Study On Machining Of Hard And Brittle Insulating Materials By Laser Compounded Electrochemical Discharge Technology

In recent years,driven by the improvement of micro-processing technology and micro-device integration technology,micro-electromechanical systems?MEMS?have ushered in unprecedented opportunities to develop.Naturally,MEMS devices are widely used in communications,aerospace,biotechnology and other fields.Thanks to the combination of outstanding high hardness,high temperature resistance and corrosion resistance,hard and brittle insulating materials,including glass and ceramics,play an extremely important role as the raw material of MEMS.However,the high hardness and brittleness of these materials makes the machining process very poor and the micro-fabrication even more difficult.After many years of research and exploration,processing technology for these materials has got considerable progress.At present,it mainly contains mechanical grinding,abrasive water jet processing,ultrasonic processing,laser processing,electrochemical discharge processing.Aiming to explore higher processing efficiency and processing quality of the process,the mechanism and experimental research on electrochemical discharge machining and laser machining were respectively carried out in this paper.Finally,the two processing methods were combined to carry out experimental research.The main contents were as follows:1.The material removal mechanism of laser back wet etching and electrochemical discharge machining as well as the processing mechanism after the combination of the two were investigated.Firstly,the mechanism of laser wet etching was explained from the aspects of photochemical reaction and vacuole cavitation effects.Then,the process of generating bubbles before the electrochemical discharge and finally converging to form a gas layer,spark discharge,or softening the material was analyzed.The effect of laser thermal composite effect on processing was simulated and analyzed by COMSOL.Finally the mechanism of laser and electrochemical discharge acting in two directions to remove glass material after compounding the two processing methods was discussed,based on the processing mechanism of laser processing and electrochemical discharge.2.The mechanical assisted electrochemical discharge processing experimental device was constructed,and experiments of micro-groove machining were carried out on the Al₂O₃ ceramics.According to the experimental results,the morphology and groove width of micro-grooves under different processing parameters were compared and analyzed.Furthermore,in order to research the effect of mechanical grinding on the machining quality,the surface roughness of micro-groove was measured.The results indicated that:reducing the frequency or raising the voltage within a certain range was helpful to output more energy,increase the width of the micro-groove,and improve the appearance.But too low frequency and high voltage might bring the opposite result.Appropriately increasing the rotational speed of the tool electrode could effectively exert the mechanical grinding effect,reduce the surface roughness and improve the appearance of the micro-groove.Finally,under the conditions of this experiment,the excellent parameters?pulse power supply voltage of 20V,frequency of 400Hz,the electrode rotation speed of 600rpm?were chosen to machine the micro-groove with better quality.3.In CuSO₄ solution,experiments of micro-groove machining were carried out on the glass with picosecond laser back injecting.The single factor method was applied to study the effect of CuSO₄ solution concentration,laser power,laser scanning times and scanning speed on micro-groove width and morphology.The experimental results illustrated that:increasing the concentration of copper sulfate solution was beneficial to the absorption of laser energy,which could improve the processing efficiency and obtain better slotting quality;increasing the laser output power could increase the etching processing rate,and improve the uniformity of the deposited layer and improve the grooving appearance.However,excessively high laser output power might cause obvious defects such as thermal erosion and burns,which may affect the processing quality;increased number of laser scans could improve processing efficiency and improve the quality of the kerf;increasing the scanning speed would reduce the material removal rate,and lead to poor coherence and poor processing quality.4.The complex processing platform was constructed,and therewith micro-hole machining experiments were carried out on the glass with laser aided electrochemical discharge.The motion control system and gravity feed method were designed to ensure the processing stability,and the effects of power supply voltage and laser power on the processing consequence of micro-holes were studied.The experimental results illustrated that:increasing the power supply voltage could improve the micro-hole processing efficiency,but the excessively high voltage would not make the processing efficiency continue to increase.Instead,it would increase the diameter of the micro-hole entrance deformation and make the micro-hole morphology worse;the increase of laser output power could obtain higher processing efficiency,and excessive increase of laser output power would not improve the processing efficiency,but would result in a decrease in processing quality.Based on the experimental research of laser processing and electrochemical discharge machining,the composite processing technology proposed in this article showed obvious advantages as follows:high processing efficiency,high dimensional accuracy and excellent surface quality.These advantages made it particularly suitable for processing transparent glass and other hard and brittle insulating materials.It provided a new technological approach to the micro machining of glass and other materials,expanding their application areas.