Research On The Erosion Characteristics Of VHF Micro-energy Pulse Discharge

In recent years,with the trend of miniaturization of products in the fields of information technology,biotechnology,environment medical treatment,optics and so on,the application of micro-structure and micro-scale parts has become more and more extensive,and the demand for surface quality and accuracy has become higher and higher,which poses a higher challenge to micro-processing technology.As one of the key supporting technologies in the field of micro-machining,micro-EDM technology still has two bottlenecks:processing speed and surface quality are difficult to meet the growing demand.In order to obtain the nano-scale high-efficiency erosion capability of micro-EDM,it is one of the most effective ways to design a micro-energy pulse power supply with good performance.In order to realize the requirements of small discharge pulse energy,large discharge gap and sustainable processing,this paper explores a very high frequency(frequency between 30MHz-300MHz)micro-energy pulse source based on the principle of circuit resonance,which breaks through the existing spark pulse.The working mode of the source can generate pulse waveforms with very narrow pulse width and very high frequency,and has nano-scale discharge etching characteristics,which improves the ultimate etching ability of micro-EDM processing.The erosion mechanism of high-frequency narrow pulse width micro-spark is studied.With the further reduction of discharge energy,the proportion of energy entering the tool electrode is gradually reduced,the proportion of energy consumed in the discharge gap is gradually increased,and the workpiece material is removed.The mode is mainly from melting to gasification and gasification.The calculation method of the discharge craters radius and energy distribution coefficient of VHF(very high frequency)and the variation law with the discharge frequency are summarized,which provides a basis for the selection of the discharge parameters of the VHF micro EDM.The open circuit state and the discharge process were simulated by Multisim circuit simulation software.The relevant circuits were designed and fabricated and pulse output experiments were carried out.The results show that the values of different high-frequency choke coils,coupling capacitors,resonant inductors and resonant capacitors at the same pulse frequency have the values that maximize the open-circuit voltage output.The parameters of the open-circuit voltage can be changed by optimizing the parameters.peak-to-peak value,which in turn adjusts the amount of discharge energy.After the circuit is optimized,a higher open circuit voltage can be further output at a higher pulse frequency,and the peak-to-peak value of the pulsed open circuit voltage of the 70 MHz frequency can be up to 165 V.The characteristics of very high frequency pulse discharge are studied,and the waveform of the intereloctrode discharge voltage and current is analyzed.The VHF pulse is very small compared to the traditional transistor pulse edge oscillation.The actual discharge waveform is in good agreement with the theoretical analysis and circuit simulation analysis.Because there are many stray electrical parameters in the actual processing,the resonance frequency is about 55MHz.The variation of discharge energy,peak heat flux density,average diameter of discharge craters and surface roughness with pulse frequency,current limiting resistance and open circuit voltage were studied.Reducing the open circuit voltage,increasing the current limiting resistance,and increasing the pulse frequency are all beneficial to obtain smaller average discharge craters and lower surface roughness.The fundamental reason is to reduce the single pulse discharge energy.When the discharge frequency is 90MHz,the peak-to-peak voltage peak value is 70V,the average discharge craters diameter can reach 0.38μm,and the surface roughness of the processed sample can reach Ra42nm.When the discharge frequency is 55MHz,compared with the traditional micro-energy pulse source,the surface of the tool electrode after processing has obvious surface quality,and the edge of the processed hole has almost no recast layer,which greatly reduces the thermal damage and recast in the process.Conventional defects such as layers and heat-affected zones improve the surface quality of the workpiece.The experimental results show that the designed VHF micro-energy pulse source has good discharge erosion characteristics.In this paper,the erosion mechanism of VHF pulse is analyzed,and the characteristics of VHF micro-energy pulse discharge erosion are studied.The high-frequency amplitude VHF pulse is generated.The nano-level of VHF pulse is verified by discharge experiment.