Abstract: This paper takes a single-machine system as the research object. The situation where the workload varies from batch to batch is considered. An extended hybrid imperfect maintenance model taking operational condition (OC) into account is developed. Maximum likelihood method is adopted to estimate the parameters. This study proposes a preventive maintenance (PM) policy with a short-term production plan for the situation where production plan is updated after the completion of each batch; meanwhile, PM can only be implemented at each batch-shift point. A numerical example is provided to illustrate the necessity of integrating OC with PM optimization and to validate the effectiveness of the proposed PM strategy.

Key words: variable workload, imperfect preventive maintenance, batch production, cost rate