Optimal CSP-1 boundary scheme based on the estimator of the proportion of conformance for specified in-control process

ABSTRACT

Single-level continuous sampling plan (CSP-1), called $\mathrm{A}\mathrm{O}\mathrm{Q}\mathrm{L}$ contour scheme, is constructed on the average outgoing quality limit ($\mathrm{A}\mathrm{O}\mathrm{Q}\mathrm{L}$) contour. However, for specified in-control process the boundary of feasible continuous sampling scheme is not established in CSP-1. The optimal CSP-1 boundary scheme is established based on the estimator of the proportion of conformance for specified in-control process. The parameters of the boundary scheme are determined by the set of equations constructed with the boundary identical equation and contour identical equation, which will guarantee that the proposed scheme is simultaneously both boundary scheme and contour scheme. The behaviour of the established boundary scheme is discussed and compared with the $\mathrm{A}\mathrm{O}\mathrm{Q}\mathrm{L}$ contour scheme. The optimal CSP-1 boundary scheme can quantitatively control the outgoing quality and tighten the inspection whether the process quality fluctuates towards the deteriorated or the improved direction. For practitioners’ convenience, three tables of the boundary scheme parameters under three quality requirements and three confidence levels are provided. The operating procedure is also presented. A real example is given to verify the effectiveness and feasibility of the proposed boundary scheme.

KEYWORDS:

• Optimal CSP-1 boundary scheme
• outgoing quality
• average outgoing quality limit
• proportion of conformance

Acknowledgements

The authors are grateful to the Editor and the reviewers for reading the manuscript carefully and providing many valuable and constructive comments.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 71572147].

Notes on contributors

Chunzhi Li

Chunzhi Li is a doctoral student in industry engineering at Northwestern Polytechnical University. Her primary research interests are in the areas of statistical process control, continuous sampling plan, cost control, and so on. She had worked for four years at Aero-Engine Company and been a technician in a heat-treatment workshop. She is now a teacher at East China Jiaotong University in Nanchang, China. Her research results will be applied in manufacturing.

Shurong Tong

Shurong Tong is a professor with the School of Management of Northwestern Polytechnical University. Professor Tong received her PhD in aviation manufacturing engineering from Northwestern Polytechnical University in 1999. Her research interests are in product design management, product knowledge management, product life cycle management, and quality management. She presided over three projects of National Natural Science Foundation of China and was the primary participant in the two projects ‘Asia-link’ and ‘A Framework Approach to Strengthening Asian Higher Education in Advanced Design and Manufacture’. Professor Tong practices long-term cooperation with the University of Strathclyde in Scotland, the University of Technology of Compiegne and University of Technology of Troyes in France, and the Technical University of Denmark.

Keqin Wang

Keqin Wang is an associate professor of Management Science and Engineering with the School of Management of Northwestern Polytechnical University. He received his PhDs from the School of Management of Northwestern Polytechnical University in 2010 and the Université de Technologie de Troyes in 2011, respectively. His research interests are in quality management, product development management, and knowledge management.

Xinwei Zhang

Xinwei Zhang is an associate professor with the School of Management of Northwestern Polytechnical University, Xi’an, China. He received his BS degree in Management Information Systems in 2005, his MS degree in Management Science and Engineering from Northwestern Polytechnical University in 2008, and his PhD in Industrial Engineering from INSA Toulouse, France in 2012. His research areas are quality management and requirements engineering.