Carryover sequence-dependent group scheduling with the integration of internal and external setup times

This paper addresses a group scheduling problem in a two-machine flow shop with a bicriteria objective and carryover sequence-dependent setup times. This special type of group scheduling problem typically arises in the assembly of printed circuit boards (PCBs). The objective is to sequence all board types in a board group as well as board groups themselves in a way that the objective function is minimized. We introduce the carryover sequence-dependent setup on machines, and call it internal setup. As an opportunity for manufacturers to decrease the costs, the focus is to completely eliminate the role of the kitting staff. Thus, we introduce the external setup (kitting) time for the next board group and require it to be performed by the machine operator during the time he is idle. Consequently, the internal and external setup times are integrated in this research, and to the best of our knowledge it is for the first time a research on PCB group scheduling is performed by integrating both setups. In order to solve this problem, first a mathematical model is developed. Then a heuristic together with two other meta-heuristic algorithms (one based on tabu search and the other based on genetic algorithm) are proposed and their efficiency and effectiveness on several problems are tested. Also a statistical experimental design is performed in order to evaluate the impact of different factors on the performance of the algorithms.