Phase A: Design Problem Analysis. 07. Pugh Evaluation. thebenshimagroup

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1 Phase A: Design Problem Analysis 1

2 Pugh Evaluation A chart showing the quantitative reasoning behind the selection of the final concept(s) accompanied by a brief description of the selection process and a detailed description of the final concept(s). System Requirements Review A review conducted during the concept development phase to ensure that the requirements and the selected concept will satisfy the project. Need equivalent set of concepts first Abstract, not detailed, unmeasurable Need to find right measure Absolute vs. relative Decision Matrix Feasibility judgment, technology readiness, go/no-go screening 2

3 Gut feel by designer Not feasible, conditionally feasible, or possibly feasible Good write up of concept Compare each remaining concept alternative to the customer requirements in QFD Eliminate any concept with too many no-go s 3

4 Why not base it on customers, based design on them? Relative (NASA Systems Engineering Handbook, SP 2007) 4

5 Finding a best design Prevents a team from falling in love with a flawed design or one not meeting all design constraints or objectives Communication tool; builds consensus Based on the voice of the customer Results in significant cost savings 5

6 Discussions reveal arbitrary criteria Team members gain insight into the problem and clearly understand the criteria which become increasingly better defined The discussion also leads to creative leaps between different concepts and idea synthesis, as flaws are attacked together and the team experiences synergy This process generates new concepts that are added to the evaluation matrix The resulting new concepts are better than the original ideas No flaws are overlooked; engineering changes are eliminated, and invulnerable products are developed that will succeed in the marketplace The team develops consensus about the best concept A best conventional design is chosen as datum against which the new concepts are compared If no benchmark exists, one of the new concepts is arbitrarily chosen as the initial datum For subsequent rounds, the best concept from the previous round is chosen as the new datum All design concepts must be improved to be able to compete or survive in the new rounds 6

7 This process is repeated several times over days or weeks/months, until a superior concept emerges that cannot be overturned since all negatives ( flaws ) have been removed For a valid evaluation, the list must be explicit, relevant, comprehensive, and include performance specifications and constraints In the early conceptual stages, do not use tight constraints or too many details 7

8 Begin with the Requirements and Objectives in the Project Analysis Statement Criteria will grow more specific, detailed, and refined in subsequent evaluation rounds Make sure the criteria involve the voice of the customer Also consider quality, manufacturability, low cost, and environmental impact in the criteria They are outline solutions to the design problem, where rough sizes and structural relationships among major parts are given This phase places the greatest demands on designers for creative thinking, and innovation can originate here Decisions are made on how each major function will be performed but consider many alternatives of how this could be achieved 8

9 Conceptual designs are worked out in some detail to allow estimates of cost, weight, overall dimensions, and assessment of feasibility Each initial concept should be worked out to about the same level of detail and format, to allow fair evaluation The Design teams brainstorm and rank a list of 15 to 20 evaluation criteria Based on customer needs and design objectives The best existing product is chosen as the benchmark or datum 9

10 The matrix is prepared on a large paper or wallboard Column1: List of criteria Column2: Datum Design concepts are posted at the top of the next columns have additional columns available for new concepts generated during the evaluation Each design concept is presented by its champion and then discussed and evaluated by the team against the list of criteria and the datum If new ideas come up during this process, they are entered on the matrix as a new concept The results of the matrix are evaluated The datum for the next round is chosen, and criteria are clarified as needed to make them more useful 10

11 The designers now work to strengthen the positives and remove the negatives of their concepts through synthesis and new ideas, for evaluation in Round 2 The evaluation and improvement process is continued for one or more rounds, with the strongest concept chosen as the datum each time Takes place in Phase B Over a period of time, teams further develop their best concepts, run analyses, and research missing information The designs/concepts are now engineered or developed to more detail Weaker designs/ideas are dropped (after their good points have been judged for use elsewhere) 11

12 The matrix and the process of concept improvement are iterated until a winning concept emerges, all team members understand why this solution is best, and all are committed to this concept which is now ready for prototyping The datum for a new round must be the best concept from the previous round -the one with the largest number of positives, not the one with the lowest negatives Do not forget to improve the datum for the next round; make it an even better concept by trying to eliminate all its weak points The overall aim must always be to try to eliminate all negatives (the weaknesses or flaws) in the higher -ranking concepts. Do not be too quick to accept shortcomings in your concepts without some very good reasons 12

