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.

Compared with a copper wire electrode, molybdenum wire with a poor conductor is usually used as the electrode in high speed wire-cut electrical discharge machining (HSWEDM), so the resistance of an ultra-fine wire cannot be ignored. To study the differences of discharge characteristics between the ultra-fine wire and the conventional diameter wire, the continuous discharge waveform of two kinds of wire electrodes was compared. It was found that there was a multi-channel discharge phenomenon in the discharge waveform cutting by ultra-fine wire. Through the establishment of a discharge equivalent circuit model and the simulation analysis of the electrostatic field, it was found that the reason why ultra-fine wire is easy to form multi-channel discharge phenomenon is that the potential difference between the wire and the workpiece increased linearly along the axis of the wire. Besides, etching products like metal particles will distort the electric field between the electrodes. Both of them make it easy to form a multi-channel discharge in machining. The results show that the distributions of the equivalent resistance and the peak current are affected by the multi-channel discharge position. Multi-channel discharge can disperse energy and increase effective discharge frequency. Compared with the 0 mm spacing, at a spacing of 100 mm, the machining efficiency increases by 8.7%, the surface roughness decreases by 37.7%, and the average recast layer thickness decreases by 46.6% under the condition of ultra-fine wire-EDM.