Complexity in rework cells: theory, analysis and comparison

Although the word complexity is often used by engineers who are trying to re-design or re-organize a system, a formal definition of the term is often lacking. This paper introduces and extends the application of the concept of entropy to the quantitative analysis of complexity in the design and study of manufacturing systems. Sequence disorder complexity and routing complexity are defined in the context of manufacturing systems specifically including rework cells. Different kinds of rework cells are defined and their parameters presented. The difference between input and output sequences is studied with respect to rework cell system parameters and we introduce a quantitative complexity metric to measure the difference between alternative rework cells. The emphasis of this paper is on providing a comprehensive comparison on system performance of several structures of rework cells in terms of complexity, cost and quality. The paper concludes that both the choice of rework cells structure and system parameter selection are important to the design of rework cells.