Processes with nearly-sequential routings: a comparative analysis

Recent advances in automated technology have made it possible to incorporate many of the benefits of flow lines in the production of low-to-medium volume products found in a batch environment. The use of automated technology and cellular manufacturing tends to induce flows that are nearly sequential – the level of flow dominance is high, but it is not as high as the level associated with a pure flow shop. While a number of prior research studies have examined the performance of specific process configurations, such as those associated with cellular manufacturing, group technology and flexible manufacturing systems, ours is the first to analyze the effect of flow dominance in a more general setting. In this paper, we study the effect on process performance of slight departures from purely-sequential flows. To obtain generalizable results, we use a full factorial simulation experiment to examine both the main and interaction effects of product attributes, such as the number of products and job size, and of process attributes, such as operation-time variance, setup time, parallel processing capability and flow dominance. Our results provide insights into the performance of a wide variety of batch production processes, including, as special cases, cellular manufacturing, job shops, and flow shops. We show that the performance of such systems, as measured by average flow times and flow time variance, can be substantially improved by eliminating even a small number of remaining non-standard routings, particularly when setup times are moderate-to-high or operation-time variation is low-to-moderate.