Lecture 5 concept appraisal and selection
- 1. 4006ME Engineering Problem Solving Concept Appraisal and Selection
- 2. Calendar You Are Here
- 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
- 6. Part 1: THE SCREENING PROCESS
- 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
- 11. The Screening Process – Your Ideas Engineering Design – Rudolph J Eggert
- 12. Part 2: SORTING OUT IDEAS
- 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
- 22. Part 3: CONCEPT SELECTION METHOD – GO-CART TRANSMISSION EXAMPLE
- 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
- 30. Part 4 WEIGHTED RATING METHOD
- 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.
- 33. Weighted rating method – Go-cart transmission Concept Alternatives Gears V-belt Chain Criteria Importance Rating Weighted Rating Weighted Rating Weighted Weight (%) rating rating rating High 30 Efficiency High 25 Reliability Low 20 Maintenance Low Cost 15 Light Weight 10 Totals 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
- 35. Weighted rating method – Go-cart transmission Concept Alternatives Gears V-belt Chain Criteria Importance Rating Weighted Rating Weighted Rating Weighted Weight (%) rating rating rating High 30 4 2 3 Efficiency High 25 4 3 3 Reliability Low 20 4 3 2 Maintenance Low Cost 15 2 4 3 Light Weight 10 2 4 3 Totals 100
- 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.
- 37. Weighted rating method – Go-cart transmission Concept Alternatives Gears V-belt Chain Criteria Importance Rating Weighted Rating Weighted Rating Weighted Weight (%) rating rating rating High 30 4 1.20 2 0.60 3 0.90 Efficiency High 25 4 1.00 3 0.75 3 0.75 Reliability Low 20 4 0.80 3 0.60 2 0.40 Maintenance Low Cost 15 2 0.30 4 0.60 3 0.45 Light Weight 10 2 0.20 4 0.40 3 0.30 Totals 100 3.50 2.95 2.80
- 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.
- 42. FINALLY