放电加工极间等离子体伏安特性与间距建模研究

Investigation of Plasma Volt-ampere Characteristics and Gap Modeling of EDM

放电加工中,工具电极和工件间的间距确定是该类加工方法中的难点,间距过大,导致放电加工过程停止,间距过小,则会产生短路或者工件表面烧伤等。因此,获得合理的放电加工过程的极间间距范围,并精确的描述其模型成为关键。以N型单晶Si的放电加工为背景,分析了极间绝缘介质被击穿后放电通道中等离子体伏安特性曲线的变化趋势,从理论上证明了放电通道可等效为纯电阻模型。通过最小二乘拟合得到等效电阻率与极间间距的模型,进一步推出极间间距与电压、电流的数学模型。在试验的基础上结合3σ检验法对模型进行验证,结果表明,所建立的模型可以描述实际加工过程中的极间间距。

During electric discharge machining(EDM),it is difficult for to determine the gap between tool electrode and workpiece,the large gap results in half of discharge machining,and small gap results in short circuit or faults such as surface burning of workpiece.The reasonable range and model of the gap between electrodes during discharge process is the key.As N type single crystal silicon for example,the variation trend of V-A characteristic curve of the plasma in discharge channel after the dielectric between electrodes breaks down are analyzed,theoretically demonstrates that the discharge channel is equivalent to a pure resistance model.A mathematic model between equivalent electrical resistivity and gap between electrodes is obtained through least square fitting.The model of gap between electrodes and voltage and current is tested based on experiment by combining 3σtest,the experiment result shows that the established gap model between electrodes can describe the gap between electrodes during actual machining process.