13 Existing Kitchen Lighting Fixtures I.D. #, Rating Type Fixture Location Switching A 3, 20 watt 2-ft fluorescent, triangular under wall cabinets individual B 4, 40 watt 4-ft fluorescent tube on top of cabinets 3-way switch C 2, 75 watt aluminum spotlight 5 ft above sink individual D 1, 20 watt 2-ft fluorescent tube under microwave plug-in cord 13

14 Improve the general and task lighting in the kitchen while upgrading the lamp quality and matching or complementing the fixture style in the adjacent dining and living rooms, at reasonable cost and without remodeling the kitchen or covering the beauty of the paneled ceiling Track Lighting Install an 8-ft long track with 4 movable spots (50 watt each, black) to match existing track light in adjacent living room. Plug into outlet over cabinet near sink. Sink Task Lighting Replace the two spotlights over the sink with new, nicer-looking, and more efficient practical lamps. Over-Cabinet Strip Lighting Replace the fluorescent tubes with a lighted strip along the top of all wall cabinets. Fluorescent Hanging Fixtures Install two 4-ft fluorescent fixtures with efficient diffusers at 8-ft level (from chains, with wood surrounds) to replace the over-the-cabinet tubes; wire to main switch. Option explored with supplier. Halogen Fixtures Install two hanging halogen down lights; wire to main switch; match chrome style of under-cabinet triangular fixtures. Option explored with supplier. Brighter Surfaces Paint walls white; install white vinyl flooring; install new white countertop; paint cherry panels in ceiling while. 14

15 # Criteria Now Adequate sink task lighting S Other countertop lighting S General lighting S S S Light to ceiling S Energy efficient Easy to clean + S S S + 7 Easy bulb replacement + S S + S 8 Allow deletion of tubes + 9 Matching adjacent room fixture + + S 10 Attractive high-tech look S 11 Low installation labor cost Low materials cost TOTAL POSITIVES (+) TOTAL NEGATIVES ( ) None of the concepts provided a complete and satisfactory solution More options are needed. Concept #5 is chosen as the new datum The other concepts are modified and synthesized, and a new concept is added after discussion with the supplier (#7) Concept #6 (painting) is dropped since it does not meet the constraints 15

16 Halogen Fixtures Install two hanging halogen down lights; wire to main switch; match chrome style of under-cabinet fixtures (DATUM). Fluorescent Track Lighting Install a black 8-ft long, 2-circuit track with 3 movable cans (150 watt incandescent bulbs or fluorescent bulb option) and one black 2-ft fluorescent, 40 watt movable parabolic louvered diffuser to match living room track light. Mount to bottom of beam; connect to main switches with conduit along beam edge. Sink Task Lighting Replace two spotlights over the sink with black cans matching the track lights of Option #7. Use fluorescent bulbs. Over-Cabinet Strip Lighting Replace the fluorescent tubes with a rope light along the top of all wall cabinets. Fluorescent Hanging Fixtures Install two 4-ft fluorescent fixtures with efficient diffusers at 8-ft level (sleek high-tech design); hang from ceiling, centered between counters. Halogen Fixtures Install two hanging halogen down lights; wire to main switch; match style of dining room chandelier, if possible. # Criteria Adequate sink task light S + S S 2 Countertop lighting (window wall) + + S S 3 Countertop lighting (stove wall) + S S 4 Ceiling illumination S S + S S 5 Low-energy night lighting S + + S S 6 Low glare S 7 Flexible (direction, additions, lumens) + + S S 8 Easy bulb replacement S S S 9 Energy efficient S S S S 10 Easy to clean S S S S 11 Preserves view of ceiling/open space S + + S 12 Allows deletion of cabinet-top tubes + + S S 13 Matching adjacent room lamp styles + + S + 14 Attractive to future owners + + S 15 Low labor cost S + + S S 16 Low materials cost + + S TOTAL POSITIVES ( + ) TOTAL NEGATIVES ( )

