OPTIMAL PROCESS-CONTROL FOR MULTIPLE DEPENDENT SUBPROCESSES

A renewal theory approach is proposed to derive the cost model for mul tiple dependent subprocesses. The optimal individual Y control chart a nd multiple cause-selecting control chart are thus constructed to moni tor the overall product quality and specific product quality contribut ed by the multiple dependent subprocesses. They can be used to maintai n the process with minimum cost and effectively distinguish which comp onent of the subprocesses is out of control. The optimal design parame ters of the proposed control charts can be determined by minimizing th e cost model using a simple grid search method. An example is given to illustrate the application of the optimal individual Y control chart and multiple cause-selecting control chart. (C) 1998 John Wiley & Sons , Ltd.