Product sequencing problem in Mixed-Model Assembly Line to minimize unfinished works

This study is concerned about how to optimize the input sequence of product models with sequence-dependent setup time in Mixed-Model Assembly Line (MMAL) using conveyor system. Usually MMAL consists of a number of stations linked by a conveyor belt and each station has a work zone limited by upstream and down stream boundaries. To avoid improper interference between operators in the adjacent stations and excess of machine moving range, operators are forced to complete their operations within their predetermined work zone. In this study, our goal is to determine the sequence of models for minimizing the total unfinished work within their work zone. A generalized formulation of the product sequencing problem in MMAL is presented. We developed an optimal procedure using Branch & Bound technique and a heuristic procedure using lower bound and local search. Experimental results show that the heuristic procedure provides reasonably good solutions with low computational costs.