大負斜角精微聚晶鑽石球型研削工具開發與微小碳化鎢模仁加工研究
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2012
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本研究旨在開發、設計及製造「大負斜角的BD-PCD球型研削工具」，並應用高剛性桌上型工具機，進行微小碳化鎢模仁的研削創成加工研究。研究之初，以粒徑10-15 µm的BD-PCD片料，利用高週波銀焊技術，將其焊至碳化鎢刀柄上。聚晶鑽石刀具粗胚再以旋轉式線切割放電加工法，成形精微含硼聚晶鑽石球型研削工具。為避免材料移除過程中，研削工具與碳化鎢模仁因高速研削與擠壓，而引發研削刃與模仁的脆性破壞，本研究提出一種「大負後斜角設計」的概念，使球型研削工具刀頂面與工具中心線具-50°的大後斜角。如此設計，可使球型研削工具上的微細鑽石切刃與碳化鎢模仁均承受壓應力，免於脆性破壞。為預防球型研削工具中心點因研削速度為0，而發生的擠壓破壞，研削工具刀頂面設計以跨越工具中心線，以避免靜態擠壓。球型研削工具採線上線切割放電成形，亦即球型研削工具被加工與球型研削工具加工碳化鎢模仁的過程中，研削工具均不拆卸，以便維持其最高同心精度，且可省卻繁複校正時間。而碳化鎢模仁以高速快淺研削技術及浸油對流方式，進行研削創成，實驗結果顯示，無論是微小溝槽或微小陣列式非球面模穴的加工，均可獲致高形狀精度與良好的表面性狀，微溝及非球面模穴的表面粗糙度分別達Ra 112 nm與1.29 µm。顯示本研究開發的精微含硼精微聚晶鑽石球型研削工具，能成功應用於精微非球面碳化鎢模仁的開發製作，其製程所需成本低、環保且加工精度高，未來可應用於照明等級的精微透鏡產業應用。
The primary purpose of the thesis is to develop a micro BD-PCD ball grinding tool with a large negative-back-rake-angle and using the finished tool to generate micro tungsten carbide die array. The BD-PCD substrate with diamond grit of 10-15 µm is first welded onto a WC shank by means of high-frequency silver brazing. Subsequently, the micro BD-PCD ball grinding tool is formed by rotary wire Electrical Discharge Machining (RWEDM). To prevent the occurrence of squeeze failure between the tool and die, the negative-back-rake-angle of the tool is designed up to -50° whereby the diamond grain and WC die can all bear uniform compression stress. In addition, the tool face is schemed with crossing the center line of tool so as to avoid squeeze effect occurs at the center of the free end of the tool due to it being devoid of cutting speed. The developed grinding tool is used to grind WC die using an in-situ HSFSG (High-Speed& Fast-Shallow Grinding) technique. Generating the aspheric micro die array in-situ saves a lot of time and fiddly pre-processing in the development of micro molds. Experimental results demonstrate that the micro aspheric die array with high dimensional and geometrical accuracy can be achieved successfully. The surface roughness of the microgroove and die-cavity is down to Ra 112 nm and 1.29 µm, respectively. The BD-PCD ball grinding tool is evaluated and discussed with regard to thermal machinability, graphitizing of diamond, orientation of spark erosion and wear processes as well as life expectancy. It is expected that the techniques used in the development of micro die array in WC should contribute greatly to the field of precision optoelectronic industry.
The primary purpose of the thesis is to develop a micro BD-PCD ball grinding tool with a large negative-back-rake-angle and using the finished tool to generate micro tungsten carbide die array. The BD-PCD substrate with diamond grit of 10-15 µm is first welded onto a WC shank by means of high-frequency silver brazing. Subsequently, the micro BD-PCD ball grinding tool is formed by rotary wire Electrical Discharge Machining (RWEDM). To prevent the occurrence of squeeze failure between the tool and die, the negative-back-rake-angle of the tool is designed up to -50° whereby the diamond grain and WC die can all bear uniform compression stress. In addition, the tool face is schemed with crossing the center line of tool so as to avoid squeeze effect occurs at the center of the free end of the tool due to it being devoid of cutting speed. The developed grinding tool is used to grind WC die using an in-situ HSFSG (High-Speed& Fast-Shallow Grinding) technique. Generating the aspheric micro die array in-situ saves a lot of time and fiddly pre-processing in the development of micro molds. Experimental results demonstrate that the micro aspheric die array with high dimensional and geometrical accuracy can be achieved successfully. The surface roughness of the microgroove and die-cavity is down to Ra 112 nm and 1.29 µm, respectively. The BD-PCD ball grinding tool is evaluated and discussed with regard to thermal machinability, graphitizing of diamond, orientation of spark erosion and wear processes as well as life expectancy. It is expected that the techniques used in the development of micro die array in WC should contribute greatly to the field of precision optoelectronic industry.
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高剛性桌上型工具機, 精微聚晶鑽石球型研削工具, 碳化鎢模仁陣列, High rigidity tabletop machine tool, micro BD-PCD ball grinding, tungsten carbide die array