New shifting method for job shop scheduling subject to invariant constraints of resources availability

In most machines scheduling models we assume that the machines are available all the time. However, in many realistic situations, machines need to be maintained and hence may become unavailable during a certain period. Indeed preventive maintenance (PM) is a vital activity in production workshops in order to eliminate risks associated with machine breakdowns. This paper deals with a heuristic algorithm based on new shifting method for solving the makespan of a nonresumable job shop scheduling problem while the resources are unavailable in some time periods. The starting times and durations of these availabilities are known in advance and fixed. The proposed method has been successfully tested on some experimental benchmarks and it is concluded that the idea can allows a satisfactory resolution of relatively important problem in a reasonable time and can be tested even to n-dimensional problems as well.