Week 6 – Tuesday

Concept Selection

ME 4054W: DESIGN PROJECTS

IDENTIFY OPPORTUNITY

DEFINE PROBLEM

GENERATE CONCEPTS

GATHER INFO IMPLEMENT SCREEN

CONCEPTS HANDOFF

Reference: Ulirich & Eppinger, Chapter 7

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Class Agenda

• Methods of Concept Screening

• Concept Screening (Pugh) Matrix

• Concept Scoring (Decision) Matrix

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Concept Selection

• While concept generation is easy (and fun),

concept selection is difficult (and fun) • You never have enough information; you must

make informed decisions nonetheless • You will likely use estimation, analysis, and

some prototyping to complete the selection process

• Weed out bad (vs. picking “best”) • Look for new concepts and synergies during

the process

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Concept Selection

Documenting the selection process is nearly as important as the result

(and must be included in your design report)

• Start with a Product Design Specification

(PDS) that is finalized

• Examine ALL concepts at the same time

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Concept Selection - Pictorially

Exhibit 7-4 “Product Design and Development” by Ulrich and Eppinger

Controlled convergence

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WRONG WAYS 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.

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

the test data is used to make the selection

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PREFERRED Concept Selection Process

• Decision Matrices – Start with a Product Design Specification – Examine ALL concepts at the same time – Can be weighted or unweighted

A (reference)

B C D E

1 0 + - 0 -

2 0 + + - -

3 0 - 0 + 0

4 0 + 0 0 +Sele

ctio

n Cr

iteria

Concepts

Decision matrices are a required method

in this course

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Benefits of a Structured Concept Selection Method

• 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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Two 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 • + = “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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Stage 2: 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

Page 135 “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 concepts

5. 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 Development” By Ulrich and Eppinger

Sensitivity analysis on criteria weighting can 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

12 Pressure

variation over panel surface

4 kPa < 40 < 20

9 Duration 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 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 application 20 1 5 5 5

Loading time 15 3 5 4 3 Set-up time 10 5 4 4 3

Cost 10 5 3 4 2 Total score 100 255 470 465 325

Rank 4 1 2 3

If the total scores of two or more concepts are close (as above), you can add selection criteria from your PDS, do a sensitivity analysis or do both.

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Concept Selection Exercise

• Review your PDS

• Identify specs to include on concept selection matrices

• If time allows, begin creating a concept screening matrix – Most promising concepts across the top – Most important specs on the side

(5 minutes)

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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!

• After following the structured process, 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

IDENTIFY OPPORTUNITY

DEFINE PROBLEM

GENERATE CONCEPTS

GATHER INFORMATION IMPLEMENT SCREEN

CONCEPTS HANDOFF