Semi-dynamic maintenance scheduling for multi-station series systems in multi-specification and small-batch production

This paper proposes a new semi-dynamic Opportunistic Maintenance (OM) policy for multi-station series systems, with considering the changing production environment brought by the multi-specification and small-batch production mode. It combines the advantages of the time-window-based OM policy, which can decrease the complexity of the solution space for PM grouping, and the dynamic OM policy, which is capable of adapting to the changing production environment. Whenever one of the stations reaches its original Preventive Maintenance (PM) moment, an OM decision cycle of the system begins. During this decision cycle, all the stations, whose original PM moments are within the presented dynamic Maintenance Time Window (MTW), form a PM group. This dynamic MTW is different for each station, and it is obtained based on the predetermined static MTW and the dynamic impacts from the current production task. The static MTW is constant, and it is derived according to the expected production plan without considering the changing production environment. To balance the maintenance cost for the obtained PM group, the PM is not performed right at the time when one of the stations reaches its original PM moment, and it is postponed. The optimal duration of the postponement is dynamically obtained by minimizing the total maintenance cost within this duration. Finally, numerical examples and comparisons are illustrated to show the effectiveness of the proposed semi-dynamic OM policy.