Wendt Daniel, Stühle Sebastian, Kawa Emilia, Thielmann Matthias, Kipfmüller Brigitte, Wendt Hermann, Hauck Florian, Vogel Bernd, Fischer Harald, Jakob Heinz
Department of Thoracic and Cardiovascular Surgery, West-German Heart Center Essen, University Hospital Essen, Essen, Germany.
Minim Invasive Ther Allied Technol. 2009;18(1):1-7. doi: 10.1080/13645700802384056.
Machining of shape memory alloys based on Nitinol (NiTi) creates difficulties due to its ductility and severe strain hardening. In this experiment, different cutting edges and grinding parameters were tested to optimize cutting results on NiTi-based blades intended for endovascular heart valve resection. The cutting procedure was performed using two counter-rotating circular NiTi blades of different diameter. A rotating/punching process should be performed. Different shapes (glazed, waved, and saw tooth), different grinding techniques (manual, manual grinder, and precise milling cutter) and additionally various velocities (50 and 200 rpm) were tested on specific test specimens. Cutting forces were measured and cutting quality was examined using digital microscopy. Preliminary tests with rotating blades showed superior results using cutting edges for the punching process (150 N vs. 200 N; n=7). In a second step special test specimens were tested. Maximum cutting-force was 265 N+/-20 N (mean+/-SD; n=7). Subsequently different shapes were tested at 50 and 200 rpm using the rotating/punching method regarding alternate grinding techniques. Cutting forces were 27 N+/-7.7 N for glazed blades (n=7) at 50 rpm and 18 N+/-4.7 N at 200 rpm, waved blades (n=7) required a maximum force of 18 N+/-5 N at 50 rpm and 11 N+/-3.3 N at 200 rpm, whereas saw tooth blades (n=7) needed 17 N+/-12.7 N at 50 rpm and 9 N+/-1.2 N at 200 rpm. Precise cutting quality was only seen when using glazed blades sharpened under accurate conditions with a high-speed milling cutter. Although shape memory alloys based on Nitinol are difficult to process, and well-defined grinding parameters do not exist, acceptable results can be reached using high-speed milling cutters. Best cutting quality can be observed by using glazed blades, performing a rotating/punching process at high velocities. Lower cutting forces can be observed by using other shape-types, however this leads to lower cutting quality. Therefore, further investigations on blade-machining and velocity-testing seem to be necessary to create optimal cutting results.
基于镍钛诺（NiTi）的形状记忆合金因其延展性和严重的应变硬化而在加工时存在困难。在本实验中，测试了不同的切削刃和磨削参数，以优化用于血管内心脏瓣膜切除的镍钛基刀片的切削效果。切削过程使用两个不同直径的反向旋转圆形镍钛刀片进行。应执行旋转/冲压过程。在特定试样上测试了不同形状（光滑的、波浪形的和锯齿形的）、不同磨削技术（手动、手动磨床和精密铣刀）以及不同速度（50和200转/分钟）。测量切削力并使用数字显微镜检查切削质量。旋转刀片的初步测试表明，冲压过程使用切削刃时效果更佳（150牛对200牛；n = 7）。第二步对特殊试样进行测试。最大切削力为265牛±20牛（平均值±标准差；n = 7）。随后，使用旋转/冲压方法，在50和200转/分钟下针对不同的磨削技术测试不同形状。光滑刀片（n = 7）在50转/分钟时切削力为27牛±7.7牛，在200转/分钟时为18牛±4.7牛；波浪形刀片（n = 7）在50转/分钟时最大力为18牛±5牛，在200转/分钟时为11牛±3.3牛；而锯齿形刀片（n = 7）在50转/分钟时需要17牛±12.7牛，在200转/分钟时为9牛±1.2牛。只有在使用高速铣刀在精确条件下磨锐的光滑刀片时才能看到精确的切削质量。尽管基于镍钛诺的形状记忆合金难以加工且不存在明确的磨削参数，但使用高速铣刀可以获得可接受的结果。通过使用光滑刀片、在高速下执行旋转/冲压过程可以观察到最佳切削质量。使用其他形状类型时可以观察到较低的切削力，但这会导致切削质量下降。因此，似乎有必要对刀片加工和速度测试进行进一步研究以获得最佳切削效果。
