Evaluation of Capacity Control and Planned Lead Time Control in a Control-theoretic Model

Reducing lead time variability of production systems has been shown to be advantageous, enabling constant flows and improved on time production. Nevertheless, fluctuating order inflows, disturbances and other factors are known to induce varying workloads, and hence produce fluctuating actual lead times. Adjusting planned lead times as a countermeasure against low due date reliability could lead into the drawbacks of the Lead Time Syndrome. The update frequency of planned lead time adjustments as well as the delay until changes take effect in a production system can significantly influence the occurrence of the Lead Time Syndrome. Nevertheless, taking these effects into account, production control via planned lead time adjustments remains a suitable means for increasing due date reliability. Another production planning and control approach is to avoid fluctuating actual lead times using capacity adjustments, which can be implemented by either lead time regulation or work in process regulation. These strategies have been integrated into a control theoretic simulation model that enables comparisons to be made of resulting performance; thus, preferable strategies can be identified for different settings of inflow fluctuations, update frequencies and delay.