Evaluation of the potential benefits of lot streaming in flow-shop systems

Lot streaming is the process of splitting a production lot into sublots, and then scheduling the sublots in overlapping fashion on the machines, in order to improve the overall performance of the production system. Simulation-based and industry-based reports have confirmed that substantial benefits are possible via lot streaming. In this paper, we present, for the first time, analytical results pertaining to the potential benefits of lot streaming in flow-shop systems. The results are developed using three common performance measures. These measures are (a) makespan (i.e., the total completion time of all the lots), (b) mean flow time, and (c) average WIP level. For each, an expression of the ratio of the measure under lot streaming to the measure without lot streaming is developed. These expressions can be used to evaluate the benefits of lot streaming under certain operating conditions. It is further shown that, in special extreme cases, these expressions purely depend upon the problem parameters (i.e., the number of machines, the number of lots, the lot-sizes, etc.).