Study of the Machining Characteristics of Polycrystalline Diamond by Wire-EDM

• Main Authors: Tzu-Ling Chen, 陳姿伶
• Other Authors: Yunn-Shiuan Liao
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/20730667998606569151

碩士 === 國立臺灣大學 === 機械工程學研究所 === 96 === PCD (polycrystalline diamond) is an intergrown mass of randomly orientated diamond particles in a metal matrix. PCD is usually used as cutting tool due to its extremely high hardness and abrasion resistance. One of its new applications is the diamond conditioner for polishing pad in CMP process. The PCD array of pyramid shapes called ADD TM by traditional machining processes is not an easy task due to its extremely high hardness and abrasion resistance. EDM process is considered one of the potential candidates to machine PCD because of the conductive element of Cobalt (Co) contained in PCD. In this paper, wire EDM process is chosen and its machining characteristics are discussed. The material properties of PCD are different from the general metallic materials owing to its multi-materials compound. In order to understand the machining characteristics of PCD by wire-EDM three parts of experiment are conducted. (1) By changing the parameters during the wire-EDM process, the tendency of machining efficiency in cutting PCD is found to be similar to that of cutting general metallic materials. But its value is lower and the suitable parameters are fewer. The defects on the upper surface of PCD increase under a larger ignition on time condition, and decrease with PCD side placing downward and under a higher water flow rate condition. In addition, after the wire-EDM process, the gap between PCD and WC becomes noticeable. (2) Using Molybdenum (Mo) wire and Tungsten (W) wire as the electrodes of wire-EDM to cut PCD, the efficiency is low because of the inferior electric conductivity and the inherent lubricant on the electrodes. The quality on the upper surface of PCD is poor after wire-EDM machining. (3) Using brass wire as the electrode, cutting a new kind of PCD which not only has a good EDM ability but also a good abrasion resistance developed by Element Six with wire-EDM process is studied. The tendency of machining efficiency approximates to that of cutting other kinds of PCD. But the quality on its upper surface is satisfactorily good and the gap between PCD and WC is also smaller.