Title: Variable sample size control chart for monitoring process capability index Cpm

Authors: Dja Shin Wang; Hau Yu Yang; Tong Yuan Koo

Addresses: Department of Business Administration, TransWorld University, 1221, Zheng Nan Rd., Douliu 640, Yunlin, Taiwan ' National Chung-Shan Institute of Science and Technology, No. 481, 6th Neighborhood, Sec. Jia'an, Zhongzheng Rd., Longtan Dist., Taoyuan City, Taiwan ' Department of Industrial Engineering and Management, National Yunlin University of Science and Technology, Douliu, Taiwan

Abstract: Process capability indices (PCIs) provide numerical measures of process reproduction capability and are effective tools for quality assurance. In the present paper, we develop a variable sample size control chart, namely VSSCpm, to monitor PCIs for industry manufacturing to improve product quality. We setup the control limits; determine the upper and lower warning limits, fixed sample size, central region sample size, and warning region sample size for the control chart; and apply them to monitor PCI Cpm. We also use the average run length (ARL) as a monitoring performance indicator. To increase the in-plant applicability of the proposed method, we tabulate the performance value of the ARL for various commonly used situations. We perform a sensitivity analysis to study the effects of model parameters on the monitoring performance and then present an example to illustrate the proposed procedure.

Keywords: process capability index; PCI; control chart; quality monitoring performance.

DOI: 10.1504/IJISE.2020.109117

International Journal of Industrial and Systems Engineering, 2020 Vol.36 No.1, pp.32 - 48

Accepted: 21 Jan 2019
Published online: 14 Aug 2020 *

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