Improving surface integrity of micro-holes in ECDM using ultrahigh-speed rotary of tool cathode and non-water-based electrolyte

The surface integrity of metal micro-hole structures produced by electrochemical discharge machining is unsatisfactory owing to the insufficient reaction area and strength of electrolysis action. A novel ultrahigh-speed Rotary Electrochemical Discharge Machining (R-ECDM) using non-water-based electrolyte is proposed to improve surface integrity by changing the breakdown medium of spark discharge and increasing the reaction area and strength of electrolysis. A mathematical model was developed to establish the relationship between rotational speed and forces acting on the bubble. Based on the magnitude of forces, controlling rotational speed changed the behavior and departure radius of bubbles on the cathode surface. High-speed photographs validate that, in the mathematical model, the number and departure radius of bubbles on the cathode surface gradually decrease with the increase of rotational speed. The experimental results show that the roughness (R_a) of the micro-hole sidewall decreases from 2.54 μm to 0.20 μm when the rotational speed increases from 500 r/min to 40000 r/min. The length loss and wear ratio of the cathode are only 9.75 μm and 6.5%, respectively. Finally, the micro-holes array with recast-free and surface roughness of 0.20 μm is fabricated, demonstrating that the proposed approach contributes to improving surface integrity of metal micro-holes.