Qed Technologies, Inc.

Qed Technologies International, Inc.

Other

Cabot Microelectronics Corporation

William Kordonski

Arpad Sekeres

Stephen Hogan

Sergei Gorodkin

Jerry Carapella

Robert O James

Gennadi Gorodkin

Eric Oswald

Andrew S Price

Michael Natkin

Marc Tricard

Keith Beadle

Andy Price

Stehen Hogan

Stephen c/o Qed Technologies Inc Hogan

A magnetorheological fluid for use in magnetorheological ultrasmooth polishing of a substrate surface, comprising an aqueous carrier vehicle; a first amount of magnetic particles having a average diameter between about 1 micrometer and about 2 micrometers; and a second amount of abrasive particles having an average diameter between about &#x3c;1 nanometer and about 15 nanometers. The fluid may further comprise a chemical stabilizer. Preferably the size of the magnetic particles is 2 to 3 orders of magnitude greater than the size of the abrasive particles. Preferably, the magnetic particles are spherical and include carbonyl iron, and preferably, the abrasive particles are selected from the group consisting of aluminum oxide, zirconium oxide, cerium oxide, silica, boron carbide, silicon carbide, natural diamond, synthetic diamond, and combinations thereof.

Magnetorheological fluid for ultrasmooth polishing

A system for magnetorheological finishing of a substrate. A spherical wheel meant for carrying a magnetorheological finishing fluid houses a variable-field permanent magnet system having north and south iron pole pieces separated by primary and secondary gaps with a cylindrical cavity bored through the center. A cylindrical permanent magnet magnetized normal to the cylinder axis is rotatably disposed in the cavity. An actuator allows rotation of the permanent magnet to any angle, which rotation changes the distribution of flux in the magnetic circuit through the pole pieces. Thus, one can control field intensity in the gaps by positioning the permanent magnet at whatever angle provides the required field strength. Because the field also passes above the pole pieces, defining a fringing field outside the wheel surface, the variable field extends through a layer of MR fluid on the wheel, thus varying the stiffness of the MR fluid as may be desired for finishing control.

System for magnetorheological finishing of a substrate

A system for sensing and controlling concentration of magnetic particles in magnetorheological fluid comprising a wire coil and an AC voltage generator that, when energized, creates a magnetic flux field including a fringing field. When the fringing field extends through the magnetorheological fluid, the impedance in the circuit is proportional to the concentration of magnetic particles. A reference wire coil identical to the sensing wire coil is connected therewith. A demodulator is connected to each of the coils sends an impedance difference signal to a feedback controller connected to controllable dispensing apparatus for adding a calculated amount of replenishing fluid to the magnetorheological fluid. The system may be incorporated into an integrated fluid management module having apparatus for receiving and replenishing spent magnetorheological fluid and a sensor system in accordance with the present invention for use in a magnetorheological finishing system having a carrier wheel.

Method and apparatus for measurement and control of magnetic particle concentration in a magnetorheological fluid

A system for magnetorheological finishing of a substrate. An integrated fluid management module (IFMM) provides dynamic control of the rheological fluid properties of the MR fluid on a conventional MR finishing apparatus, and dispensing of the fluid to the wheel. A magnetically shielded chamber charged with MR fluid is in contact with the carrier wheel. A transverse line removes the spent MR fluid from the wheel as the ribbon leaves the work zone. Replenishment fluid is added to the chamber via a dripper, and preferably an electric mixer agitates MR fluid in the chamber. A grooved magnetically-shielded insert at the exit of the chamber forms a polishing ribbon on the carrier wheel as the wheel is turned. A sensor sensitive to concentration of magnetic particles provides a signal for control of MR fluid properties, particularly, water content in the MR fluid. Means is provided for cooling fluid within the chamber.

