Disjunctive and time-indexed formulations for non-preemptive job shop scheduling with resource availability constraints

In many real industrial situations machines may be non-available for processing jobs for instance when a machine breaks down or when a preventive maintenance activity is scheduled. This paper deals with the job shop scheduling problem when machines are not continuously available and this for better modeling of the industry reality. We assume that no preemption is allowed and we introduce flexibility on machine unavailability periods by assuming that these latter are planned in time windows. This flexibility is relevant when scheduling preventive machine maintenance. Two mathematical models are presented and compared. The first one is based on the disjunctive graph and the second one is time-indexed. Numerical experiments on generated benchmarks were performed with ILOG CPLEX 10.