A Study of the Chamfer Grinding on Glass Substrate of a Mobile-Phone with Arc Type by Five-Axis Machining Technique

• Main Authors: Min-Xin Jan, 詹民歆
• Other Authors: Shen-Yung Lin
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/nzuuhf

碩士 === 國立虎尾科技大學 === 機械與機電工程研究所 === 103 === The non-smart phones from early times have developed into flat-surfaced and arc-shaped smart phones nowadays. Arc-shaped phones serve ergonomic in design, so when on the calls, speakers'' cheeks can adjust closely with the phones. The audio quality of arc-shaped phones is much clearer than the flat-surfaced ones. They have flexibility, and have become a hit of new generation smart phones. The touch glass panel left countless micro-crack after its outer-edge profile cutting and a high stress concentration is deduced around there. Hence, this defect should be improved by chamfer grinding technique. But the hardness and brittleness of the glass substrate are too high to easily induce surface crack and edge-indentation while performing the mechanical machining. Also, a lot of difficulties encountered during the machining process due to its natures of high strength and low thermal conductivity. It belongs to a typically difficult-to-cut material. Furthermore, the chamfer of the outer-edge profile with arc-surface is more difficult to process than that of the flat-surface due to its bent surface configuration. In order to comply with the variations of geometrical style of phones and breakthrough the embarrassment in chamfer machining of the related curved-surface products in industry, seeking the development and establishment of the key technique for chamfer has become an important concern that the industry needs to strive. This study used CAD/CAM software to construct the geometrical model of a mobile-phone with arc type. Appropriate cutting-path and machining strategy are designed and planned, and confirmed by a simulation pertaining to cutting-tool moving path. Furthermore, a commercial software for cutting simulation is used to verify the numerical control program generated from the above plan and to check the correctness of the proposed methodology in a virtual reality cutting environment. The contact situations between the wheel and workpiece during the chamfer grinding processes are investigated and these actions whether fulfill a five-axis chamfer machining manipulation requirement are further confirmed. Vacuum chuck fulfilling this arc-surface geometry is designed and fabricated and used to clamp the thin glass substrate on a jig platform. A five-axis machining center associated with grinding wheel is used to perform the experiment for the chamfer grinding of the glass substrate. Full-factorial experiment of process parameter combinations such as wheel profile, grinding velocity, feed rate, chamfer width and working environment was organized for chamfer grinding. Grinding wheels with flat or round profile along the peripheral direction, and a traditional diamond electroplated burs were used as chamfer grinding tools. In addition, the bent-surface glass substrate chamfer experiments were conducted by two kinds of five-axis controller, respectively. Tool maker microscope was used to detect the chamfer surface morphology, edge-indentation and dimension uniformity on the chamfer width zone, and the experimental results are analyzed thoroughly and compared crossly with each other. The chamfer surface edge-indentation is used as an objective function for better process parameter determination, which is subjected to surface damage constraint. It is expectedly that the quality of surface damage and edge-indentation may fulfill the requests for industry. The results show that the controller made in Taiwan may not work properly in pair with a newly developed machine-tool in the laboratory, a small rotation error is deduced accompanied by B-axis, which results in worse dimension uniformity on chamfer width grinding. An undercut phenomenon occurred at the bottom of the arc-surface when the chamfer grinding on the concave surface side of the arc-glass by using a flat profile grinding wheel. An inclination angle of the grinder-axis should be adjusted in machining strategy design to avoid the interference point between the grinding wheel and arc-surface. But the results pertaining to chamfer surface damage has only a little difference by using these two geometrical profile wheel. Smaller chamfer surface damage is obtained under the condition of higher grinding velocity and lower feed rate. Water soluble cutting fluid offers a better cooling and lubrication actions in the primary grinding zone, the edge-indentation is thus reduced as compared with that of blowing air. Smaller surface damage and edge-indentation are obtained from the innovative strategy of chamfer grinding used in this study as compared with that of the traditional diamond electroplated burs due to a higher grinding velocity attained in the former grinding technique.