Simulation And Experiments Of Small-Hole EDM By Current Dividing

With the development of science and technology, small-hole and micro-hole are widely used in the fields of aviation, spaceflight, military, machine, and so on. The requirements for machining precision and speed of small-hole become higher and higher. Electrical discharge machimng (EDM) is one of the most extensively used non-conventional material removal processes. Its unique feature of using thermal energy to machine electrically conductive parts regardless of hardness to ensure high precision and good surface quality has been its distinctive advantage in the manufacture of small-hole. So, EDM is potentially very suitable for small-hole, which has caused a lot of research attention. New machining process like combined machining technology of EDM with others have been carried out, such as ultrasonic EDM, mixed-powder EDM and EDM by current dividing attracts the author's attention. It that improves the drilling condition for small-hole is a new method of EDM.Discharging-area equalization and current dividing are introduced in the method of drilling small-hole by EDM. Small-hole whose sizes are less than critical value of machining stably can be produced using the stable parameters. The guidance of small-hole EDM by current dividing is that dividing peak current through single electrode replaced by multi-electrodes on discharging-area equalization. The study details are as followed:With a detailed theoretical analysis of drilling process, the effect of electro erosion removing materials in pulse discharge for EDM by current dividing is studied and the principle of dividing peak current through single electrode replaced by multi-electrodes on discharging-area equalization is recognized. The mechanisms of EDM by current dividing in processing are studied, and dividing peak current achieves the aim of decreasing surface roughness and improving the processing conditions. It provides a reliable base in theory for the following studies.The simulation mode of temperature field was achieved with the benefit of finite element analysis software ANSYS using APDL language. Numerical model of single pulse electrical discharge machining is established and analyzed giving reference for EDM drilling of small-hole. Based on this, the numerical simulation of material removal and temperature variations in the EDM for small-hole is done. The results show that there is a consistency in process of experiment and simulation, and the method helps to control the dimension precision.The experiment of EDM-7125 shaping machine drilling holes on discharging-area equalization by current dividing was conducted. According to the experimental results, the function relations of drilling speed, electrode wear and one-sided discharge gap with the electrodes numbers are developed by MATLAB. The results show that the drilling speed and discharge gap decrease a little, but electrodes wear increases slightly, and there is a consistency in process ability between single and multi-electrodes. It verifies that the small-hole produced by original critical value of stable machining can be smaller than before. So EDM for small-hole on discharging-area equalization by current dividing is feasible and stable, and the holes after drilled meet the requirements of precision and quality.This thesis supplies theory base, simulation model and experimental dates for EDM by current dividing on discharging-area equalization. The results are that small-hole whose size less than critical value of machining stably can be produced using the stable parameters through single electrode replaced by multi-electrodes on discharging-area equalization. It presents a novel technology and thought for small-hole and can be used as reference for micro-hole.