Study on Electro-Discharge Micro-Machining --- Machining of Micro-Spindles, Using a Travelling Wire Electrode ---

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Methods for producing very thin spindles are required to obtain an electrode for micro-electro-discharge drilling or a punch for micro-punching. This project regards with developing a system which meets this demand. The wire electro-discharge grinding mehtod is tested of its possibility. The machining characteristics, applicabilities to a very thin spindle, micro-hole ED drilling, formation of rods with various shape etc. are tested. This method is a kind of electro-discharge grinding. A wire which travels along a wire-guide is used as the electrode. Differently from the usual WEDM, the discharge takes place at the guided position of the wire. It gives a high machining accuracy. Main experimental results using a prototype 2-axis-controlled equipment are as follows; (1) Longitudinal deviation of the diameter was less than 1 <mu> m. (2) Accuracy of the zero-adjustment of x-axis affected the finished diameter. (3) The descharge gap increased when the depth of cut or the discharge capacity was increased. These influences were reduced by setting the offset value as a table in the memory of the controller. (4) Change of the workpiece material gave little influecnce on the machining accuracy. However, the machining time and the machined surface integrity were affected. (5) Micro-holes were able to be ED drilled in various materials, using the spindle machined by this method. (6) A taper spindle could be machined by simultaniously controlling the X- and Z-axis. Finally, a 4-dimension-controlled equipment was constructed and the possibility of forming a poligon rods was confirmed.