Single-pulse discharge machining with different electrode shapes

Electro-arc machining (EAM) is a new electrical discharge machining method based on thermal energy. A large amount of thermal energy is released during arc formation to melt and vaporize the workpiece material. Many factors affect arc machining performance, such as electrical parameters (peak current, etc.), non-electrical parameters (flushing pressure, etc.), workpiece and electrode shape, and material parameters. The electrode shape influences the machining performance. Single-factor, single-pulse arc discharge experiments are carried out to evaluate the effect of the electrode’s shape. The polarity effect is verified, and the following results are obtained. For the same workpiece conditions, the arc pit diameter is larger for positive polarity than for negative polarity, suggesting that the arc machining performance is also better for positive polarity. The radius of curvature of the crater has a larger influence than the crater diameter. If a larger etching volume is required, the radius of curvature can be increased, but the etching depth is slightly reduced. The positive and negative polarity also affect the arc plasma characteristic. The compression-expansion effect of the plasma is more pronounced when the direct current is large and positive polarity is used. Waveform analysis shows that the processing stability is higher for positive polarity, whereas negative polarity is more likely to result in bridges and short circuits. As the radius of curvature increases, the processing time, processing instability, and the height of the crater wall increase. The height of the crater wall is higher for positive polarity than for negative polarity.