Sequencing of mixed models on U-shaped assembly lines by considering e ective help policies inmake-to-order environment

Mixed-Model Assembly Line (MMAL) is a type of production line where a variety of products models similar to products characteristics are assembled in the same line. Many manufacturers tend to use mixed-model assembly line in their production lines, since this policy makes it possible to assemble various products in 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 storage of kits as e ective help policies for reducing total line stoppages and tardiness in delivery time of products 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 e ectiveness of the proposed algorithm. To the best of our knowledge, this is the rst study that considers getting help from downstream worker or using storehouse of kits, which has ready-toassemble parts in the conditions that workers cannot complete the remained task in the work horizon.