| 研究実績の概要 |
Electrical discharge slicing (EDS) of SiC ingot using thin foil tool electrodes (copper or brass) with thickness of 0.03mm was conducted successfully. Kerf width less than 0.1mm was achieved.
In foil EDS method, when the foil running speed is sufficiently high, the foil tool wear is little and can be neglected and the slicing process is similar to common wire electrical discharge machining (EDM). On the other hand, at a low foil running speed, the foil tool wear is significant owing to a long dwelling time. At steady state, the foil tool wear shape is an inclined straight line at the working area. The tool wear length is proportional to the tool area wear ratio, workpiece thickness and inversely proportional to the foil running speed.
Negative polarity of tool electrode and short pulse duration are confirmed more suitable for foil EDM slicing of SiC which can result in a higher machining speed and a lower tool wear ratio. Thinner foil electrode can result in a higher area cutting speed, however the tool wear ratio also increases. When the ingot workpiece is fixed upside relative to the tool electrode and fed downwards to the tool, higher machining rate can be obtained. In addition, it was confirmed that both enchantment of flushing and higher foil running speed can improve the machining rate by improving the discharge gap conditions.
Foil EDM of SiC in deionized water featured higher cutting speed, higher tool wear ratio and larger kerf width compared to those in EDM oil. On the other hand, the surface integrity is better by EDM oil.
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