The Mechanical Design Process by Unknown

Author:Unknown
Language: eng
Format: mobi
Published: 2014-08-03T11:53:54.578000+00:00

ullman-38162

ull75741_08

December 23, 2008

18:24

C

H8

A

P

T

E

R

Concept Evaluation

and Selection

KEY QUESTIONS

■

How can rough conceptual ideas be evaluated without refining them?

■

What is technology readiness?

■

What is a Decision Matrix?

■

How can I manage risk?

■

How can I make robust decisions?

8.1 INTRODUCTION

In Chap. 7, we developed techniques for generating promising conceptual solu-

tions for a design problem. In this chapter, we explore techniques for choosing the

best of these concepts for development into products. The goal is to expend the

least amount of resources on deciding which concepts have the highest potential

for becoming a quality product. The difficulty in concept evaluation and decision making is that we must choose which concepts to spend time developing when

we still have very limited knowledge and data on which to base this selection.

How can rough conceptual ideas be evaluated? Information about concepts

is often incomplete, uncertain, and evolving. Should time be spent refining them,

giving them structure, making them measurable so that they can be compared with

the engineering targets developed during problem specifications development?

Or should the concept that seems like the best one be developed in the hope that

it will become a quality product? It is here that we address the question of how

soon to narrow down to a single concept.

Ideally, enough information about each concept is known at this point to

make a choice and put all resources into developing this one concept. However,

it is less risky to refine a number of concepts before committing to one of them.

This requires resources spread among many concepts and, possibly, inadequate

213

ullman-38162

ull75741_08

December 23, 2008

18:24

214

CHAPTER 8

Concept Evaluation and Selection

development of any one of them. Many companies generate only one concept

and then spend time developing it. Others develop many concepts in parallel,

eliminating the weaker ones along the way. Designers at Toyota follow what they

call a “parallel set narrowing process,” in which they continue parallel develop-

ment of a number of concepts. As more is learned, they slowly eliminate those

concepts that show the least promise. This has proven very successful, as seen

by Toyota’s product quality and growth. Every company has its own culture for

product development and there is no one “correct” number of concepts to select.

Here we try to balance learning about the concepts with limited resources. In this

chapter, techniques will be developed that will help in making a knowledgeable

decision with limited information.

As shown in Fig. 8.1, after generating concepts, the next step that needs to be

accomplished is evaluating them. The term evaluate, as used in this text, implies comparison between alternative concepts relative to the requirements they must Generate

concepts

Refine

Evaluate

concepts

concepts

Make

concept

decisions

Document and

communicate

Refine

plan

Refine

To product

specifications

design

Approve

concepts

Cancel

project

Figure 8.1 The conceptual design phase.

ullman-38162

ull75741_08

December 23, 2008

18:24

8.2

Concept Evaluation Information

215

If the horse is dead, get off.

meet. The results of evaluation give the information necessary to make concept

decisions.

Be ready during concept evaluation to abandon your favorite idea, if you

cannot defend it in a rational way. Also, abandon if necessary “the way things

have always been done around here.” Reflect on the above aphorism and, if it

applies, use it.

Before we get into the details of this chapter, it is worth reflecting on the

basic decision-making process introduced in Chap. 4 where we were selecting

a project. In Fig. 8.2 (a reprint of Fig.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.