Design and fabrication of a novel magnetorheological finishing process for small concave surfaces using small ball-end permanent-magnet polishing head

摘要

In order to overcome the defects of conventional magnetorheological finishing (MRF) processes that are unable to finish small curvature radius concave surfaces of diameter within 10 mm, a novel precision MRF process using small ball-end permanent-magnet polishing head with a diameter of 4 mm is proposed in this paper. And experimental setup of a four-axis linkage MRF machine tool is fabricated. Magnetostatic simulation of the distribution of magnetic flux density indicates that the magnetic field uniformity of produced polishing head is 93.3 %. Magnetizing force analysis is done to analyze the formation of magnetorheological fluid in finishing region. In addition, the suitable range of C-axis angular position for finishing is generated to be 60A degrees similar to 70A degrees. Finishing experiments on both nonmetallic and metallic specimens with different surface shapes have been conducted. The ability of the developed method of finishing process to improve surface characteristics of a workpiece is demonstrated to reach the surface roughness of finished surfaces below Ra 6 nm. It confirms that the present MRF process is capable of improving surface quality and performing the nanofinishing on small curvature radius concave surfaces.