Eng design 5
- 1. CONCEPT EVALUATION/SELECTION CUPE 125 By Bamhare J Engineering Design Principles
- 2. Journey So Far ■ Need/Mission statement/Design Brief ■ Stakeholder Identification – Active, Passive ■ Requirements capture, grouping & prioritization – Stakeholder needs ■ Functional Decomposition ■ Concept Generation – Number of alternate solution concepts attempting to satisfy the need
- 3. Next Step ■ Decide which conceptual solutions are good potential candidates for further investigation/ product development – ALL ? – Some ? – One ? ■ Concept Evaluation – Evaluation criteria – Compare generated concepts: strengths & weaknesses wrt criteria ■ Concept Selection – Decision making: Eliminate, Retain, Combine, Modify – One Shot / Stages/ Iterative (?) – Final Selection Resources,Time, Risk, Policy, Culture
- 4. Difficulties/Issues ■ Limited knowledge/data ■ Conceptual solutions - Rough/abstract ideas ■ Concensus among team members ■ Other ??
- 5. Some methods ■ External Decision – company chairman?, customer ■ Product Champion – personal preference ■ Voting – team concensus (subjective) ■ Intuition – feel good factor ■ Prototype & test – Expensive & time consuming ■ Decision Matrices – relatively more objective
- 6. Process overview ■ Initial filtering – qualitative, absolute comparison ■ Quantitative screening based on decision matrix – Pugh Matrix – Prepare matrix – Rate concepts – Rank concepts – Combine/improve/retain promising concepts – Select one or more concepts ■ Concept Scoring – similar steps, weighted scores, more refinement and advancement over Pugh matrix
- 7. Evaluation Criteria ■ Extracted from stakeholder requirements ■ Identify a few key requirements through prioritization – Primary, secondary, tertiary ■ Level of abstraction/refinement of requirements must be consistent with concept abstraction/ refinement There is No Sense in Being Exact About Something if You Don’t Even Know What You are Talking About (John von Neuman, 1950)
- 8. Initial Filtering (absolute) (In case of large number of concepts) ■ “Gut feel” feasibility judgment – Comparison made with prior experience (“design knowledge”) ■ Concept will not work – Too radical – Not original ■ Conditional feasibility – something else required ■ Feasible -Worth considering ■ Go - No go screening ■ Customer requirements ■ Technology readiness/maturity/availability
- 9. Pugh Matrix ■ Select one concept as a reference or datum – Familiar, straightforward concept – Existing similar benchmark product in market – Existing product in case of re-design/ modification problem – Arbitrarily picked from the generated concepts ■ Pair-wise relative rating of each concept vs datum for each criteria – Better than datum: + – Same as datum: 0 – Worse than datum: - ■ Count number of pluses and minuses for each concept. Overall rating is difference between no. of pluses and no. of minuses. ■ Rank the concepts based on overall rating
- 10. Pugh Matrix Structure Concepts Selection Criteria A B C D E F G Handling ease 0 0 - 0 0 - - Ease of use 0 - - 0 0 + 0 Readibility of settings 0 0 + 0 + 0 + Metering accuracy 0 0 0 0 - 0 0 Durability 0 0 0 0 0 + 0 Ease of Manufacture + - - 0 0 - 0 Portability + + 0 0 + 0 0 Sum of +’s 2 1 1 0 2 2 1 Sum of –’s 0 2 3 0 1 2 1 Net rating 2 -1 -2 0 1 2 1 Rank 1 6 7 3 2 3 3 Continue? Yes No No Comb Yes Comb Rev
- 11. Concept Scoring Matrix ■ Select one concept as a reference or datum – Best in Pugh Matrix ■ Select weights for each criteria – Importance rating of each criterion: scale of 1 to 5 or %age with total = 100% etc. ■ Relative rating of each concept vs datum for each criteria. Datum maybe different for each criterion – Much better than datum: 5 – Better than datum: 4 – Same as datum: 3 – Worse than datum: 2 – Much worse than datum: 1 – Finer scales (1 to 9) etc. may also be used. ■ Weighted score for each concept – criterion pair ■ Rank the concepts based on total score (sum of weighted scores) ■ Combine/ Improve/ Retain concepts ■ Select one or more concepts
- 12. Concept Scoring Matrix Structure Concepts Selection Criteria A DF E G+ Weights R Scor R Scor R Scor R Scor Handling ease 3 0.15 3 0.15 4 0.2 4 0.2 5% Ease of use 3 0.45 4 0.6 4 0.6 3 0.45 15% Readibility of settings 2 0.2 3 0.3 5 0.5 5 0.5 10% Metering accuracy 3 0.75 3 0.75 2 0.5 3 0.75 25% Durability 2 0.3 5 0.75 4 0.6 3 0.45 15% Ease of Manufacture 3 0.6 3 0.6 2 0.4 2 0.4 20% Portability 3 0.3 3 0.3 3 0.3 3 0.3 10% Total Score 2.75 3.45 3.10 3.05 Rank 4 1 2 3 Continue? No Develop No No
- 13. Selection process Generation Screening Scoring Selected