Process modeling and manufacture: Where we stand

The term "process" is broadly defined as the means by which a manufacturing organization converts raw materials into a finished product. This includes people and equipment operating together in a managed and planned system. In addition to the efficient use oflabor and production equipment, an ideal process turns out a product with a 100% yield and no waste of raw materials. Typical real processes produce products with variations in characteristics, suffer from equipment downtime, and waste raw materials. Real processes also are sensitive to human behavior, machine performance, and the characteristics of raw materials. Often, attempts to increase the throughput of a process lead to an increase in the sensitivity to such variances. The traditional approach to maintain product quality within acceptable limits has been increasingly intensive product inspection to remove unacceptable products from the production line. Of course, such inspection is costly and time-consuming. In today's environment, which places an emphasis on total quality control (TQC), the trend is to couple process design and control together. An ideal, properly controlled process will yield only good products. Complete process control obviates the need for product inspection (or at least limits it to first article verification or occasional spot checks). The need to control manufacturing processes is forcing manufacturing technologists to seek a scientific description of manufacturing processes and the response of raw materials, equipment and semi-finished products to these processes in order to simulate the entire manufacturing process, and thus obtain near-optimal solutions for producing the desired product qualities. This is process modeling. The objective is to achieve efficient manufacturing processes without the need for the costly trial-and-error search for viable manufacturing processes. Analyses of this type rely on the