Continuous caster scheduling: An optimization approach using column generation

Scheduling of certain major production operations remains a chronic concern for integrated steel producers. One operation in particular, the twin strand Continuous Slab Caster, is a major contributor to overall plant profitability when utilized effectively. In this thesis, we describe the optimization based heuristic that has been implemented to support Continuous Caster scheduling needs at Dofasco Inc. (Hamilton, Ontario, Canada). The basic scheduling problem addressed is a variation of the multiple Travelling Salesman Problem with competing objectives and complex, cross tour synchronization constraints. An integer programming formulation for this scheduling problem is presented and a decomposition and column generation based heuristic solution strategy is described. The quality of the heuristic model is evaluated using statistical methods for optimal solution value estimation. In addition, economic benefits of using this approach, estimated at {dollar}1.7 million per year, are developed from direct comparison with real production schedules, using actual production system measures.