(A) study on scheduling problems in a PCB assembly process

Abstract

In this study we consider scheduling problems in a factory producing printed circuit boards (PCBs) which are used as components for facsimiles, personal computers, printers, etc. The PCB assembly process in this factory can be regarded as a flowshop which has two specific characteristics. One is that jobs have sequence dependent setup times. The other is that it is possible to process a job on a following machine before the job is entirely completed on a previous machine since a job consists of a lot of identical PCBs, that is, there is time-lag between machines. We madel this PCB assembly process as a flowshop problem with sequence dependent setup times and time-lag. In this paper we study this generalized flowshop scheduling problem with the objective of minimizing mean tardiness. Also we present several properties to calculate a lower bound on total tardiness of jobs for a given sub-sequence. Because it is difficult to solve the problem optimally in reasonable time, we propose two heuristics and compare them with existing heuristics on randomly generated test problems. Computational test results indicate that proposed heuristics are good for both performance and CPU time.