Assembly line balancing for two cycle times: Anticipating demand fluctuations

Unpredictable crises such as pandemics, as well as predictable oscillations such as seasonality, can produce significant demand fluctuations. Although it is possible to adapt the manufacturing system to these perturbations, there are significant opportunities in anticipating them in the design stage. This paper proposes the Economically Robust Assembly Line Balancing Problem (ERALBP), which addresses the issue by designing assembly lines to allow flexible alternation between two or more cycle times. A Mixed-Integer Linear Programming (MILP) model is introduced to describe the problem. Moreover, a heuristic procedure is implemented in order to quickly produce high-quality solutions. While the model failed to find solutions for most medium and large instances, the heuristic quickly produced high-quality solutions, reaching low solution gaps even for large instances. Finally, a case study with industrial data further highlights the advantages of the proposed strategy: by anticipating demand fluctuations, the proposed heuristic’s solution facilitates alternation between two demand scenarios, both with the optimal number of stations. This approach is less costly than the re-balancing alternative, which requires re-assigning and re-positioning tasks. By enabling companies to perform this fast switching between output rates, we allow them to benefit from economic opportunities tied to increased seasonal effects or unexpected demand spikes.