Control Policy for Production Capacity Modulation with Waiting-Time-Constrained Work in Process

Reducing scrap is one of the key objectives of manufacturing companies to increase production efficiency and sustainability. Although many causes of scrap can be attributed to deviations at level of single processes, there are other causes inevitably related to dynamics at system level, as in presence of perishable material. In such situations the amount of time material waits in buffers, and therefore its level of degradation, is a consequence of the interaction among dynamics of the different production resources. This work presents an analytical model of a two-stage production system with perishable work in process. The model includes a control policy that modulates production capacity of parallel machines based on buffer and machines state, to reduce average waiting time and therefore scrap. Results from an industrial case in the semiconductor manufacturing sector show the usefulness of the policy in reducing scrap when the maximum waiting time of work in process is constrained.