Development and analysis of all-ceramic micro end mills with diameters ≤ 50 µm

与其他微细加工方法相比，微细磨削具有显著的优势。这些优势是可加工材料的范围广，可实现的几何复杂性以及高表面质量。由于其良好的材料性能和可加工性，目前直径为≤50µm的立铣刀几乎全部由硬质合金制造，但硬质合金刀具直径较小，导致刀具稳定性降低，比切削力增加不成比例。此外，由于刃口半径的影响越来越大，出现了所谓的犁削效应，即工件材料被压在刃口下方，在不被切割的情况下被推过。除了表面质量的恶化和毛刺的形成，犁削效应还会导致加工力的增加和丝状微刀具的强烈磨损。由于所用硬质合金的显微组织和晶粒度的原因，刀具的最小刃口半径受超细晶硬质合金的晶粒度(0.2µm)的限制。由于超细晶硬质合金的微观结构，使用陶瓷作为刀具材料可以进一步减小刀具的可实现刃口半径，从而减小所产生的加工力。此外，陶瓷具有比硬质合金更高的热硬度和耐磨性，但目前还不适用于刀具直径≤50μm的刀具。本研究项目的总体目标是首次开发和应用直径为≤50μm的全陶瓷微型刀具。与宏观刀具类似，新型陶瓷端面刀具有望减少刀具磨损。此外，还可以改善工件的表面质量，减少毛刺的形成，并提高刀具寿命。为此，选择了合适的切割陶瓷，并进行了磨损模拟试验研究。在此基础上，通过数值模拟和运动仿真，建立了全陶瓷立铣刀的刀具几何模型。通过磨削生产的微型立铣刀用于铣削试验。将计算结果与实验室现有硬质合金立铣刀的铣削结果进行了比较。

Micro milling offers significant advantages compared to other micro machining methods. These advantages are the high range of machinable materials, the achievable geometric complexity as well as the high surface quality. Today, end mills with diameters ≤ 50 µm are almost exclusively made of cemented carbide, due to its good material properties and machinability.However, the low tool diameters of the cemented carbide tools lead to a reduction of tool stability, while the specific cutting forces increase disproportionately. Furthermore, due to the increasing influence of the cutting edge radius, the so-called ploughing-effect occurs, which means that the workpiece material is pressed underneath the cutting edge and pushed through without being cut. In addition to a deterioration of the surface quality and increasing burr formation, the ploughing-effect leads to increased process forces and a strong wear of the filigree micro tool. Due to the microstructure and the grain size of the cemented carbides used, the minimum cutting edge radii of the tools is limited by the grain size of ultra-fine-grained carbides (0.2 µm).Caused by their microstructure, using ceramics as cutting material can further reduce the achievable cutting edge radii of the tools and thus the occurring process forces. In addition, ceramics have a higher hot hardness and wear resistance than cemented carbides, but are currently not applied for milling tools with tool diameters ≤ 50 μm.The overall goal of the research project is the first-time development and application of fully ceramic micro milling tools with diameters ≤ 50 μm. In analogy to macro cutting tools, the novel ceramic end mills are expected to reduce tool wear. In addition, improved surface quality of the workpieces, reduced burr formation and a higher tool life are expected. For this purpose, suitable cutting ceramics are selected and analogy tests for wear investigations are carried out. On this basis, the tool geometry of the fully ceramic end mills is developed by numerical and kinematic simulation. The micro end mills produced via grinding are used for milling tests. The results are compared with milling results of existing cemented carbide end mills produced in the proposer’s lab.