The effect of combining simple priority heuristics in flow-dominant shops

Previous scheduling research indicates that no single priority heuristic is effective on all the relevant performance criteria. However, few heuristics have shown to be effective on particular performance criteria. This study examines this issue further by applying various scheduling heuristics at different states of three flow-dominant shops (i.e. entrance, intermediate, and exit workstations), under a variety of experimental conditions. The experimental factors used are shop load, due date tightness, and shop structures. Twenty-eight different combinations of heuristics were investigated. The results indicate that the application of particular priority heuristics at various stages of the production process has a positive impact on the shop performance. By selectively utilizing different scheduling heuristics, it is possible to gain the advantages of each heuristic and at the same time minimize their associated shortcomings. Furthermore, the relative rankings of the heuristic combinations are fairly robust to the shop structure factor on all performance measures. Finally, it is shown that the selective use of the shortest processing time heuristic significantly impacts the performance measures across all experimental conditions.