Improving the Production Planning in Manufacturing Systems by Controlling the WIP

In this paper, the researcher discusses a manufacturing system with a single-part-type production line 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. Manufacturing systems are complex. Large numbers of machines, workers, and part types are often involved. The large number of random events makes the scheduling of manufacturing systems difficult. Hundreds of part types are produced simultaneously by hundreds of workers on dozens of machines. Each part type follows a predefined process which consists of hundreds of operations. Machines are subject to random failures, and need set-up changes for different part types. Maintenance and rework must be considered. Workers are absent at random. These factors result in long throughput time, large work- (WIP) inventory, and significant lateness. To improve the efficiency of production, in-process we would like to reduce inventory, throughput time, and tardiness simultaneously. Thus effective control policies are necessary to maintain high quality service with minimum inventory at a minimum cost. Production control systems that control material flow and inventory are therefore necessary for balancing such objectives. In this paper a production control policy, based on minimizing the WIP, is determined to meet the system performance requirements concerning low WIP inventory and tardiness.

Keywords:

WIP inventories , manufacturing system , inventory control , CONWIP method