System for magnetorheological finishing of substrates

A system for determining magnetic permeability of a material. Two electrical inductors formed as primary and secondary concentric coils share a common magnetic core space. A first AC voltage applied to the primary coil creates a magnetic flux in the core proportional to the magnetic permeability of the material. The magnetic flux induces an AC voltage in the secondary coil indicative of the apparent magnetic permeability of the sample. The apparent permeability is corrected for conductivity by imposing a second AC voltage and resistor in series across first and second electrodes disposed in the material. When the material is a magnetorheological fluid, the magnetic permeability is proportional to the concentration of magnetic particles in the sample and can be back-calculated from the amplitude of the secondary voltage signal.

Method and apparatus for measurement of magnetic permeability of a material

A system for determining the magnetic permeability of a material is provided. Two electrical inductors formed as primary and secondary concentric coils share a common magnetic core space. An AC voltage applied to the primary coil creates a magnetic flux in the core proportional to the magnetic permeability of a sample of the material positioned within the core space. The magnetic flux induces an AC voltage in the secondary coil indicative of the sample magnetic permeability. When the material is a magnetorheological fluid, the magnetic permeability is proportional to the concentration of magnetic particles in the sample and can be back-calculated from the amplitude of the secondary voltage signal. Sensitivity and resolution can be increased by using two identical sets of coils wherein a reference material forms a core for the primary set and the MR fluid sample forms a core for the secondary set.

An arcuate, preferably cylindrical, magnetic shunt bar supports a plurality of pin magnets having alternate north and south orientations, defining a ring-shaped array of magnets of alternating orientation. The magnet free ends opposite the shunt bar are positioned to conform closely to the shape of a surface to be sealed, forming a narrow gap therebetween containing a multi-polar magnetic field extending beyond the free ends in a direction substantially orthogonal to the surface. The axes of the magnets may be disposed at any desired angular orientation to the surface. Magnetorheological fluid (MRF) in the gap is magnetically stiffened and held as a dynamic seal. The arrangement is useful as a shaft seal, wherein the seal surface passes axially through the array, and also as a wiper for MRF from a carrier surface wherein the surface passes by the array.

Method and apparatus for forming a dynamic magnetic seal using magnetorheological fluid

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. A planar-diaphragm flush-mounted pressure transducer at the entrance to the nozzle and flowmeter inferentially measure relaxed viscosity and provide signals to a computer for dispensing metered amounts of carrier fluid into the mixing vessel to assure correct composition of the reconstituted fluid as it is dispensed.

Delivery system for magnetorheological fluid

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. The second valve is deactivated, and the measurement cycle is repeated, as may be desired.

Method and apparatus for measuring and controlling solids composition of a magnetorheological fluid

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.

Uniform thin films produced by magnetorheological finishing

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. The invention is generally useful for finishing optical elements, and especially for inexpensive forming of microlenses.

Jet-induced finishing of a substrate surface

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.

Apparatus and method for abrasive jet finishing of deeply concave surfaces using magnetorheological fluid

An improved system for magnetorheological finishing of a substrate comprising a vertically oriented bowl-shaped carrier wheel having a horizontal axis. The carrier wheel is preferably an equatorial section of a sphere, such that the carrier surface is spherical. The wheel includes a radial circular plate connected to rotary drive means and supporting the spherical surface which extends laterally from the plate. An electromagnet having planar north and south pole pieces is disposed within the wheel, within the envelope of the sphere and preferably within the envelope of the spherical section defined by the wheel. The magnets extend over a central wheel angle of about 120&deg; such that magnetorheological fluid is maintained in a partially stiffened state ahead of and beyond the work zone. A magnetic scraper removes the MRF from the wheel as the stiffening is relaxed and returns it to a conventional fluid delivery system for conditioning and re-extrusion onto the wheel. The system is useful in finishing large concave substrates, which must extend beyond the edges of the wheel, as well as for finishing very large substrates in a work zone at the bottom dead center position of the wheel.

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. Magnetorheological fluid conveyed into the gap by the carrier surface is magnetically stiffened to a very stiff paste which is retained in the gap by the fringing field, forming a dynamic liquid seal such that additional magnetorheological fluid carried by the carrier surface is wiped away from the surface and into the trough formed by the inner polepiece. Thus, the magnet forms an effective remover of magnetorheological fluid from the carrier surface without any mechanical contact with the surface.

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Webster, NY, United States of America

William Kordonski