lec 14 conc gen sel testing
TRANSCRIPT
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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
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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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3/14/2012
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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ENME 371 - C. Thamire - 8 -3/14/2012
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.
(From Ulrich and Eppinger, Product Design and Development, McGraw Hill, NY, 1995 [2]).
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New and Revised Concepts
(From Ulrich and Eppinger, Product Design and Development, McGraw Hill, NY, 1995 [2]).
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New and Revised Concepts
(From Ulrich and Eppinger, Product Design and Development, McGraw Hill, NY, 1995 [2]).
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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
(From Ulrich and Eppinger, Product Design and Development, McGraw Hill, NY, 1995 [2]).
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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
(From Ulrich and Eppinger, Product Design and Development, McGraw Hill, NY, 1995 [2]).
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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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Step 4 - Concept Communication
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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Step 4 - Concept Communication
Photos and Renderings
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Step 4 - Concept Communication
Story Board - Series of images conveyingtemporal sequence
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Step 4 - Concept Communication
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