Design Of Nanosecond-grade Pulse Power Supply For Micro-ECM And Experiment

Electrochemical machining(ECM) is an anodic dissolution process of workpiece in a flowing electrolyte where the shape of the tool as cathode is copied into the workpiece as anode with the removal of the anode ion by ion. It will be tremendous potential in the micro-manufacturing field with advantages as high machining efficiency, wide materials suit to fabricate, no residual stress and no heat treatment borne on the workpiece surface.Many research and applications show that, by using high frequency pulse power supply the ECM precision and surface quality can be improved effectively. And by using nanosecond pulse power the localization could be significantly enhanced. This will help ECM aplly in the micro-scale machining fields.In this paper, a nanosecond pulse power supply for micro-ECM is designed and made. It can produce the pulse shortened to 50ns and independent frequency and duty-cycle adjustments, which is providing the foundation for micro-ECM. The fast over-current-protection circuit can be controlled within five microseconds.The power supply is developed by adopting the scheme of DC-plus-chopper. This can reduce the cost and weight of the power supply, and improve its efficiency. The rise time and fall time of the driver waveform could be in few nanoseconds, so it will offer guarantee to drive the chopper device. Complementary MOSFET is applied in the chopper circuit which avoid the waveshape distortion in machining. Therefor, the power supply achieve such advantages as good waveform, small volume, high efficiency, and it can be easily carried.With the application of nanosecond power supply, the technical experiment has been done. The effects of voltage on the shape of electrodes were investigated with experiments. In the experiment, the pulse width is 100ns and the voltage is 5.2v. Uniform cylinder of tungsten filament electrode which has 20μm diameter and 900μm length and screw electrode with 60μm diameter and 4.2mm length can be machined with micro-electrochemical machine. With same power supply, we tried to machine micro finestra in another experiment. In this experiment a finestra of 170μm diameter machined with pulse of 300ns and electrode of 130μm diameter. The experimental results show that decreasing pulse duration and voltage can enhance the localization and improve electrochemical micro-machining accuracy and that the power supply can be used in reality and have stable capability and reliability.