Concept selection

The lesson outcomes are to identify the concept selection methods, apply different concept selection methods to select an appropriate concept for a design, and discuss the benefits of the concept selection process.

1. Concept selection Design Philosophy Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial & Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

2. Lesson outcomes Identify the concept selection methods Apply different concept selection methods to select an appropriate concept for a design Discuss the benefits of concept selection process Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

3. Concept Selection Helps to maintain objectivity throughout the concept phase of the development process Helps to remove any sort of doubt while selecting the most appropriate concept Methods: Pugh's Concept Selection Method Weighted Decision Matrix Analytical Hierarchy Process Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

4. Pugh's Concept Selection Method Widely accepted method for comparing concepts Ex: Comparison of the effectiveness between three different types of hinges that can use for the door of cabinet type dehydrator

5. Pugh's Concept Selection Method Steps: 1. Choose/develop the criteria for comparison The criteria can be identified by examining the customer requirements and generating a corresponding set of engineering requirements and targets cost of the part, durability, time to produce, and reliability 2. Select the alternatives to be compared The alternatives refer to the alternate ideas developed during concept generation All concepts should be compared at the same level of generalization and in similar language Butt hinge, flush hinge, and barrel hinge are three alternatives selected Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

6. Pugh's Concept Selection Method 3. Generate Scores Designers should pick one of the design concepts that they think is the most appropriate and call it the datum The barrel hinge is taken as the datum and the other two hinges are compared with this datum level Now all the other concepts compared to the datum concept as measured by each of the customer requirements For each comparison, the product should be evaluated as being better (+), the same (S), or worse (-) Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

7. Pugh's Concept Selection Method Criterion Butt Hinge Flush Hinge Barrel Hinge Cost of production - + DATUM Durability + S Time to produce S - Reliability - + Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

8. 4. Compute the total score Scores - number of plus scores, minus scores, overall total The totals should not be treated as absolute in the decision-making process but as the guidance only If the two top scores are very close or very similar, then they should be examined more closely to make a more informed decision Pugh's Concept Selection Method Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

9. Pugh's Concept Selection Method Criterion Butt Hinge Flush Hinge Barrel Hinge Cost of production - + DATUM Durability + S Time to produce S - Reliability - + Ʃ+ 1 2 Ʃ- 2 1 ƩS 1 1 Overall -1 +1 For our example, we can clearly see that the overall score for the flush hinge is +1 and that for the butt hinge is -1

10. Weighted Decision Matrix Ranking competing design concepts with weighting factors and scoring the degree to which each design concept meets the criteria Simple tool that can be very useful in making complex decisions (many alternatives and many criteria to be considered) Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

11. procedure for weighted decision matrix Example: Consider the three different types of hinges (1) butt hinge, (2) flush hinge, and (3) barrel hinge – that are used in cabinet type dehydrator. These hinges are required to be produced in bulk. Identify the Criteria The more specific the criteria are, the better will be the results of the evaluation While it is also desirable to have the criteria that are independent of one another , it is rarely possible The criteria are the cost of the part, the time to produce, durability, and reliability. Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

12. 2. Rank and Weigh the Criteria Some criteria are probably more important than the others The relative ranking of the criteria affects the evaluation So find out a way of assigning weights to the criteria so that their relative importance can be quantified (e.g., cost of the hinge may be more important than reliability) Consider the following criteria and the respective weights within parenthesis Cost of the part (0.50) Durability (0.30) Time to produce the part (0.10) Reliability (0.10) procedure for weighted decision matrix Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

13. 3 . Choose a Ranking Scale In order to evaluate each design concept option, we need to confirm which one is better (with respect to each criterion) A linear, symmetrical scale is often used procedure for weighted decision matrix

14. 4. Calculating the rating for each criterion This is achieved by multiplying the weightage of the criteria by the score of the criteria for each of the design concept procedure for weighted decision matrix Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

15. 5. Overall score rating This is the sum of the ratings of all the criteria for a particular design concept in step 4. For example, the overall rating for the butt hinge is 4.0+2.1+ 0.6 +0.6 =7.3 6. The one with the highest score is the best design concept The Barrel Hinge Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

16. Analytical Hierarchy Process Designed to solve multi-criteria decision problems Several alternatives are compared in AHP on the basis of the same set of attributes Steps: (a) make pairwise comparisons (b) synthesize judgments (c) check for consistency Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

17. Make pairwise comparisons Pairwise comparison is widely found to be effective with the assignment of relative weights Compare alternative with each other in a pairwise manner for each criterion Scale/rating used for selection of hinge Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

18. Pairwise comparison of cost, durability and time to produce When compare cost and durability, the cost criteria is strongly preferred than durability criteria for hinges Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

19. Pairwise comparison of three different hinges for “cost” When compare butt hinge with flush hinge with regard to cost, butt hinge is moderately to strongly preferred than flush hinge Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

20. Pairwise comparison of three different hinges for “durability” When compare flush hinge with butt hinge with regard to durability, flush hinge is strongly to very strongly preferred than butt hinge Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

21. Pairwise comparison of three different hinges for “time to produce” When compare butt hinge with flush hinge with regard to time to produce, butt hinge is strongly preferred than flush hinge Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

22. Synthesis The priority of each criterion in terms of its contribution to the overall goal is computed in this step. It involves the following step. [a] Sum the values in each column of pairwise comparison matrix [b] Divide each element by its column total (gives normalized pairwise comparison matrix) [c] Compute average in each row by dividing each element by the column total (gives estimate of relative priorities of elements being compared) Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

23. Assign priority rating of each criterion for pairwise comparison of “cost” Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

24. Compute average priority of each criterion for pairwise comparison of “cost” These relative priority means that with respect to Cost, the barrel hinge will be preferred first (65%), followed by butt hinge (27%) and flush hinge (8%). We can do similar calculations for durability and time to produce. Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

25. Assign priority rating of each criterion for pairwise comparison of “durability” Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

26. Compute average priority of each criterion for pairwise comparison of “durability” Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

27. Assign priority rating of each criterion for pairwise comparison of “time to produce” Compute average priority of each criterion for pairwise comparison of “time to produce”

28. Assign rating of each criterion for pairwise comparison of “relative priority” Compute average rating for pairwise comparison of “relative priority”

29. Overall ranking of the three hinge alternatives Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

30. Check for Consistency A key step in the making of several pairwise comparisons is considering the consistency of the pairwise judgments. Example: If A compared to B = 3 and B compared to C = 2 then A compared to C should be 6 (3 x 2). Otherwise, an inconsistency will occur. Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)

31. Benefits of concept selection Customer-focused product – customer-oriented criteria Competitive design – benchmarking concepts Better product-process coordination – clear evaluation w.r.t. manufacturing criteria Reduced time to product introduction – structured methodology Effective group decision making Documentation of the decision process Dr. (Ms.) Jayaruwani Fernando, Ph.D. (Ag. & Biosystems Engineering), M.S. (Industrial and Ag. Technology), M.Phil. (Ag. & Biosystems Engineering), B.Sc. (Agriculture)