Abstract
Micro electrical discharge machining (EDM) is extensively used in high precision machining of conductive materials. In realizing the process, relaxation pulse generator is commonly utilized in micro EDM machine in order to achieve low discharge energy. Studies show that effective flushing and holes with high aspect ratio can be achieved if tool is rotated at very high speed. However, this is difficult to be realized using relaxation pulse generator since the power supply to the tool must be connected using brush and can cause vibration at high speed rotation. On the other hand, electrostatic induction feeding method allows tool to be rotated up to 50 thousand rpm without vibration because the electrical feeding is carried out by electrostatic induction. However, since small capacitance is formed in the narrow gap between feeding electrode and tool electrode holder, discharge energy per pulse is too small and insufficient to conduct rough machining. By controlling the duration of discharges, the discharge energy can be increased without limit by using the same small feeding capacitance. With this, numbers of small discharges are allowed to occur at the same location and thus size of discharge crater can be enlarged. In this study, crater size, removal volume per discharge crater and material removal rate (MRR) using controlled pulse train method were investigated and compared with the relaxation pulse generator under the same discharge energy.
