Development of micro BD-PCD ball grinding tool with a large negative-back-rake-angle and research of micro tungsten carbide die machining

• Main Authors: Wei-Ren Huang, 黃暐仁
• Other Authors: Shun-Tong Chen
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/64002668243556197908

碩士 === 國立臺灣師範大學 === 機電科技研究所 === 100 === 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.