Research On Temperature Control And Removal Mechanism By Cool Electrode Of Electrical Discharge Machining

Electrical discharge machining(EDM)is a special processing method with non-existent macro-force,it can process all kinds of difficult-to-machine materials,complex shape parts and special requirements of the parts.However,EDM also has the disadvantages of large electrode loss,unstable process,low profile accuracy and poor machined surface quality.In particular,the processing of high strength,low thermal conductivity of refractory materials such as titanium alloy,the shortcomings are more obvious.Aiming at the problems in conventional EDM,a cool electrode temperature control method was proposed in which the forced cooling system was installed on the tool electrode.Through the asymmetric cooling between the two electrodes control electrode at a lower temperature,made the rapid elimination of ionization between the electrodes,reduced the probability of arc discharge,improved processing stability,reduced electrode wear,improved the accuracy of contouring and surface quality of processing.The main contents of this paper are as follows:(1)The cool electrode structure and temperature control system were designed,and a single pulse discharge test platform was designed.The performance of cool electrodes of heat pipe type and cool electrodes of semiconductor refrigeration piece type was analyzed,and the electrode cooling device was composed of semiconductor refrigeration piece.The electrode temperature control system is designed to control the electrode temperature effectively.A single pulse test platform based on discharge current detection is designed and built,which lays a good foundation for studying the erosion mechanism of EDM in cool electrode.(2)The effect of electrode temperature on the inter-electrode discharge characteristics was analyzed.The effects of the electrode temperature on the radius of the discharge channel,the radius of the pits and the density of the electron emission current were analyzed theoretically.The compression effect of the cool electrode on the discharge channel and the characteristics of the cool electrode with low loss and small gap are explained.(3)The influence of electrode temperature on the temperature field between two electrodes was simulated and the simulation results were validated by single pulse test.The inter-electrode electrical discharge model was established,and the finite element analysis was carried out by using ANSYS software to analyze the inter-electrode temperature field of the electrical discharge at different electrode temperatures.The effect of electrode temperature on the material erosion of EDM was analyzed.The simulation results showed that the low loss characteristics.The effect of electrode temperature on the morphology of the electrical erosion pits were investigated by using a single pulse test platform to conduct single pulse discharge experiments at different electrode temperatures.(4)The effect of electrode temperature on discharge gap was studied.The contrast experiment between the cool electrode and the conventional electrode showed that the reduction of the electrode temperature could make the discharge gap smaller and improve the forming accuracy.(5)The processing performance of cool electrode EDM was compared and analyzed.The comparison of the processing performance between the cool electrode and the conventional electrode EDM for processing titanium alloy was carried out.The discharge waveform,electrode wear,material removal rate,machined surface roughness and surface crack were compared and analyzed.The results showed that the cool electrode EDM has low electrode loss,better processing stability,higher material removal rate and better surface quality.Through the cool electrode machining spiral bevel gear test,verified that the cool electrode had the ability of high precision of complex curved surface processing.