Scheduling maintenance tasks with time-dependent synchronization constraints by a CP modeling approach

Ensuring a high uptime for manufacturing machines is crucial for efficient and cost-effective production. In opposite, preventive maintenance tasks (PMs) are necessary to assure the reliability of manufacturing processes. This also prevents serious and unpredictable machine crashes, which affect uptime and process scheduling. However, PM tasks themselves lower the uptime and are to be smartly scheduled within their given domain considering some requirements as ensuring the availability of a sufficient number of qualified engineers for the concerning period. This work investigates a PM scheduling problem with time-dependent synchronization constraints for a lithography work center. For this, a constraint programming (CP) modeling approach including decomposition is used. Multiple objectives are considered. For example, the minimization of crew backup violations or scheduling PMs according to the work in process (WIP) for embedding upcoming PMs smoothly into the system work load. This minimizes negative effects on throughput and tardiness.