design evaluation methods -...
TRANSCRIPT
Design Evaluation Methods
C h r i s t o p h e r S a l d a n a , P h . D.W o o d r u f f S c h o o l o f M e c h a n i c a l E n g i n e e r i n gG e o r g i a I n s t i t u t e o f T e c h n o l o g yA t l a n t a , G e o r g i a U S A
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Understand the importance of evaluation in the design process
Identify criteria for evaluation
Utilize three levels of evaluation matrices for product development through concept screening and scoring
Strategies for Visual/Descriptive Communication of Designs
Learning Objectives
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Design Tools – Current Progress
House of Quality Specification Sheet Function Tree
Morphological ChartConcept Generation
Place Masson Target
Moveto
Target
Navigateto
Target
Brake onTarget
GeneratePower
TransmitPower
HitTarget
Generate Power
Transmit Power
Brake on Target
Move to Target
Navigate to Target
Gravity Mouse Traps
Car Hit by Trap Rip Cord Effect Ramp Catapult
Friction String Break Anchor Rubber Stopper Weighted Skid
Equal Size Wheels Larger Front Wheels
Rolling Sliding Projectile Launch
Problem Understanding
Design Alternatives
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Customer Wants1. Dose metering accuracy2. Portability3. Durability4. Ease of handling5. Readability of settings6. Ease of use7. Ease of manufacture
Example: Insulin PenRedesigning the Insulin Pen
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Example: Insulin PenRedesigning the Insulin Pen
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Example: Insulin PenRedesigning the Insulin Pen
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Benefits• Customer-focused product, competitive design• Better product-process coordination, faster product introduction• Effective group decision-making• Documentation of design process
Challenge• Need to make informed decisions despite lack of information• Selection requires estimation, analysis, prototyping• Identify bad concepts versus picking optimal ones
Structured Evaluation
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How do we evaluate each of these designs?
What criteria do we use for evaluation?
What is the best design?
Structured Evaluation
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Multi-voting: team members vote independently, work together to resolve differences and/or average results
Strengths/Weaknesses: list strengths and weaknesses of design concepts, use this to evaluate based on specific opinions
Prototype and Test: build or simulate, use empirical or simulated test data!
Concept Selection Strategies
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Concept Selection Process
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Concept screening
• First-level evaluation matrix
Concept scoring
• Second-level evaluation matrix
• Third-level evaluation matrix
Stages and Types of Concept Selection
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1. Identify the criteria for comparison. 2. Select the alternatives to be compared.
• Alternatives are developed during concept generation. • All concepts should be compared at e same level of abstraction.
3. Generate scores. • Use a design concept as datum, with all the other being compared to it • Evaluate each alternative as better (+), same (S), or worse (-) relative to datum.
4. Compute the total score • Sum the total number of (+)’s, (-)’s, (S)’s • Compute overall score with +1 for (+)’s, -1 for (-)’s, 0 for (S)’s
5. Note: other variations on scoring in the first-level evaluation• Optional scale: +3 if extremely better than datum +2, +1, 0, -1, -2, -3
First Level Evaluation (Pugh Matrix)
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+ = better than datum; - = worse than datum; S = same as datum
First Level Evaluation (Pugh Matrix)
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First Level Evaluation Matrix (example)
+ = better than datum; - = worse than datum; S = same as datum
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• Ranking depends on choice of datum
• Does not factor in how much better a specific alternative is compared to others
• Some criteria may be more important
• Consider: (i) no datum, (ii) numerical rating, (iii) criteria weighting• Second-level evaluation matrix – (i), (ii)
• Third-level evaluation matrix – (i), (ii) and (iii)
First-Level Evaluation Matrix
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Second Level Evaluation Matrix Common Scale:4 = very good (ideal)3 = good2 = adequate1 = just tolerable0 = unsatisfactory
Alternate Scale:10 = ideal solution9 = solution exceeds requirement8 = very good solution7 = good solution6 = good solution with drawbacks5 = satisfactory solution4 = adequate solution3 = tolerable solution2 = weak solution1 = very inadequate solution0 = useless solution
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Second Level Evaluation Matrix
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Third Level Evaluation Matrix
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Third Level Evaluation Matrix
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Summary - Evaluation MatrixElements• Designs rated relative to customer
requirements in HOQ
• Level 1: sum +/-/S relative to datum
• Level 2: numerical rating
• Level 3: weighted sum of num. rating
Describing this figure in text• Which design performed best? Why?
• Which performed worst? Why?
• Use numerical information from figure
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• Not doing it • Running with the first idea • Forgetting the customer • Evaluation matrix doesn't correspond to HOQ • Letting an "experienced" designer make the choices • Going by gut feel • Letting a manager decide • Not buying into the process as a team • Ignoring cost
Concept Selection Pitfalls
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Design Tools – Complete Process
House of Quality Specification Sheet Function Tree
Morphological Chart Evaluation MatricesConcept Generation Concept Selection
Place Masson Target
Moveto
Target
Navigateto
Target
Brake onTarget
GeneratePower
TransmitPower
HitTarget
Generate Power
Transmit Power
Brake on Target
Move to Target
Navigate to Target
Gravity Mouse Traps
Car Hit by Trap Rip Cord Effect Ramp Catapult
Friction String Break Anchor Rubber Stopper Weighted Skid
Equal Size Wheels Larger Front Wheels
Rolling Sliding Projectile Launch
Problem Understanding
Design Alts. Final Design
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Detailed Design - Communication23
General organization• Primary systems and subsystems
• Mechanisms, operation/sequencing, construction and materials
• Performance relative to specificationsClarity in written descriptions• Be clear in describing design features. Match
words in the body to label text in figures.• Avoid describing things that are not shown with
evidence or detail. Don’t rely on the reader’s imagination.
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Detailed Design - CAD24
Important CAD elements:
Labels match text explanations
Mechatronics (see ME2110 website)
Common COTS components (fasteners, etc.)
Detail views
Dimensions
Formatting (text, resolution, annotations)
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Understand the importance of evaluation in the design process
Identify criteria for evaluation
Utilize three levels of evaluation matrices for product development (First-level, Second-level, Third-level)
Strategies for Visual/Descriptive Communication of Designs
Evaluation Tools Summary
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Introductory Project Report
Goal: conceptual design of a collection device
Design tools: HOQ, specification sheet, function tree, morphological chart, alternative generation
Detailed design: labels, triggering, mechanisms, sequencing, materials
Similar restrictions as final competition (cost, size, power, etc.)
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• Cover Page: See book for example cover page. • Abstract: One-paragraph summary with key findings/results. • Introduction: Restatement of the problem, goal and
inherent design challenges in achieving this goal. • Problem Understanding: Important customer needs,
engineering specifications to address needs, tradeoffs and synergies, functions and concept generation.
• Design Overview: Presentation of a single concept alternative, detailed description of design including drawings that shows its parts and how it operates.
• Conclusions: Summary with key results, potential next steps and final thoughts.
• Appendix: Figures and Tables
Introductory Project Report - Layout