An exact algorithm for the mixed-model level scheduling problem

The Monden Problem, also known as the Output Rate Variation Problem (ORV), is one of the original formulations for mixed-model assembly line level scheduling problems in a just-in-time (JIT) system. In this paper, we develop a new branch-and-bound procedure as an efficient solution of this problem that uses several new and previously proposed lower and upper bounds. The algorithm also includes several dominance rules that leverage the symmetry in the problem as well as a new labelling procedure that avoids repeated exploration of previously examined partial solutions. The branching strategy exploits the capabilities of current multi-processor computers by exploring the search tree in a parallel fashion. The proposed algorithm has been tested on several sets of instances from the literature and is able to optimally solve problems that are double the size of those addressed by other procedures previously reported in the literature for the ORV problem.