Finish polishing of optics with magnetic media has evolved extensively over the past decade. The newest process is called magnetorheological finishing In MRF, a magnetic field is used to stiffen a magnetorheological (MR) fluid consisting of micron size particles of iron and cerium oxide in water. When a part is brought into contact with a moving ribbon of this stiffened fluid, a polishing spot is created on its surface. The MR fluid polishing "spot" is effectively an abrasive-charged, subaperture lap which automatically conforms to the local shape of the part. Finishing is accomplished by mounting the part on a rotating spindle and sweeping it through the stationary polishing "spot". The process is deterministic. A computer program can be derived to generate both a dwell time schedule for the MRF machine and a prediction of finished surface shape.
