The Benefit of Integrating Production and Transport Scheduling

Abstract

The production of many goods comprises several production steps at different places along a supply chain. Therefore, transportation of intermediate products can be necessary between consecutive production steps. The efficient coordination of resources requires a detailed scheduling. In current industry processes, the scheduling of production and transport is usually performed separately. As a consequence, the optimization of each schedule can only be based on local criteria, which do not necessarily result in optimal solutions from the overall supply chain perspective. Consequently, the integrated scheduling of production and transport processes is regarded as a promising approach for the improvement of scheduling systems. Due to the combinatorial nature of both subproblems, the integrated problem is also very hard to solve. Therefore, the research focuses on the development of powerful methods that are able to compute solutions in reasonable time. However, to show the importance of an integrated view on production and transport scheduling, it is also necessary to quantify its benefit. This paper aims to close this research gap to accelerate the consideration of integrated scheduling within advanced planning systems. First, it is shown how the production and transport scheduling problems can be formalized in terms of mixed-integer programs (MIP). Then, it is highlighted how these two problems can be integrated and which impact the integration has on the constraints of the optimization problem. All MIP-formulations are implemented and used for a numerical study comprising test scenarios of different sizes. The benefit of an integration of the problems is determined by investigating the impact on several performance indicators such as lead-times, storage times or delays.