Research On Multi-micro Hole Synchronous EDM Technology

Micro-EDM technology has broad application prospects in advanced industrial technology fields,such as precision mechanical engineering,micro-machinery,micro-electronics technology,biomedical engineering and aerospace,because of its high accuracy,high surface quality and no macro-force.At present,single-electrode EDM is widely used in micro-EDM machine tools.For parts with multiple micro-holes,only hole-by-hole processing can be done,so the processing efficiency is low.Aiming at the technical problem of low efficiency of EDM,the technology of fabricating array micro-holes with group electrodes has been put forward at home and abroad.The group electrodes are fabricated by micro-array holes based on the principle of anti-copy of EDM,and the array holes are fabricated by micro-single electrodes.Although the group electrode technology has greatly improved the efficiency of micro-hole processing,there are still some technical defects:single electrode can not be controlled independently,if a electrode is short-circuited,the concentrated energy discharge will cause this electrode to burn down;The electrode can not rotate,and can not use the rotation function to improve chip removal so that the ratio of depth to diameter in hole processing is limited;The fabrication of group electrodes is difficult and the process is complicated.Based on the current research status of EDM,a multi-micro hole synchronous EDM rotary vibration machine tool is proposed in this paper.It is devoted to improving the efficiency and accuracy of multi-micro hole processing.Based on the functional requirements of multi-micro hole synchronous EDM system,a multi-micro hole synchronous EDM machine tool was developed independently.The machine tool is composed of a mechanical platform and a control system.It can realize multi electrode independent micro-energy pulse discharge,real-time detection of each electrode gap state and servo feed adjustment,and synchronous rotation assisted vibration of each electrode.It has high processing efficiency,processing stability,processing accuracy,and high automation.The mechanical platform is mainly composed of servo feed mechanism,vibration mechanism and multi-electrode synchronous rotating mechanism,which has reasonable structure design and high reliability.The control system is composed of motor control module,servo motion control module and pulse power module.It uses STM32F103RCT6 single chip microcomputer to detect the machining state in real time and coordinate the work of each module,and uploading the processing data to upper computer.The design of micro-energy pulse power supply is one of the key technologies in micro-EDM.The power supply outputs high-frequency PWM signals from the processor STM32F103RCT6,which processed by the discharge control loop can drive the high power field effect transistor to control the capacitance charge-discharge.Capacitance quantitative energy storage and pulse width adjustment of micro energy pulse are realized by changing the duty cycle of PWM.It combines with gap state detection technology to distinguish the gap state of each electrode and adjust the gap between the workpiece and electrode in time.The power supply is designed to achieve micro-precise control of multi-electrode pulse energy.The selected STM32F103RCT6 processor uses 72MHz clock,the minimum output pulse is 13.9ns,and the precision of pulse adjustment is 13.9ns,which meets the requirements of micro-energy processing.Based on the structure of machine tool and the hardware design of micro-energy pulse power supply,the program of multi-micro-hole synchronous EDM system is developed by C language and STM32 library function.The program design of the processing system includes manual mode program of machine tool,serial communication program of DC adjustable power supply based on Modbus,pulse discharge and multi-parameter closed-loop control program,and man-machine interface based on LabVIEW.The software can realize the switch between manual processing and automatic processing mode of EDM machine tool,multi-electrode rotating vibration compound micro-energy pulse discharge,discharging gap state identification and real-time adjustment of multi-processing parameters.Finally,a friendly man-machine interface is established to realize parameter online setting and processing status display.Finally,the machining experiment proves that the multi-micro-hole synchronous EDM machine tool performs three-electrode synchronous EDM at different vibration frequencies and rotating speeds,and no abnormal situation occurs in long-term work.The machine tool has good stability and processing effect.The factors affecting the efficiency and quality of multi-micro-hole EDM were explored,including the parameters of electrode speed,amplitude,capacitance charging energy,current limiting resistance and processing thickness.Meanwhile,three-factor and three-level orthogonal experiments were designed to explore the optimum conditions for maintaining stable and efficient EDM.