Closing the loop in the Assembly Line Balancing Problem: the operator’s point of view on the repetition of similar tasks

In an assembly line, a product passes through different stations, undergoing every task of the precedence graph that describes its assembly process, until it reaches the state of a finished product. Modeling the occupational (ergonomic) and mental workload of assigned tasks requires careful control of task sequencing at each station. From the operators’ point of view, the task sequence repeats with period equal to the cycle time. The operator that is assigned to a station performs only a subset of the total tasks, repeating it in a loop on every product that flows in the line. We present a new model that accurately considers these loops, integrating pauses between physically or mentally demanding tasks, or inserting alternative tasks as a way to rest. The result is a tool that places the human at the center of the production systems, in line with Industry 5.0 indications and mitigating the risks of workforce shortages.