Lot sizing and throughput times in a job shop

In the process of hierarchical production planning lot sizing has to be done in a medium time horizon. From that point of view, in a job shop environment the production time and material flow can be regarded as stochastic. Using results of Queuing Theory for lot sizing, ther average throughput time can be minimized and realistically forecast, as workload, production time and other orders competing for the same resources can be incorporated. Taking all these aspects into account, a queuing theoretical approach to production planning is suggested.