Capacity failure rate based opportunistic maintenance modeling for series-parallel multi-station manufacturing systems

In a series-parallel multi-station manufacturing system, the failure of the series station may cause the loss of the whole system capacity, while the failure of the parallel station only causes the loss of part of the system capacity. To quantitatively describe the impacts of these comprehensive failure modes on the system capacity, an evaluation index called Capacity Failure Rate (CFR) is developed based on the universal generating function. Then, a rule-based Opportunistic Maintenance (OM) policy is proposed with the CFR involved. The Preventive Maintenance (PM) opportunity occurs whenever one of the stations reaches its optimal PM interval or the CFR of the system reaches the threshold. A variable maintenance time window is developed to group the PM activities of the stations. The optimal PM scheme of the system is obtained by maximizing the maintenance efficiency of the system, defined as the availability of the system capacity driven by per unit maintenance cost, within the whole maintenance scheduling horizon. Finally, numerical examples are illustrated to show the application of the CFR and the advantage of the proposed OM policy.