Application of search methods to scheduling problem in plastics forming plant: a binary representation approach

In this paper, a scheduling problem in a plastics forming plant is studied. This problem basically belongs to the class of unrelated parallel machine problems, but includes several restrictions which originate from the necessity to use auxiliary equipment. Thus it can be regarded as a representative example of complex scheduling problems arising in industries. The paper presents a new scope for the study of practical scheduling problems by proposing a method to solve them without relying upon dispatching rules. First, we transform the scheduling problem to a mathematical programming problem, and represent feasible schedules by binary strings. This formulation enables us to use the search methods (such as simulated annealing methods, genetic algorithms, etc.). We actually coded several search-methods and carried out computational experiments for the problems of practical size. Results indicate that our methods can give satisfactory solutions to the considered scheduling problem