Scheduling Multiple Groups of Jobs for a Multi-Line Steel Hot Rolling Mill

This work addresses the optimal scheduling for a multi-line steel hot rolling mill with two parallel production lines. Groups of products are manufactured at one of these lines in an alternate sequence. An optimal schedule minimizes the sum of the required setup times between all products and optimally fills up retooling times necessary at one line by processing a group of products at the other line. This requires both sequence optimization and, for some groups, the optimal selection of jobs. The optimization problem is a combination of traveling salesman and orienteering problems and considers all groups simultaneously. To iteratively solve the combined problem, an algorithm consisting of a heuristic simulated annealing and a local search procedure is employed. The effectiveness of the algorithm is analyzed in a case study. Copyright (C) 2022 The Authors.