Study on discharge characteristics and process of multi-channel high-speed wire electrical discharge machining for metal workpieces

Multi-channel wire electrical discharge machining (WEDM) is widely used for slicing semiconductor materials and improving cutting rate through multi-channel discharge. However, enhancing the cutting rate of integral metal workpieces through the utilization of multi-channel WEDM remains a challenge. This paper investigated the discharge characteristics of metal workpiece using multi-channel high-speed WEDM (HSWEDM). It was discovered that due to the high conductivity of the metal workpiece, there is electrical signal coupling between each channel, which inhibits the independent discharge of each channel and severely impacts the improvement of cutting rate. To solve this problem, a new power supply with a decoupled circuit was designed, and the potential difference between adjacent channels was formed by using a current-limited resistor at each output, reducing coupling between the channels and enabling independent discharges at each channel, thereby improving the cutting rate of metal materials. The effect of current-limited resistance (R_c) on multi-channel synchronous discharges was analyzed through online acquisition of discharge signals, demonstrating that reducing the R_c can improve the discharge ratio. In the two-channel HSWEDM with the new power supply, when the R_c is reduced from 15 to 5/3 Ω, the gap voltage is increased from 31 to 64 V, the discharge ratio is increased from 0.967 to 1.566, and the increase in cutting rate was from 19.06% to 83.02%. Furthermore, when R_c is 5/2 Ω, the cutting rate was 1.660–1.971 times that of conventional power supply. Since each channel can implement independent servo control after electrical signal decoupling, the dimensional uniformity and surface topography of grooves are improved, and the thickness of the recast layer is reduced. Lastly, the new power supply was applied to the four-channel HSWEDM, resulting in a significant increase in cutting rate, which was 3.538 times higher than that of conventional power supply.