C pm MPPAC for manufacturing quality control applied to the precision voltage reference process

Abstract

The multiprocess performance analysis chart (MPPAC) based on the process capability index C pm , called C pm MPPAC, is developed for analysing the manufacturing quality of a group of processes in a multiple process environment. The C pm MPPAC conveys critical information of multiple processes regarding the departure of the process and process variability from one single chart. Existing research works on MPPAC are restricted to obtaining quality information from one single sample of each process ignoring sampling errors. The information provided from existing MPPAC charts, therefore, is unreliable and misleading and results in incorrect decisions. In this paper, we consider the natural estimator of C pm based on multiple samples. Based on the natural estimator of C pm , we consider the sampling errors by providing an explicit formula with the Matlab program to obtain the estimation accuracy of the C pm . We tabulate the sampling accuracy of C pm for sample size determination so that the engineers/practitioners can use it for their in-plant applications. An example of multiple precision voltage reference (PVR) processes is presented to illustrate the applicability of C pm MPPAC for manufacturing quality control.