The Phased Release of Batches into a Job Shop

Much research has been reported on the possibilities of using various heuristic priority rules to sequence batches through a job shop. The SPT (Shortest Priority Time) heuristic, or modifications to it, has been proved useful in many studies. This paper reports on the results obtained when simulating the work flow through a real machine shop. The simulation model has been used to test the effect on well known priority rules of releasing batches into the shop in order of decreasing expected throughput time. The important effect of this “phased release” of batches was to increase the percentage of batches delivered in finished parts stores on time, particularly in the case where priority rules were in use which might otherwise have resulted in poor delivery. This has important repercussions for management because it implies that by “phased” release of batches in the manner discussed, a large proportion of batches will be delivered on time whatever priority rule is in operation in the shop.