Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

3.9 Evaluating Alternatives 63

3.9 Evaluating Alternatives

Once you have narrowed down your design to a few workable concepts, it is customary to use

an evaluation table similar to the one shown in Table 3.3 to evaluate alternative concepts in more

detail. You start by assigning a level of importance (I) to each design criterion. For example, you

may use a scale of 1 to 5, with I1 indicating little importance, and I5 signifying extremely

important. Next you will rate (R) each workable concept in terms of how well it meets each

design criterion. You may use a scale of R3 for high, R2 and R1 for medium and

low, respectively.

Note that the design criteria that we have listed in Table 3.3 are to serve as an example, not

as absolute design criteria. The design criteria vary depending on a project. For your class proj-

ect, you should list the design criteria that you feel are important. Moreover, note that it is

customary to divide the design criteria into positive and negative criteria. After you assign the

I and R values to your design options, you add the RI scores for each design and select the

design with the highest overall rating. An example demonstrating how to evaluate alternatives

is shown in Table 3.4.

TABLE 3.3 Table Used to Evaluate Alternative Concepts

Design I Design II

Design Criterion I R RIR RI

Positive

Originality

Practicability

Manufacturability

Reliability

Performance

Durability

Appearance

Profitability

Other

Negative

Production cost

Operating cost

Maintenance cost

Time to complete

the project

Environmental impact

Other

Net score

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