Study on the Time-Varying Characteristics of Discharge Plasma in Micro-Electrical Discharge Machining

Abstract

Micro electrical discharge machining (micro-EDM) has been widely applied in the field of precision machining, but the machining mechanism is still unclear. In this paper, the relationship between the characteristics of discharge plasma and discharge duration is clarified by analyzing the formation and expansion process of the discharge plasma channel under micro-scale discharge conditions. Based on the experimental results, the effects of discharge duration on the discharge current, discharge voltage and discharge crater size are discussed. The results show that the expansion acceleration, internal pressure, temperature, and electron density of the discharge plasma decrease as the discharge duration increase, while the radius and expansion velocity of the discharge plasma increase, and finally the discharge plasma reaches the state of shape–position equilibrium. The resistance of discharge plasma is estimated to fluctuate in the range of 38–45 Ω by the ratio of discharge maintenance voltage to discharge current. The energy utilization rate of micro-EDM is very high when discharge duration is less than 4 μs, and then decreases gradually as the discharge duration increased. There is a positive linear relationship between discharge crater volume and discharge duration. The discharge duration has no significant effect on the discharge crater depth. This study provides a theoretical basis for further study of discharge plasma characteristics in micro-EDM.

Research on Electrostatic Field-Induced Discharge Energy in Conventional Micro EDM

“…A drop in surface charge density and a small diameter of the jet result in a very short duration, and a minor charge depletion leads to a decrease in electric field forces and results in jet retraction. Because the interelectrode voltage is directly connected to the plasma characteristics during the discharge process, the greater the maintenance voltage, the larger plasma discharge gap [27]. Simultaneously, lowering the charge density and jet diameter decreases the strength of the discharge between the jet and the workpiece, causing the voltage to progressively rise as the electrode moves away from the workpiece, as shown in Figure 6c.…”

Effect of cathode pulse square-wave on the microstructure and corrosion resistance of PEO coatings of AZ91D magnesium alloy prepared in the Na2C4H4O6–KF–Na2SiO3 system

“…PEO is a multi-factor controlled physicochemical process and the quality of the PEO coating depends mainly on many technical parameters such as power supply parameters, current pattern, electrolyte composition, and substrate composition [13][14][15][16]. At present, there are a lot of research on the effect of the electrolyte species on the microstructure and properties of PEO coatings on magnesium alloy, such as the main alkaline salts (Na 2 SiO 3 , NaAl 2 O 4 or Na 3 PO 4 ) and its additives (KF, KMnO 4 or K 2 ZrF 6 ) was used to prepared the composite ceramic coatings on magnesium alloys.…”

Discharge Energy as a Key Contributing Factor Determining Microgeometry of Aluminum Samples Created by Electrical Discharge Machining

“…The surface roughness is influenced by EDM parameters, mainly the current, voltage, polarity, and duration of the electric impulse, the multiplication of which is the energy of electric discharges-a key factor determining the surface finish. Additionally important are the dielectric liquid, electrode material, and the type of machining movement [9][10][11]. Surface microgeometry is mainly determined by the energy of the electrical discharge between the electrode and the workpiece [12].…”