Optimizing a U-Shaped Conveyor Assembly Line Balancing Problem Considering Walking Times between Assembly Tasks

This research deals with a U-shaped assembly line balancing problem in which items are fixed on the conveyor. Operators execute the assembly tasks without removing items from the conveyor as the assembly items are assumed to be unsuitable for manual handling. The operators have to walk beside the conveyor at the same speed as the conveyor while they execute assembly tasks. If the operators want to assemble other items, they may have to walk to other positions at their normal walking speed. Therefore, the cycle time of an operator should include assembly times and walking times between assembly tasks. In this research, a mathematical model of the proposed U-shaped conveyor assembly line balancing problem was developed. Given a number of operators, the mathematical model can optimize the sequence of tasks and allocation of tasks to workstations using the commercial software LINGO 17. Because LINGO 17 requires a long computing time, simulated annealing (SA), which can accept worse new solutions in the search procedure, is proposed. The experimental results show that the proposed SA can optimize the problem efficiently.