ABSTRACTWe study a class of capacitated assembly systems operated by base‐stock policies and address the problem of finding base‐stock levels that minimize holding costs under beta‐service level (fill rate) constraints over an infinite horizon. To solve this nonconvex constrained optimization problem, we develop a new simulation‐based optimization approach using the constrained level method (CLM) and infinitesimal perturbation analysis. The key idea of the algorithm is a novel family of convex approximations of the beta‐service level, which is iteratively refined during the course of the algorithm. The algorithm can easily handle integrality requirements for the base‐stock levels by combining the CLM with a cutting plane approach without significantly increasing the solution time on typical instances. We apply our approach to a comprehensive multi‐echelon assembly benchmark system from the literature and study the algorithm's behavior for different target service levels, capacity configurations, and simulation horizons. A comparison with a state‐of‐the‐art interior point algorithm shows that for realistic capacity constraints, our algorithm is on average 8%–20% better. Compared with the guaranteed service model, our approach reduces costs by 10%–15% while keeping the same service level.
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