Lead time prediction in unbalanced systems

Whether job due dates are set internally or externally, it is critical for the shop floor controller to be able to accurately predict job lead times. Previous research has shown that utilizing information on the congestion levels along a job's route is more valuable than overall shop congestion levels when predicting job lead times. While this information is easily attained in a simulation model, in industrial applications the task may be considerably more difficult, especially when lot splitting is used to accelerate material flow. We examine the effectiveness of three lead time estimation procedures which utilize different shop information in bottleneck-constrained production systems where lot splitting is practiced under a variety of experimental conditions. The results indicate that accurate lead time estimates can be obtained using information pertaining solely to the bottleneck work centre when the bottleneck is at an entry work centre. This offers operations managers a substantial ease in implementation over previously reported methods. The results also show that the operations managers interested in accurately estimating job lead times are well advised to take advantage of the excess capacity at non-bottleneck work centres by performing additional setups, and take measures that reduce bottleneck shiftiness.