The Research On The Evolution And Control Strategy Of Spark Discharge In Titanium Alloy

EDM is a kind of material removal technology which relies on the high temperature generated by the process of spark discharge.However,the arc discharge in the process of EDM often leads to serious burns on the workpiece surface,making the machining results deviate from the expected.So how to avoid or reduce the occurrence of arc discharge is one of the bottlenecks restricting the further development of EDM technology.Therefore,it is of great significance to study the gap discharge characteristics,stability of discharge state and control strategy of arc discharge suppression in EDM.Aiming at the evolution of the discharge state in the discharge gap of EDM,the process of the discharge gap from the spark discharge state to the arc discharge is studied experimentally.Single factor experiments of DC discharge on titanium alloy material(TC4)were carried out by using the EDM triaxial machining tool independently developed by the research group.The influence rule of electrical and non-electrical parameters such as gap distance,power supply voltage,current-limiting resistance,working fluid,flushing method and rotating electrode about change of inter-electrode discharge state was explored,and the specific requirements of oscillation and hysteresis of the gap equivalent circuit model are formulated according to the specific waveform characteristics.Based on the experimental study on the evolution of discharge state in discharge gap,the discharge gap equivalent circuit model was studied,and the rule of discharge state transformation was analyzed.The discharge gap equivalent circuit model in TR pulse power mode is determined,and the rationality of the physical model was proved by simulation,experimental waveform and theoretical derivation.According to the voltage and current of discharge waveform,fitting volt-ampere characteristic curves of specific parameter combination and discharge gap equivalent resistance,respectively.Combining with equivalent circuit model,using the method of lyapunov stability criterion theory in the evolution of the discharging conditions is presented.It is found that the main reason for the change of gap discharge state in the process of EDM in TR pulse power mode is the damage to spark discharge the gap discharge environment in the discharge phase of the spark,and the more the spark discharge energy,the more serious the damage is.Aiming at the problem of discharge control strategy,the spark discharge energy value before the gap arc discharge state is studied.The effects of power supply voltage,current-limiting resistance,pulse width and gap distance on the depth of discharge pit,burn area of arc and average discharge energy of spark were analyzed by single pulse discharge experiment;In order to study the influence rules of each parameter on electrode wear,the orthogonal experiments of single channel discharge milling with 4 factors and 4 levels were carried out and analyzed by SNR analysis method.According to the electrode wear rule and the analysis results of single pulse discharge energy,the compensation strategy of the electrode wear and the fuzzy control strategy of arc discharge suppression based on energy control were formulated.