Bi‑level integrated optimization of production and preventive maintenance in serial manufacturing systems with quality‑dependent failures

This article proposes a comprehensive optimization strategy that integrates through a bi‑level framework production, maintenance, and quality in serial manufacturing systems prone to random failures. The system consists of multiple interconnected machines, each subject to degradation and varying quality rates. We develop a bi-level optimization framework: in the first level, production quantities are optimized to satisfy customer demand while minimizing production, inventory and shortage costs; in the second level, the results feed into the maintenance model through failure rates that depend on production rates. This integration ensures consistency between production and maintenance decisions. The maintenance strategy determines the optimal number of preventive maintenance (PM) actions for each machine to reduce degradation and improve quality, thereby minimizing total maintenance costs. Numerical experiments on a three-machine case study demonstrate that the proposed approach reduces total costs by up to 29%, by decreasing shortages, and improving average product quality compared with traditional independent planning. Sensitivity analyzes confirm the model’s adaptability under different service levels and maintenance cost scenarios. These results provide a practical framework for enhancing operational efficiency, cost reduction, and customer satisfaction in failure-prone manufacturing environments.