Scheduling Problems with Preventive Maintenance on Two Parallel Production Lines

Most of papers on integrating scheduling problems with preventive maintenance have focus on a signal production line or preventive maintenance that can restore a production line to a ´as-good-as-new´ status, which is depart from the real production, limiting its use in practice. This paper deals with the problem of jointly scheduling and imperfect preventive maintenance which can not restore a production line to a ´as-good-as-new´ status on two parallel production lines. In order to compare, two integrated models of scheduling two different kinds of jobs with multiple demands in different periods and preventive maintenance are considered. In the first model, it is assumed that the preventive maintenance activities are performed periodically and can restore the production line to an ´as-good-as-new´ status, while in the second integrated model, it is assumed that preventive maintenance activities are imperfect, performed dynamic but not periodically, a hybrid evolution factor is proposed based on the concept of age reduction factor and hazard rate increase factor to describe the imperfect status after preventive maintenance. The objective is to minimize the total completion cost. Finally, an illustrative example is presented, this paper optimizes with adaptive genetic algorithm, and the results are discussed in details.