Job sequencing and component set-up on a surface mount placement machine

In this paper, the problem of sequencing PCB assembly jobs on an automatic SMD placement machine is addressed. The objective is to minimize the makespan. Moreover, both the job arrival times and the precedence constraints for those jobs requiring component placement on the primary and secondary side of the same board must be taken into account. A considerable set-up time occurs when switching from one board type to another, which depends on the number of component feeders to be replaced in the magazine of the assembly machine. The exchange of component feeders is complicated by the fact that each feeder occupies a different number of magazine positions. Theoretically, the minimum makespan required for a given batch of jobs could be derived by solving the order sequencing and the component set-up problems simultaneously. However, optimal solutions are practically unattainable for problems of realistic size. Therefore, efficient heuristic solution procedures are developed which exploit component commonality between PCB types. The numerical results obtained indicate the practicality of the proposed heuristics in an industrial application.