Optimization of a Part Holder Design Considering Dynamic Loads during Return Stroke of Tool and Ram

Abstract

Increasing production efficiency in modern press shops achieved by boosting stroke rates of press lines poses new challenges for die designers with regard to die loads arising. Especially servo-mechanically driven presses used for producing sheet metal body parts provide great potential in terms of production efficiency due to their increased stroke velocities. However, the acceleration processes of moving masses inside dies are design-critical loads. In line dies, the part holder acceleration in the upper die causes impact-like loads acting on the die structure and ram. Here, in particular, the structural strength of the tool and the load during the return stroke of ram today limit the maximum stroke rate of the press. By considering the changing production requirements in die design, for example, by generating specific part holder geometries through topology optimization, ram velocities can presumably be increased, or process limits extended. In this respect, this paper presents an approach that leads to reduced dynamic tool loads by lowering the weight of the part holder in the early design phase. Here, the part holder stiffness of a series part holder of a roof tool is improved while reducing its weight by topology optimization of the moving mass. After optimizing the geometries mass and shape taking into account process-related parameters, such as dynamic loads during the acceleration, the new design is evaluated based on comparison measurements with a conventionally designed roof part holder. Similarities in part holder geometries lead to standardized optimizations for future tool design. The main finding of this contribution is that the approach used can improve tool durability and thus allows increased press stroke rates without significant additional design effort.