The design process for a product first requires a clear understanding of the functions and the performance expected of that product. The product may be new, or it may be a revised version of an existing product. We have all observed, for example, how the design and style of radios, toasters, watches, automobiles and washing machines have changed. The market for a product and its anticipated uses must be defined clearly, with the assistance of sales personnel, market analysts, and others in the organization. Product design is a critical activity because it has been estimated that 70 to 80 percent of the cost of product development and manufacture is determined at the initial design stages.
During product design and once a part design is finalized, the production processes must be planned. In process planning, the general characteristics of the part, such as the general part configuration, material, surface finish, and tolerances, and must be determined first. These characteristics will affect part handling, the type of tooling and machines, the sequence of operations, assembly, and rate of production .
What is lean?
Lean Enterprise — A business system for organizing and managing product development, operations, suppliers, and customer relations. Business and other organizations use lean principles, practices, and tools to create precise customer value-goods and services with higher quality and fewer defects-with less human effort, less space, less capital, and less time than the traditional system of mass production.
Many of the key principles were pioneered by Henry Ford, who was the first person to integrate an entire production system, under what he termed "flow production." Following World War II, the Toyota Motor Company adapted Ford's principles as a means of compensating for its challenge of limited human, financial and material resources. The Toyota Production System (or TPS), which evolved from this need, was one of the first managerial systems using lean principles throughout the enterprise to produce a wide variety of products at lower volumes and many fewer defects than competitors.
Leaders today in a wide range of industries, nonprofit organizations, government agencies, healthcare, and other areas are finding ways to apply the principles of lean as a means of producing goods and delivering services that creates value for the customer with the minimum amount of waste and the maximum degree of quality .
 Kalpakjian, S. "Manufacturing Engineering and Technology, Third Edition." Reading, Mass.: Addison-Wesley, 1995.
 "What is Lean?" Lean Enterprise Institute, 2006.