Sizing of Heijunka-controlled Production Systems with Unreliable Production Processes

Heijunka is the notion to level a production system by removing ups and downs in volume caused by batch processing and customer order fluctuation in order to reach a mixed model production system with a constant flow of parts. We show how to implement lean production principles in systems with unreliable production processes. Process unreliabilities occur because tool machines may have small overall equipment effectiveness. Our present results were derived during performed implementation projects, where supermarketpull-systems had to be dimensioned. In particular, the calculation of required inventory levels is presented which uses analytical mathematical models on the basis of discrete time queuing systems. By considering variable capacities we essentially extend the content of reference [1]. The application of our model is demonstrated by an example.