生醫支架(Biomedical Stent)為一種中空管狀結構的醫療器材，主要目的為支撐血管壁，使阻塞的血管保持暢通，可降解支架使用的材料為PLA(Po -lylactic Acid)，PLA支架在人體中會自行溶化吸收，故不須再進行二次手術將支架取出，並具有足夠的機械強度及生物相容性。
現今的心血管支架，大多是以雷射加工製造而成，使得支架側壁呈現垂直的銳角結構，在醫療上需避免因支架直角而造成血管非預期性的損傷，因此，本研究以微銑削的方式進行可降解支架的製程，利用微小徑球刀將支架結構圓角化，改善支架壁邊銳利的問題。
本研究以五軸加工機銑削生物可降解支架，過程中以主軸固定法將PLA圓管固定在治具上，確保圓管的垂直度與工作座標的對位，並量測不同刀軸下的切深差取得旋轉中心誤差值，配合齊次座標轉換對NC程式進行補償，降低刀具軌跡誤差。加工方面，利用交錯式切削法與水解膠，可增加管壁附著力，預防支架斷裂，使支架線寬從0.6mm降低至0.3mm，經實驗證實以銑削方式確實能將支架銳角去除，成功製作出直徑6mm、厚度0.3 mm、圓角0.1R之生物可降解支架。

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 m.

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