| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 105 === Polycrystalline diamond (PCD) is a high-performance synthetic material which has several outstanding properties, such as good thermal conductivity, high hardness, and high wear resistance. These features of polycrystalline diamond can obtain good effects in the application of cutting tool, but they also enhance the fabrication difficulty for conventional manufacturing techniques, like milling and turning. Therefore, the new processing technique development of polycrystalline diamond becomes very important.
This study used fiber laser to research cutting and finishing process of polycrystalline diamond then verified the feasibility of the process. The experiment used reactive fusion cutting mechanism to cut PCD and then finish the cutting surface. This study also investigated the influence of different finishing methods on the cutting surface. In addition, a finishing method with different deflection angles was used to improve the beam shading and taper cutting problem. After finishing, the surface roughness Ra 0.202 μm was obtained and the finished surface quality is significantly better than the surface after cutting. Besides, it could attain similar results when the process was applied to the PCD cutters machined by wire electrical discharge machining(WEDM).
This research also used a method, clamping silicon wafer on the PCD, to solve the problem of cutting edge passivation caused by overcutting, and then studied the effect of the thickness of silicon wafer clamped on the machined surface. The results showed that clamping silicon wafer process would aggravate the surface striation. However, this problem could be improved by decreasing the thickness of the silicon wafer. It is proved that by clamping 100 μm silicon wafer in the finishing process the ideal square cutting edge can be achieved and the surface striation would be eliminated. After the treatment, the surface roughness Ra 0.272 μm was achieved.
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