STANDARD HANDBOOK
STANDARD HANDBOOK OF MACHINE DESIGN The designer’s task is then to create this specification set for the manufacture, assembly, testing, installation, operation, repair, and use of a solution to a problem. Although primarily decision making and problem solving, the task is a complex activity requiring special knowledge and abilities. A designer cannot effectively operate in a vacuum, but must know, or be able to discover, information affecting the design, such as the state of the art, the custom of the industry, governmental regula¬tions, standards, good engineering practice, user expectations, legal considerations (such as product liability), and legal design requirements. In addition, an effective designer possesses the ability to make decisions; to innovate solutions to engineering problems; to exhibit knowledge of other tech-nologies and the economics involved; to judge, promote, negotiate, and trade off; and finally, to sell an acceptable problem solution which meets the imposed constraints. The designer must also be an effective communicator, not only with design super¬visors and peers, but also with the public, as represented by federal, state, and local governments, the courts, and the news media. Most of the time design proceeds by evolution rather than revolution. Thus many of the requirements may have already been met by contributions of others, and most of the time the engineer has to work on only a small portion of the design, requiring only some of the requisites previously identified. 1.1.2 Design Criteria Although the general criteria used by a designer are many, the following list addresses almost all concerns: • Function • Safety • Reliability • Cost • Manufacturability • Marketability The inclusion of safety and reliability at or near the level of importance of function is a recent development that has resulted from governmental regulation, expansion in the numbers of standards created, and development of product liability law, all of which occurred in the late 1960s and early 1970s. Although cost is explicitly fourth on the list, its consideration permeates all the criteria just listed and is part of all design decisions. As taught and practiced in the past, design criteria emphasized function, cost, manufacturability, and marketability. Reliability was generally included as a part of functional considerations. If product safety was included, it was somewhere in the function-cost considerations. Design critiques were accomplished at in-house policy committee meetings or their equivalent involving design engineers, a production representative, a materials representative, and possibly representatives of marketing and service. In the current design climate, the traditional design criteria are still valid; how¬ever, the additional constraints of governmental regulations, standards, and society’s desire for safety, as exemplified in product liability litigation, have to be included in