Design and Implementation of an Effective Decision Support System: A Case Study in Steel Hot Rolling Mill Scheduling

The work described here was largely performed at a medium-sized European steel mill, with an unusually diverse product portfolio, and hence a difficult scheduling problem to solve. The decision support system developed as a result has been successfully used, with minor modifications, at many steel mills worldwide. The work was carried out while the author was employed at A. I. Systems, Belgium, a software house building software for planning and scheduling decision support. A steel hot rolling mill transforms steel slabs into steel coils. First, slabs must be moved from a storage area to the furnace area using manual or semi-automatic cranes. After heating, the slabs are subjected to very high pressures in a series of rolls to produce a steel coil of a few millimetres thickness. The rolls which are in contact with the hot steel band quickly become worn, so coils are milled in programmes of a few hours. Between programmes some or all rolls must be replaced. Several different types of programmes may be chosen, where the programme type chosen determines the types of coil which may be rolled in the programme and the preparation which must be carried out prior to executing the programme. The correct choice of programme type is an important planning decision. A rolling schedule is a sequence of 100 to 300 coils to be milled in a programme lasting several hours, which satisfies complex technical, commercial and logistical constraints. Producing such a rolling schedule is a difficult task, which is carried out by a small group of experienced schedulers. A schematic diagram of the production processes surrounding steel hot rolling is given in Figure 11.1.