Abstract
Micro electrical discharge machining (micro-EDM) has been widely applied in the field of precision machining, but the machining mechanism is still unclear. In this paper, the relationship between the characteristics of discharge plasma and discharge duration is clarified by analyzing the formation and expansion process of the discharge plasma channel under micro-scale discharge conditions. Based on the experimental results, the effects of discharge duration on the discharge current, discharge voltage and discharge crater size are discussed. The results show that the expansion acceleration, internal pressure, temperature, and electron density of the discharge plasma decrease as the discharge duration increase, while the radius and expansion velocity of the discharge plasma increase, and finally the discharge plasma reaches the state of shape–position equilibrium. The resistance of discharge plasma is estimated to fluctuate in the range of 38–45 Ω by the ratio of discharge maintenance voltage to discharge current. The energy utilization rate of micro-EDM is very high when discharge duration is less than 4 μs, and then decreases gradually as the discharge duration increased. There is a positive linear relationship between discharge crater volume and discharge duration. The discharge duration has no significant effect on the discharge crater depth. This study provides a theoretical basis for further study of discharge plasma characteristics in micro-EDM.
Highlights
In recent years, more and more attention has been paid to precision machining technology and methods [1,2]
The discharge of micro-EDM happens in a very short period of time and very small space with very low discharge energy, which leads to the machining mechanism of micro-EDM being different from that of macro-EDM, due to size effects [6,7]
It can thatthat discharge duration voltage have have no significant effect on either discharge voltage or discharge current, both of which fluctuate in a certain range
Summary
More and more attention has been paid to precision machining technology and methods [1,2]. A comprehensive model was proposed to predict the material removal characteristic of micro-EDM, and the discharge temperature and crater radius can be more. The exploration of material removal mechanism of micro-EDM is still one of the research emphases of EDM. It is indicated that the current waveform can be changed by changing the electrical parameters, and, the micro-EDM performance can be optimized by obtaining optimal discharge plasma [9]. Wang et al [13] indicated that the reverse current during micro-EDM has a beneficial effect on machining performance. Because it is difficult to accurately observe the discharge plasma expansion process, the material removal process and instantaneous temperature distribution cannot be directly obtained by existing technical means. Further clarification of the material removal mechanism of micro-EDM is helpful to improve its machining performance. Based on the experimental results, the effects of the discharge duration on the discharge current, discharge voltage, and discharge crater size were discussed
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