| EDM has great processing advantages in processing high strength and high hardness materials,but it has the disadvantage of low processing efficiency.The high efficient EDM technology improves the processing efficiency by several times,and even exceeds the mechanical processing efficiency of some materials.However,the high efficiency EDM in liquid has the disadvantage of remelting layer thickness,and the efficiency of high efficiency EDM in gas is greatly reduced.In this paper,in view of the advantages and disadvantages of the above two different high efficiency EDM processing methods,the high-speed EDM milling using gas-liquid composite is proposed,and theoretical and experimental research of the machining mechanism and process law is carried out.High-speed EDM milling using gas-liquid composite is the comprehensive utilization of liquid and gas as working medi?m.The ordinary air and the emulsion act as the working medi?m,and the central through hole of the tubular graphite is used as the internal punching,and the outer tube of the electrode is used as the external flushing to realize the two processing methods which are the inner punching liquid with the outer flushing gas and the inner punching gas with outer flushing liquid.The melting of gaseous materials promotes the cooling and discharge of materials and realizes the rapid removal of nickel base superalloys.The characteristics of the discharge channel and the mechanism of material removal are studied.Through a large n?mber of continuous pulse discharge tests,the effects of the parameters such as peak current and breakdown voltage on the parameters of single discharge pit and the distribution of multiple discharge pits are analyzed.By analyzing the characteristics of the length,width and depth of single discharge pits under different parameters,the cooling and chip discharging capacity of two kinds of mixed dielectric are studied.By analyzing the influence of different processing parameters on the distribution of discharge pits,the superposition and migration of plasma discharge channels with different parameters and different gas and liquid mixing ratios are studiedA new method of measuring discharge gap is proposed,which realizes automatic acquisition of discharge gap and reduces manual measurement error.By measuring the discharge gap between the two processing modes of internal liquid and internal liquid and external gas,the influence of the change of dielectric pressure on the discharge gap is studied,which provides data for the flow field analysis model.Based on the gas-liquid two-phase flow theory,the flow field characteristics of machining gap are studied,and the mathematical model of the working medi?m flow in gas liquid composite high efficiency EDM is established.The distribution rule of working fluid pressure,velocity and gas-liquid mixture ratio at side clearance is analyzedA large n?mber of external liquid gas and external gas internal liquid nickel based superalloy GH4169 processing tests are carried out.The effects of peak current and breakdown voltage on the material removal rate,relative electrode loss rate and over cutting amount are analyzed.The processing rules are then obtained,and the best method is obtained when the nickel base superalloy is processed by gas liquid composite high efficiency EDM Processing parameters.The microcosmic characteristics of the sample are observed,and the influence of the parameter variation on the thickness of the melting layer,the surface roughness,the micro crack and the microhardness are analyzed,and the processing mechanism in different medi?m is revealed. |
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