Genetic Algorithm for Sequencing in Mixed Model Non-Permutation Flowshops using Constrained Buffers

In the classical production line, only products with the same options were processed at once. Products of different models, providing distinct options, were either processed on a different line or major equipment modifications were necessary. For today’s production lines this is no longer desirable and more and more rise the necessity of manufacturing a variety of models on one line, motivated by offering a larger variety of products to the client. Furthermore, the stock for finished products is reduced considerably with respect to a production with batches, and so are the expenses derived from it. Mixed model production lines consider more than one model being processed on the same production line in an arbitrary sequence. Nevertheless, the majority of publications are limited to solutions which determine the job sequence before the jobs enter the line and maintain it without interchanging jobs until the end of the production line, known as permutation flowshop. Exact approaches for makespan minimization can be found in [10], [15], and [4], among others. In two recent reviews [6], [7] heuristic methods for sequencing problems are presented.