Indirect approach to ultrasonic superposition in micro-EDM

Micro Electro Discharge Machining is a well known process for machining microstructures with highest precision in hard and brittle or tough materials. The deeper the structures and therefore higher the aspect ratio, the more difficult it is to remove the ablated particles from the discharge zone and keep the process in stable condition. Flushing can be aided by vibration of either tool or workpiece. Thus, applying ultrasonic vibration to micro EDM has proven to enhance the process significantly. The vibration is most efficiently induced via the tool or workpiece directly to the discharge zone. However, to achieve an ultrasonic vibration of the tool or workpiece, a complex vibration system that operates in resonant mode is needed. Any crucial change of the vibrating parts results in a demanding and therefore expensive adjustment of the vibrating system. With this setup, the application of ultrasonic vibration is only profitable for large scale serial production. In this work a different approach of ultrasonic superposition to the EDM is proposed. A highly focused ultrasonic vibration is induced into the dielectric in a way to directly influence the discharge zone. This indirect ultrasonic superposition can be easily applied since it is independent of the tool or workpiece geometry. Experiments are carried out to examine the effects of the indirect ultrasonic superposition on the EDM process. First results show the possibility of enhancing micro-EDM by this approach.