Job rescheduling by exploring the solution space of process planning for machine breakdown/arrival problems

In parts manufacturing, rescheduling (revising the affected process plans and schedule) is required when machine breakdown occurs. This paper presents a new rescheduling method by exploring the solution space of process planning. First, the scheduling problem is modelled by integrating a process planning module and a scheduling module. The process planning module employs an optimization approach in which the entire plan solution space is first generated and a search algorithm is then used to find the optimal plan with minimum machining cost, while the scheduling module is based on commonly used heuristics. With an integrator module linking these two modules, a satisfactory plans/schedule solution can be achieved iteratively by modifying the process planning solution space with respect to a scheduling target, e.g. minimizing the number of tardy jobs. Second, a machine breakdown problem is described by two rescheduling events: when a machine breaks down, it is considered to be unavailable; once it is recovered, it is considered as a new machine arrival. These two events are modelled in the process planning solution space of the affected jobs. In this way, rescheduling can be conducted by the integrated system effectively. The proposed rescheduling method has been implemented for the manufacturing of prismatic parts in job shops. An application example and a comparative study are presented to demonstrate the effectiveness of the presented method.