Lec 14 Conc Gen Sel Testing

7/31/2019 Lec 14 Conc Gen Sel Testing

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ENME 371 - C. Thamire - 0 -3/14/2012

Concept Generation,Concept Selection, &

Concept Testing

ENME 371

Product Engineering & Manufacturing


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ENME 371 - C. Thamire

- 1 -

Announcements and Outline

Lecture Topics

Lecture Topics

Concept Generation, Selection, and Testing

Concept Generation, Selection, and Testing

Announcements

Announcements

Quiz 3

Mid-term Exam on 3/28

Quiz 3

Mid-term Exam on 3/28


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Problem Formulation

Product Specification

Concept Generation

Concept Selection

System Design

Detail Design

Fabrication, Testing, and Modification

Design and Build Tooling

Production and Distribution

Tracking and Assessment

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Next Steps in the PDP Process

Service

Center


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Functional Decomposition

Concept Generation

Concept Selection

Concept Testing

Concept Generation and Selection

Constraints These are limits in design Ignore constraints completely or

relax them at first Leads to a very large set of

possible solutions initially Reimpose constraints later -

remove infeasible concepts (tooheavy? Too weak? ...)

Criteria These are design

objectives (minimizeweight, improve

performance, ) Apply and choose the

optimum concept


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Concept Generation

Define subsystems

Find existing Concepts

Generate new concepts

Eliminate poor ideas

Prepare Design Proposals

Some Popular Methods

Generate ideas in a brain-storming session

Reasoning by Analogy

Get ideas from others

Design can be ..

Ill defined

Recursive

Open ended


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Concept Generation

Some Formal Concept Generation Methods

Morphological Approach - divide into sub-problems, generate concepts, combine

concepts into complete solutions

Synectics analogies

Theory of Problem Solving (TIPS/TRIZ) - systematic engineering procedure

From: Pahl et al., Engineering Design: A SystematicApproach, 1996 [5].


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Some Simple Concept Generation

Methods

Reverse Engineering

Patents

Traditional Library: Books (Encyclopedias (Enc.

Britannica, Enc. Americana, McG.-Hill Enc. Of Sci. and

Tech., ) and Subject-related text books (focusedsearch)), Journals, Science-Citation Index,

Electronic Library: Internet (Basic-search Engines and

On-line Libraries)

Using existing ideas

Reasoning by Analogy

1. http://www.uspto.gov/

2. http://www.google.com/patents

3. http://scilib.ucsd.edu/howto/guides/find

patents.html

4. http://www.us-patent-search.com/

5. www.pat2pdf.org

6. http://www.freepatentsonline.com/

7. http://www.delphion.com/

8. http://web.mit.edu/invent/invent-

main.html


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Example Product(All materials in this section, including illustrations, are takenfrom Ulrich and Eppinger, Product Design and Development,

McGraw Hill, NY, 1995 [2]).


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Example Product: Reusable Syringe

Goal: To develop a reusable syringe with precise

dosage control for outpatient use

Current Problems: cost (original product was madew/ s.s.) and accuracy of dose metering

(Source: Ulrich and Eppinger, Product Design and Development, McGraw Hill, NY, 1995 [2]).


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Ease of handling

Ease of use

Readability of dose settings

Dose metering accuracy Durability

Ease of manufacture

Portability

Criteria Established


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Concepts

(From Ulrich and Eppinger, Product Design and Development, McGraw Hill, NY, 1995 [2]).


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Concept Selection

Concept Screening

- Select the top one-third concepts using the

Pugh matrix

- Combine and improve the concepts

Concept Scoring

- Weigh criteria

- Select the final concept using the conceptscoring matrix


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The Concept Screening Matrix/ Pugh Matrix

Note: A B/W/S Scale is also used some times;

B = Better; W = Worse; S = Same

It is recommended that the net scores not be displayed unless the PDP team is confident of near equivalent weightsof the criteria.



