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U of U MEEN 4000 - Concept Selection

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ME EN 4000 – Engineering Design I – Concept Selection 1Concept SelectionTopic 7ME EN 4000 – Engineering Design I – Concept Selection 2Product Design and DevelopmentKarl T. Ulrich and Steven D. Eppinger4th edition, Irwin McGraw-Hill, 2008.Chapter Table of Contents1. Introduction2. Development Processes and Organizations3. Product Planning4. Identifying Customer Needs5. Product Specifications6. Concept Generation7. Concept Selection8. Concept Testing9. Product Architecture10. Industrial Design11. Design for Manufacturing12. Prototyping13. Product Development Economics 14. Managing ProjectsME EN 4000 – Engineering Design I – Concept Selection 3Select Concepts in Relation to Concept Development ActivitiesIdentifyCustomerNeedsEstablishTargetSpecificationsGenerateProductConceptsSelectProductConceptsTestProductConceptsSetFinalSpecificationsPlanDownstreamDevelopmentTimeline of Concept DevelopmentPerform Economic AnalysisBenchmark Competitive ProductsBuild and Test Models and PrototypesSource: Ulrich K, Eppinger S, Product Design and DevelopmentME EN 4000 – Engineering Design I – Concept Selection 4Facts About Concept Selection• Concept selection is a convergent process.• Concept selection is also an iterative process that does not always produce the dominant concept immediately.• Better concepts may be found through recombination of pre-screened concepts.• Recombination may temporarily enlarge the number of available concepts.• The final concept is chosen after several iterations.Source: Ulrich K, Eppinger S, Product Design and DevelopmentME EN 4000 – Engineering Design I – Concept Selection 5Concept Development Funnelconcept generationconcept screeningconcept scoringconcept testingME EN 4000 – Engineering Design I – Concept Selection 6Selection Methods• External decision. Concepts are turned over to the customer or other external entity.– No: Customer should not be bothered with hundreds of concepts.– Maybe: Final concept selection.• Product champion. An influential member of the product development team chooses a concept based on personal preference.– No: Group consensus is preferable both for confidence and harmony.• Intuition. The concept is chosen by its feel. No explicit criteria are used. The concept simply seems better.– No: Design decisions need to be objective and justifiable. Source: Ulrich K, Eppinger S, Product Design and DevelopmentME EN 4000 – Engineering Design I – Concept Selection 7Selection Methods (contd.)• Multivoting. Each member of the team votes for a set number of projects.– Maybe: Depends on how objectively the team members vote..• Pros and cons. The team lists strengths and weaknesses of each concept and makes a choice based upon group opinion.– Yes: The decision is group based and (presumably) objective.• Prototype and test. The organization builds and tests prototypes of each concept, making a selection based upon test data.– No: Too costly for hundreds of concepts.– Yes: Final concept selection.Source: Ulrich K, Eppinger S, Product Design and DevelopmentME EN 4000 – Engineering Design I – Concept Selection 8Selection Methods (contd.)• Decision matrices. The team rates each concept against pre-specified selection criteria, which may be weighted.– Yes: Preferred method.Source: Ulrich K, Eppinger S, Product Design and DevelopmentME EN 4000 – Engineering Design I – Concept Selection 9Two Stage Process1. Concept Screening– Quick, approximate evaluation aimed at producing a small number of viable solutions.2. Concept Scoring– Much more careful analysis of a relative small number of concepts in order to choose the single best option.Source: Ulrich K, Eppinger S, Product Design and DevelopmentME EN 4000 – Engineering Design I – Concept Selection 10Concept Screening: Steps 1-3 • Step 1 – Prepare the Selection Matrix.– Enter concepts and criteria into the matrix.– Select reference concept (industry standard, main competitor, current product). Its performance is rated using 0’s.• Step 2 – Rate the Concepts.– Concepts that perform better than the reference are rated with +’s.– Concepts that perform similarly compared to the reference are rated with 0’s.– Concepts that perform worse than the reference are rated with –’s.• Step 3 – Rank the Concepts.– Sum up “better than”, “same as”, and “worse than” and enter the sum for each category in the lower rows of the matrix.– The net score is calculated by subtracting the number of “worse than” from the number of “better than”.Source: Ulrich K, Eppinger S, Product Design and DevelopmentME EN 4000 – Engineering Design I – Concept Selection 11Concept Screening: Steps 4-6• Step 4 – Combine and Improve Concepts.– Is there a generally good concept which is degraded by a single bad feature?– Are there two concepts which can be combined to preserve the “better than” qualities while canceling the “worse than” features?• Step 5 – Select One or More Concepts.– After the team has gained sufficient understanding of each concept and its relative quality, a small number of concepts arechosen for further analysis and refinement (and perhaps testing).• Step 6 – Reflect on the Results and Process.– All team members should be comfortable with the outcome. Differences between team members may indicate missing criteria or rating errors.Source: Ulrich K, Eppinger S, Product Design and DevelopmentME EN 4000 – Engineering Design I – Concept Selection 12Outpatient SyringeConcept A – Master CylinderDisplaced fluid from master cylinder actuates pusher. Upon release, sealed fluid cavity is filled with more fluid if necessary.Dose is set by length of stroke.Source: Ulrich K, Eppinger S, Product Design and DevelopmentEach concept should include a sketch and short descriptionAll concepts should include a similar level of detailME EN 4000 – Engineering Design I – Concept Selection 13Outpatient SyringeConcept B – Rubber BrakePushnut grips shaft when pushed but releases when being pulled (rubber clutch offers resistance).Dose is set by length of stroke.Source: Ulrich K, Eppinger S, Product Design and DevelopmentME EN 4000 – Engineering Design I – Concept Selection 14Outpatient SyringeConcept C - RatchetRatchet engages pusher when plunger is being pushed and disengaged is plunger is being pulled.Dose is set by length of stroke.Source: Ulrich K, Eppinger S, Product Design


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