MRP-controlled manufacturing environment disturbed by uncertainty

Most identified research on uncertainty in material requirements planning (MRP)-controlled manufacturing environment, while purporting to represent such environment, does not truly model a multi-level dependent demand system, with multi-product and controlled by planned order release (POR) schedule based on planned lead times. This research has developed an MRP-controlled batch manufacturing simulation model using ARENA simulation software to represent such environment. In this paper, the delivery performance of the environment, measured with parts delivered late (PDL) and finished products delivered late (FPDL), when disturbed by uncertainty is examined. Design of experiments and simulation studies are carried out for these uncertainties: external late supply, internal late supply, planned set-up time exceeded, machine breakdowns, labour unavailability, tooling unavailability, demand batch size enlargement and customer design changes. Analysis of Variance (ANOVA) results identify significant effects from individual uncertainty as well as combination of uncertainties. The knock-on and the compound effects cause more PDL and FPDL. The main finding is that the higher is the level of the significant uncertainties, the higher is the level of PDL and FPDL. It is suggested that MRP-controlled manufacturing enterprise must diagnose for the significant uncertainties, so that optimum use of buffer or slack can be implemented. Some practical implications of this work and required further work are also discussed.