Abstract: A method for accurately synthesizing a full-aperture data map from a series of overlapped sub-aperture data maps. In addition to conventional alignment uncertainties, a generalized compensation framework corrects a variety of errors, including compensators that are independent in each sub-aperture. Another class of compensators (interlocked) include coefficients that are the same across all the sub-apertures. A constrained least-squares optimization routine maximizes data consistency in sub-aperture overlap regions. The stitching algorithm includes constraints representative of the accuracies of the hardware to ensure that the results are within meaningful bounds. The constraints also enable the computation of estimates of uncertainties in the final results. The method therefore automatically calibrates the system, provides a full-aperture surface map, and an estimate of residual uncertainties.

Abstract: A magnetorheological fluid delivery system includes a mixing and tempering vessel. Fluid is admitted to the vessel via a plurality of tangential ports, creating a mixing of the fluid in the vessel and promoting homogeneity. Fluid may be reconstituted in the vessel by metered addition of carrier fluid. A fixed-speed centrifugal pump disposed in the vessel pressurizes the system. Fluid is pumped through a magnetic-induction flowmeter and a magnetic flow control valve having solenoid windings whereby MR fluid is magnetically stiffened to restrict flow. A closed-loop feedback control system connects the output of the flowmeter to performance of the valve. A nozzle having a slot-shaped bore dispenses MR fluid for re-use in the work zone.

Abstract: A system for dispensing magnetorheological fluid to an MR finishing machine includes a pump for pressurizing the system; a first magnetic valve for regulating MR fluid flow by magnetically varying the structure and apparent viscosity of the fluid through a first flow passage; a similar second magnetic valve magnetically controlling a second flow passage in line with the first valve and flow passage; a pressure sensor disposed between the first and second valves; and an electronic control means. MR fluid flow through the system is controlled to a predetermined flow rate solely by the first valve. When the second valve is deactivated, a reference pressure is determined and saved. When the second valve is activated, a second pressure is determined and saved. From the pressure difference, the solids concentration of the fluid is determined, and a computer algorithm adds a calculated amount of water to the fluid reservoir as needed.

Abstract: A system for dispensing magnetorheological fluid to an MR finishing machine includes a pump for pressurizing the system; a first magnetic valve for regulating MR fluid flow by magnetically varying the structure and apparent viscosity of the fluid through a first flow passage; a similar second magnetic valve magnetically controlling a second flow passage in line with the first valve and flow passage; a pressure sensor disposed between the first and second valves; and an electronic control means. MR fluid flow through the system is controlled to a predetermined flow rate solely by the first valve. When the second valve is deactivated, a reference pressure is determined and saved. When the second valve is activated, a second pressure is determined and saved. From the pressure difference, the solids concentration of the fluid is determined, and a computer algorithm adds a calculated amount of water to the fluid reservoir as needed.

Abstract: An improved method for producing a thin layer having highly uniform thickness, which layer may be pre-coated on an undulating surface of a substrate element. A working layer of the material is formed having a thickness greater than the final thickness desired. An areal (XY) determination of working layer thickness is made by ellipsometry, laser interferometry, or x-ray diffraction, or other known means. A map of thicknesses to be removed from the free surface of the working layer is entered into the control system of a magnetorheological finishing apparatus. The working layer is mounted on a workpiece holder of the apparatus and correctly indexed to the machine. The machine then removes material by magnetorheological finishing as instructed by the control system to leave a residual layer having a very high degree of thickness uniformity at a nominal average thickness and a very high surface integrity.

Abstract: Jet-induced finishing of a substrate surface includes means for covering the surface with an abrasive liquid slurry and means for impinging a jet of fluid, either a gas or a liquid, against the slurry to create a high-shear work zone on the substrate surface whereby portions of the substrate are lifted and removed to alter the shape of the surface towards a predetermined shape and/or smoothness. The surface may be covered as by cascading a flowing layer of slurry over it or by impinging slurry onto the work zone or by immersing the substrate in a pool of the slurry. A nozzle for dispensing the jet fluid is precisely located at a predetermined distance and angle from the surface to be finished. A coarse removal function is provided by disposing the nozzle tip at a first distance from the substrate surface, and a fine removal function is provided by disposing the nozzle closer to the substrate surface.

