Effect Of Contact Force And Motion Direction On Discharge And Material Transfer In Electric-spark Deposition

Electric-spark Deposition(ESD)is a technology that uses high-energy pulse discharge to melt electrode materials and deposit them on the surface of the workpiece,and is widely used in surface strengthening and repair of parts,and has become one of the important surface engineering technologies in the field of green manufacturing engineering.However,the discharge and material transfer mechanism and automatic control technology of ESD technology have not yet been perfected,which hinders its promotion and application.The influence of automatic control and movement direction of contact force on the ESD process has a positive effect on the realization of ESD automatic technology and its popularization and application.In order to study the influence of the contact force and direction of motion of the rotating electrode on the ESD process,an ESD automatic system with automatic control of the contact force was designed.The ESD test is carried out under different contact forces and different directions of motion,and the influence of contact force and motion direction on the parameters and material transfer of ESD discharge process is studied by analyzing the changes of discharge waveform and its parameters,material transfer efficiency,deposition efficiency and surface roughness during the deposition process.The main findings of this paper are as follows:An automatic contact force control system for ESD is designed,and the contact force transposition control realizes the indirect closed-loop control of the contact force,which can control the automatic feeding of the electrode,and the contact force between the automatic control workpiece and the electrode is dynamically stable.Based on the automatic contact force control system,a set of ESD automatic system is built,which can control the start and stop of the output pulse of the deposition power supply and the forward and reverse of the welding torch,and control the workpiece relative to the electrode in accordance with the set trajectory for flat motion.Changes in contact forces affect the number and proportion of various discharge types during the automatic deposition of the electric spark of the rotating electrode.With the increase of the contact force,the contact discharge ratio gradually decreases and the short-circuit discharge ratio gradually increases,and the average voltage and average power of the discharge pulse gradually decrease and the average current gradually rises.The contact force has a greater influence on the material transfer efficiency and deposition efficiency of ESD,and has little effect on surface roughness.When the contact force is 1-2N,the contact discharge ratio in the automatic deposition process is higher,and the transfer efficiency and deposition efficiency are also higher;as the contact force continues to increase,the transfer efficiency and deposition efficiency gradually decrease.In the process of automatic deposition of electric sparks of rotary electrodes,the amount of material transfer caused by contact discharge is significantly higher than that caused by short-circuit discharge.The change in the direction of motion affects the quantity and proportion of various discharge types in the automatic deposition process of the rotating electrode ESD,and changes the discharge parameters and material transfer during the ESD process.Under different directions of motion,the change trend of the average voltage and average power of the discharge pulse is similar to the change trend of the contact discharge ratio,and the change trend of the increase in the workpiece is the same as the change trend of the contact discharge ratio,indicating that the material transfer during the ESD process is mainly generated by the contact discharge.