Scheduling Manufacturing Systems With Work-in-Process Inventory Control: Single-Part-Type Systems

In this paper, a real-time feedback control algorithm is developed for scheduling single-part-type production lines in which there are three important classes of activities: operations, failures, and starvation or blockage. The scheduling objectives are to keep the actual production as close to the demand as possible, and to keep the level of work-in-process inventory as low as possible. By relating the starvation and blockage to the system capacity, the buffer sizes and the target buffer levels are chosen according to the demands and machine parameters. The processing time for each operation is deterministic. Failure and repair times are random. Whenever a machine fails or is starved or blocked, the scheduling system recalculates short term production rates. To begin with, we study a very simple case, a two machine and one part type system, to get insight into the buffer effects and production control policies. Using the relationship between system capacity and starvation or blockage, we find desirable buffer levels and buffer sizes. The production control policy is determined to meet the system performance requirements concerning low WIP inventory and tardiness. The results from the simple case are extended to N-machine, one-part-type systems