member is strong champion• Influence of experienced designer

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BETTER WAYS TO SCREEN CONCEPTS

• Multi-voting– Each team member votes for several concepts. The

concept with the most votes is selected.

• Pros and cons– The team lists the strengths and weaknesses of each

concepts. The group then selects the best concept based on group opinion.

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PREFERED Concept Selection Process• Start with a Product Design Specification• Examine ALL concepts at the same time

• Prototype and test– Prototypes of each concept are built and tested and the

selection is made based upon the test data

• Decision matrices– Unweighted– Weighted

#1 #2 #3 #4 #5

Criteria 1

Criteria 2

Criteria 3

Criteria 4

++

0

-

++

+

0

0

-

0

0

0

0

--

-

0

-

--

--

0

-

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Benefits of a Structured Methodfor Concept Selection

• A customer-focused product• A competitive design• Better product-process coordination• Reduced time to product introduction• Effective group decision making• Documentation of the decision process

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2 Stages of Concept Selection

1. Concept screening• Reduce the many product concept ideas

generated to a relative few that will get additional refinement and analysis

2. Concept scoring• Use objective methods to select to your

consensus final concept selection

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Concept Screening

1. Prepare the selection/screening matrix– Selection criteria must relate to key customer needs

2. Rate the concepts– e.g., + = “better than”, 0 = “same as”, - = “worse than”

3. Rank the concepts– As objectively as possible using the concept rating

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Concept Screening

4. Combine and improve the concepts– Is there a generally good concept that is downgraded by

one feature?– Can two concepts be combined to preserve the “better

than” features while simultaneously removing any “worse than” features?

5. Select one or more concepts for further refinement and analysis

6. Reflect on the results and process– Are all team members “comfortable” with the decisions? If

not, what needs to be resolved?

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Concept Screening Matrix Example

Exhibit 7-5“Product Design and Development”By Ulrich and Eppinger

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Concept Scoring

1. Prepare the selection matrix– An optimized version of the concept screening matrix– Determine % weighting for each selection criteria

2. Rate the concepts

5“Product Design and Development”By Ulrich and Eppinger

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Concept Scoring

3. Rank the concepts

Page 136“Product Design and Development”By Ulrich and Eppinger

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Concept Scoring

4. Combine and improve the concepts5. Select one or more concepts for further

refinement and analysis• Sensitivity analysis• Build and test prototypes

6. Reflect on the results and process• Down-select to the consensus final concept selection

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Concept Scoring Example

Exhibit 7-7“Product Design and DevelopmentBy Ulrich and EppingerSensitivity analysis on criteria

weighting may provide insight

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Project Example: Heated Veneer Press, Spring 2000

• Specifications taken from the product design specification • If a specification does not differentiate one implementation

over another, remove it from the selection chart • Limit specifications to 10 or less of the most important • New specifications may arise associated with

manufacturability, etc. Add them to your PDS!

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PDS (Abbreviated): Veneer Press

Need #'s Metric Importance Units Marginal Value Ideal Value

5 Surface flatness 5 mm/m < 2.0 < 1.0

10 Cost 3 US $ < 800 400

4 Laminating pressure 5 kPa 50-60 50-100

12Pressure

variation over panel surface

4 kPa < 40 < 20

9Duration of

pressure application

3 hours 0-2 0-24

8 Set-up time 2 min < 30 < 10

7 Loading time 3 minutes < 10 < 1

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Concept Screening Matrix:Veneer Press

Criteria Roller Clamp Dead Weight Vacuum

Surface flatness - 0 0 -

Pressure variation over panel

surface- 0 0 0

Duration of pressure

application- 0 0 0

Loading time - + 0 -

Set-up time + + 0 -

Cost + 0 0 -

Net score -2 +2 0 -4

Rank 3 1 2 4

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Concept Scoring Matrix:Veneer Press

Criteria Weighting Factor Roller Clamp Dead Weight Vacuum

Surface flatness 25 2 5 5 2

Pressure variation over panel surface

20 2 5 5 4

Duration of pressure

application20 1 5 5 5

Loading time 15 3 5 4 3

Set-up time 10 5 4 4 3Cost 10 5 3 4 2

Total score 100 255 470 465 325Rank 4 1 2 3

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Concept Selection Exercise

• Review Evolving PDS• Identify Specs to Include on Concept Selection

Charts• If Time: Construct a Concept Screening Matrix

– Fill in w/ Top Concepts

(5 minutes)

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AFTER SCREENING

• Do results make sense?• Do you have client (advisor) buy-in ?• Do you have to generate more concepts?

– Or combine elements from several concepts?• Document the process

– ME4054: for Design Show and report

BOTTOM LINE: Have a structured process for concept screening. Document and defend your choices.

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Commons Pitfalls in Concept Selection

• Not doing it• Running with the first idea• Forgetting the customer• Selection chart criteria don't correspond to PDS• Letting an "experienced" designer make the choices• Going by gut feel• Letting a manager decide• Not buying into the process as a team• Ignoring cost

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Congratulations!

• You are now ready to implement a design solution that addresses the customer’s needs (PDS).

• Implementation includes, but is not limited to:– Design and analysis– Fabrication of prototype(s)– Testing– Optimization– Documenting the design and design process

IDENTIFYOPPORTUNI

TY

DEFINE PROBLEM

GENERATE CONCEPTS

GATHER INFORMATIO

NIMPLEMENTSCREEN

CONCEPTS HANDOFF

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Unweighted (Pugh) methodBattery Pneumatic Corded Electric Int. Combustion

Ease of Use

Setup + S + +

Operating + S S +

Weight - S - -

Manufacturing Cost - S - -

Time to Market - S - -

# of Pluses 2 0 1 2

# of Minuses 3 0 3 3

Keep? Y N N Y

Cordless nailer

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Weighted selection matrix

Wght Battery Pneumatic Corded Electric Int. Combustion

Ease of Use 40

Setup 20 5 1 2 4

Operating 20 4 2 2 3

Weight 30 2 4 3 2

Manufacturing Cost 20 3 4 3 2

Time to Market 20 3 4 3 3

Total Score 360 340 290 300

Rank 1 2 4 3

Cordless nailer

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Lab kit: Hall-effect sensors are cheap, compact and non-contact

Design Criteria Servopot Hall Effect IR EncoderCost 0 + +

Accuracy 0 0 0Size 0 + +

Reads Position 0 0 -Friction 0 + +

Net Score 0 3 2

Current setup uses a Potentiometer and two gears$11.19 + 2*$4.31 = $19.81

Hall effect sensor~$1 each

Source: Vishay Intertechnology, Inc.

Source: Honeywell International, Inc.

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Rubber band is a good solution but non-ideality leads to consideration of others

Selection CriteriaRubber

Band

Tension spring

w/wrapping

non-wrapped

spring

rotary spring

sElastomer

Torsionlinearity 0 + - + 0ease of

installation 0 0 0 0 -size 0 - - 0 0

price 0 - - - -range of motion 0 0 - - -

longevity 0 + + + +Net Score 0 0 -3 0 -2

Rotary Springs Source: Xiamen Shuangyuan Springs Co., Ltd

Tension spring w/wrapping

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Air vane damping shows potential improvement over Newton friction

Selection Criteria Friction

Rotary Damper(oil) Fan

Deforming an Elastomer

linearity 0 + + 0ease of

installation 0 - 0 -size 0 - - -

Small B 0 - + -Net Score 0 -2 1 -3

Rotary DamperSource: McMaster-Carr Online Catalog

Fan / Air Vane

concept screening

Documents