Research Of Micro-machining Of Glass Based On Electrochemical Discharge Machining

Human society has been developing rapidly in recent decades. In particular, the rise of micro-electromechanical systems(MEMS) has added a powerful force for the progress of science and technology. Glass, a kind of non-conductive and hard brittle material, has been achieved wider and wider application in the field of MEMS. However, it is hard to micro-machining on them because of their hard and brittle properties. Electrochemical discharge machining(ECDM) has been demonstrated to be a promising non-traditional machining technology for the micro-machining of non-conductive and hard brittle materials. ECDM has various excellent properties, such as higher machining efficiency, simpler equipment, lower cost and better machining flexibility. In this dissertation, the mechanism of electrochemical discharge machining was discussed; then the experimental platform was built based on the electrochemical discharge effect, and the experimental investigations of the micro holes drilling, micro grooves machining and 3D micro-structures machining of glass were carried out. The main contents were as follows:1. The mechanism of electrochemical discharge machining was investigated. The formation of gas film and the removal of material in the process of electrochemical discharge machining were discussed. The evolution process of gas film was categorized into three steps: bubble generation, bubble departure and formation of stable gas film. Then they were theoretical analyzed respectively by combining with the previous researches. The mechanism of material removal was discussed, and was explored mainly from two aspects of the high temperature melting and the chemical etching. The temperature distribution model under the action of spark discharge was established for the study of material removal by high temperature melting. Then the heat transfer process in the electrochemical discharge machining process was analyzed and the minimum temperature required for the material removal was estimated.2. The properties of electrochemical discharge effect were investigated. The critical voltage of the electrochemical discharge was discussed under different external parameters, such as the effect of the electrolyte and its concentration, the diameter and the rotational speed of the tool electrode, the pulse frequency and the duty cycle of the pulse power supply. The results indicate that changes of the parameters, except changing the rotational speed, have great influence on the critical voltage. In addition, the film formation time and the mean electric current were also analyzed in this study by measuring electric current signal when loading different pulse voltage.3. The experiment of micro-hole drilling was carried out. The effects of pulse power voltage and frequency on the micro-hole machining during the electrochemical discharge machining was analyzed through experimental comparison. Those effects including the machining efficiency, the extreme machining depth, the hole-entrance diameter and the hole-entrance surface quality of the holes processed by ECDM. The results indicate that the machining efficiency increases and the extreme machining depth increases with the increase of power voltage or the decrease of pulse frequency. However, it will also cause some defects such as the increase of the hole-entrance diameter and a poor hole-entrance surface quality. In this experimental condition, higher quality micro-holes were processed when the power voltage and the pulse frequency were selected as 21 V and 600 Hz respectively.4. The experiments of micro-grooves and 3D micro-structures machining were carried out. The effect of external parameters on the roughness of the micro-grooves processed by electrochemical discharge machining was discussed. The external parameters mainly including different pulse power voltage and frequency, different feeding rate and different tool rotating speed. The results indicate that the roughness increases with the increase of the supply voltage and decreases with the increase of the power frequency and the feedrate. But the change of electrode speed has little effect on the surface roughness of the micro-grooves. Finally, with reasonable parameters, the 3D micro-structures were carried out by using layer by layer processing.