Study Of Discharge Machining Accuracy Based On The Numerical Simulation

Discharge machining as a special process technology has a unique advantage in plastic mold processing. Electric-discharge machining technology in the mold processing field will play a more and more important role in the future. The in-depth study of the material removal mechanism in the discharge machining and the main influence factors for determining the quality of processing the mould and its influence mechanisms will provide corresponding theoretical support for pulse power design and process improvement.The paper has a research on the relationship between the discharge accuracy and the transient temperature field distribution, HAZ distribution, heat stress concentration, heat deformation distribution, which is based on the finite element simulation and the metal phase change principle. The main work and conclusions are as follows:1. The complex Gaussian heat flux is applied by the second development for the finite element software. The result showed that:every moment’s temperature is more than40Cr material melting temperature, the highest temperature of discharge is to8946℃. The material is mainly removed by melting and gasification, and μgasification is70.99%, μmelting is29.01%. The paper draws the time evolution curve by the radial and the depth and concludes that the bigger the radial depth than is, the lager the surface roughness, the better the discharge accuracy is.2. Based on the principle of metal phase change, according to the coordinates related to the temperature node, the temperature nodes related to the phase change, the phase change related to the organization performance, it draws that the HAZ average thickness is9.17μm. Along the thickness direction, the hardness has a increase tendency at first, then has a slow drop tendency, in which, the quench hardened layer hardness is the highest. On the change voltage simulation condition, the expansion of HAZ thickness is rapid and is then quite. The expansion of HAZ thickness on the condition of change pulse width is opposite to the expansion of HAZ thickness on the condition of change voltage. It has a conclusion that the discharge accuracy is better when the voltage is lower and the pulse width is smaller.3. The thermal stress concentration and the thermal strain distribution is simulated and calculated by the temperature nodes calculation result and the element types change. The result shows that the vulnerable to stress concentration occurs in the junction between the HAZ in the discharge machining and the cold basis material. The material deformations take place a displacement deliver and the maximum thermal deformation is0.79μm and occurs in the model border, which is enough to affect the discharge accuracy.The research result is used for the electric parameters selection, its optimized combinations, the mould surface hardness forecast and the failure prediction, which is able to provide the theory support and deserves the further study.