Optimizing Makespan in Single-Model Assembly Lines with Human-Robot Collaboration

Within the framework of the industry 4.0, robotics plays a crucial role, leading to a widespread diffusion of Collaborative Robots (Cobots). Cobots can work alongside human operators, focusing on tasks with a high biomechanical risk. However, the design of workstations in which humans and cobots can perform tasks in collaboration poses new challenges. In such a scenario, models for manual and automated assembly line design need to include both humans and cobots able to perform the same task in the same station. In addition, contributions assessing the influence of cobots introduction on the assembly line makespan are missing and expected. To fill this gap, this study proposes a mathematical optimization model to design a single-model assembly line. The evaluation of the minimum achievable makespan is carried out by considering different line configuration scenarios, starting from a fully manual assembly line up to including one cobot per station. The main results show that the use of cobots leads to significant time benefits, at the expense of a weak load balancing among the assembly workstations, paving the way for future studies aiming to explore such clear diverging trends.