A hybrid algorithm for the cyclic hoist scheduling problem with two transportation resources

•We propose a hybrid algorithm to solve the two-hoist cyclic scheduling problem.•This algorithm searches the best hoists’ assignment.•Also, the best sequence for each hoist.•All sequences generated avoid collision between hoists.•Optimal solutions are found in many benchmarks.

In automated electroplating lines, computer-controlled hoists are used to transfer parts from a processing resource to another one. Products are mounted into carriers and immersed sequentially in a series of tanks following a given sequence.The aim of this study is to propose an algorithm to solve the two-hoist cyclic scheduling problem. This problem consists in finding a repetitive sequence of hoists’ moves, while avoiding collision between the hoists which share a common track. The objective is to minimize the period of this repetitive cycle.First, a set of sequences is generated. After that, for each sequence, an algorithm is applied to assign moves to hoists. Finally, a mixed integer linear programming model is formulated by taking into account the two sequences of hoists moves. Then it is solved to give the starting times of moves.