A chart allocation strategy for multistage processes

Abstract

Statistical Process Control (SPC) in multistage manufacturing has attracted a great deal of attention recently. Applying conventional SPC methods in a multistage environment may not work well because these methods do not consider the inherent structure of the process, such as the interrelationship information between stages. In this paper, a strategy is proposed to properly allocate control charts in a multistage process in order to enhance the fast detection of out-of-control behaviors of conventional SPC. Based on the proposed chart allocation strategy, inherent structural information is involved in decision making to achieve quicker detection of a potential fault. Two automotive assembly examples are used to demonstrate the applications of the chart allocation strategy. The impact of uncertainty in the structural parameters is also considered, which may allow practitioners to make more realistic decisions in multistage manufacturing processes.

Keywords:

• Multistage process
• chart allocation
• average time to signal

Acknowledgements

The authors gratefully appreciate the editor and referees for their valuable comments and suggestions. This research was supported by RGC Competitive Earmarked Research Grants numbers 620606 and 620707.

[Supplemental materials are available for this article. Go to the publisher's online edition of IIE Transactions for the following free supplemental resource: Appendix containing detailed derivations of formulas, DOE data table and values of parameters]