Modeling of material removal mechanism on free-form surface in magnetic abrasive finishing process

Knee prosthesis is a common metal implant in the medical field. However, the complex curvature expression of its surface often hinders its further precision machining. Through the simulation software Ansys Maxwell, the influence of curvature on the distribution of magnetic field generator on the free surface was determined. In this work, spherical diamond magnetic abrasives were used as a grinding tool to polish the multi-curvature knee prosthesis. Different morphologies were formed on the surface of titanium alloy prosthesis after polishing. The depth of scratches under different morphologies was studied by 3D digital microscope. The results showed that the different degrees of scratches on surface of titanium alloy knee prosthesis were caused by different curvature of each position. The process parameters such as rotational speed, working gap and magnetic abrasive powders (MAP) size also affected the scratch depth. The polishing mechanism of magnetic abrasive finishing (MAF) on the surface of Ti-6Al-4V alloy knee prosthesis was studied. Based on the experimental data and simulation results, a theoretical model considering the influence of workpiece surface curvature, magnetic pole speed, machining gap and abrasive powders size on the process results of free-form surface material removal based on spherical diamond abrasives was established. Comparing the experimental data with the model results, the prediction model was consistent with the experimental data and can accurately predict the material removal rate of the MAF process. The model can deeply understand the machining mechanism of MAF process on free complex surfaces and the influence of curvature on its material removal rate.