Micro EDM aided by ultrasonic vibration in nitrogen plasma jet and mist

Dielectric (e.g., kerosene-based oil, deionized water, air) is an essential part of electrical discharge machining (EDM), insulating the workpiece and the electrode and removing the gaseous bubbles and debris. In this paper, ultrasonic vibration (USV) and mist are added to micro-EDM in nitrogen plasma jet (NPJ) to improve machining performance. Water contact angle on the workpiece surface becomes very small due to increased hydrophilicity of the NPJ-treated surface. Experimental results indicate that the discharge distance is about 3.5 times of that without adding mist. Compared to results in NPJ under the same conditions, the material removal rate (MRR) has increased by four when aided with mist and increased more than six times further when aided with USV. Meanwhile, the surface roughness increased. In addition, the tool electrode wear rate (TWR) in NPJ and mist significantly decreased, especially, aided by USV. 3D micro feature has been generated in Brass successfully by the proposed method, and the TWR (-0.04%) is near zero.