Study On Electrode Wear And Work Gap Discharge Phenomena In Micro-EDM Milling With High-speed Spindle

With the rapid development of advanced technology, the demand for micro components is increasing, and new opportunities is brought to micro-EDM(Micro electrical discharge machining), however, a series of problems caused by the micro machining dimension restrict the development and application of the micro-EDM. The problems mainly focus on unstable discharge condition, low processing efficiency, serious electrode wear, etc.The high speed rotating electrode with tens of thousands rpm speed in the high-speed spindle micro-EDM milling technology based on non-contact electrostatic induction feeding can effectively improve the discharge condition between the work gaps, and then increasing the efficiency of processing, and decreasing the electrode wear. It has very important theoretical significance and application value to promote the practical of microEDM and expand its application field.This paper set up the micro-EDM milling experimental device based on based on analyzing the principle of the micro-EDM milling using non-contact electrostatic induction feeding. It mainly included high-speed spindle module, the discharge condition detection circuit, high frequency pulse power supply, etc. The experimental device finally achieved stable micro-EDM and laid the hardware foundation for the high-speed spindle micro-EDM milling experiment based on non-contact electrostatic induction feeding.Based on the established discharge process equivalent circuit model of the microEDM using non-contact electrostatic induction feeding, the simulation of the discharge process was carried out with circuit simulation software multisim. Through the simulation, this paper analyzed the influence of the oscilloscope impedance on work gap voltage, observed the reaction of the non-contact detection on the different work gap discharge conditions and analyzed the discharge process of the micro-EDM. The simulation provided the theoretical foundation for the non-contact detection.This paper studied the block electric discharge grinding of micro-EDM using noncontact electrostatic induction feeding. Through analyzing the installation error of tool electrode on the spindle, confirmed the minimum removal in volume to eliminate the deflection of electrode. Eventually a micro electrode with Φ 12μm in diameter, length 1250μm, the length to diameter ratio of greater than 100 was worked out.This paper studied the processing features of the micro-EDM using non-contact electrostatic induction feeding through process experiment, and analyzed the influence of spindle speed on the material removal rate, the electrode wear and the form accuracy. The research results shows that as the spindle speed increasing from 1000 rpm to 60000 rpm, the machining efficiency increases 5.5 times, while the electrode wear ratio is reduced by 7% or so.The experiment study was carried out on the electrode wear of the bottom discharge milling and side discharge milling, the result shows that with higher spindle speed the discharge point is more spread out which can decrease the electrode wear and improve the quality of processing surface. In the bottom discharge milling, when the spindle speed is 60000 rpm, processing surface roughness dropped 18.7% relative to 1000 rpm.