Certain Implementation of the PCIsCpm and Cpp

Lu, H. K., and Chiou, H. C. 2000. Certain Implementation of the PCIsCpm and Cpp. NTU Management Review, 10 (2): 205-226

Kuen Horng Lu, Associate Professor, Industrial Engineering and Management, National Kaohsiung University of Science and Technology
Chien Hui Chiou, Research Assistant, Department of Applied Mathematics, National University of Kaohsiung

Abstract

A process capability index (PCI) is a unitless function of the process parameters and the process specifications (LSL,T,USL) designed to provide a common, easily understood language for quantifying the performance of a process (Boyles, 1991). It is used to determine whether a production process is capable of producing items within a specified tolerance. However, most people using the PCI simply consider the value of the index calculated from the given sample to make a conclusion on whether the given process is capable or not. Several authors (Montgomery (1985), Chou et al (1990) and Cheng (1992)) have point out that it is not an appropriate approach. Based on the application of Cpm index, this paper persents approaches for evaluating the quality capability of both the single process and multiple process in order to correctly and easily evaluate the quality performance of the process. Hence, this study constructs a testing procedure for RMV of Cpm to help judge whether a single process is capable or not, and proposes a graphic approach which uses the Cpm index for evaluating the quality performance of multiple processes. Finally, two numerical examples which illustrates the usage of the indices are proved.  


Keywords

Process capability index Recommended minimum value Multiprocess performance analysis chart Cpm and Cpp


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