Research On Electrode Wear And Prediction In Micro-EDM Of Titanium Alloy

Aeroengine Aeroengine manufacturing technology is a key technology for the sustained and rapid development of aircraft and aviation industry in a country.Its turbine blades work in extremely harsh working environment such as high temperature and high pressure for a long time,so it needs to be equipped with efficient and excellent cooling system and technical equipment(such as film cooling holes)to effectively guarantee the normal heat dissipation and rapid cooling of turbine blades.Because the aeroengine is mainly made of titanium alloy,Superalloy and other materials with high hardness and difficult to cut,and the diameter of the film cooling hole on the turbine blade is small(usually 0.25-1.24mm),the traditional cutting is extremely difficult and difficult to guarantee the processing quality.Micro-EDM can achieve "soft cutting hard",not limited by the strong hardness of materials,without any macro cutting force,especially suitable for the machining of micro-holes in difficult cutting materials such as titanium alloy.However,there is electrode wear in the process of machining,and the depth and surface roughness of micro hole after machining are difficult to guarantee,which affects the service life and function of parts.Therefore,it is of great practical significance to study the electrode wear and prediction in micro-EDM of titanium alloy.In order to deeply study the internal causes and mechanism of electrode wear,the temperature field simulation of single pulse discharge of micro electrode is carried out in this paper.The maximum surface temperature of micro electrode after heat source loading,the area of melting area and heat affected area of heat source loading surface and the change rule of melting area and heat affected area depth with loading time are explored.The peak current and interelectrode voltage are studied.The effects of heat source loading time,peak current and interelectrode voltage on electrode loss are analyzed.In order to further study the influence of non-electric factors(electrode diameter and workpiece thickness)on electrode wear,this paper has carried out an experimental study of electrode wear in micro-EDM.Based on the analysis of the whole process of electrode morphology evolution with the increase of the number of holes,the characteristics of electrode wear in group hole machining are summarized.The process is roughly divided into four stages: small axial wear,significant increase of axial wear,stabilization and taper.The ellipse mathematical model of arc-shaped contour area of electrode front-end morphology in the stabilization stage is established.At the same time,the electrode diameter(60?m,90 m,120?m)and the workpiece thickness(400?m,600?m)were changed respectively.The variation rules of the axial wear length of the electrode,the influence area of the electrode wear and the relative wear ratio of electrode volume with the increase of the number of holes were studied.In order to predict the electrode wear of micro-EDM in the process of small hole machining,based on the single pulse discharge mentioned above,the "cone" is taken as the simulated shape of discharge pit,and the wear model of micro electrode is established to predict the wear process of micro electrode at different depths.At the same time,according to the idea of "counter compensation",starting from the final contour of the electrode needed for the target cavity after machining,only the polarity of the electrode and the workpiece and the material removal rate are adjusted,the initial shape of the electrode before machining is deduced,and the reverse simulation model of micro electrode wear is established.Finally,according to the characteristics of group hole machining,the group fixed length compensation is used in the experiment to offset the influence of electrode wear in group hole machining.