High-efficiency EDM based on a composite pulse current

Abstract

EDM technology is still facing a big bottleneck problem unsolved: low molten material removal rate, resulting in low machining speed and poor surface quality. To improve the material removal amount in each discharge process of EDM, the composite pulse current waveforms were proposed. The single pulse discharge experiments demonstrate that under the same discharge energy, the material removal volume in the discharge with the end composite pulse could be twice as high as that with the square pulse. Furthermore, due to high molten material removal rate of the end composite pulse, the thickness of the recast layer generated in the discharge with the end composite pulse was much thinner than that with the square pulse under the same discharge energy. The MD simulation results also revealed that in the discharge with the end composite pulse, the basic current mainly melted the material to form a larger molten pool, then, the inrush current, which had higher energy density and higher material removal motivity, could remove the molten pool material largely. Thus, the end composite pulse can improve the molten material removal rate and decrease the recast layer. Finally, EDM milling experiments show that higher average material removal volume in each discharge process of EDM milling with the end composite pulse was the main reason for higher material removal rate (MRR) in EDM milling with the end composite pulse. In addition, the relative tool wear ratio (RTWR) in EDM milling with the end composite pulse can be approximately equal to or slightly lower than that with the square pulse at a high material removal rate in EDM milling, which shows a great application potential of the end composite pulse in EDM.