Effects of Longitudinal and Torsional Ultrasonic Vibration on Milling of Hard Mold Steel

• Main Authors: ALEXANDER CHANG-CHENG KO, 高章琛
• Other Authors: Yunn-Shiuan Liao
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/gz79rb

碩士 === 國立臺灣大學 === 機械工程學研究所 === 107 === STAVAX ESR materials with great mechanical properties, and it has been widely used in aerospace in recent years. However, tool easily wears when machining STAVAX ESR. Therefore, machining efficiency and quality decline. The purpose of this research is to investigate the mechanism and influence of ultrasonic vibration on cutting force and surface roughness by using torsional-direction ultrasonic vibration. The mechanism of torsional ultrasonic vibration assisted milling is that the tool removes material intermittently during machining. The mechanism of ultrasonic vibration assisted milling is that ultrasonic vibration changes the cutting trajectory, so the trajectory makes the cutting edge go through the crest along the feed direction. Therefore, the crest was eliminated due to the overlap trajectory. The model of the spindle was built and simulated by Ansys Workbench. Modal analysis were applied to find the modal of the spindle system. After the simulation, vibration displacements were measured by laser displacement sensor and analyzed through Fast Fourier Transform. It proves that there is a relation between frequency and realistic ultrasonic vibration amplitude. This relation proves that the actual equipment matches the computer model. According to the results, torsional ultrasonic vibration assisted end milling decreases surface roughness of STAVAX ESR, and results in a better surface. When the material is removed with longitudinal ultrasonic vibration assisted milling, instead of removing the crest, vertical vibration causes bad surface roughness. Also, feed-direction cutting force in ultrasonic vibration assisted grinding decreases causing smaller tool wear. However, the longitudinal ultrasonic vibration assisted milling increase cutting force and generates more surface crest so that the tool wear is larger than the traditional milling. Besides, cutting chips were shorter.