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New and Revised Concepts



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New and Revised Concepts



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Weighting Factors

The Pugh method assumed all

criteria had equal weight

But, as you gain more knowledge

about your design you may realize

that this is not true

For example, should serviceability

rate as highly as functionality?


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Concept Scoring

Step 1:Prepare weights for the criteria

Step 2:Prepare the selection matrix

Step 3:Rate the concepts

Step 4:Rank the concepts

Step 5:Select one (or more concepts)

Step 6:Reflect and process


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Weighting Factors

Good Rule: Make sum of theweighting factors equal to unity.

criteriaevaluationofnumbertotaltheiswhere

100.1

1

n

wwi

n

i

i=

=

Three ways to do this


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Weighting Factors

First way to do this:

1. Assign 100 points between differentcriteria

2. Normalize weights by dividing eachcriterion by 100 based on informationfrom HOQ and any additionalinformation


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The Concept Scoring Matrix



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Weighting Factors

Second way: Pairwise Comparison (Use for ourproject!)

1. Compare each criterion with others.

2. Decide which is important.

3. Assign a 1 to the more important criterion and a 0 tothe other.

4. Sum the values assigned to each criterion (rowtotal) to determine its relative importance

5. Normalize by dividing by the sum of the row totals

to give the weighting factor.


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Weighting Factors

Second way: Pairwise Comparison

Criteria A B C D Row

totals

Weight

factor

A - 1 0 0 1 0.17

B 0 - 1 1 2 0.33

C 1 0 - 0 1 0.17

D 1 0 1 - 2 0.33

6 1.00


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Example Concept Selection Problem


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Weighting Factors

Third way: Objective tree

Useful in advanced stages of design(when decisions are made based ontechnical as well as less subjective

criteria)

For example, you may want to chooseamong materials or motors, on the basisof performance data, while at the sametime including durability or time to makea replacement part.


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Weighting Factors

Third way: Objective tree

Example: Choose between three designs formaking a large steel crane hook for hoistingheavy ladles of molten steel. The three

designs are:

1. Built-up with welded steel plates

2. Built-up with riveted steel plates

3. A monolithic cast steel crane hook


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Weighting Factors by Objective Tree

Construct a hierarchical objective tree.

Start with the crane hook and successively

break it down into finer and finer criteria. Sum ofthe weights must add to 1.0.

Matl. Cost (0.3)

0.6x0.3=0.18

Crane Hook

1.0

Cost(0.6)Quality in Service (0.4)

Mfg. Cost (0.5)

0.6x0.5=0.30

Repair(0.2)

0.6x0.2=0.12

Durability(0.6)

0.4x0.6=0.24

Reliability(0.3)

0.4x0.3=0.12

Prod. Time (0.1)

0.4x0.1=0.04


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Crane Hook Example

Criteria:

1. Material cost

2. Manufacturing cost

3. Ease of repair

4. Durability

5. Reliability

6. Time to make a replacement crane hook

3 Concepts generated!


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Weighted Decision Matrix First take the magnitude of the design criterion

and apply the best appropriate scale factor.

Multiply this score by the weighting factor.

Built-up plates

welded

Built-up plates

riveted

Cast steel hookDesigncriterion

Weight

factor

Units

Magni-

tude

Score Rating Magni

-tude

Score Rating Magni-

tude

Score Rating

Material

cost

0.18 /lb 60 8 1.44 60 8 1.44 50 9 1.62

Mfg.

cost

0.30 $ 2500 7 2.10 2200 9 2.70 3000 4 1.20

Repair 0.12 Exper Good 7 0.84 Excel. 9 1.08 Fair 5 0.60

Durab-

ility

0.24 Exper High 8 1.92 High 8 1.92 Good 6 1.44

Reliab-ility 0.12 Exper Good 7 0.84 Excel 9 1.08 Fair 5 0.60

Time to

make

0.04 Hours 40 7 0.28 25 9 0.36 60 5 0.20

7.42 8.58 5.66


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Evaluation of Design Parameters

Parameters have different values and units.

