Article ID: | iaor20091233 |
Country: | United Kingdom |
Volume: | 35 |
Issue: | 3 |
Start Page Number: | 916 |
End Page Number: | 932 |
Publication Date: | Mar 2008 |
Journal: | Computers and Operations Research |
Authors: | Arenales Marcos N., Clark Alistair R., Araujo Silvio A. de |
Keywords: | scheduling, programming: integer, mineral industries |
A lot sizing and scheduling problem prevalent in small market-driven foundries is studied. There are two related decision levels: (1) the furnace scheduling of metal alloy production, and (2) moulding machine planning which specifies the type and size of production lots. A mixed integer programming (MIP) formulation of the problem is proposed, but is impractical to solve in reasonable computing time for non-small instances. As a result, a faster relax-and-fix (RF) approach is developed that can also be used on a rolling horizon basis where only immediate-term schedules are implemented. As well as an MIP method to solve the basic RF approach, three variants of a local search method are also developed and tested using instances based on the literature. Finally, foundry-based tests with a real-order book resulted in a very substantial reduction of delivery delays and finished inventory, better use of capacity, and much faster schedule definition compared to the foundry's own practice.