The Pugh Method of Creative Concept Evaluation

USE THE ENGINEER’S MINDSET

Problem Solving Process

Data Collection, Analysis

PROBLEM DEFINITION

Brainstorming

IDEA GENERATION

Pugh Method

IDEA EVALUATION

IDEA JUDGMENT

IMPLEMENTATION

Related Task

Goals, Objectives

Customer/Market Analysis,

Design Criteria

CONCEPTUAL DESIGNS

Engineering, Cost Analyses

Tolerances

PROCESS PLANNING

OPTIMIZED DESIGNS

Design Review

Go/No Go Decision

BEST DESIGN

Detail Drawings

PROTOTYPE

Steps and Documentation in Engineering Design

DESIGN STEP1. Identify the forces driving the

design

2. Identify design constraints

3. Identify user needs

4. Define the objectives or design specifications

5. Analyze the design problem and its context

6. Plan the design process

7. Develop concepts and select best alternatives

8. Complete system level design

9. Complete the detailed design

10. Test effectiveness of design

11. Review design at each stage

12. Iterate, refine, optimize design and communicate the results

DOCUMENTATIONDP1 Project concept statement

DP2 Table of design constraints

DP3 Customer survey

DP4 Table of design objectives

DP 5 Design problem analysis and statement

DP6 Project plan, design proposal

DP7 Pugh matrix, design concept descriptions, drawings

DP8 Progress report, BOM, analyses

DP9 Production specs, drawings

DP10 Prototype test plan

DP11 Design evaluation results report

DP12 Final project report and team evaluation/presentations

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What Is the Pugh Method?

EVALUATION SCALE

+ means substantially better

― means clearly worse (or flawed)

S means more or less the same

It is a creative design idea or concept evaluation technique that uses criteria derived from the “voice of the customer”

in an advantage-disadvantage matrix.

Each concept is evaluated against a datum using a three-way evaluation scheme.

Additional Features

1. A “best” conventional design can be used as datum against which the new designs are compared.

2. While the team completes the evaluation matrix, it generates new ideas and thus adds new concepts to the matrix.

3. This process is repeated several times over days (for students) or weeks/months (in industry), until a superior concept emerges that cannot be overturned since all negatives (“flaws”) have been removed.

Benefits of the Pugh Method

1. Discussions reveal arbitrary criteria. Team members gain insight into the problem and clearly understand the criteria which become better defined.

2. The discussion also leads to creative leaps between different concepts and idea synthesis, as flaws are attacked together and the team experiences synergy.

3. The team develops consensus about the best solution.

4. 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.

5. The method results in cost savings.

The Pugh Method — Phase I 1. The design teams brainstorm and rank a list of 15 to

20 evaluation criteria (based on customer needs).

2. The design teams develop imaginative concepts.

3. The matrix is prepared on a large wallboard, and the best existing product is chosen as benchmark/datum.

4. Each team’s design concept is discussed and evaluated against the list of criteria and the datum.

5. The ratings are evaluated.

6. The design teams work to strengthen the positives and removed the negatives through synthesis and new ideas; these concepts are added to the matrix which is rerun for one or more rounds, with the strongest concept chosen as the datum each time.

The Pugh Method — Phase II

1. Over a period of time, the teams further develop their best concepts, run analyses, and research missing information. The designs/concepts are now engineered or developed to more detail.

2. Weaker designs/ideas are dropped (after their good points have been judged for use elsewhere).

3. The matrix and concept improvement process are iterated until a winning concept emerges. All team members understand why this solution is best—all good points have been strengthened and all negatives overcome.

OUTCOME: Everyone is committed to the “best” or optimized

design which is now ready for development into a commercial product.

Cost Impact of Decisions

Committed

Manufacturing

Cost

CONCEPT PROTOTYPE PRODUCTION

Design Cycle Phase

85%

Influence on Product Cost (Car Example)

Labor

Design

Materials

Overhead

PRODUCT COST INFLUENCE ON COST

30%

15%

50%

5%

5%5%

20%

70%

Comparison of Engineering ChangesUS and Japan

Job #1

-24 -18 -12 - 6 0 6 Months

Number of Engineering Changes Processed

JAPANESE COMPANY

US COMPANY

© 2004 Edward Lumsdaine

Kitchen Lighting Example

I.D. #,Rating Type Fixture Location Switching

A 4, 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

Table 1 Existing Kitchen Lighting Fixtures

Problem BriefingA large Pullman-type kitchen in a 1940s house is quite dark at night, worst at the sink and chopping board located in front of the window. The cherry paneled ceiling has an average height of almost 11 ft and is traversed by a 14 in. x 6 in. wood-laminate beam supporting the flat roof above. All walls, countertops and metal wall cabinets are beige; the vinyl floor has a brownish brick pattern. Bottom cabinets are brick-red. The fluorescent tubes lying on top of the cabinets, as well as the spotlights, are ugly, look cheap, and are hard to clean. None of the lighting fixtures give adequate light for their tasks.