Need an evaluation scale to put things on the same basis

Use a 5-point scale (0-4) when knowledge about theparameters is not very detailed, or an 11-point scale when

the information is more complete.

11-point

Scale

Description 5-point scale Description

0 Totally useless solution1 Very inadequate solution

0 Inadequate

2 Weak solution3 Poor solution

1 Weak

4 Tolerable solution5 Satisfactory solution6 Good solution with a few

drawbacks

2 Satisfactory

7 Good solution8 Very good solution

3 Good

9 Excellent (exceeds therequirement)

10 Ideal solution

4 Excellent


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Concept Testing



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Concept Testing

Cannot test more than a few concepts with customers so mustnarrow concepts first!

Identifycustomerneeds

EstablishTargetSpecifications

GenerateProductConcepts

SelectProductConcept(s)

PlanDownstreamDevelopment

Set FinalSpecifications

TestProductConcept(s)

Development

Plan

When?


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Concept Testing- Why?

Solicit response to product concept(s)

Select the final concept Improve the final concept

Estimate the sales potential of the

concept

No testing when:testing times are hightesting costs are large


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Concept Testing - Steps

Define purpose

Choose population

Choose survey format

Communicate concepts Measure responses

Interpret results

Reflect and process


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Example Product

A three-wheeledelectric-powered

scooter that could befolded and carriedeasily

Need to assess theconcept to decidewhether to proceedor not


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Step1 - Define Purpose

Which of the alternative concepts?

How to improve to better meet needs? How many units will be sold?

Continue development?


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Step2 - Choose Population

Does population reflect

target market? Biased population? Multiple target markets

(college/urban)? Sample size?

Multiple surveys: Smaller for early test Larger later


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Step 3 - Survey Format

Face-to-face interaction - intercepts,

prearranged interviews, trade-show

booth, focus groups,..

Telephone - specific individuals

Postal mail

Electronic mail Internet

Risk of bias!


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Step 4 - Concept Communication

Verbal Description - paragraph or summary of

points, read by customer or surveyor

Sketch - Line Drawing

Photos and Renderings

Story Board - Series of images conveying

temporal sequence Video

Simulation

Interactive Multimedia

Physical Appearance Models

Working Prototypes


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The Product is a light-weight electric scooter that

can be easily folded and taken with you inside a

building and public transportation.

Weighs 25 pounds

Travels at speeds of up to 15 miles/hr Can go about 12 miles on a single charge

Can be recharged from std. Electric outlets

Easy to ride and control - has only an acceleratorbutton and a brake

Verbal Description


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Photos and Renderings


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Story Board - Series of images conveyingtemporal sequence


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Physical Appearance Models


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Step 5 - Measure responses

Ask to choose from two or more concepts

Ask why he/she favors that one Ask how to improve

Rate

Definitely would buy

Probably would buy

Might or Might not buy

Probably would not buy

Definitely would not buy


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Step 6 Interpret Results

If results are conclusive, choose that concept,provided customers understood the product

Otherwise, offer a concept based on cost orother considerations

Estimate the sales potential

Absent past history, take Cdefinitely = 0.4 and Cprobably = 0.2


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Step 7

Reflect and process


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Conclusion

In this lecture, we have:

Introduced you to Concept generation and selection Process

Next class:

Product Architecture

1. Schmidt, Zhang, Herrmann, Dieter, and Cunniff, Product Engineering andManufacturing, College House Enterprises, LLC, Knoxville, TN.

2. E. B. Magrab, Integrated Product and Process Design and Development, CRCPress, New York, 1997.

3. Ulrich and Eppinger, Product Design and Development, McGraw Hill, NY, 1995.4. J. R. Dixon and C. Poli, Engineering Design and Design for Manufacturing, A

structured Approach, Field Stone Publishers, MA, 1995.5. Pahl, G. and W. Beitz, ., Engineering Design: A Systematic Approach, Springer-

Verlag, London,1996.

References

Lec 14 Conc Gen Sel Testing

Documents

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