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

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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.