Electrical discharge slicing of single crystal SiC by utilizing ultra-thin foil tool electrode

采用厚度为0.03mm的薄箔工具电极（铜或黄铜）对SiC铸锭进行了电火花切割（EDS）。在箔材EDS法中，当箔材运行速度足够高时，箔材刀具的磨损很小，可以忽略不计，切片过程与普通电火花线切割加工（EDM）相似。另一方面，在低的箔运行速度下，由于长的停留时间，箔工具磨损显著。稳态时，箔材刀具的磨损形状在工作区为一条倾斜的直线。刀具磨损长度与刀具面积磨损率、工件厚度成正比，与箔材运行速度成反比，确定了刀具电极负极性和短脉冲宽度更适合SiC箔材电火花切割，可获得更高的加工速度和更低的刀具磨损率。薄箔电极可以导致更高的面积切削速度，但也增加了刀具磨损率。当铸锭工件相对于工具电极向上固定并向下进给到工具时，可以获得更高的加工速率。此外，实验还证实了强化冲洗和提高箔材运行速度都可以通过改善放电间隙条件来提高加工速度，去离子水介质中SiC箔材电火花加工与油介质中相比，具有更高的切削速度、更高的刀具磨损率和更大的切缝宽度。另一方面，电火花加工油的表面完整性更好。

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.