3. Today’s Session
• Today’s session will briefly present some
concept selection and appraisal
techniques, which can be used in your
problem solving portfolio
• We will also discuss the requirements of
CSWK1 due for submission on Friday 18th
November 2011
4. Books for Reference
• Total Design – Integrated methods for
successful product engineering
Stuart Pugh
• Engineering Design
Rudolph J Eggert
• Engineering Design Methods – Strategies
for product design
Nigel Cross
5. Books for Reference
• Strategies for Creative Problem Solving
H Scott Fogler, Steven E. LeBlanc
7. The Screening Process
• Before appraising possible concept
solutions Eggert suggest the following
screening questions should be asked to
avoid wasting time:
Engineering Design – Rudolph J Eggert
8. The Screening Process
1. Will the concept be likely to function?
2. Will the concept likely meet the
customers minimum performance
requirements? (the ‘musts’ not the
‘should’)
Engineering Design – Rudolph J Eggert
9. The Screening Process
3. Will the concept be likely to survive the
operating environment?
4. Will the concept be likely to satisfy other
critically important customer
requirements?
Engineering Design – Rudolph J Eggert
10. The Screening Process
5. Will you be able to manufacture the
concept?
6. Will the concept satisfy financial and/or
marketing requirements?
Engineering Design – Rudolph J Eggert
13. Sorting Out Ideas
• Once the concept have been screened
and any unsuitable concepts removed
Pugh recommends the following steps.
14. Sorting Out Ideas
1. It is essential that all ideas/solutions are
related to the project design specification
or statement.
2. Sketch each solution by hand to the
same level of detail.
Total Design – Stuart Pugh
15. Sorting Out Ideas
3. Apply a concept selection and evaluation
matrix.
4. It is essential that the matrix incorporates
‘visuals’ or sketches.
Total Design – Stuart Pugh
16. Sorting Out Ideas
5. Ensure that the comparison is valid – all
concepts of same basis and to the same
generic level of development.
6. Choose your evaluation criteria – these
should be unambiguous, understood and
accepted by all team members.
Total Design – Stuart Pugh
17. Sorting Out Ideas
7. Apply chosen evaluation matrix
technique.
8. Assess individual scores of all the
concepts. Certain concepts will have
exceptional strengths, others will have
exceptional weaknesses.
Total Design – Stuart Pugh
18. Sorting Out Ideas
9. Look at negatives in the strong concepts.
What can be altered in the design to
make it a positive?
10.Look at the weak concepts, attack the
negatives to see if they can be improved
upon.
Total Design – Stuart Pugh
19. Sorting Out Ideas
11. Having carried out steps 9 and 10
anything truly weak can now be
eliminated.
12. If concepts do not converge its is usually
an indication of the following:
Total Design – Stuart Pugh
20. Sorting Out Ideas
• Criteria are ambiguous and capable of
interpretation by group members. Examination of
criteria will reveal that it already incorporates one
or more of the other criteria – decompose into a
single one.
• Persistence of uniformity of strengths between
concepts usually means that one or more
concepts are subsets of others (they are the
same)
Total Design – Stuart Pugh
21. Sorting Out Ideas
13. When one strong concept persists, re-
run the matrix using this concept as the
datum. Does the pattern persist? If it does
this confirms the first run. If not repeat
steps 9 and 10.
Total Design – Stuart Pugh
23. Go-cart transmission
example
CRITERIA CONCEPT ALTERNATIVES
GEARS V-BELT CHAIN
DECIDE CRITERIA AND ENTER
Σ+ IN LEFT COLUMN
Σ-
ΣS
24. Go-cart transmission
example
CRITERIA CONCEPT ALTERNATIVES
GEARS V-BELT CHAIN
HIGH EFFICIENCY
HIGH RELIABILITY
LOW MAINTENANCE
LOW COST
LIGHT WEIGHT
Σ+
Σ-
ΣS
SELECT ONE CONCEPT AS DATUM
DESIGN
25. Go-cart transmission
example
CRITERIA CONCEPT ALTERNATIVES
GEARS V-BELT CHAIN
HIGH EFFICIENCY D
HIGH RELIABILITY A
LOW MAINTENANCE T
LOW COST U
LIGHT WEIGHT M
COMPARE EACH CONCEPT AGAINST
Σ+ THE DATUM USING ‘+’ ‘-’ OR ‘S’
N/A
Σ- N/A
ΣS N/A
26. Go-cart transmission
example
CRITERIA CONCEPT ALTERNATIVES
GEARS V-BELT CHAIN
HIGH EFFICIENCY + D +
HIGH RELIABILITY + A +
LOW MAINTENANCE + T S
LOW COST - U -
LIGHT WEIGHT - M -
Σ+ Sum all the ‘+’ 3 N/A 2
Σ- Sum all the ‘-’ 2 N/A 2
ΣS Sum all the ‘S’ 0 N/A 1
27. Go-cart transmission
example
CRITERIA CONCEPT ALTERNATIVES
GEARS V-BELT CHAIN
HIGH EFFICIENCY + D +
HIGH RELIABILITY + A +
Can ‘-’ be turned
LOW MAINTENANCE
into ‘+’?? + T S
LOW COST - U -
LIGHT WEIGHT - M -
Σ+ 3 N/A 2
Σ- 2 N/A 2
ΣS 0 N/A 1
28. Go-cart transmission
example
• Results tallied, more +’s = strong design.
• Can –’s be improved on.
• Major weakness – it gives all concepts an
equal weighting.
29. Go-cart transmission
example - modified
CRITERIA CONCEPT ALTERNATIVES
Importance GEARS V-BELT CHAIN
(%)
HIGH EFFICIENCY 30 + D +
HIGH RELIABILITY 25 + A +
LOW MAINTENANCE 20 + T S
LOW COST 15 - U -
LIGHT WEIGHT 10 - M -
100%
Σ + Σ + = (1x30)+(1x25)+(1x20) 75 N/A 55
Σ- 25 N/A 25
ΣS 0 N/A 20
31. Weighted rating method
• Similar to modified concept selection
method.
• Also called the weighted sum method or
the Pahl and Beitz method.
32. Weighted rating method
1. Team selects evaluation criteria.
2. A matrix is prepared listing the evaluation
criteria in the first column.
3. Importance weights given for criteria
usually as percentage points, adding to
100.
34. Weighted rating method
4. Concepts identified in columns.
5. Team rates each concept as:
Unsatisfactory 0
Just tolerable 1
Adequate 2
Good 3
Very Good 4
36. Weighted rating method
6. Each concept rating is multiplied by its
respective weight and summed to
produce an overall rating for the concept.
7. Strong concepts are achieve higher
scores.
38. Weighted rating method
• Problems – the method is subjective,
fuzzy and abstract.
• Positives – designs for further
development will be identified and it
allows teams to reach a consensus.
40. Problem Solving portfolio
• 18 Nov 2011 - Your coursework should be
submitted in two ways:
• A physical copy should be handed in via the campus
centre.
• An electronic version should be created using your
group Wiki tool on blackboard. It is very important
that each person enters their individual work to allow
for the assessment of individual contribution to the
portfolio.
41. Problem Solving portfolio
• Feedback will be given when your
coursework is returned to you within three
weeks of submission.
