Proposal for Abrasive Layer Fabrication on Thin Wire by Electrical Discharge Machining
Department of Advanced Science and Technology, Toyota Technological Institute, 12-1, Hisakata 2-chome, Tempaku-ku, Nagoya 468-8511, Japan
This paper deals with a method of fabricating an abrasive layer on a thin wire by means of electrical discharge machining (EDM). An electrodeposited wire saw is useful for slicing a silicon ingot. However, strong acids are used in the production process and the depositing speed is slow. To overcome these problems, a fabrication process for an abrasive layer on a thin wire by EDM is proposed. The layer deposited by EDM with a green compact electrode is porous under certain electrical conditions so that the layer is composed of abrasive grit, pores and bond. A mixture of WC, Co, and the abrasive was compressed to make the green compact electrode. Two green compact electrodes were placed facing each other and were reciprocally fed during the process. The WC layer was deposited in 1s on an area in a preliminary experiment. The feed rate of 0.12-mm piano wire was set to 50mm/min. Al2O3 abrasive powders with a size of 35-50µm were able to be contained in the WC layer on the wire. The deposit containing the abrasive firmly adhered. Because the deposited WC layer was very hard, tight gripping of the grit can be also expected. A copper block was cut with a raw piano wire, with wires with or without the abrasive deposited by EDM, and with electrodeposited or resinoid wire saws available on the market to compare their cutting performance. The initial tension was set to 5N and the cutting load was changed from 5.5 to 9.0N. The average feed speed of the wire was set to 8m/min. After 2000 reciprocating motions, the amounts machined with the deposited wire were larger than those with the wire saw available on the market. The deposited wire endured the same cutting load as the electrodeposited wire saw.
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