Maintenance policies considering production rate and quality

The maintenance of modern manufacturing systems aims at keeping satisfactory production functions, and enhancing the overall profitability of manufacturers. This paper investigates the maintenance planning problem for manufacturing systems by considering the dynamic variation of production rate and product quality. We formulate the degrading production rate and product quality as a generalized bivariate Wiener process, in which the interdependence of them is addressed with appealing tractability. Next, we develop the optimal condition-based maintenance policy that maximizes the manufacturer’s profit by observing the online production rate and product quality as input. Markov decision processes are utilized to formulate the dynamics of manufacturer’s profit and glean structural properties of the optimal policy. Two practical scenarios that address different types of production cost are considered in the model: one with the time-dependent cost and the other with the yield-dependent cost. Then, we extend the model by introducing the mixed defects model and production termination mechanism to enable its application to systems that may produce latent defective products. Numerical examples verify the advantages of the proposed policies over several classic maintenance policies. In addition, the optimal policies can be remarkably different under various production cost schemes. Furthermore, the existence of mixed defects and/or production termination mechanism also remarkably influences the optimal maintenance decisions.