Finishing Line Scheduling in the steel industry

A new solution for large-scale scheduling in the steelmaking industry, called Finishing Line Scheduling (FLS), is described. FLS in a major steel mill is a task to create production campaigns (specific production runs) for steel coils on four continuous processes for a one-month horizon. Two process flows are involved in FLS, and the balancing of the two process flows requires resolving conflicts of due dates. There are also various constraints along the timeline for each process with respect to sequences of campaigns and coils. The two types of constraints—along process flows and timelines—make the FLS problem very complex. We have developed a high-performance solution for this problem as follows: Input coils are clustered by two clustering algorithms to reduce the complexity and size of the problem. Campaigns are created for each process from downstream to upstream processes, while propagating upward the process timings of the clusters. Timing inconsistencies along the process flows are then repaired by scheduling downward. Finally, coils are sequenced within each campaign. The FLS system enabled a steel mill to expand its scheduling horizon from a few days to one month, and to improve decision frequency from monthly to daily.