Ultrasonic air bearing spindle for micromachining

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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.