| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 105 === Biomedical stent is a medical device which is a metal tube and can be inserted into a vascular to relieve narrowing problem. Two types of stent can be distinguished, including balloon-dilatation type and self-expandable type. The most common materials are nickel-titanium alloy, called Nitinol, and 316L stainless steel. Both are high biocompatible.
The goal of this paper is to optimize the post laser machining treatment for biomedical stents. The experiment is divided into two main parts, slurry jet grinding (SJG) and electropolishing. Because of unsteadiness in previous slurry jet grinding study, the first part is changing the slurry driving-source from gas flow into a liquid pump to improve stability of fluid. The new slurry jet grinding experiment is based on previous process parameters and further to investigate the influences of grain size. In the past, the structure of the NiTi stent is uneven after electropolishing if the length of stent is long. Uneven structure may be due to the rotating magnetic stirrer in electropolishing tank. For the reason in the second part a self-designed gas stirred system is used in electropolishing tank and test if it can make whole stent uniformly. Several electropolishing parameters were investigated in this work to optimize the electropolishing process, including applied position of gas released, gas inlet pressure, voltage and total removed weight percentage. The results indicate slurry flow machining with middle grain size (82.5m) has better surface roughness and edge rounding effect. In the electropolishing study applied voltage 25V, 40% total removed weight percentage and pressure 16kPa can achieve good finished stent shape and surface quality.
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