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Multi-skill Project Scheduling Problem and Total Productive Maintenance

In this paper, we propose a multi-skill project scheduling problem model for maintenance activities organization. Preventive maintenance activities are usually planned in advance: production is stopped and all maintenance activities should be processed as fast as possible in order to restart production. Moreover, these human resource handled activities require specific skills and are subject to precedence constraints. The main difference with Multi-Skill Project Scheduling Problem is that some activities may be submitted to disjunctive constraints due to material constraints of the production channel that we consider. We describe how we use these constraints to improve usual MSPSP resolution methods. This study, based on a real industrial case found in MDGBB 1 SKF factories, deals with the prac- tical organization of Total Productive Maintenance activities. Total Productive Maintenance (also known as TPM (7)) is a maintenance concept that includes scheduled maintenance downtime of pro- duction channels. The idea is to achieve all preventive tasks during one single period. A preventive task is something that has to be done periodically on the machines of the channel. For example, if a filter has to be changed on a machine every 3 months, it may be interesting to change it every 2 months during the scheduled downtime so that there is no specific unscheduled downtime due to this filter. Considering there is a large number of such tasks, the productivity of the channel can be greatly improved if one single downtime period can be scheduled during which all maintenance activities can be done. In this paper, we study how the tasks planned for a given maintenance downtime can be scheduled in order to restart production as soon as possible. Here, we consider that the number of tasks, their duration and the resources they require are given. We describe how this problem can be modeled as a Multi-Skill Project Scheduling Problem and how exact method can be adapted for solving TPM problem. Finally, we show how the disjunctive constraints that are due to material constraints of the production channel are modeled and how they can be used to improve the efficiency of the exact method.