Functionalization of additively manufactured press hardening dies by roller burnishing

开发了一种新的冲压硬化模具技术，其中刀具是通过激光粉末沉积的方法进行附加制造的。通过工具表面的成形操作来局部调整和完成热要求。其想法是利用成形过程中产生的热量来系统地平整模具表面，以便在板材温热成形过程中影响材料流动，并调整模具和工件之间的热传递。实施将在IUL提供的组合机中进行，以通过激光粉末沉积和球磨进行添加制造。在研究项目中，机器将配备用于滚轮抛光的工具(例如，静液压支承的滚压工具)。在一台机器和一次夹紧中通过成形操作来执行激光粉末沉积和精加工，允许在模具的附加制造期间不能或仅难以达到的平滑区域/表面。分析模型用于描述添加制造的零件轧制后的表面形貌。该模型考虑了轧制路径距离、不同球体直径、不同原始表面等重要因素对成形过程的影响，与粉末床工艺相比，在激光粉末沉积过程中，不存在未熔化粉末支撑悬臂的可能性。在本项目中，应详细说明冷却通道制造的制造策略。通过改变焊道的悬臂和焊接单元的入射角度，冷却通道的几何复杂性将增加到三维运行通道。使用演示工具，分别研究和演示微结构刀具表面和三维运行冷却通道的集成对冲压硬化过程中局部热平衡和局部部件性能的影响。从长远来看，其目的是利用激光熔化过程中工件中的余热进行轧制处理，以增加成形能力和降低流动应力。

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.