| Through-Mask Electrochemical micromachining(TMEMM)is a widely used machining technology,which has unique advantages in the machining of metal microstructure,such as high machining speed,no residual internal stress in the workpiece after machining,no loss of tool electrode,etc.When conventional mask electrochemical machining of metal microstructure is carried out,the edge electric field intensity under the influence of edge effect is higher than the center,resulting in poor overall size uniformity of metal microstructure.In order to solve this problem,a moving jet mask electrochemical machining technology is proposed in this paper,which reduces the cathode area to weaken the edge effect,uses the moving cathode to balance the current density and processing time,and discharges the electrolytic products in time,so as to improve the uniformity of metal microstructure.Firstly,the electrode reaction and anodic polarization in the process of TMEMM are analyzed according to the principle of ECM,and the appropriate process parameters are selected accordingly.According to Faraday’s law,the current density and processing time will affect the amount of anodic dissolution in the process of TMEMM.In conventional mask ECM,the processing time of the microstructure at the edge and center of the anode is the same,and the difference of the current density distribution leads to the difference of the etching depth of the microstructure at different positions.On the one hand,the area of the cathode is reduced and the edge effect is weakened,so that the current density is evenly distributed,and then the current density and processing time are balanced by the movement of the cathode in the two-dimensional plane;On the other hand,the electrolytic products are discharged in time by spray machining,which avoids the influence of electrolytic products and improves the uniformity of microstructure.Secondly,the moving TMEMM process is simulated by COMSOL software.Based on the physical model and geometric model of moving TMEMM,the boundary conditions are set and the mesh is divided to solve it.After extracting the simulation results,the profile and depth distribution of the anode micro pit array structure are drawn by MATLAB software,and the depth unevenness of the micro pit array is calculated.The distance between cathode and anode,the diameter of cathode and the moving distance of cathode will affect the uniformity of micro pit array structure.Therefore,numerical simulation is carried out under different parameters to obtain better process parameters.Compared with the simulation results of conventional TMEMM,the non-uniformity of the micro pit array structure is reduced by65.8%.Finally,a mobile jet TMEMM device is built,and experimental research is carried out on this basis.The electrochemical machining device comprises a two axis moving platform,an electrolyte circulating system and a pulse electrolytic power supply.After the anode substrate was pretreated,the micro pit array mask was prepared by exposure and development.The effects of cathode cathode distance,cathode diameter,cathode moving distance and electrolyte flow rate on the structural uniformity of the micro pit array were investigated by experiments,and better experimental parameters were obtained.Under the optimized parameters,the moving jet TMEMM experiment was carried out.Compared with the conventional cathode fixed TMEMM,the uniformity of the metal micro pit array structure was improved by 70.7%.The experimental results show that the moving jet TMEMM method proposed in this paper can effectively improve the uniformity of metal micro pit array structure. |
