Resumo:
The large elderly population has naturally led to an increase in the number of orthopedic surgeries, such as knee and hip replacements. In developing countries, the growing demand for this type of surgery is already a reality, highlighting the need to develop machining manufacturing technologies that meet the quality requirements of the prosthesis. ABNT 316L austenitic stainless steel is used in the manufacture of joint prostheses and, although it is considered a material with low machinability, it is an economical alternative to the application of other biomaterials such as titanium alloys and ceramics. In this context, this work presents the optimization of the turning of femoral heads for a total hip prosthesis, comparing two different tool geometries: round and rhombic ISO format. To this end, it has used the response surface methodology and the design of robust parameters to model and optimize the main process responses: roughness and sphericity. The experiments were carried out based on a combined array considering three control variables and two noise variables. The control variables studied were: cutting speed, feed rate and depth of cut; and the noise variables considered were: fixed length of the workpiece and cutting fluid flow. As quality characteristics, the surface finish and the sphericity of the femoral heads were analyzed using the mean roughness and total circularity deviation, respectively. Robust optimization was performed by combining two methods: mean square error and normal boundary intersection. Therefore, the formulation of the optimization problem was to minimize the roughness in the turning process of ABNT 316L stainless steel, limiting the sphericity to 10 μm. The results showed that the rhombic tool is preferable when it is desired to simultaneously obtain components with the best surface quality and the least shape deviation.
