Reduction in total completion time in a sequential manufacturing environment

Abstract

In any manufacturing environment, the materials are to be processed to the required geometry using different processes. The processes usually indicate the actions to be completed in a set of machines. Among the processes, some may have to follow a sequence means, after completing a particular process only we can move to the other one. In such cases, permutation flowshop layouts are preferred over other layouts. Out of several parameters, minimization of makespan has been studied much over the years by many researchers. The problems are widely regarded as NP-hard if the number of machines is more than three. As the computation time grows exponentially with the problem size, heuristics with acceptable level of accuracies have been proposed by many authors. The NEH algorithm proposed in 1983 is still considered as one of the best simple, constructive heuristics for the minimization of makespan. This paper proposes a simple tie-breaking rule to reduce the total completion time (makespan) further without increasing the time complexity. The concept of Slope Indices is used for this purpose. The computation results using the Taillard test bed indicate improvement up to 5.85% over the reference NEH algorithm.