Sequencing of mixed models on U-shaped assembly lines by considering effective help policies in Make-to-Order environment

Mixed-model assembly line (MMAL) is a type of production line where a variety of products’ models similar to products’ characteristics is assembled in the same line. Many manufacturers tend to use mixed-model assembly line in their production lines, since this policy make possible to assemble various products with the Make to order (MTO) environment. In this research, the sequence of U-type mixed model assembly line is achieved through considering downstream help and kits’ storage as effective help policies for reducing total line stoppages and tardiness of products’ delivering time to customers. Since this problem, is NP-hard, hybrid GA-Beam search algorithm is developed to solve the problem. Numerical experiments are used to evaluate the performance and effectiveness of the proposed algorithm. To the best of our knowledge, this is the first study that considers getting help from downstream worker or using kits’ storage, which has ready to assemble parts in the conditions that workers cannot complete the remained task in the work horizon.