Effect of multi-channel discharge distribution on surface homogeneity in super-high-thickness WEDM

The multi-channel discharge phenomenon for super-high-thickness (more than 1000 mm) cutting is studied in high-speed wire electrical discharge machining (HS-WEDM). In super-high-thickness cutting, the length of the wire electrode with a poor conductor is longer in the machining area, so the resistance of wire electrode cannot be ignored. It is found that the main reason for the formation of multi-channel discharge is that there is a high voltage between electrodes after dielectric breakdown due to the resistance characteristics of the wire electrode. When the conventional discharge circuit is used for machining, the voltage between electrodes in the middle of the workpiece is much higher than that at the upper and lower ends, which is easier to generate multi-channel discharge. Multi-channel discharge has the characteristic of dispersing discharge energy, which results in inhomogeneous surface roughness on the whole section of the workpiece. To improve the distribution characteristics of the inter-electrode voltage after dielectric breakdown, a novel discharge circuit is proposed, which gradually increases the inter-electrode voltage of discharge points distributed along the thickness direction of the workpiece, and significantly improves the formation probability of multi-channel discharge on the whole cutting surface. A super-high-thickness workpiece with a thickness of 1000 mm is used for continuous cutting. The cutting speed of the two types of discharge circuit is basically the same. But the surface roughness machined by the rear-end parallel circuit is reduced by 15.8%, and the surface homogeneity is greatly improved.