Solving a Rich Intra-facility Steel Slab Routing Problem

We optimize the routing of steel slabs between locations in a steel production facility during a one hour-long operational period. Steel slabs are heterogeneous items that appear at locations at different release times. Certain slabs need to be delivered to another location before their specified due time. They are transported by fleets that include standard vehicles as well as truck-and-trailer type vehicles. The vehicles visit several locations multiple times. The input is such that not all slabs can be delivered in time, therefore two objective functions are provided that are organized in a lexicographic fashion: First, we maximize the throughput. Second, we aim to minimize travel times. An exact solution can only be obtained for small problem settings. In order to solve larger instances, we developed a heuristic. The results show that the solutions obtained by the heuristic reveal significant improvements to the real world solutions provided by our industrial partner.