Abstract: A method for accurately synthesizing a full-aperture data map from a series of overlapped sub-aperture data maps. In addition to conventional alignment uncertainties, a generalized compensation framework corrects a variety of errors, including compensators that are independent in each sub-aperture. Another class of compensators (interlocked) include coefficients that are the same across all the sub-apertures. A constrained least-squares optimization routine maximizes data consistency in sub-aperture overlap regions. The stitching algorithm includes constraints representative of the accuracies of the hardware to ensure that the results are within meaningful bounds. The constraints also enable the computation of estimates of uncertainties in the final results. The method therefore automatically calibrates the system, provides a full-aperture surface map, and an estimate of residual uncertainties.

Abstract: Apparatus and method for abrasive jet of a deeply concave surface using magnetorheological fluid. A ferromagnetic nozzle recessed within a solenoid magnetically shields the fluid within the nozzle and serves as a core for the solenoid, thereby increasing the strength of the magnetic field approximately 100-fold, permitting a significant reduction in the size of the solenoid. The exit orifice of the nozzle is recessed within the solenoid, creating a free space within the solenoid having an intense, shaped, axial magnetic field in and near the nozzle. Stiffening of the magnetorheological fluid begins as the fluid enters the magnetic field upon leaving the nozzle; thus, there is no buildup of viscous drag through the nozzle. Stiffening of the jet occurs principally in free space within the solenoid. The nozzle has peripheral longitudinal channels through which compressed air is conveyed to form an air curtain surrounding the jet, preventing spent MR fluid from re-entering and fouling the nozzle.

Abstract: A magnetic wiper for removing magnetorheological fluid from a carrier surface includes a horseshoe magnet having north and south polepieces elongated in a first direction orthogonal to a second direction of magnetic flux in the magnet. The polepieces are generally parallel at their free ends in the first direction and are preferably arcuate such that the inner polepiece forms a trough for receiving magnetorheological fluid removed from the carrier surface and conveying it to an exit tube. The free ends are shaped to conform closely to the shape of the carrier surface, forming a narrow gap therebetween containing a magnetic fringing field extending beyond the free ends.

Abstract: A fluid having magnetorheological (MR) properties and including a finely-divided abrasive material is directed through a non-ferromagnetic nozzle disposed axially of the helical windings of an electric solenoid. The MR fluid may contain magnetosoft or magnetosolid particles or mixtures thereof. A magnetic field created by the solenoid orients and aligns the magnetic moments of the particles to form fibrils thereby stiffening the flowing MR fluid which, when ejected from the nozzle, defines a highly-collimated jet. Collimation of the MR material persists for a significant time outside the magnetic field, permitting use of the abrasive jet to shape and/or polish the surface of a workpiece at some distance from the nozzle. The jet is directed into a shroud against a workpiece mounted for multiple-axis rotation and displacement to meet predetermined material removal needs for shaping. The solenoid may be similarly mounted to also move the jet over the surface of the workpiece.

Abstract: An improved system for increasing the effectiveness of magnetorheological finishing of a substrate. An inline flowmeter is close-loop linked to the rotational speed of a pressurizing pump to assure that the flow of magnetorheological fluid (MRF) to the work zone is constant. A simplified capillary viscometer is disposed in the fluid delivery system at the exit thereof onto the wheel surface. Output signals from the flowmeter and the viscometer pressure sensor are sent to a computer which calculates the viscosity of MRF being delivered to the work zone and causes replenishment of carrier fluid to the work-concentrated MRF to return the viscosity to aim to assure that a constant concentration of magnetic solids is being provided to the work zone.