Claims
- 1. A method of polishing an object comprising the steps of:
creating a polishing zone within a magnetorheological fluid; determining the rate of material removal for the object; determining the direction and velocity of movement of the polishing zone relative to the object; determining the number of cycles of polishing required; controlling the consistency of the fluid in the polishing zone; bringing the object into contact with the polishing zone of the fluid; and causing the object and the polishing zone to move with respect to each other.
- 2. The method of claim 1 wherein the step of determining the rate of material removal for the object comprises determining the spatial distribution of material removal.
- 3. The method of claim 1 wherein the step of determining the number of cycles of polishing required comprises:
determining the initial surface roughness of the object; determining the thickness of the subsurface damage layer; determining the thickness of the material layer to be removed during one cycle of polishing; and determining the number of cycles according to the expression 1initial surface roughness+subsurface damage layermaterial layer to be removed.
- 4. The method of claim 1 wherein the movement of the polishing zone relative to the object is continuous.
- 5. The method of claim 4, wherein the step of determining the direction and velocity of movement of the polishing zone relative to the object comprises:
determining the size of a contact section of the object in contact with the polishing zone at any given time; determining the thickness of the material layer to be removed during one cycle of polishing; and determining the velocity of the polishing zone according to the expression 22×contact section×material removal ratematerial layer to be removed.
- 6. The method of claim 1 wherein the movement of the polishing zone relative to the object is in discrete steps.
- 7. The method of claim 6, wherein the step of determining the direction and velocity of movement of the polishing zone relative to the object comprises:
determining the size of a contact section of the object in contact with the polishing zone at any given time; determining the displacement of the polishing zone in a single step; determining the coefficient of overlapping according to the expression 3displacement in a single step2×contact section;determining the thickness of the material layer to be removed during one cycle of polishing; determining the dwell time for each step of polishing according to the expression 4material layer to be removed×coefficient of overlappingmaterial removal rate;anddetermining the number of steps required according to the expression 5radius of the object to be polisheddisplacement in a single step
- 8. The method of claim 1 further comprising displacing the object from its vertical axis to an angle α.
- 9. The method of claim 8 wherein the object is displaced from its vertical axis to an angle α at a continuous velocity.
- 10. The method of claim 9 wherein displacing the object from its vertical axis to an angle α at a continuous velocity further comprises:
determining the angle dimension of the contact spot; determining the thickness of the material layer to be removed during one cycle of polishing; and determining the angular velocity of the displacement of the object to angle α according to the expression 6angle dimension of contact spot×material removal ratematerial layer to be removed.
- 11. The method of claim 8 wherein the object is displaced from its vertical axis to an angle α in discrete steps.
- 12. The method of claim 11 wherein displacing the object from its vertical axis to an angle α in discrete steps further comprises:
determining the angle dimension of the contact spot; determining the thickness of the material layer to be removed during one cycle of polishing; determining the value of the angle displacement of a single step; determining the coefficient of overlapping; and determining the dwell time at each step according to the expression 7material layer to be removed×coefficient of overlappingmaterial removal rate.
- 13. The method of claim 1, wherein the magnetorheological fluid comprises:
a plurality of magnetic particles; a stabilizer; and a carrying fluid.
- 14. The method of claim 13, further comprising the step of controlling the properties of the magnetorheological fluid by replenishing the carrying fluid during polishing.
- 15. The method of claim 1, wherein the magnetorheological fluid is contained within a vessel.
- 16. The method of claim 15, wherein the vessel is moved relative to the object.
- 17. The method of claim 16, wherein the vessel is rotated at a constant velocity.
- 18. The method of claim 15, wherein the polishing zone is not larger than one third of the surface area of the object.
- 19. The method of claim 15, wherein the step of creating a polishing zone within a magnetorheological fluid comprises:
inducing a magnetic field in the vicinity of the magnetorheological fluid; and controlling the direction and intensity of the magnetic field.
- 20. The method of claim 15, wherein the step of creating a polishing zone within a magnetorheological fluid comprises:
subjecting the magnetorheological fluid to a nonuniform magnetic field, having magnetic field lines of equal-intensity which are perpendicular to the gradient of said field, in a region adjacent to the object.
- 21. The method of claim 20, wherein the gradient of the magnetic field is directed toward the bottom of the vessel, perpendicular to the surface of the object.
- 22. The method of claim 19, wherein the magnetic field is created by a means for inducing a magnetic field which is located outside of the vessel.
- 23. The method of claim 15, further comprising the step of determining the clearance between the bottom of the object and the interior surface of the vessel.
- 24. The method of claim 19, further comprising controlling the polishing of the object by controlling the magnetic field intensity and the location of the polishing zone relative to the surface of the object.
- 25. The method of claim 24, wherein the polishing is controlled by a programmable control unit.
- 26. A device for polishing an object comprising:
a magnet selected from the group consisting of electromagnets and permanent magnets; a magnetorheological fluid held in the vicinity of a magnetic field generated by the magnet; and a means for causing relative movement between the object to be polished and the magnet.
- 27. The polishing device of claim 26, wherein a polishing zone is formed within the magnetorheological fluid.
- 28. The polishing device of claim 27, further comprising a programmable control unit for controlling the polishing of an object.
- 29. The polishing device of claim 28, wherein the programmable control unit comprises:
an input device for receiving a measure of the magnetic field intensity, a material removal rate, a set of initial parameters of the object, and a set of desired parameters of the finished object; a processing unit for calculating the direction and velocity of movement of the polishing zone relative to the object and the number of cycles of polishing required; and a signal generator for generating signals representative of the magnetic field intensity and the relative direction and velocity at which the polishing zone and the object are to move.
- 30. The polishing device of claim 26, further comprising a means for continuously stirring the magnetorheological fluid during polishing.
- 31. The polishing device of claim 26, further comprising a vessel having an interior cavity in which the magnetorheological fluid is contained, and a nap material on the interior cavity of the vessel.
- 32. The polishing device of claim 26, further comprising a vessel having an interior cavity in which the magnetorheological fluid is contained, wherein the radius of curvature of the interior cavity of the vessel is larger than the largest radius of curvature of the object.
- 33. A magnetorheological fluid composition comprising a plurality of ferromagnetic particles coated with a polymer which inhibits their oxidation, a stabilizer, and a carrying fluid selected from the group consisting of water and glycerin in proportions sufficient to provide substantially no agglomeration or sedimentation of said magnetic particles.
- 34. The magnetorheological fluid composition of claim 34, wherein the ferromagnetic particles are coated with teflon.
Parent Case Info
[0001] This application is a continuation-in-part of pending U.S. Ser. No. 966,919, filed Oct. 27, 1992, which is a continuation-in-part of pending U.S. Ser. No. 930,116, filed Aug. 14, 1992, which is a continuation-in-part of pending U.S. Ser. No. 868,466, filed Apr. 14, 1992, and this application is a continuation-in-part of pending Ser. No. 966,929, filed Oct. 27, 1992, which is a continuation-in-part of pending U.S. Ser. No. 868,466, filed Apr. 14, 1992.
Divisions (1)
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08525453 |
Sep 1995 |
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08676598 |
Jul 1996 |
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Continuations (2)
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Continuation in Parts (3)
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07930116 |
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