Models for scheduling charges in continuous casting: application to a Brazilian steel plant

摘要

In this paper we propose models for the scheduling of charges considering the alternatives of intermix slabs or setups between consecutive jobs. The study is motivated by the practical need of a steel plant in Brazil to reduce costs in a low volumes/wide range of products environment. An intermix slab is formed when two jobs with different grades and/or widths are processed without stopping the machine. This may generate a poor material, which has low commercial value or is used as scrap. The machine may also be stopped between two consecutive jobs to allow a setup. The setup operation has an associated cost, but no intermix slab is created. Thus, the scheduling problem consists of defining the sequence of charges and whether an intermix slab or a setup operation must take place to minimize the total cost. We report computational experiments on real data. This study, by comparing results with actual schedules planned, shows that significant cost savings upon practice can be achieved by running the proposed models on standard optimization packages.