Fabrication of precision meso-scale diameter ZrO2 ceramic bars using new magnetic pole designs in ultra-precision magnetic abrasive finishing

Ultra-Precision Magnetic Abrasive Finishing (UPMAF) is a technique for enhancing the surface quality of products, such as medical devices. In the UPMAF process, magnetic poles connect magnets and magnetic abrasive particles to form magnetic abrasive brushes for controlling the surface finishing process. Different edge shapes of the magnetic pole achieve different surface finish results. In this study, three magnetic pole designs, with a sharp edge, a square edge, and a round edge, were studied regarding their resulting surface quality and roundness precision for meso-scale diameter ZrO2 bars. Experiments were conducted to quantify critical input parameters, including magnetic pole shape, diamond particle grain size, and magnetic pole vibration frequency at an ultra-high rotational speed of 35000 rpm. An FEM model for magnetic field is used to evaluate the magnetic flux density results of the different magnetic pole shapes. The results show that stock ZrO2 bars with an Ra surface roughness of 0.18 mu m and a roundness error of 3.5 mu m can be improved to 0.02 mu m and 0.2 mu m, respectively, with the following process parameters: magnetic poles with 2-mm square edges, 1-mu m diamond abrasive particles, magnetic pole vibration frequency of 8 Hz, and a workpiece rotational speed of 35000 rpm for 40 s of finishing time.