The design process is iterative in that a design is continuously modified until it meets acceptance criteria defined by safety, cost, performance, convenience, and shape. An initial design can go through many product development cycles before mass production. A product development cycle includes:
This process continues until a satisfactory solution is reached.
Design cycles are expensive and time-consuming due to prototyping and field testing. Because of time and cost constraints, most designers accept a solution that may not be optimum.