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EML4550 2007 1 EML4550 - Engineering Design Methods Concept Selection Settling on one or more promising ideas to pursue to final design Hyman: Chapter.

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Presentation on theme: "EML4550 2007 1 EML4550 - Engineering Design Methods Concept Selection Settling on one or more promising ideas to pursue to final design Hyman: Chapter."— Presentation transcript:

1 EML4550 2007 1 EML4550 - Engineering Design Methods Concept Selection Settling on one or more promising ideas to pursue to final design Hyman: Chapter 9, Sec. 9.1 & 9.2 Ulrich and Eppinger: Chapters 5 and 6 Dym and Little: Sections 6.1 – 6.3

2 EML4550 1-07-2 Concept Development Diagram Identify Customer Needs Establish Target Specs Generate Product Concepts Select Product Concept Refine Specs Analyze Competitive Products Perform Economic Analysis Plan Design/ Development Project Mission Statement Action Plan

3 EML4550 1-07-3 Concept Selection nThe ‘Concept Generation’ phase spawned many ideas (good and bad) and potential solutions to the problem at hand nHow do we select from all these competing concepts? nA ‘method’ is needed to systematically weed out poor concepts and select the best one to proceed with to Final Design

4 EML4550 1-07-4 Concept Selection Methods nExternal decision (customers, consultants, etc.) nProduct “Champion” (strong personal decision) nIntuition (no rational method) nPros and Cons (systematic but subjective) nPrototype and test (hardware, expensive and time- consuming) nDecision matrices (match characteristics vs. pre-specified and weighted criteria)

5 EML4550 1-07-5 Concept Selection Methods (Cont.) nAlthough all methods are used in practice, most of the ‘subjective’ methods are very case-specific nDecision matrices represent the most ‘rational’ approach to concept selection nWe will focus this section on the Decision Matrix method

6 EML4550 1-07-6 Concept Selection: Why a Structured Approach? lA customer-focused product (use the needs as guidelines) lA competitive design (do not overlook competing designs) lBetter product-process coordination (forces manufacturing issues into the trade-off) lReduced time to market (accelerated ‘downselect’) lEffective group decision-making (minimize ‘arbitrary’ decisions and maximize team exposure) lDocumentation of decision process (not lost in someone’s ‘memory’)

7 EML4550 1-07-7 Concept Selection: Why a Structured Approach? (Cont.) nNeed to balance: lDesire to have an expedient ‘downselect’ §Expediency: proceed to design sooner §Faster time-to market §Less cost of ‘carrying’ many concepts forward lDesire ‘to know more’ before deciding §Risk of making a mistake (pick a loser) §Risk of avoiding a concept because it is new (potential big winner) §Engineers tend to be conservative

8 EML4550 1-07-8 Decision Matrix Method nStage 1: Concept Screening lApply an initial ‘filter’ to ‘weed out’ bad concepts and determine likely ‘winners’. Apply some elements of ‘scoring’ for the purposes of ranking only nStage 2: Concept Scoring lApply weighted criteria to the concepts and proceed with a quantitative ‘scoring’ system to pick a winner (or winners)

9 EML4550 1-07-9 Decision Matrix Method (Cont.) nEach Stage has 6 steps: nPrepare the selection matrix nRate the concepts nRank the concepts nCombine and improve the concepts nSelect one or more concepts nReflect on the results of the process

10 EML4550 1-07-10 Concept Screening

11 EML4550 1-07-11 Screening: Step 1 - Prepare Selection Matrix nDevelop a set of criteria lCustomer needs (condensed into criteria) lCorporate needs (cost, manufacturing, liability, image, etc.) nGive equal weight to all criteria

12 EML4550 1-07-12 Screening: Step 2 - Rate the Concepts nGive +, -, or neutral rating to each concept based on criteria nUse general notions (no need to get ‘specific’) nUse team consensus (or majority vote) nRefine or split criteria if team consensus is hard to reach

13 EML4550 1-07-13 Screening: Step 3 - Rank Concepts nAdd scores and build a ranking nIdentify a “benchmark” concept (from ranking or from external products - competition) nGroup the concepts into three categories: “possible winners”, “neutral”, and “losers”

14 EML4550 1-07-14 Screening: Step 4 - Combine and Improve Concepts nAre we throwing away as ‘loser’ a ‘good’ concept because it has one or two negatives? Can they be neutralized? nCan two concepts be combined to preserve ‘better than’ qualities while neutralizing ‘worse than’ items? Can we derive a concept that takes the ‘best of both worlds’?

15 EML4550 1-07-15 Screening: Step 5 - Select one or more concepts nIf there is a ‘clear’ winner, then select it and proceed with it èMISSION ACCOMPLISHED nHowever, usually more than one concept will survive the screening nNumber of concepts to carry forward will depend on resources and time available

16 EML4550 1-07-16 Screening: Step 6 - Reflect on the Process nDid we achieve consensus? nWere all the team members treated equally? No trampling? nDid we avoid personal agendas? Department politics? It is very disruptive to team spirit to ‘drop’ a concept that someone was championing. Grudges linger for a long time within a team

17 EML4550 1-07-17 Concept Screening An example

18 EML4550 1-07-18 From Screening to Scoring (quantitative)

19 EML4550 1-07-19 Scoring: Step 1 - Prepare Selection Matrix nUsing the same selection criteria used in screening give relative weight to each (must add to 100%) lIt is possible to slightly modify the criteria in light of the surviving concepts lWeights to each criterion are given by team consensus or related to customer needs An example

20 EML4550 1-07-20 Scoring: Step 2 - Rate the Concepts nAs with screening, give a ‘score’ to each concept based on a ‘quantitative’ (yet still subjective) numbering scale as follows: Relative Performance 1 - Much worse than reference concept 2 - Worse than reference concept 3 - Same as reference concept 4 - Better than reference concept 5 - Much better than reference concept

21 EML4550 1-07-21 Scoring: Step 3 - Rank the Concepts nCompute score for each concept

22 EML4550 1-07-22 From Screening to Scoring

23 EML4550 1-07-23 Scoring: Step 4 - Combine and Improve Concepts nAs before, can concepts be combined to arrive at a better solution? lLooking at the concepts in the new light of ‘scoring’ can encourage the team to improve on the initial ideas

24 EML4550 1-07-24 Scoring: Step 5 - Select One or More Concepts nThe final selection is never easy nDo ‘parametric’ studies by assigning different weight distributions and see which concepts come on top on each try

25 EML4550 1-07-25 Scoring: Step 6 - Reflect on the Process nAre we ready to proceed with the ‘winning’ concept? nDid the method facilitate the selection? nCan the method be improved?

26 EML4550 1-07-26 Concept Selection: Caveats! nDecomposition of product quality lFailure to capture relationship among criteria nSubjective criteria lMethodical, but still high content of subjectivity nWhere to include cost lDerived from customer needs, but how about ‘manufacturing’ the product, not all parameters known nSelecting elements of complex systems lCan a complex concept be reduced to a set of simpler concepts? How about interactions between sub-concepts? nApplying concept selection throughout the development process lThe same approach can apply to the selection of concepts within a design effort when developing sub-systems of a larger system

27 EML4550 1-07-27 Concept Selection: Implications to Project nIf many concepts are considered, perform a screening nRecord results of screening (and criteria used) nDecision matrix for the selection and scores for each concept nPresentation of the ‘winning’ concept

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