Job shop leadtime requirements under conditions of controlled delivery performance

A model that facilities setting due dates on the basis of forecasted flowtimes and estimated forecast error has recently been developed. This model, called the Dynamic Forecasting Model, allows job shop delivery performance to be controlled. Quoted leadtimes can therefore be used as a measure of shop floor control performance. This paper investigates the leadtime performance under various types of dispatch. Results show that when the percentage of tardy jobs desired is low and the utilization level is high, due-date dependent dispatch facilitates using lower leadtimes than due-date independent dispatch. Within the due-date dependent group of dispatch rules tested, leadtime behaviour is very similar. Furthermore, performances using operation and job due dates are quite similar. When due dates are set in a manner allowing delivery performance to be controlled, evidence suggests that differences in leadtime requirements are less affected by the dispatch rule choice than by the utilization level and the desired level of delivery performance.