Alternative process plans in wire harnesses production

This paper deals with a scheduling problem with alternative process plans that was motivated by a production of wire harnesses where certain parts can be processed manually or automatically by different types of machines. Only a subset of all the given activities will form the solution, so the decision whether the activity will appear in the schedule has to be made during the scheduling process. The problem considered is an extension of the resource constrained project scheduling problem with unary resources, positive and negative time-lags and sequence dependent setup times. We have proposed the problem representation by a special graph allowing to define alternative process plans. For this representation of the problem, an integer linear programming model is formulated. Finally a heuristic algorithm based on priority schedule construction with an unscheduling step is proposed and used to solve the case study of the wire harnesses production.