Utilizing Five-axis Machining Technology to Fabricate Biodegradable Stents

• Main Authors: YAN-CHIAU CHEN, 陳彥喬
• Other Authors: Fu -Yu Chang
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/jg49kp

碩士 === 國立臺灣科技大學 === 機械工程系 === 104 === Biomedical stent is a medical device which is a tube type and can be inserted into a vascular to relieve the narrowing problem. Biodegradable stents have attracted much attention recently because they can be dissolved in human body and therefore a second operation to remove it is not required. The most widely used material for biodegradable stents is PLA (Polylactic Acid) due to its sufficient mechanical strength and biocompatibility. Nowadays, mostly biomedical stents are made by laser cutting process. The sidewalls of stent struts made by laser cutting are vertical and sharp. For medical implanted usage, the stent sharp corners are not preferred since they may cause unexpected damages to human vascular. According to this reason, a five-axis machining method with ball nose cutters was tried to fabricate biodegradable stents for improving the stent strut dimension accuracy and creating round corners on the sidewalls. In this research, an innovative setting method by utilizing the five-axis machine spindle fixture and a UV curable gel was applied to ensure the workpiece, a PLA tube, to be vertical, coaxial and concentric to the milling cutter and the C-axis of five-axis machine. In addition, a meansuring method was performed to investigate the center position errors of A-axis and C-axis, and the measured resullts were used to increase the machining accuracy by adding compensation in our NC program. For preventing broken stent struts when the strut width under 300 micrometers, a staggered cutting procedure and a gel-assisted method were applied to increase the stent strut strength and tube wall adhesion. The experiment confirmed that the proposed milling method can remove acute stent wall corners successfully. The five-axis machining technology for biodegrdable stents has completely been developed, with dimensions of stent diameter 6 mm, thickness 0.3 mm, strut width from 0.6 mm to 0.3 mm, and round corner radius 0.1 ?慆.