Electrical Discharge Machining of Micro-rod using Self-Drilled Holes

This paper proposes a new micro electrical discharge machining method which can machine micro rods and holes quick and cheap without a special equipment. With this method, a rod electrode with negative polarity is rotated and fed into a plate electrode to form a hole. After the rod electrode returns to the initial position, the axis of the rod electrode is off-centered from the center of the hole at a certain distance. The polarity of the rod electrode is then reversed, and the rod electrode is fed into the plate electrode, either with or without rotation. Since holes are formed by the rod electrode itself, the rod electrode can be machined very precisely. Since this method does not need initial positioning of the tool electrode with respect to the plate electrode, the operation is easy and short. However, a straight and long rod electrode is difficult to be formed because of the plate electrode wear. Moreover, when the axis of the rod electrode does not coincide with the axis of rotation, the rod electrode cannot be machined precisely. Thus the two step method, run-out measuring method, and dummy hole diameter measuring method were newly proposed to obtain more improvement of accuracy. High accuracy axis was formed using these methods even when the rod electrode does not coincide with the axis of rotation.