Finding Cost-Effective Re-Layouting Solutions in Modern Brownfield Facility Layout Planning

In facility layout planning (FLP) for shop floor optimization, the goal is to find an optimal arrangement for a number of machines in a given space. Despite the significance of machine selection for the FLP, the integration of arrangement and selection problems is neglected in the literature. This paper presents a methodology for solving an extended facility layout problem where not only the arrangement of machines is con-sidered, but also how many machines should be allocated and of which type. We assume the context of a modern brownfield planning project, where an initial layout already exists, which is to be re-purposed for manufacture of products with high variability. We apply our methodology in a case study where three objectives are to be minimized simultaneously. The results demonstrate that a standard NSGA-II introduces bias for this problem type that leads to an inadequate search space exploration. We test adapted mutation and crossover operators to overcome this challenge. While modified crossover had little impact, the new mutation operator was key to outperform the standard approach in all computed metrics. With this operator, we obtain diverse Pareto sets which strictly dominate up to 80% of the solutions found by the standard approach on average.