An assembly scheduler for TFT LCD manufacturing

This paper presents development of a scheduling system for Thin Film Transi stor Liquid Crystal Display (TFT LCD) assembly process. With given daily pr oduction plan that is rough-cut capacitated, the scheduler generates shift- based capacity feasible schedules at each assembly step. The scheduling pro blem is a parallel-machine scheduling problem with sequence dependent setup s and some manufacturing environments, which make the problem considerably difficult. The scheduling objective is to minimize the mean flow time and m aximize the production progressiveness. Two scheduling heuristics are propo sed for each production step of assembly process. The first scheduling heur istic is applicable for the first three steps of assembly process, i.e. coa ting, rubbing, and attaching step, and for the later steps another similar heuristic is employed. We also propose a simple method for computing produc tion requirements for each step where daily production demand is unknown. T he proposed scheduling procedures are implemented in a real TFT LCD manufac turing line and their performances are investigated. The experimental resul ts show that the proposed scheduler provides quite better schedules than th e current practice employed in the line in terms of both mean flow time and fulfillment of production demands. (C) 2001 Elsevier Science Ltd. All righ ts reserved.