Three-dimensional Shaping by Dot-matrix Electrical Discharge Machining with Miniaturized Electrode Feeding Devices

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A new prototyping method called a dot-matrix electrical discharge machining (EDM) with scanning motion is proposed, and a prototype of a machining unit by the dot-matrix method is developed. The machining process by the dot-matrix method is similar to printing motion with a dot impact printer. This method can be applied to not only EDM but also electrochemical machining and forming. A prototype of the machining unit has six feeding devices for thin wire electrodes. The electrodes of 300 mum in diameter are arranged with the pitches of 760 mum. It measures 55*55*80 mm. To obtain a smooth surface, a planetary motion in the xy plane is added to the feeding of the machining unit in the zdirection, the same area is machined repeatedly or the machining unit is moved with fine feed. By compensating the wear of the electrode during the scanning EDM,various shapes with the accuracy of micrometers order can be obtained without a formed tool electrode.Discharge concentration causes cracks on the machined surface. Discharge current is supplied to each wire electrode independently to realize complete discharge dispersion so that a crack-less surface can be obtained. The discharge dispersion does not depend on the resisitivity of a workpiece by divided supplying in the dot-matrix EDM.The surface modification by EDM with thin wire electrodes is also investigated.