Integrated Sequencing and Scheduling in Coil Coating

Wiebke Höhn (), Felix G. König (), Rolf H. Möhring () and Marco E. Lübbecke ()
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Wiebke Höhn: Institut für Mathematik, Technische Universität Berlin, 10623 Berlin, Germany
Felix G. König: Institut für Mathematik, Technische Universität Berlin, 10623 Berlin, Germany
Rolf H. Möhring: Institut für Mathematik, Technische Universität Berlin, 10623 Berlin, Germany
Marco E. Lübbecke: Department of Operations Research, RWTH Aachen University, 52056 Aachen, Germany

Management Science, 2011, vol. 57, issue 4, 647-666

Abstract: We consider a complex planning problem in integrated steel production. A sequence of coils of sheet metal needs to be color coated in consecutive stages. Different coil geometries and changes of colors necessitate time-consuming setup work. In most coating stages one can choose between two parallel color tanks. This can either reduce the number of setups needed or enable setups concurrent with production. A production plan comprises the sequencing of coils and the scheduling of color tanks and setup work. The aim is to minimize the makespan for a given set of coils. We present an optimization model for this integrated sequencing and scheduling problem. A core component is a graph theoretical model for concurrent setup scheduling. It is instrumental for building a fast heuristic that is embedded into a genetic algorithm to solve the sequencing problem. The quality of our solutions is evaluated via an integer program based on a combinatorial relaxation, showing that our solutions are within 10% of the optimum. Our algorithm is implemented at Salzgitter Flachstahl GmbH, a major German steel producer. This has led to an average reduction in makespan by over 13% and has greatly exceeded expectations. This paper was accepted by Dimitris Bertsimas, optimization.

Keywords: sequencing; scheduling; integrated steel production; coil coating; 2-union graphs; independent set; branch-and-price (search for similar items in EconPapers)
Date: 2011
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Persistent link: https://EconPapers.repec.org/RePEc:inm:ormnsc:v:57:y:2011:i:4:p:647-666

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