A mixed integer linear programming approach for multi-degree cyclic multi-hoist scheduling problems without overlapping

This paper considers multi-degree cyclic multi-hoist scheduling problems without overlapping. Identical parts are produced in tanks for stages with processing time window constraints. The objective of this research is to obtain a schedule that can maximize the throughput of the line at steady state, equivalently minimize the cycle time. There are three kinds of constraints in cyclic hoist scheduling problems, i.e. hoist available constraints, tank capacity constraints and time window constraints. Moreover, schedules must void hoist conflicts in multi-hoist scenarios, since multiple hoists use the same overhead track and they cannot cross over each other. In this paper, the hoist assignment strategy without overlapping is used to void hoist conflicts. In order to obtain the optimal schedule, a mixed integer linear programming model is formulated. Then, a numerical example is used to illustrate the model proposed.