New solution approaches for balancing assembly lines with setup times

Abstract

The objective of an assembly line balancing problem is to find an efficient allocation of tasks to the stations of the line according to time and technological (precedence) constraints. In this work we study the setup assembly line balancing and scheduling problem (SUALBSP) in which the time required to perform the tasks depends on their sequence within each station. In order to solve the problem, we propose different lower and upper bounds and check the efficiency of the proposed methods when compared to the state of the art. We show experimentally that the proposed methods lead to better primal and dual bounds, and that our new exact method optimally solves over 75% of all instances from the literature with a mean relative gap of less than 2% with a two minutes time limit. Moreover, for the subset of instances previously considered by exact approaches, our new exact approach obtains and proves the optimal solution for 150 of the 167 previously open instances, a significant improvement over previous exact methods.