Machining of electrically conductive CVD diamond tool blanks using EDM

The paper reviews the manufacture, microstructure and physical/mechanical properties of thick film chemical vapour deposited (CVD) diamond in relation to its use for cutting tools. In contrast to polycrystalline diamond (PCD), CVD diamond contains no metallic second phase, its microstructure comprising solely of columnar diamond grains. Experimental research involving an L27 Taguchi orthogonal array is presented relating to the electrical discharge wire machining (EDWM) of boron-doped CVD diamond. The work was carried out in order to establish the effect of generator operating parameters (voltage, current, on-time, off-time) on cutting speed and diamond surface/edge roughness (Ra, μm), when rough machining. Cutting speed results were obtained between ∼0.2 and 1.5 mm/min. Surface roughness ranged from ∼0.6 to 1.3 μm Ra while edge roughness was from ∼0.7 to 2.0 μm Ra.