Local Search for Solving a Hybrid Flowshop Sequencing Problem: A Case Study of a Crane Manufacturer

This study deals with a real hybrid flowshop sequencing problem: case of Manitowoc, a company producing a wide variety of cranes. The sequencing problem is classified as NP-hard, and the real problem contains a complex process with many stages and different conflicting objectives. To simplify the decision-making, each objective was evaluated and normalized in euros to establish an overall goal of cost minimization. Given the complexity of the problem, a Local Search algorithm has been provided and shows significant cost improvements. These improvements vary depending on the size of the sets, with an average improvement of 51% for 30 tasks and up to 68% for 120 tasks. However, the execution time of the algorithm increases as the size of the instances increases.