USING METAHEURISTICS FOR SOLVING A PRODUCTION SCHEDULING PROBLEM IN ACHEMICAL FIRM - A CASE-STUDY

The problem is raised by a workshop management team in a chemical indu stry producing materials of different types. The workshop contains sev eral equipments in parallel and in series which can be used for the pr oduction of each job. The equipments in series are connected by a pipi ng system forming a network by which the material runs out. Some conne ctions are shared by several pairs of equipments so that the use of su ch a connection for one pair of equipments makes this connection unava ilable at the same time for other pairs. Several particular constraint s must be satisfied and deadlines exist for some jobs. The objectives are to minimize the makespan and the tardiness. A method is proposed t o heuristically obtain a satisfying production schedule. The procedure involves two stages. In a first step, given a fixed order of the jobs , a conventional heuristic is proposed to successively assign the jobs to the available equipments. In a second step, the simulated annealin g or tabu metaheuristics are applied to optimize the order of the jobs . The method was implemented on a PC and applied to an instance of the problem. Some comparisons are made to analyse and compare the efficie ncy of the heuristics.