Integration of Multivariate Statistical Process Control and Engineering Process Control

Two independent methods for improving quality are engineering process control (EPC) and statistical process control (SPC). The first method tries to minimize variability by handling process variables so as to keep the outputs of the process on target. While the latter method, SPC does the same basic task of minimizing variability by supervising and eradicating the assignable causes of variation. This paper compares EPC working alone with integrated use of EPC and SPC for multivariate cases. Simulations are performed to evaluate the average of performance measures. Simulations results indicate that MEPC and MPSC combination performs better than using either of them individually. Furthermore, two different schemes of integration are discussed and evaluated namely application of SPC on the output and input of the process. It is concluded by the simulations that application of both of them simultaneously is better, in general, than using either of them alone.