EDM Machinabilities of EC-PCD Using Ultrasonic Assisted EDM and Bipolar Pulse Current EDM

In order to achieve a high efficient and high quality EDM of PCD, the authors have developed a new PCD having superior electrical conductivity by using boron diamond as a source material. On the other hand they applied a method to give ultrasonic vibrations to the electrode, and have made it clear that even the standard PCD could be machined at the similar level of efficiency to the cases of EDMing die steels and cemented carbides. With a purpose to obtain a good surface roughness on the PCD at high efficiency, various EDM conditions and methods were compared in this paper. Firstly, influence of discharge duration time was examined, and it was found that a shorter pulse duration time as te=0.5μs showed high efficiency and smaller electrode wear rate. Secondary, influence of bipolar pulse current method was examined, and it was found that the method effected higher efficiency but rather large amount of electrode wear resulted. Thirdly, ultrasonic assisted EDM was conducted, and it was found that the method showed superior result regarding efficiency and wear rate on both standard PCD and EC-PCD. A combination use of ultrasonic assisted and bipolar pulse current EDM methods was also attempted in this research. On the contrary to the expectation, efficiency and electrode wear rate became worse in EDM of standard and EC-PCD in comparison with other methods tested before.