Process-Machine Interaction in Sheet-Bulk Metal Forming

The present contribution deals with the process-machine interaction and its impacts on the workpiece quality by forming parts with sheet-bulk metal forming. It focuses on the manufacturing of complex asymmetrical parts with functional elements. The functional applications of these elements such as fixation, motion and load transmission require compliance with high geometrical accuracy as well as high precision regarding the final mechanical properties of the part. The high process forces in horizontal as well as in vertical direction to form these elements cause displacements of the tool and press components, which lead to workpiece defects retroactively. Although the interaction between the forming machine and process affects the quality of the finished part significantly, the machine influence is usually ignored in the analysis of the forming process with the Finite-Element-Method. The challenges mentioned are demonstrated by forming of a complex asymmetrical part with gear teeths and carrier elements. As typical for sheet-bulk metal forming, the dimensions of the finished gear teeths (4mm) are much higher as the initial thickness of the sheet metal (3mm). The displacements of the press components during the process have been determined by means of optical measuring systems. The results are presented in all three spatial directions. The conclusions about the acting process forces in horizontal and vertical direction have been made by analyzing the press displacements by means of a new developed three-axial load device. Finally, this paper introduces a suitable approach to represent the machine characteristics in order to improve the computational accuracy of sheet-bulk metal forming simulations and gives an overview about the possibilities to improve the process stability by improving the mechanical components of forming machines.