| EDM process is widely used to fabricate shaft, hole and 3D structure in nontraditional machining area because of little cutting force and the ability to machine difficult-to-cut material. By using simple electrode with circular or square cross section, scanning EDM method can realize 3D structure, avoiding the defect of making complex electrode. In scanning EDM process, arc shapes appear on electrode and workpiece, which will influence machining accuracy. Starting from single pulse discharge, which is a basic unit of EDM process, the laws behind the generation of arc shapes on both poles and the effect on the discharge integration possibly imposed by several factors are researched. The main research contents are as follows:(1) FEM simulation and experimental research of single pulse discharge. At first, the temperature distribution in single pulse discharge is analyzed from the view of surface heat source, and considering the material phase change, the temperature field is simulated based on Gauss distributed heat source with FEM software. After analyzing some influence factors of single pulse discharge, the experiment using copper electrode and workpiece is designed. The size of crater is measured and the erosion rule is studied. The results indicate that the volume of positive machined crater is bigger than the negative one, whose shape is more irregular, in addition, when the pulse energy is small, its efficiency is relatively low.(2) Analyzing discharge integration effects in single channel scanning process. According to the characteristics of single channel scanning EDM process, the factors influencing the discharge integration effect are analyzed, the cross section profile model of slot scanning machined by cylinder electrode is established, then the influence of material removal rate, electrode diameter and scanning speed on contour is acquired.(3) Modelling and experimental research of single channel scanning EDM process. According to the material removal rate and the removal volume ratio obtained in single pulse discharge research, single channel scanning process using two types of electrodes is simulated with Matlab software. The cross section profiles of slot and electrode are gained. Correspondingly, scanning machining experiments with two types of electrodes are carried out. The experimental results are in good agreement with simulation results, it is obvious that the discharge integration effect has an influence on the profiles of both sides. In order to improve accuracy, a proper electrode should be chosen.By means of modelling and experimental research, rules of single pulse discharge and integration effect in single channel scanning EDM process are explored, which have a certain significance to enhance understanding the mechanism of EDM and improving the accuracy of scanning EDM process. |
PDF Full Text Request