In our previous report, the electrical discharge machining (EDM) of polycrystalline diamond (PCD) using a carbon diffusion reaction with transition metal electrodes was proposed. The material removal rate and surface roughness were improved using a rotary cupronickel electrode for finish machining. In this work, we performed sinking EDM of PCD with a piezo-electrically vibrated cupronickel electrode for microstructure generation. Results showed that the material removal rate was improved by 2.3 times compared with a copper electrode even in rough machining. By observation of the machined surface and removed debris, it was found that molten cupronickel induced the carbon diffusion reaction and the promoted graphitization of diamond grains. Precise three-dimensional structures of PCD were successfully fabricated by vibration-assisted sinking EDM using the cupronickel electrode.
Silicon carbide (SiC) single crystal was machined using a disc-type hybrid tool of polycrystalline diamond (PCD). The tool can be used to perform electrical discharge machining (EDM) as a roughing process and grinding as a finishing process. The width of the discharge gap and the thickness of the resolidified layer caused by EDM were measured, the results of which were then used to optimize the subsequent grinding conditions. As a result, ductile mode grinding was realized by removing the EDM-induced resolidified layer completely. In addition, a low surface roughness was obtained after grinding by utilizing the electrical discharges in EDM to dress the PCD tool surface. Finally, high surface integrity and productivity were successfully sustained by optimizing the EDMgrinding cycles.