C Rajendran

This paper presents a comparative study on the performance of dispatching rules in the following sets of dynamic manufacturing systems: flowshops and jobshops, and flowshops with missing operations and jobshops. Three new dispatching rules are proposed. We consider a total of 13 dispatching rules for the analysis of the relative performance with respect to the objectives of minimizing mean flowtime, maximum flowtime, variance of flowtime, proportion of tardy jobs, mean tardiness, maximum tardiness and variance of tardiness. First, we carry out the simulation study in flowshops with jobs undergoing processing on all machines sequentially and in jobshops with random routeing of jobs. The results of the study reveal some interesting observations on the relative on the performance of the dispatching rules in these two types of manufacturing systems. Next, we consider flowshops with missing operations on jobs and jobshops with random routeing of jobs. We observe some interesting results in the sense that the performance of dispatching rules is being influenced by the routeing of jobs and shopfloor configurations.

We consider in this article the development of new and efficient dispatching rules with respect to the objectives of minimizing mean flowtime, maximum flowtime, variance of flowtime, proportion of tardy jobs, mean tardiness, maximum tardiness and variance of tardiness. We present five new dispatching rules for scheduling in a job shop. Some of these rules make use of the process time and work-content in the queue of the next operation on a job, by following a simple additive approach, in addition to the arrival time and dynamic slack of a job. An extensive and rigorous simulation study has been carried out to evaluate the performance of the proposed dispatching rules against those rules such as the SPT, WINQ, FIFO and COVERT, and the best existing rule. It has been observed that the proposed rules are not only simple in structure, but also quite efficient in minimizing several measures of performance. The important aspects of the results of experimental investigation are also discussed in detail.

We present two new dispatching rules for scheduling in a job shop. These rules combine the process-time and work-content in the queue for the next operation on a job, by making use of additive and alternative approaches. An extensive and rigorous simulation study has been carried out to evaluate the performance of the proposed dispatching rules compared with those by the SPT rule, the WINQ rule, a random rule based on the SPT and WINQ rules, and the best existing rule. The important aspects of the results of the experimental investigation are also discussed in detail.