| Summary: | 碩士 === 國立虎尾科技大學 === 機械與電腦輔助工程系碩士班在職專班 === 104 === Hardened and brittle material such as quartz glass has gradually become the important materials for light source, electronic, optical communication, laser and aerospace technology industry applications in recent years. In which electro-optical system and semiconductor applications are particularly active. As its demand is increased constantly, various requests on machining qualities of quartz glass are also more stringent. At present, the main machining ways on quartz glass are almost with engraving milling, grinding lapping or polishing and these machining processes are too complicated and too much wasted. Therefore, seeking a breakthrough for shortening the process and saving the cost effectively is an important issue for the machining workers. Because quartz glass have the properties of high hardness, large brittleness, less malleability, low thermal conductivity and hence low machinability, it causes the cutting-tool wear quickly during the machining process. Also, the crack and damage, and edge-indentation are easily generated on the machined surface and around outer edge, respectively. In order to solve the above problems, this project applies the diamond cutting tool to conduct quartz glass machining through a combination of an ultrasonically assisted machining and laser assisted machining under the conditions of high cutting speed, low depth of cut and suitable feed rate. It is expected to handle the material removal process corresponding to different ductile-brittle transition modes properly for quartz glass machining and enhance the processing efficiency, improvement of surface quality and reduction of production cost consequently.
The four stage experiments including without assistance, single and hybrid assisted machining systems on quartz glass milling were constructed in this study in order to verify the assisted effect on cutting performance and to compare the difference, merit and drawback among them. First of all, the milling experiment without assistance was performed to investigate the variations of cutting performance and the results were used for the suitable process parameter planning in the next stage experiments. Next, uniaxial ultrasonically assisted system, combination of laser assisted system and a biaxial ultrasonically assisted system with only one-axis oscillation (x or y direction), and combination of laser assisted system and a biaxial ultrasonically assisted system with simultaneous two-axis oscillations (x and y directions) were subsequently introduced at the second to the fourth stage experiments, respectively. At each stage experiment, the effects of process parameters on the variations of surface roughness, side-edge surface morphology and cutting-tool wear are investigated. It is expected that the machinability of this high brittle material can be promoted resulting in good cutting performance and better cutting-tool wear. Before the use of laser assistance, the laser preheating time related to the workpiece surface fragmentation should be tested in advance for a proper spacing distance setting between laser-spot and cutting-tool. Finally, a biaxial ultrasonically assisted machining system is designed, fabricated and mounted on a machine-tool work-table. At the meantime, a long-term oscillation test including calibration and detailed adjustment is conducted repeatedly until the whole normal manipulation of the system is assured. Thus, a hybrid assisted machining system can be established through the integration of this biaxial ultrasonically assisted system and a laser assisted system. Under these assistances, milling experiments of quartz glass by cutting-tool of extra-fine particle tungsten carbide with coating were conducted. And the full factorial experiments of process parameter combinations such as feed rate, cutting velocity and radial depth of cut were also planned. During the experiments, dynamometer is used to monitor the variation of cutting force. Tool wear, edge-indentation and side-edge surface morphology of the quartz glass will be measured by tool-microscope off-line. Surface roughness measurement through a probe contact type instrument is also performed. The results show that the milling experiment with both laser assisted system and an ultrasonically assisted system with simultaneous two-axis oscillations has the better results than those experiments without, with single assisted and the other hybrid assisted combinations. Because the use of this complete hybrid assisted system, the cutting performance of tool wear and surface roughness are improved significantly.
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