To design is either to formulate a plan for the satisfaction of a specified need or to solve a problem. If the plan results in the creation of something having a physical reality, then the product must be functional, safe reliable, competitive, usable, manufacturable, and marketable. To remind us that designs are constrained, and have to exhibit qualities known at the outset, a design imperative can be expressed as follows:
(subject to certain problem-solving constraints) a component, system, or process that will perform a specified task (subject to certain solution constraints) optimally.
The parenthetical expressions refer to qualifications placed on the design. The solution methodology is constrained by what the designer knows, or can do; the solution, in addition to being functional, safe, reliable, competitive, usable, manufacturable, and marketable, must also be legal and conform to applicable codes and standards.
It is important that the designer begin by identifying exactly how he or she will recognize a satisfactory alternative, and how to distinguish between two satisfactory alternatives in order to identify the better. From this kernel, optimization strategies can be formed or selected. Then, the following tasks unfold:
- Invent alternative solutions.
- Through analysis and test, simulate and predict the performance of each alternative retain satisfactory alternatives, and discard unsatisfactory ones.
- Choose the best satisfactory alternative discovered as an approximation to Optimality.
- Implement the design.
The outputs of the design process are decisions concerning components and their connectivity, geometry, “forming” processes, thermo-mechanical treatments, and associated tolerances. All this is laid out in the plans and specifications. In Fig. 1-1, the “black box” representing the design process is a light bulb, a reminder to the reader that without the creative-inventive component, useful results are rare.
The need in Fig. 1-1 may be well-defined, such as “We need a solar-powered car,” or the nature of the problem may be unclear, as in “We need a safer automobile.” Often the designer’s initial task is to clearly define (identify) the need, including preferences of engineering managers, marketers, and customers, before doing anything else. The needs, or problems, include opportunities, and they may be multiple.
The characterization of a design task as a design problem can introduce the idea that, as a problem, it has a solution. This may not be so. The design space may be empty, some situations may simply have to be endured. To relieve the absence of solutions, some constraint(s) may have to be renegotiated in order to admit solutions. Then again, even when solutions are possible, the designer may not be creative enough, inventive enough, to conceive of them. This admits to the design problem the necessity of individual talent or skill in this area.
There may be more than one solution, and distinguishing among them to choose the best may require the ability to handle a large number of solutions without being overwhelmed. Solutions, if they exist, can be characterized as satisfactory, some better than others, some clearly good, and one, the best by some criterion. Solutions can have a time dependency, for what is acceptable today may not be so tomorrow, and vice versa.
Design is an innovative and iterative process. It is also a decision-making process. Decisions sometimes have to be made with too little information, occasionally with just the right amount of information, or with a surfeit of partially contradictory information. A man with a watch knows what time it is; with two watches, he is never sure. Decisions are sometimes made tentatively, reserving the right to adjust as more becomes known. The point is that the engineering designer has to be personally comfortable with a decision making, problem-solving role. It should be a satisfying and welcomed activity. If it is not, there can be personal ramifications (such as stress) that can interfere, even threatening the designer’s health.
Design is a communication-intensive activity in which both words and pictures are used, and written and oral forms are employed. Engineers have to communicate effectively, and persuade people who know more than they do, or less than they do. These are important skills, and an engineer’s ability to function depends on them.
Designs are subject to problem-solving constraints. A designer can only apply methods he or she knows and understands. Corporations performing design tasks know and apply more methods than an individual designer does, and the problem-solving con; straints are less severe. A corporation can tap the knowledge of consultants and reduce constraints even more. Eventually, the limit of what is known by humankind is reached (the state of the art). Thus time, money, and corporate collective knowledge are common problem-solving constraints imposed on a design. A designer’s personal resources of creativeness, communicative ability, and problem-solving skill are intertwined with knowledge of technology and first principles. Engineering tools (Such as mathematics, statistics, computer, graphics and language) are combined to produce a plan, which, when carried out, produces a product that is functional, safe, reliable, competitive, usable, manufacturable and markable regardless of who builds it or who uses it.