- Sequencing and Scheduling in Coil Coating with Shuttles Wiebke Höhn(hoehnmath.tu-berlin.de) Felix G. König(fkoenigmath.tu-berlin.de) Marco E. Lübbecke(luebbeckemathematik.tu-darmstadt.de) Rolf H. Möhring(rolf.moehringtu-berlin.de) 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. Di erent coil geometries and changes of coatings may necessitate time-consuming setup work. In most coating stages one can choose between two parallel color tanks in order to reduce setup times. As a complicating consequence, setup times for a coil may depend on the whole sequence of predecessors. 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 scheduling. It is instrumental for building a fast heuristic which 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. Keywords: sequencing, scheduling, integrated steel production, coil coating, 2-union-graphs, independent set, branch-and-price Category 1: Applications -- OR and Management Sciences (Production and Logistics ) Category 2: Integer Programming ((Mixed) Integer Linear Programming ) Category 3: Combinatorial Optimization (Graphs and Matroids ) Citation: TU Berlin, Institut für Mathematik, Preprint 2009/1 Download: [PDF]Entry Submitted: 03/18/2010Entry Accepted: 03/19/2010Entry Last Modified: 03/18/2010Modify/Update this entry Visitors Authors More about us Links Subscribe, Unsubscribe Digest Archive Search, Browse the Repository Submit Update Policies Coordinator's Board Classification Scheme Credits Give us feedback Optimization Journals, Sites, Societies Optimization Online is supported by the Mathematical Programming Society.