Effect of electrode material on electrical discharge machining of alumina |
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| Authors: | A Muttamara Y Fukuzawa N Mohri T Tani |
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| Affiliation: | 1. Faculty of Engineering, Thammasat University, Khlongluang Pathumthani 12120, Thailand;2. Nagaoka University of Technology, Niigata 940-2188, Japan;3. Tokyo University, Tokyo, Japan;4. Tsukuba College Technology, Tsukuba, Japan;1. Indian Institute of Technology Gandhinagar, Ahmedabad 382424, India;2. Bundelkhand Institute of Engineering and Technology, Jhansi 284128, India;1. Department of Mechanical Systems and Design, Tohoku University, Aramaki Aoba 6-6-01, Aoba-ku, Sendai 980-8579, Japan;2. Department of Mechanical Engineering, Faculty of Science and Technology, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522, Japan;3. Manufacturing Process Department, Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia;1. Department of Mechanical Engineering, KU Leuven, Leuven, Belgium;2. Department of Mechanics, Politecnico di Milano, Milano, Italy;3. Department of Electronic Engineering, KU Leuven, Leuven, Belgium |
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| Abstract: | Technologies for machining advanced insulating ceramics are demanded in many industrial fields. Recently, several insulating ceramics, such as Si3N4, SiC and ZrO2, have been successfully machined by electrical discharge machining (EDM). As unstable discharges occur during the machining of Al2O3 ceramics, inferior machining properties have been obtained. The formation mechanism of the electrical conductive layer on the EDMed surface is much different as compared to other ceramics. In addition to this, the electrically conductive layers are not formed sufficiently to adhere to the EDMed workpiece surface and keep a stable and continuous discharge generation on the ceramics. Graphite is widely used as electrode material in EDM. It is expected that carbon from graphite electrode implant and generate a conductive layer. Copper, graphite (Poco EDM-3) and copper-infiltrated-graphite (Poco EDM-C3) electrodes were used to compare the effects of generation of a conductive layer on alumina corresponding to EDM properties. The electrical discharge machining of 95% pure alumina shows that the EDM-C3 performs very well, giving significantly higher material removal rate (MRR) and lower electrode wear ratio than the EDM-3 and copper electrodes. The value of MRR was found to increase by 60% for EDM-3 with positive electrode polarity. As for EDM-C3, MRR was increased by 80% under the same condition. When the results were investigated with energy dispersive spectroscopy (EDS), no element of copper was observed on the conductive layer with both EDM-3 and EDM-C3. However, surface resistivity of a conductive layer created with EDM-C3 is less than with EDM-3. Surface roughness was improved to 25 μm with positive polarity of EDM-C3. |
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