| Summary: | 碩士 === 國立中興大學 === 機械工程學系所 === 98 === The purpose of this research is to develop an automation process on a single machine for machining a medical implant－Dynamic Lag Screw. Dynamic Lag Screw is an important component of Dynamic Hip Screw System.
In this research, the discontinuous complicated procedures, machining operations for deep hole, internal thread, polygon shank, and asymmetric thread…etc., are simplified and integrated as an automatic machining procedure on a single machine. Such process decreases machining time, reduces expenses of machines and fixtures, and improve resulting precision. With such a process, the requirements for production of small orders with a variety of specifications can be met.
In this research, a new machining method for machining the polygonal shank, two-side synchronous turning, is developed. Two power driven tools are installed on two sides of the workpiece. The tool for machining cylindrical faces is on one side and that for machining planar faces is on the opposite side. This procedure can produce the planar faces as well as the cylindrical faces simultaneously, such that the making of the polygonal shank can be completed in a single operation.
In two-side synchronous turning, the tool for machining cylindrical faces, a disk equipped with a number of cutting teeth, rotates with a speed ratio of non-integer number with respect to the workpiece for circular cutting. The cutting can produce a polygon with huge number of edges to form a near circular curve. The result is almost the same as it was machined by turning. The locus of the tool tip for the above method can be simulated and analyzed. The number of edges and the error between the near circle and the required circle can be calculated by setting parameter values for rotation ratio and tool tooth number. With considerations of machine performances and material properties, the optimized parameter settings can be obtained.
In implementation, difficult-to-machine materials for medical implants such as titanium alloys Ti-6Al-4V and stainless steel 316L are used in the experiments. With the machining method developed in this thesis, the experiments have been carried out on the Swiss type automatic machine
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