Routing-based reactive scheduling policies for machine failures in dynamic job shops

Abstract

A scheduling and control system can be viewed as a vital component of modern
\nmanufacturing systems that determines companies’ overall performance in their
\nrespective supply chains. This paper studies reactive scheduling policies developed
\nagainst unexpected machine failures. These reactive policies are based on rerouting
\nthe jobs to their alternative machines when their primary machine fails.
\nDepending on the subset of the jobs considered for rerouting, the long-term
\nperformance of four policies are tested under various conditions. Expecting
\nthat these rerouting policies would bring an extra load for a material-handling
\nsystem (MHS), a dynamic job shop environment was studied with and without a
\nMHS. It is shown that the proper selection of a good reactive policy is based not
\nonly on the system characteristics such as utilization, machine down times and
\nfrequency of machine failures, but also on the MHS capacity (in terms of speed
\nand number of MH devices). The extensive experiments show that when the MHS
\nis not a bottleneck and/or the down times are long enough to compensate the cost
\nof extra rerouting, rerouting all aOEected jobs to their alternative machines proves
\nto be the best policy. However, when the MHS cannot handle the extra load due
\nto rerouting or the down times are relatively short, then rerouting only the jobs
\nthat will arrive to the failed machine during repair performs the best.