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

W.l. Pearn*, M. H. Shu, B. M. Hsu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


The multiprocess performance analysis chart (MPPAC) based on the process capability index Cpm, called Cpm MPPAC, is developed for analysing the manufacturing quality of a group of processes in a multiple process environment. The Cpm 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 Cpm based on multiple samples. Based on the natural estimator of Cpm, we consider the sampling errors by providing an explicit formula with the Matlab program to obtain the estimation accuracy of the Cpm. We tabulate the sampling accuracy of Cpm 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 Cpm MPPAC for manufacturing quality control.

Original languageEnglish
Pages (from-to)140-147
Number of pages8
JournalInternational Journal of Advanced Manufacturing Technology
Issue number1-2
StatePublished - 23 Aug 2004


  • Maximum likelihood estimator
  • Multiprocess performance analysis chart
  • Process capability index
  • Sample size determination

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