Experimental Study On Modeling Of Aspect Ratio For Micro Holes Drilled By EDM

Micro electrical discharge machining (EDM) is widely used to drill micro holes in super alloy. It was found that the achievable aspect ratio of micro hole by micro EDM is limited. It is necessary to explain the mechanism of the limited aspect ratio of micro hole by micro EDM. Previous results indicate that the limited aspect ratio of micro hole is caused by the bubbles blocking the liquid flow in the narrow discharge gap. The theoretical values agree with experimental results. However, the errors exist, some of them are larger than20%. To predict the achievable aspect ratio of micro hole by micro EDM more accurately, it is necessary to analyze the factors causing the errors between the theoretical values and experimental results.In this project, an efficient, stale and reliable control software is designed used for micro hole drilled by EDM. A large number of micro holes were drilled under different conditions. Lomnaofski norm is applied to process the experimental data. The random errors of experimental results were analyzed by statistical theory. Experimental results indicate that the large errors distribute randomly. The gross error caused by random characteristics of micro EDM, surrounding conditions and operations should be eliminated by means of correct experimental data processing method. Meanwhile, the error propagation formula is used to analyze the influence of material removal rate, electrode feed speed and discharge gap on theoretical model. It is proved that the theoretical model is valid.With the consideration of dynamic viscosity and surface tension of working fluid, the influence of temperature on the theoretical model of aspect ratio was quantitatively analyzed. According to the working liquid’s surface tension coefficients, the linear regression model between temperature and surface tension is established. Applying the linear regression model and empirical formula of viscosity-temperature, combining with the experimental data, temperature’s influence on theoretical model of aspect ratio was analyzed. It was found that the accuracy and validity of theoretical model of aspect ratio have been improved by applying the linear regression model and empirical formula.