Reducing total tardiness cost in manufacturing cell scheduling by a multi-factor priority rule

Current literature about scheduling problems contains numerous studies on the use of dispatching rules with performance measures that are based only on time criteria. Various methods have been proposed to consider job processing time, job completion time, job due date, and combinations thereof. Considerations of tardiness cost, which offers a realistic reflection on the manufacturers' business concern, are usually ignored. One exception is the Weighted COVERT rule with the weighted tardiness cost concern. It has been tested and performs well in costbased performance. However, the performance of Weighted COVERT strongly depends upon the selected parameter values for estimating the expected waiting time of jobs. In this research, we present a multi-factor priority rule to improve the Weighted COVERT rule. Our new rule combines job processing time, job routing, job due date, and job-dependent tardiness cost for the scheduling in a manufacturing cell. The objective is to reduce the total tardiness cost. The central idea of this multi-factor priority rule is to give a higher priority to those jobs that have longer expected waiting time, shorter slack time, and higher ratio of tardiness cost over processing time. Performance comparisons (i.e. total tardiness cost, percentage of tardy jobs, and mean flow time) by simulation include five priority rules: SPT, EDD, Weighted COVERT, ATC, and our proposed multi-factor rule. The results have shown that the new rule is not only effective in reducing the total tardiness cost, but also performs well with respect to percentage of tardy jobs and mean flow time.