Integrated control chart systems

Abstract

A multi-stage and multi-stream manufacturing system has several process stages, each of which consists of one or more parallel streams (or machines). A number of methods have been developed for implementing Statistical Process Control (SPC) for multistream manufacturing processes, but none of them has designed an SPC scheme for a multi-stage and multi-stream manufacturing system in an integrative and optimal manner. This research presents a number of algorithms for the optimization designs of the integrated control chart systems. They consist of several control charts for monitoring the multi-stage and multi-stream manufacturing processes. It is believed that the studies on the SPC for multi-stage and multi-stream manufacturing systems, and the development of the integrated control chart systems are original contributions to the literature and practice of quality engineering. The studies are conducted in two phases. The first phase (Chapter 3 and Chapter 4) presents the statistical and economical designs of the x control chart systems monitoring process mean. Chapter 3 presents two models for the statistical designs of the integrated x control chart systems. In Chapter 4, two economical models for single process are first designed based on random mean shifts. The models are implemented through a three-phase SPC operational scenario proposed in this thesis. The same concept is then applied to the design of the integrated x control chart system for a multi-stage and multi-stream manufacturing system. The second phase (Chapter 5 and Chapter 6) develops the statistical and economical models for the designs of the x&S control chart systems for monitoring process shifts in both mean and variance. In Chapter 5, two optimization models for the statistical designs of the integrated x&S control chart systems are developed. In Chapter 6, two economical models for a single process are first designed, and then the same concept is applied to developing the economical designs of the integrated x&S control chart system. The performance of all the models are compared to that of the conventional approaches and also illustrated through examples. Software systems for automating the designs of the SPC systems are also developed.