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

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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


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

Original languageEnglish
Pages (from-to)712-719
Number of pages8
JournalInternational Journal of Advanced Manufacturing Technology
Issue number9-10
StatePublished - May 2004


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

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