Download citation file:
Chapter 3 illustrated how to specify tolerances for both higher-level and lower-level objective characteristics. As described in Chapter 2, the limits imposed by manufacturers to control the variance of objective characteristics of products are different from the tolerance specifications for these characteristics. Right now, many American industries use very sophisticated equipment to measure the objective characteristics of their products. However, because some quality managers of these companies do not interrupt the production process as long as their products are within control limits, the objective characteristics of their products are usually uniformly distributed, not normally distributed. In fact, control limits (the adjustment limits used in quality management systems) of products are quite different from the tolerance specifications for these products. This chapter explains how quality management should set control limits for production processes.