Electrical Discharge Machining Using Electrically Conductive CVD Diamond as an Electrode

In order to improve EDM operation efficiency and accuracy along with the possibility of realizing a good quality EDMed surface, electrically conductive thick CVD diamond film was employed for the very first time as an electrode in die sinking EDM operation. This CVD diamond film of 0.5mm thickness, having a very high coefficient of thermal diffusivity and a low specific resistance suitable for carrying out EDM operation, has recently become commercially available. Die sinking EDM on high speed steel (SKH51, HRC63) was performed using this electrically conductive CVD diamond film as an electrode.

Significantly high stock removal rate can be achieved along with virtually no wear of the CVD diamond electrode using kerosene oil as working fluid for various pulse durations at reversed polarity (workpiece: negative). The EDM can be performed at high current densities (~10A/mm2), which are impossible with copper and graphite electrodes. Significantly high stock removal rate of 0.11mm3 /min along with an insignificant amount of electrode wear shows an excellent possibility of successful application of the CVD diamond electrode at reversed polarity. On the other hand, when this electrically conductive CVD diamond is used as a workpiece in EDM with the diamond or copper electrode, an excellent shape control along with insignificant amount of electrode wear can be achieved. From the overall results of the experiments it can be concluded that the electrically conductive CVD diamond film has a great future potential application as an electrode material in micro EDM.