An effective approach for measuring the capability of manufacturing processes

Abstract

Process capability indices (PCIs) have been proposed in the manufacturing industry to provide numerical measures on process capability, which are effective tools for quality assurance. Usual practices in measuring production quality have focused on the precise specification limits (SLs). If vagueness is involved into SLs, we face quite new, reasonable and interesting processes and the ordinary capability indices are not appropriate for measuring the capability of these processes. In this article, similar to the traditional PCIs, we develop a fuzzy analogue by operations defined on fuzzy SLs and we extend the traditional PCIs, using an imprecise (fuzzy) quality. Some interesting relations among these extended capability indices are proved. A real industrial application and numerical examples are given to clarify the method.

Keywords:

• fuzzy quality
• linear and exponential fuzzy specification limits
• process capability index

Acknowledgements

The first author is partially supported by Fuzzy Systems and its Applications Center of Excellence, Shahid Bahonar University of Kerman, Kerman, Iran.