Enhancing industrial efficiency in an integrated lot sizing and scheduling problem

This paper addresses an integrated lot-sizing and scheduling problem in a complex industrial production system, characterized by non-identical parallel production lines, performing the same operations at different rates over a multi-period horizon for several products. The contribution of this work focuses on downtime (idle-time), which significantly impacts planning and scheduling by generating high launching costs for production lines. This adds an additional constraint to managers’ decision-making processes. The study highlights the importance of optimally managing transitions between periods, based on operational approaches inspired by real industrial environments. These transitions include setup carryover; where the manufacturing of a product is carried over to the next period without needed setup, setup crossover; where the setup is split between two periods, and setups after idle times, to either restart the same product or initiate a change. These strategies aim to reduce interruptions and enhance production system efficiency. The objective of this work is to provide realistic and efficient solutions that address the challenges of real industrial environments while minimizing costs associated with stoppages, changeovers, production, and storage. A mathematical model has been proposed and solved using the CPLEX, and a metaheuristic inspired by Simulated Annealing has been adapted to handle large instances.