The Effects of Controlled Release and Congestion in a Flow Shop With Prohibited Early Shipments

Experiments were conducted with a simulation model of a flow shop with prohibited early shipments under a wide variety of conditions including congestion, which was modeled separately as “blocking” and as “material handling cost (MHC).” Congestion was found to significantly degrade most standard measures of shop performance, with stronger effects at high utilization and with blocking. Contrary to intuition, controlled release was found to be of little benefit under blocking. Further, controlled release under both blocking and MHC would appear to have a negative effect on flow time, percent of jobs tardy, work in process (WIP) cost, and late cost. Early cost and MHC were shown to benefit from controlled release under some circumstances, so total cost can benefit from controlled release depending on system configuration and cost parameters. With one such combination, a moderate level of release control was found to perform better on total cost than either immediate release or a stronger level of control.