Title: Developing robust design: determining critical limits for signal-to-noise ratio based on process capability index

Authors: Arash Shahin; Arash Geramian

Addresses: Department of Management, University of Isfahan, Hezarjarib St., 81746-73441, Isfahan, Iran ' Department of Management, University of Isfahan, Hezarjarib St., 81746-73441, Isfahan, Iran

Abstract: In design of experiments (DOE), the higher the ratio of signal-to-noise (S/N) is, the better the experiment would be. However, there might be cases in which, process capability is not desirable, while the S/N ratio is high. To resolve such problem, in this study an approach has been proposed to control the ratio. For this purpose, the process capability indices, i.e., C_p and C_PK ratios have been integrated with S/N ratio, and critical ratios have been determined for the two mentioned indices. The determined ratios not only have been used in measuring the value of S/N ratio, but also have been compared with the critical ratio. In this comparison, the changes of denominator has been studied and it has been found that selecting the experiment with highest S/N ratio is done in respect of controlling its undesirable changes within acceptable limits.

Keywords: quality engineering; design of experiments; DOE; process capability index; PCI; orthogonal arrays; active statistical method; critical S/N ratio; robust design; signal-to-noise ratio; quality improvement; statistical process control; SPC.

DOI: 10.1504/IJPQM.2014.064477

International Journal of Productivity and Quality Management, 2014 Vol.14 No.2, pp.228 - 246

Published online: 06 Sep 2014 *

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