© 2004 Monika Lumsdaine

Table 2 Pugh Evaluation Round 1: Kitchen Lighting Concepts

1Track 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.

2Sink Task Lighting Replace the two spotlights over the sink with new, nicer-looking, and more efficient practical lamps.

3Over-Cabinet Strip Lighting Replace the fluorescent tubes with a lighted strip along the top of all wall cabinets.

4

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.

5Halogen Fixtures Install two hanging halogen down lights; wire to main switch; match chrome style of under-cabinet triangular fixtures. Option explored with supplier.

6Brighter Surfaces Paint walls white; install white vinyl flooring; install new white countertop; paint cherry panels in ceiling while.

Table 3 Pugh Method Round 1 Kitchen Lighting Concept Evaluation

# Criteria Now 1 2 3 4 5 6

1 Adequate sink task lighting S + ― + + ―

2 Other countertop lighting ― S ― + + ―

3 General lighting S S S + + +

4 Light to ceiling ― S + ― ― +

5 Energy efficient ― + ― + + +

6 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 ― + + ― ― ―

12 Low materials cost ― ― ― ― ― ―

TOTAL POSITIVES (+) 4 5 4 5 7 3

TOTAL NEGATIVES (―) 6 2 6 5 5 6

DATUM

Table 4 Pugh Evaluation Round 2: New or Improved Lighting Concepts

5Halogen Fixtures Install two hanging halogen down lights; wire to main switch; match chrome style of under-cabinet fixtures.

7

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 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.

8Sink Task Lighting Replace two spotlights over the sink with black cans matching the track lights of Option #7. Use fluorescent bulbs.

9Over-Cabinet Strip Lighting Replace the fluorescent tubes with a rope light along the top of all wall cabinets.

10Fluorescent 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.

11Halogen Fixtures Install two hanging halogen down lights; wire to main switch; match style of dining room chandelier, if possible.

Table 5 Pugh Method Round 2 Kitchen Lighting Concept Evaluation

# Criteria 5 7 8 9 10 11

1 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 B 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 (+) 6 10 6 2 1

TOTAL NEGATIVES (―) 2 2 9 4 0

DATUM

Table 6 Pugh Evaluation Round 3: New or Improved Lighting Concepts

8Sink Task Lighting Replace two spotlights over the sink with black cans matching the track lights of Option #7. Use fluorescent bulbs.

12

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.

11Halogen Fixtures Install two hanging halogen down lights; wire to main switch; match style of dining room chandelier, if possible.

Criteria 12 11

1 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 S ―

11 Sun-type lighting quality + +

12 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

DATUM

8

Table 7 Pugh Method Round 3 Kitchen Lighting Concept Evaluation

Comments to Kitchen Lighting Example

Round 1: None of the concepts provided a satisfactory solution. More options are needed. Concept #6 (painting) is dropped.

Round 2: Concepts #9 and #10 are eliminated. Concepts #7 and #8 are combined into Concept #12. Concept #11 (which had no negatives) is carried forward unchanged.

Round 3: Concept #12 is shown to be superior (no negatives); it solves the original problem with added value (flexibility and lighting that exceeded the customer’s expectations). Note how the list of criteria became more “demanding” in each round. The total cost of $742 was acceptable since the system is very functional as well as attractive.

CONCLUSION: The Pugh method was crucial for clarifying criteria, generating viable options, and identifying the optimal solution. The customer is very pleased with the new lighting.

Accessing the Car Horn Example (Stuart Pugh)

1. Get online at www.engineering-creativity.com

2. In left-hand menu, click on “Teaching Aids”

3. Scroll to File 8 and click on“Teaching Chapters 10, 11, 12 of Textbook”

4. Scroll to File 8b “Teaching Chapter 11.” See Page 18 for Design Criteria for Car Horn (11-3), with discussion on Page 19.

4. Click on Pugh Design Concepts for Car Horn (11-4)

6. Click on Pugh Round 1 Evaluation for Car Horn (11-5)

Pugh Method Matrix for Heat Transfer Syllabus (Partial List)

Relevant to Subject + S + + + + + +

Useful + ― + + + S + +

Teachable + ― + + + S + +

Duplication S S S + S S + S

Fit with Context S S S + + S + S

Need in Later Courses + ― S S + ― S +

Need in Industry + ― + + + ― + +

Need in Design + ― + + + S + S

Integrated in Other Courses + ― S S S S S +

TOTALS 7+

0 –

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KEY: S = Satisfactory + = Advantage― = Disadvantage

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