Workload Balancing and Inventory Minimization for Job Shops

Source: The Journal of INDUSTRIAL ENGINEERING  Date: April, 1968

The purpose of this article is to discuss a specific algorithm for forecasting and balancing the workload in a job shop. This algorithm provides a procedure for combining economic analysis and workload forecasts into an efficient economical schedule for a job shop. The studies resulting in the preparation of this article were performed in an aerospace company possessing a rather large and complicated job shop. The complexity of the jobs passing through the job shop was such that in some cases six to nine months of flow time was required to process a single job in its entirety. In almost all cases, the planning and release of orders occurred months ahead of the actual time that the finished product was needed, because no method of forecasting and controlling the workload in the job shop existed, and, in order to provide efficient utilization of labor and machines, it was necessary to have a large inventory of work waiting behind every machine on the floor. This unnecessarily large inventory enabled most machines to be used continually and most jobs to be turned out on a timely basis. This situation of excess inventory and its associated carrying cost is typical in the aerospace industry and may be to a limited extent characteristic of all job shops.
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