Analysis and experimental study on influencing factors to magnetorheological finishing for ultra-precision optical mirror surfaces

This paper proposes a method of planar disc magnetorheological polishing of permanent magnets as a solution to the problem of difficult removal of spiral cutting lines on the surface of NiP coating of aluminum alloy mirrors. This method improves the material removal rate by increasing the contact area between the workpiece and the polishing fluid. This study analyzes the effects of machining gap, abrasive volume fraction, workpiece speed, and polishing disc speed on surface roughness and material removal rate in relation to the polishing mechanism.. Subsequently, the significance of the influencing factors was verified and analyzed using a four-factor, four-level orthogonal experiment. The results demonstrate that the optimal process for this equipment is achieved when the mass fraction of abrasive grains is 2%, the machining gap is 1 mm, the workpiece speed is 300 rpm, and the polishing disc speed is 10 rpm. After 30 min of polishing under the optimal conditions, the surface roughness was reduced from Ra 3.190 nm to Ra 0.293 nm. The spiral cutting pattern was eliminated, with a material removal rate of 51.77 nm/min, and the spatial frequency was realized to improve the full error of the NiP plated surface in the frequency band of 0.0012–12.7 μm −1 .