Considering scheduling and preventive maintenance in the flowshop sequencing problem

The aim of this paper is to propose tools in order to implicitly consider different preventive maintenance policies on machines regarding flowshop problems. These policies are intended to maximize the availability or to keep a minimum level of reliability during the production horizon. It proposes a simple criterion to schedule preventive maintenance operations to the production sequence. This criterion demonstrates the significance of taking into consideration preventive maintenance together with sequencing and the consequences of not doing so. The optimization criterion considered consists in minimizing the makespan of the sequence or C-max. In total, six adaptations of existing heuristic and metaheuristic methods are evaluated for the consideration of preventive maintenance and they are applied to a set of 7200 instances. The results and experiments carried out indicate that modem Ant Colony and Genetic Algorithms provide very effective solutions for this problem. (C) 2006 Elsevier Ltd. All rights reserved.