| With the development of microfabrication technology,micro-size parts structure of difficultto-machine metal materials is widely used in the fields of national defense equipment,aerospace and civil precision equipment.The traditional machining technology is difficult to meet the machining requirements of the difficult-to-process metal materials.Micro-electrochemical(micro-ECM)machining technology has the characteristics of no tool loss,no contact machining and better surface quality,so it is an ideal method to realize the micro-dimensional parts structure forming processing.In view of the difficulties in improving machining accuracy and the poor localization of machining,the external rotating magnetic field assisted microelectrochemical machining technology was studied,mainly from four aspects: the effect of rotating magnetic field on machining process,the development of rotating magnetic field auxiliary device,the distribution characteristics of rotating magnetic field and the process experiment.(1)In order to obtain the theory of the influence of the external rotating magnetic field on the micro-electrolytic machining process,the research on the effect of the external rotating magnetic field on the motion of charged particles and the motion of bubbles was carried out.The rotating magnetic field was combined into the micro-ECM.Based on the fixed magnetic field and the classical electromagnetic theory and the fluid dynamics theory,the variable of rotating magnetic field was introduced to study the influence of the external rotating magnetic field on the trajectory of charged particles and the movement of bubbles during the micro-ECM.The results show that: under the influence of rotating magnetic field,the movement trajectory of charged ions changes from simple one-way movement to "spiral complex movement",and the bubble movement trajectory changes and quickly escapes from the processing area,which can promote the updating of electrolyte and improve the localization of processing.(2)In order to provide external rotating magnetic field environment to meet the requirements of the topic in the process of micro-ECM machining,a set of controllable and adjustable rotating magnetic field auxiliary device and cathode auxiliary device was developed.The core parts of the rotating magnetic field auxiliary device such as height adjustment,tilt,horizontal rotation,magnetic field intensity adjustment and the structure size of the cathode auxiliary device are designed,and the structure of the cathode auxiliary device is optimized.Finally,the rotating magnetic field auxiliary device realized the requirements of horizontal rotation,tilt,height adjustable and magnetic field intensity adjustable.The device reached the adjustable and controllable indexes of horizontal continuous rotation in the range of 0～30RPM,magnetic field intensity in the range of 0～0.2T,and magnetic pole inclination in the range of-60°～60°.An external rotating magnetic field assisted micro-ECM system was successfully constructed with existing ECM machine tools.(3)In order to study the distribution characteristics of rotating magnetic field,the simulation of the distribution characteristics of rotating magnetic field in space and machining domain was carried out.Firstly,the magnetic field distribution of the rotating magnetic field auxiliary device is measured and simulated under the same parameter,which verifies the structure rationality of the device.Furthermore,the distribution characteristics of rotating magnetic field in space and machining domain were studied when different angles of 0°,10°,20° and 30° acted on different magnetic field speeds of 5RPM,10 RPM,15RPM and 20 RPM.The results indicate that the distribution characteristics of the rotating magnetic field in space are such that the fluctuation of magnetic field strength decreases less as the distance to the machining center gets closer,and the attenuation of magnetic field strength shows a quasi-linear trend.In the processing domain,the distribution characteristics of the rotating magnetic field show that the magnetic field strength fluctuates more violently with an increase in the inclination angle of the magnetic pole,and the effect of rotational speed on the intensity change is relatively weak,mainly affecting the frequency of the rotating magnetic field in the processing domain.(4)In order to study the influence of the external rotating magnetic field on the precision of micro-electrolytic machining,the single factor experiment and orthogonal experiment of key machining parameters on the machining accuracy were carried out,and the parameter optimization was carried out to determine the optimal parameter combination for verification.Single factor and orthogonal experiments were carried out on the influence of five key machining parameters,including cathode feed speed,machining voltage,magnetic field rotation speed,magnetic pole Angle and magnetic field intensity,on machining accuracy.The influence law of process parameters on machining accuracy was obtained through single factor experiments.Through orthogonal experiment and grey correlation analysis,the machining parameters were optimized and the ideal machining parameter combination was obtained,namely,the cathode feed speed was 0.4μm/s,the machining voltage was 4.5V,the magnetic field rotation speed was5 RPM,the magnetic pole Angle was 10° and the magnetic field intensity parameter was 0.09 T.The comprehensive experimental results show that the surface quality of micro-holes produced by micro-ECM in superposed rotating magnetic field environment is significantly improved compared with that without magnetic field assisted ECM,and the measurement indexes of machining accuracy of micro-hole lateral clearance and micro-hole taper are increased by 26.3%and 60.8% respectively.Theoretical analysis and experimental study show that the adjustable and controllable rotating magnetic field auxiliary device can meet the practical requirements of rotating magnetic field assisted micro-electrochemical machining,and the external rotating magnetic field can improve the precision of micro-electrochemical machining,providing a new way to solve the difficult machining problem of micro-size parts of metal materials. |
PDF Full Text Request