17 Concepts #9 and #10 are eliminated (#9 does not provide sufficient light to help solve the basic problem; #10 obstructs the daytime view of the paneled ceiling) Concepts #7 and #8 are combined into new Concept #12 Since the customer was not familiar with the wall washer fixture, the supplier suggested she see one in use at the MTU bookstore (she especially liked the warm quality and brightness of the light) Concept #11 (which had no negatives) is carried forward unchanged Sink Task Lighting Replace two spotlights over the sink with black cans matching the track lights of Option #7. Use fluorescent bulbs. Fluorescent Track Lighting System Install a black 8-ft long, 2-circuit track with 3 movable cans with fluorescent bulbs and two 2-ft fluorescent, 40-watt movable parabolic louvered diffusers ( wall washers ). Mount to bottom of beam; connect to main switches with conduit along beam/ceiling edge. Replace the two spotlights over the sink with matching cans and fluorescent bulbs to achieve a flexible, attractive, and easily modified, adjustable lighting system. Halogen Fixtures Install two hanging halogen down lights; wire to main switch; match style of dining room chandelier, if possible. 17

18 Criteria Adequate sink task light + 2 Countertop lighting (window wall) + 3 Countertop lighting (stove wall) + 4 Indirect lighting to ceiling (eliminate cave look) + S 5 Low-energy night lighting + 6 Low glare, especially for eye-glass wearers + 7 Flexible in direction, light level, future additions + 8,9 Easy bulb replacement; easy to clean of grease buildup S,S S.S 10 Energy efficient, cool burning (safety concern) S 11 Sun-type lighting quality Preserves view of beautiful paneled ceiling S 13 Allows deletion of all plugged-in tubes S 14 Matching adjoining living and dining room light fixtures + S 15 Attractive to future owners; good selling point S 16 Reasonable installation costs + S 17 Material cost in line with value added S S TOTAL POSITIVES ( + ) 10 1 TOTAL NEGATIVES ( ) 0 10 Concept #12 is shown to be superior (no negatives); it solves the original problem with added value (flexibility and lighting that exceed the customer s expectations) Round 3 confirmed the superiority of combining Concepts #7 and #8 (with further improvements), it overcame the two serious flaws of Concept #8 18

19 Concept #11 (without negatives in Round 2) now rated very poorly against the high-quality datum of Round 3. Also, the hot halogen bulb is a safety concern Note how the list of criteria became more demanding in each round The total cost of $742 was acceptable to get such a functional, flexible, as well as attractive system The Pugh method was crucial for clarifying criteria, generating options, and identifying the optimal solution (with input from the supplier and research by the customer) The best solution did not emerge until Round 3 The customer is very pleased with the new lighting, both initially and over time, and the system was an enhancement that helped sell the house The slight delay in start-up of the wall washers has not proved to be annoying, since the spots respond immediately when the switch is operated; on the contrary, the two-stage sequence increases appreciation for the bright, warm light supplied by the wall washers 19

20 From PUBLICATIONS / TEACHING AIDS / Pugh Method Example Although this only shows Round 1, the discussion brings out some important points and features of the Pugh method 20

21 What? It examines the functional and performance requirements defined for the system and the preliminary program or project plan and ensures that the requirements and the selected concept will satisfy the project When? This review is conducted during the concept development phase (NASA Systems Engineering Handbook, SP 2007) 21

22 Results Successful completion of the System Requirements Review freezes program /project requirements and leads to a formal decision by the cognizant program administrator to proceed with the proposal request preparation for project implementation (NASA Systems Engineering Handbook, SP 2007) Entrance criteria Successful completion of the Project Concept Review in Pre-Phase A A preliminary SRR agenda and success criteria Following technical products are available to the cognizant participants System requirements document Risk management plan Updated cost estimate Concept sketches (NASA Systems Engineering Handbook, SP 2007) 22

23 Success Criteria The project utilizes a sound process for the allocation and control of requirements throughout all levels, and a plan has been defined to complete the definition activity within schedule constraints Requirements definition is complete with respect to top-level project requirements Requirements allocation and flowdown of key driving requirements have been defined down to subsystems Preliminary approaches have been determined for how requirements will be verified and validated down to the subsystem level Major risks have been identified and technically assessed, and viable mitigation strategies have been defined (NASA Systems Engineering Handbook, SP 2007) 23