A single-pulse experiment was conducted to study the mechanism of electrical discharge machining (EDM) ablation. An equivalent model of EDM ablation was established to explain the changes in the oxide layer of electrodes. Theoretical analysis was performed to understand the machining mechanism behind EDM ablation. Four stages and three models of EDM ablation were proposed to explain the machining mechanism of this process. Tests were performed to compare normal EDM, EDM spark-induced combustion, and EDM spark-induced explosion. The processing depth and surface morphology of the machined workpiece in the experimental results are coincident with those in the theoretical analysis results.

Polycrystalline diamond (PCD) is a type of ultra-hard material that is widely used in the industry. However, the high manufacturing costs caused by low machining efficiency impede the affordability and application of products made of PCD. Electrical discharge machining (EDM) is a thermal erosion process using recurring electrical sparks to machine materials unrestricted by their physical properties such as hardness and is suitable for the fabrication of PCD products. However, as the electrical conductivity of PCD is poor, its machining efficiency is still very low. This paper proposed a novel high-efficiency machining method using moving arcs generated by a rotating disk electrode to enlarge the material erosion range of a single discharge. The principle and mechanism of the new method were introduced, and the theoretical analysis of the temperature field was performed. Experiments of single-pulse discharging were conducted together with comparative experiments to validate the results of theoretical analysis and investigate the machining performance of the new approach. The results show that moving arcs can increase the discharge probability and improve the stability of the machining process. Material removal rate could be increased by five times and surface roughness be reduced by 16.7%.