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Rochester New York Section
of the
American Society of Mechanical Engineers 

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QED Technologies

PLANT TOUR By Don Golini President Thursday, December 14th, 2000

Magnetorheological finishing (MRF) is an innovative and powerful new polishing technology for fine figuring of high precision glass optics. In MRF, a workpiece is installed at some fixed distance from a moving spherical wheel, so that the workpiece surface and the wheel surface form a converging gap. An electromagnet, placed below the moving wheel, generates a non-uniform magnetic field gradient in the vicinity of the gap, normal to the wheel. Magnetorheological polishing fluid is delivered to the wheel just above the electromagnet pole pieces. The MR fluid is pressed against the wheel surface by the magnetic field gradient, acquires the wheel velocity, develops high stresses, and becomes a subaperture polishing tool.
    A fundamental advantage of MRF is that the polishing removal rate correlates with the viscosity of the magnetorheological fluid, therefore, the polishing tool never gets "dull". MRF has the additional unique attribute that it is truly a polishing technique, i.e. it improves microstructure. Very high precision optical surfaces, with figure accuracy exceeding 30nm p-v and surface roughness under 10 Angstroms rms, have been produced.
    MRF will be described in detail, along with a technical description of how the process works. Polishing examples will include flats, spheres.