Electrical discharge machining of polycrystalline diamond: A review

Owing to its ultra-hardness and exceptional wear resistance, polycrystalline diamond (PCD) is widely used in numerous applications such as bearing, nozzle, metal cutting, oil and gas, and hard rock mining. However, the hardness of diamond means PCD products are incredibly difficult to manufacture. Electrical discharge machining (EDM) is one of the most effective non-traditional methods used for machining PCD materials, although the unique composite structure and low electrical conductivity of PCD lead to low machining efficiency. This paper presents an overview of the methods and newly emerged state-of-the-art technologies to improve material removal rate and surface quality as well as the mechanisms behind these methods. Literature analysis shows that efficiency improvement could be achieved by increasing energy utilization and the sparking gap in EDM. The utilization of discharge energy is highly sensitive to the expansion of single discharge sparks. Further improvement in machining efficiency could be achieved by enhancing discharge expansion and explosive force through changing processing forms, dielectric, electrode shape, and power generator in the future. To provide a comprehensive insight of the machinability of PCD, EDM processes of using PCD as tool electrodes to machine other materials to improve machining performance are also discussed.