SCHEDULING OF PRINTED WIRING BOARD ASSEMBLY IN SURFACE MOUNT TECHNOLOGY LINES

The paper presents a new mathematical programming approach for scheduling of printed wiring board assembly in SMT (Surface Mount Technology) lines. Various configurations of SMT lines encountered in the electronics industry are described and compared. An 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 which 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 minimum time. New mixed integer programming formulations are presented for blocking scheduling of various configurations of SMT lines that are found in the electronics industry. The proposed models can be used for optimization of assembly schedules by using commercially available software for discrete programming. Numerical examples are provided to illustrate the proposed approach. The influence of process time variability and machine breakdowns on an SMT line's performance is discussed.