Functionalization of additively manufactured press hardening dies by roller burnishing

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A novel tooling technology for press hardening is to be developed in which the tools are manufactured additively by means of laser powder deposition. The thermal requirements are locally adjusted and finished by a forming operation of the tool surface. The idea is to use the heat resulting from the building process in order to systematically level the die surface for the purpose of influencing the material flow during warm sheet metal forming as well as to adjust the heat transfer between the die and the workpiece. The implementation is to be carried out in the combination machine available at the IUL for additive manufacturing by means of laser powder deposition and milling. In the research project the machine is to be equipped with tools for roller burnishing (e.g. hydrostatically supported rolling tools). The execution of the laser powder deposition and the finishing by forming operations in one machine and one clamping allows smoothing regions/surfaces which are otherwise not or only hard to reach during the additive manufacturing of the dies. An analytical model is to be used to describe the surface topography after rolling of additively manufactured components. The model is used for the process result of significant factors, e.g. the rolling path distance, different ball diameters, and different original surfaces resulting from the building process.In contrast to processes working in the powder bed, in laser powder deposition there is no possibility of supporting overhangs by unmelted powder. In this project manufacturing strategies for the manufacturing of cooling channels shall be elaborated. By varying the overhangs of the weld beads and the angle of incidence of the welding unit, the geometrical complexity of the cooling channels will be enhanced increasingly right up to three-dimensionally running channels. With a demonstrator tool the effectiveness of micro-structured tool surfaces and the integration of three-dimensionally running cooling channels on the local heat balance and the local component properties during press hardening shall be investigated and demonstrated, respectively.In the long term, it is the aim to use the heat remaining in the workpiece from the laser melting process for the rolling process in order to increase e.g. the forming capacity and to reduce the flow stress.