Inventory coordination for homogeneous and heterogeneous independent suppliers and a single manufacturer under stochastic demand and asynchronous deliveries

The COVID-19 pandemic and recent geopolitical disruptions have exposed the vulnerability of small and medium-sized enterprises (SMEs), highlighting the need for resilient and collaborative supply chain frameworks. This study presents an optimization model for a multi-SME, single-manufacturer system operating under stochastic demand and a (Q, R) inventory policy. Independent SMEs, located at varying distances from the manufacturer, deliver raw materials asynchronously but make an equal number of trips per production cycle to ensure sustained coordination. Each SME operates with its own production capacity and dispatch schedule governed by the manufacturer’s replenishment plan. Two coordination strategies are examined: an integrated model that minimizes the total system cost and a decentralized Stackelberg approach. Numerical results show that the integrated strategy yields greater cost savings when the consumption of raw materials per unit of production is high. The findings provide theoretical and managerial insights for enhancing resilience in SME-driven supply chains.