Scheduling a hot rolling mill

This paper presents a heuristic algorithm to schedule a hot rolling mill in the aluminium industry. One problematic issue is the tight coupling between the homogenizing furnaces and the mill, which needs to be integrated into the heuristic design. The latter also takes into account standard technological constraints like alloy hardness transitions, roll wear, homogenization code compatibilities and width transitions. The objective is to minimize the idle time on the mill and penalties for soft constraint violations related to production quality. The heuristic is divided into two phases. First batches of ingots are constructed for the furnaces. These batches, called blocks, are then sequenced on the mill. Numerical results are reported on test instances derived from real-world data.