Production logistics and ergonomic evaluation of U-shaped assembly systems

In the context of production logistics, U-shaped assembly systems often present several advantages compared to straight-line systems. Therefore, such systems are usually evaluated in the planning phase using production logistics and cost-related criteria. However, some published papers illustrate that these advantages may face ergonomic drawbacks. For decision making, the evaluation must be expanded in order to consider these systems from both perspectives. In this way, unfavorable forms of work organization in U-shaped assembly systems can be detected already during the planning phase. In addition, the static methods such as spreadsheet calculations generally used for planning prove to be poorly applicable due to the overly optimistic results they generate, especially in case of model-mix systems. These aspects are especially addressed here and the difference between static and dynamic approaches are illustrated. Consequently, planning solutions must be validated dynamically by means of simulation. Only then can be judged whether the planned production logistics criteria are achievable at all. In addition, the simulation allows for more realistic statements also concerning ergonomic criteria. This approach will be demonstrated here by a near-to-reality planning case. For a comprehensive multi-criteria decision making in the face of production logistics and ergonomics the use of lexicographic ordering is shown.