Experimentation on MR fluid using a 2-axis wheel tool

This paper is focused on magnetorheological (MR) fluid assistive polishing of optical aspheric components. MR fluid is a functional mixture of non-colloidal magnetic particle of micrometer size suspended in a host fluid, with the special property that its viscosity can be varied by the application of a magnetic field. This paper introduces the basic principles of the methodology and presents experiment results on MR fluids using a 2-axis wheel-shaped tool supporting dual magnetic fields. Mathematical models taking into account the pressure and the tool velocity are derived. The experiments serve to evaluate the effects of process parameters on material removal and performance using a K9 glass parabolic lens of 60 mm diameter as work-piece. It is shown that surface roughness can be reduced from an initial value of 3.8-1.2 nm after 10 min of polishing. The form errors can also be improved from an initial 2.27 mu m rms and 7.89 mu m peak-to-valley to become 0.36 mu m rms and 2.01 mu m peak-to-valley after 60 min of polishing. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.