Optimization design of the charts for monitoring process capability

A new algorithm for designing theX & S control charts is presented in this article. It allocates the detection power between theX chart and theS chart in an optimal manner and associates the in-control and out-of-control process conditions with the process capability index,Cpk. Specifically, whenCpk decreases to a hazardous level, theX & S control while, the sample size of theX & S charts is made as small as possible to reduce the cost for the statistical process control (SPC). Moreover, the users are allowed to decide the signaling time with desired probability. Generally, the new algorithm will provide the users with more control on the design and operation of theX & S control charts.