Mixed integer programming for scheduling surface mount technology lines

This paper presents new mixed integer programming formulations for blocking scheduling of SMT (Surface Mount Technology) lines for printed wiring board assembly. The SMT line consists of several processing stages in series, separated by finite intermediate buffers, where each stage has one or more identical parallel machines. A board that has completed processing on a machine may remain there and block the machine until a downstream machine becomes available for processing. The objective is to determine an assembly schedule for a mix of board types so as to complete the boards in a minimum time. Scheduling with continuous or with limited machine availability is considered. Numerical examples and some computational results are presented to illustrate applications of the models proposed.