Planning and scheduling of industrial supply chains with reverse flows: A real pharmaceutical case study

This paper presents a modeling approach for the sequential planning and scheduling of supply chain (SC) structures with reverse flows. At the planning level an aggregated description is proposed to represent the supply chain operational problem. A master representation is defined to support supply chain resources, operational occurrences (events), involved materials and associated markets. Based on this master representation a mathematical formulation is proposed for the optimal supply chain planning. The planning solution is then processed at the scheduling level, where an increased level of detail is considered, through the solution of a scheduling mathematical formulation. The link between the planning and the scheduling levels is performed sequentially by setting up common time domain bounds. At each operational level both supply chain structural and dynamic characteristics are accounted for where different topological, operational and marketing characteristics (market supplies, demands and price levels) are considered. Furthermore, the presence of reverse flows is also modeled allowing for the analysis of the closed supply chain. As final solution the models provide two levels of information: (1) the optimal aggregated plan for a given planning time domain (e.g. 6 months) and (2) its concretization at the scheduling level (e.g. 1 week) where detailed information on supply, production, inventory, transportation and recovery of products is optimized based on a pre-defined economical performance criterion. The models developed and the associated planning/scheduling methodologies are validated through the solution of a real industrial pharmaceutical case study.