Ultrasonic air bearing spindle for micromachining

超声波辅助切削在加工钛、陶瓷、碳化钨或玻璃等难切削材料时提供了极好的技术潜力。常规切削运动与超声范围内的附加刀具振动的叠加导致改进的材料去除以及改变的切削条件。因此，它可以显著提高切割过程的效率。对于旋转刀具，超声振动是由超声激励主轴引起的。然而，为了利用超声波切割的潜力进行微加工，需要新的主轴。今天的超声波激励主轴提供相对较低的转速，并有高的运行错误。因此，现有的主轴无法实现微型刀具（d <50 µm）所需的切削速度和精度。此外，传统的超声激励主轴难以集成在台式机器中，台式机器由于其大尺寸而越来越多地用于微加工。因此，需要研究紧凑的高速超声主轴，其允许高旋转速度与低跳动误差的组合。因此，拟议的研究项目的目标是开发和应用一种新型的超声波空气轴承主轴，用于微切削，具有高转速（>100.000 rpm），低跳动误差，紧凑的尺寸。主轴转子中集成的磁致伸缩超声执行器将为微细铣削和磨削提供轴向超声运动。使用这种新的主轴，降低切削力和摩擦，减少刀具磨损以及更好的表面质量是预期的。

Ultrasonic assisted cutting provides an excellent technological potential when machining difficult-to-cut materials such as titanium, ceramics, tungsten carbide, or glass. The superposition of the conventional cutting motion with an additional tool vibration in the ultrasonic range leads to improved material removal as well as to changed cutting conditions. Therefore, it can increase the efficiency of the cutting process significantly. For rotating tools, the ultrasonic vibration is induced with ultrasonic excited main spindles. However, in order to exploit the potential of ultrasonic cutting for micro machining, new spindles are necessary. Today´s ultrasonic excited main spindles provide comparatively low rotational speeds and have high run out errors. Consequently, the existing spindles are not able to achieve the required cutting speeds and accuracies for micro tools (d <50 µm). Furthermore, conventional ultrasonic excited spindles are difficult to integrate in desktop machines which are increasingly used for micromachining due to their large dimensions. Hence, there is a need for research on compact, high speed ultrasonic spindles, which allow for high rotational speeds in combination with a low run out error. The objectives of the proposed research project are therefore the development and application of a novel ultrasonic air bearing spindle for micro cutting with high rotational speed (>100.000 rpm), low run out error, and compact dimensions. An integrated magnetostrictive ultrasonic actor in the spindle rotor will provide the axial ultrasonic movement for micro milling and grinding. Using this new spindel, lower cutting forces and friction, reduced tool wear as well as better surface quality are expected.