Two new rules to minimize tardiness in a job shop

SUMMARY

In this paper we present two new dispatching rules for minimizing tardiness in a job shop. Both rules are closely related to the modified operation due date (MOD) rule. The first is a combination of the shortest processing time (SPT) rule and the critical ratio (CR) rule, and the second is a combination of the SPT rule and the slack per remaining work (S/RPT) rule. The two new rules are simple to implement and can easily be adapted to minimize weighted tardiness. Moreover they do not require any parameter estimation for their implementation, which is a notable disadvantage of some earlier rules such as COVERT. Simulation results show that the performance of the two new rules is better than that of other rules that have been developed to minimize total weighted and unweighted tardiness. This holds true across a range of shop conditions. Furthermore, the rules are effective in minimizing the number of tardy jobs.