Marily in performance
Marily in performance (including safety), time (how soon the solution will be avail¬able and how long it will last), and cost (including price, maintenance cost, and, today, litigation and insurance costs). The designer, in order to meet the requirements of the customer, generally uses as design criteria function, safety, economy, manufacturability, and marketability. To achieve these criteria, the designer may use as a problem statement the design imperative as presented in Mischke (see Sec. 1.1 or Ref [1.2]) and then make basic product decisions of the types listed in Table 1.8. From this point on, the decisions required to establish the solution to the design problem appear to be without bound. A second level of more detailed decisions then needs to be reached. Examples are shown in Table 1.9. Neither Table 1.8 nor Table 1.9 is represented as being complete, all-inclusive, or in any order of priority, since priority is established on a job-by-job basis. 1.2.2 Approach to Problem Solving To make decisions effectively, a rational problem-solving approach is required. The first step in problem solving is to provide a statement defining the problem to be solved. The essential ingredients as stated and discussed in Dieter [1.15] are • A need statement • Goals, aims, objectives • Constraints and allowable tradeoffs • Definitions of terms or conditions • Criteria for evaluating the design TABLE 1.8 Basic Product Decisions to Be Made by the Designer* Anticipated market Expected maintenance Controls Component elements Types of loadings Materials Fabrication methods Target costs Expected life Evolutionary design or original design Energy source(s) Permissible stresses Permissible distortions fNo significance is to be attached to order or extent. SOURCE: J. P. Vidosic, Elements of Design Engineering, The Ronald Press Company, New York, 1969. TABLE 1.9 Second-Level Decisions to Be Made by the Designer* Strength of each element Reliability of each element Maintenance required Allowable distortion Style Noise allowable Governing regulations Governing standards Governing codes Control requirements Surface finish Corrosion anticipated Friction anticipated Lubrication required Wear anticipated Geometry Tolerances fNo significance is to be attached to order or extent