Due date based scheduling in a general flexible manufacturing system

Abstract

Dynamic scheduling of manufacturing systems for due date based objectives has received considerable attention from practitioners and researchers due to the importance of meeting due dates in most industries. Research investigations have focused primarily on the relative effectiveness of various dispatching rules in job shops. These rules operate by prioritizing jobs using a “criticality index” based on job and system status. Jobs are then scheduled from most critical to least, with the indexes typically being updated as the system changes. This study considers two important issues which have not been addressed previously in the literature. First, we investigate the impact of unequal machine workloads on the relative effectiveness of dispatching rules. This is significant because workloads are likely to be unbalanced in most real systems. While it is clear, intuitively, that this imbalance in machine workloads is likely to deteriorate system performance, it is not obvious whether the superiority of certain dispatching rules established in earlier studies for balanced workloads is carried forward to this case. We show that the performance of different dispatching rules does indeed depend upon the degree of workload imbalance. We also propose and test a scheduling procedure which performs well in both balanced and unbalanced systems. Next, we develop a scheduling approach which shows promise as being an improved alternative to the use of dispatching rules. This approach decomposes the dynamic scheduling problem into a series of static problems. These static problems are then solved using an optimum‐seeking method, and the solutions are implemented on a rolling basis. We show through a simulation experiment that adopting this approach over dispatching rules leads to an improvement in the overall solution quality, even in a dynamic environment. The two very practical implications of our study are: (1) that commonly used dispatching rules in job shops or automated manufacturing systems may not be the best approach when capacity utilization is unbalanced (2) a job shop or automated manufacturing system would likely benefit from implementing optimal‐seeking scheduling rules instead of the traditional job dispatching rules.

Rescheduling Problems with Agreeable Job Parameters to Minimize the Tardiness Costs under Deterioration and Disruption

“…There are several papers on rescheduling approaches in manufacturing systems. Raman et al [10] developed a branch-and-bound procedure to reschedule a flexible manufacturing system in the presence of dynamic job arrivals. Church and Uzsoy [11] addressed a similar problem for which they describe periodic rescheduling policies and analyze their error bounds.…”

A Distributed Search and Simulation Method for Job Flow Scheduling

“…These solutions are often very close to the optimal solution. Therefore, the gain in computation speed is worth a slight loss in optimization [15]. In the examples discussed in later sections, we used heuristics that bound the maximum schedule time, prevent needless cycling when the factory has reentrant loops, impose restrictions on the portion of the schedule that has already been formed, and impose restrictions on the remaining steps in the plan.…”

The effect of work content imbalance and its interaction with scheduling method on sequential flow line performance

“…Raman, Talbot, and Rachamadugu (1989) examined the impact of three dispatching rules, modified job due-date, modified operation due-date and a hybrid of the two, comparing balanced vs. unbalanced stations. They determined that these dispatching rules impact the mean tardiness of the schedule.…”