Modelling of multi-stage production lines with maintenance operations

A multi-stage production line consists of a series of machines, which are subject to failures owing to wearouts and other random causes. While random failures are unavoidable and need corrective maintenance (CM), wearout failures can be avoided by preventive maintenance (PM), including tool change operations. Both types of maintenances can cause significant production losses, particularly if the production line is automated and the stations are rigidly linked. Therefore, intermediate buffers are introduced to decouple the rigidly linked machinery and to localize the losses caused by equipment stoppages. Reliability and productivity calculations of multi-stage lines with storage units can be quite complex. Furthermore, closed form solutions are generally not possible when preventive and corrective maintenances are incorporated into the model. In this paper, we present a discrete mathematical model integrated into an iterative simulation procedure to determine the production output rate of a multi-stage line with corrective and preventive maintenance operations.