On the integration of card-allocation and dispatching decisions in POLCA systems: an assessment by simulation

Abstract

POLCA is an important card-based control system for low volume, high variety production contexts. A job can only be produced at an upstream station if it has acquired a POLCA card that has returned from its downstream station. A common assumption in the POLCA literature is that cards are allocated to jobs as soon as they return to the upstream station. This dissects the queue in front of a station into jobs that have a card (and can be produced) and those that do not have a card (and cannot be produced). This artificially and prematurely constrains the dispatching decision, i.e. the decision concerning which job to produce next at a station. In response, this paper proposes integrating the card-allocation and dispatching decisions such that the allocation of POLCA cards to jobs is postponed until the dispatching decision is made. Simulation results demonstrate that this integrated approach does not improve performance under simple ERD dispatching, as is commonly applied in the POLCA literature. But when a more powerful rule is applied, percentage tardy and mean tardiness performance improve by more than 75% and 50%, respectively, for an integrated decision. Most importantly, results suggest that in production environments like the one considered in this study, the integrated approach dispenses with the use of POLCA altogether if a suitable priority rule is used.