7.1 PUGH CONCEPT SELECTION METHOD

Invented by Stuart Pugh, both the Pugh method and Pugh Concept Selection is a quantitative technique used to rank the multidimensional options of an option set. It is frequently used in engineering for making design decisions but can also be used to rank investment options, vendor options, product options or any other set of multidimensional entities. A basic decision matrix (also called Pugh method) consists of establishing a set of criteria upon which the potential options can be decomposed, scored, and summed to gain a total score which can then be ranked. Importantly, the criteria are not weighted to allow a quick selection process. The advantage of this approach to decision making is that subjective opinions about one alternative versus another can be made more objective. Another advantage of this method is that sensitivity studies can be performed. An example of this might be to see how much your opinion would have to change in order for a lower ranked alternative to out rank a competing alternative

CONCEPT SELECTION (EVALUATION)

Concept selection is one of the most critical decision-making exercises in a product development. To make decisions effective, one must basically carry out two steps:

v  Minimize the possibility of misrepresenting a solution that may be effective.

Eg : engineer is not familiar with the technology

v  Fully consider the different ramifications of a decision.

Eg : not considering the costumer’s need may lead to the product failing in the marketplace.

v  Design Evaluations

-  occurs at all phase of product evaluation, from concept to detailed design phases.

v  Quality of Information

Low quality of information - how well each alternative design would meet criterion cannot be fully understood.

High quality of information -  the alternative solutions is well understood.

v  Technology Readiness Assessment

-          if a technology is to be used as part of a product design, it must be mature enough that its use is a design issue, not a research issue.

MECHANISM OF THE PUGH’S CONCEPT:

It is implemented by establishing an evaluation team, and setting up a matrix of evaluation criteria versus alternative embodiments. This is the scoring matrix usually associated with the QFD method and is a form of prioritization matrix. Usually, the options are scored relative to criteria using a symbolic approach. These get converted into scores and combined in the matrix to yield scores for each option. Comparison of the scores generated gives insight into the best alternatives.

1.                  Comparing alternative concepts

2.                  Scores concepts relative to one another

3.                  Iterative evaluation method

4.         Comparing result of a design team which performed independently

CONCEPT SELECTION (PUGH’S METHOD)

Based on the Decision-Matrix (Pugh’s method), this method is very effective for comparing concepts that are not refined enough for direct comparison with the engineering requirement. The method is an iterative evaluation that tests the completeness and understanding of requirements, quickly identifies the strongest concept. It is most effective if each member of the design team performs it independently. The results of the comparison will usually lead to repetition of the method, with iteration continued until the team reaches a consensus.

Steps to design Pugh Matrix

1.     Develop criteria for comparison

• Examine customer requirements.
• Generate a set of engineering requirements and targets.

2.      Select alternatives to be compared

·         The alternatives are the different ideas developed during concept generation. All concepts should be compared at the same level of generalization.

3.      Generate scores

·         Comparison usually measured by each of the customer requirements. If the problem is to redesign an existing product, then the existing product can be used as the datum.

4.      Compute the total score

• Four scores will be generated, the number of plus scores, minus scores, the overall total and the weighted total.
• The overall total is the number of plus scores- the number of minus scores.
• The weighted total is the scores times their respective weighting factors, added up.

5.      Variations on scoring

                  For example a seven level scale could be used for a finer scoring system where:

• +3 meets criterion extremely better than datum
• +2 meets criterion much better than datum
• +1 meets criterion better than datum
•   0  meets criterion as well as datum
• -1  meets criterion not as well as datum
• -2  meets criterion much worse then the datum
• -3  meets criterion far worse than the datum

General Format for a Pugh Matrix:

     

		Concepts
Criterion	Wt	(Step 2)
(Step 1)	:	Generate score (step 3)
	:
:		:
:		:
Total +
Total -
Overall Total		Generate totals (step 4)
Weighted Total

                                               

 Example of Pugh Matrix

 This example is looking was looking at alternatives for buying a cellphone here in the US in early 2007. Based on what what’s filled in so far, the Nokia 6682 with T-Mobile is the best choice. But if that doesn’t feel like the right decision, or things change, it’s a signal to spend more time refining the criteria and weights.

The basic steps of the Pugh Concept Selection Process are

1. Brainstorm alternatives, list them across columns of sheet. Make one alternative the “default” — often it’s the “do-nothing” or status quo choice. This choice is rated zero for all criteria.
2. Brainstorm criteria and characteristics important to the customer. List them down rows of sheet.
3. Begin filling in 1, 0, or -1 ratings in the main area of sheet, based on whether that alternative is better, equivalent, or worse than the status quo for that criteria.
4. If some criteria are more important than others, adjust the weights. If some products are much better than others, adjust the rating weights in the main area of the sheet. Don’t go overboard with this.
5. Look at what the spreadsheet tells you is the best choice. Do you and the group feel good about that decision? If so, you’re done.
6. If not, look again at steps 1-5 — do you have a complete set of criteria, or was something important to the decision missed? Are the weights you’ve assigned close enough?

                                          

CONCLUSION

·         The feasibility of the concepts is based on the design team’s knowledge. It is often necessary to augment this knowledge with research and development of simple models.

·         The decision matrix (Pugh’s method) provides means of comparing and evaluating concepts. The method gives insight into strong and weak areas of the concepts.

·         In order for a technology to be used in a product, it must be ready.