电火花穿孔加工中管状电极振动幅值特性

在采用管状电极高压冲液的电火花穿孔加工中，较大幅值的电极随机振动将导致加工中侧壁短路和二次放电，这对穿孔加工精度和效率造成不利影响。本文以高压冲液管状电极为研究对象，采用仿真、实验验证及对比分析的方法研究了电极微观振动幅值特性。基于ANSYS有限元软件平台，建立了描述电极振动特性的有限元模型，通过数值模拟分析了冲液压力、导向器间隙、穿孔深度、放电间隙、主轴转速、电极悬长多因素对电极振动幅值的影响，分析了多因素耦合情况下各因素对电极振动幅值的影响程度，并进一步进行了实验验证。研究表明导向器间隙、穿孔深度、冲液压力与电极振动幅值成正相关性，减小导向器间隙由10 μm至1 μm，可有效降低孔径误差20 μm。多因素耦合分析得到电极振动幅值影响因素主次顺序为:穿孔深度、冲液压力、放电间隙、主轴转速、电极悬长。此项研究为优化电火花穿孔加工工艺与主轴设计提供依据。 

Vibration amplitude characteristics of tubular electrode in EDM drilling

In the drilling of electric discharge machining (EDM) by use of a tubular electrode with high-pressure dielectric fluid, the random electrode vibration causes short circuit and second discharge which have a bad effect on machining accuracy and efficiency. In this paper, the microscopic amplitude characteristics of the electrode vibration are researched by adopting methods of simulations, experiments and comparative analysis. Based on ANSYS simulation platform of finite-element software, a finite element model was established to simulate the vibration characteristics of the tubular electrode, and then the effects of multiple factors including hydraulic pressure of dielectric fluid, electrode-guide gap, drilling depth, discharge gap, spindle speed and electrode overhanging length on the electrode vibration amplitude were analyzed. In addition, the significant level of every factor was analyzed by numerical simulation under the condition of coupling these factors. The EDM drilling experiments were carried out to verify the simulation results. Our research shows that the guide gap, drilling depth and hydraulic pressure have positive correlation with the electrode vibration amplitude, and reducing the guide gap from 10 μm to 1 μm can effectively reduce 20 μm of the error of the aperture. By analyzing these coupling factors, the order of significance affecting the electrode vibration is drilling depth, hydraulic pressure of dielectric fluid, discharge gap, spindle speed and electrode overhanging length. This research provides a basis for optimizing machining process and spindle design of EDM drilling using a tubular electrode.