Polca simulation of a unidirectional flow system

Polca is a material control system that focuses on shop floor throughput time control in production situations with high variety and customization. It uses an authorization mechanism that consists of route-specific capacity signals (polca cards) and product-specific release signals (ERP system). The route-specific capacity signals level the maximum amount of work in progress within a loop. Each loop connects two route segments, e.g. two cells in the production system. The number of Polca cards in this loop is an important design parameter. If the number of cards is set too high, the system functions unconstrained and the Polca system does not regulate the control of shop floor throughput times at all. If the number is set too low, the system will not be able to cope with the amount of orders issued, and hence total throughput time (the sum of pool waiting time and shop floor throughput time) will steadily increase. Literature offers an approach to determine the number of Polca cards in a system, based on the expected utilization of the loops. This paper shows the effect of variation in several parameters of the arrival and service process while maintaining the expected utilization at the same level. Experiments with order arrival pattern, batch size, demand variation, product mix, priority rule, and occurrence of breakdowns have been performed.