Experimental study on the polishing of aspheric surfaces on an S-136 mould steel using magnetic compound fluid slurries

S-136 (STAVAX ESR) as a mould material has been extensively used in the optical lens manufacturing industry. In this study, the aspheric surface made of S-136 fixed by a six-degree of freedom (DOF) manipulator was polished using magnetic compound fluid (MCF) slurry. The effects of experimental parameters included rotational speed of workpiece and MCF slurry composition on surface roughness Ra and shape retention were investigated. The results demonstrated that the cutting marks on the initial surface reduced obviously under the given experimental parameters. Therefore, the smoothest surface with Ra 20 nm was obtained with MCF3 containing micro-sized Fe3O4 particles with lower saturation magnetisation at nw = 1,000 rpm. The material removes uniformly during the polishing process and the Pearson correlation coefficient (Pcc) of the aspheric surface was kept above 0.994. The MCF slurry polishing was demonstrated as a potential method to smooth the S-136 aspheric surface.