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  Device and method for surface machining a workpieceUSPTO Application #: 20060234606Title: Device and method for surface machining a workpiece Abstract: The invention relates to an apparatus and a method for surface machining. The apparatus for surface machining a workpiece, i.e., for abrasive flow machining, has at least two opposite pressure devices, such that the workpiece to be machined is arranged between the opposite pressure devices and an abrasive can be moved past the workpiece to be machined. According to the invention, the opposite pressure devices can be pressurized with a defined pressure to establish a uniform pressure in the entire abrasive on every side of the workpiece to be machined. The movement of the abrasive relative to the workpiece to be machined is adjustable by a movement of the pressure devices in the same direction while maintaining the uniform pressure. (end of abstract) Agent: Crowell & Moring LLP Intellectual Property Group - Washington, DC, US Inventor: Goetz Lebkuechner USPTO Applicaton #: 20060234606 - Class: 451036000 (USPTO) Related Patent Categories: Abrading, Abrading Process, Utilizing Fluent Abradant The Patent Description & Claims data below is from USPTO Patent Application 20060234606. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application claims the priority of International Application No. PCT/DE2004/000106, filed Jan. 24, 2004, and German Patent Document No. 103 09 456.3, filed Mar. 5, 2003, the disclosures of which are expressly incorporated by reference herein. BACKGROUND AND SUMMARY OF THE INVENTION [0002] The present invention relates to an apparatus for surface machining a workpiece. The invention further relates to a method for surface machining a workpiece. [0003] In the surface treatment of workpieces a distinction is drawn between chip removal processes and nontraditional material removal processes. Chip removal processes use the mechanical action of cutters on the workpiece and thereby cause material to be removed from the workpiece surface being machined. Nontraditional material removal processes use chemical or thermal processes for the surface treatment. [0004] The chip removal processes include so-called lapping. The cutter used in lapping is an abrasive that consists of abrasive grains and a carrier medium. In lapping, the surface of the workpiece to be machined is treated by means of the abrasive grains loosely distributed in the carrier medium, such that the abrasive grains are guided in random cutting paths relative to the workpiece to be machined. [0005] A special form of lapping is abrasive flow machining or AFM. In abrasive flow machining the workpiece to be machined is usually clamped between two opposite, vertically disposed pressure pistons or pressure cylinders. The abrasive is pushed back and forth between the two pressure pistons or pressure cylinders by lifting and lowering the pressure pistons and is thereby guided past the workpiece surface to be machined. The removal of material from the surface being machined is determined by various process parameters, such as the pressure of the abrasive, temperature of the abrasive and viscosity or flow behavior of the abrasive. The greatest removal of material occurs in the region with the highest flow resistance. The present invention relates to abrasive flow machining. [0006] The prior art methods for surface machining a workpiece relating to abrasive flow machining has the drawback that the work results that can be achieved are inconsistent. This is due, in particular, to the large number and inconsistency of the process parameters responsible for the removal of material. Particularly if the workpiece to be machined has curved surfaces, there are substantial differences in the removal of material along the surfaces being machined, depending on whether the surface is facing toward or away from the flow direction or moving direction of the abrasive. Further irregularities in the removal of material according to the prior art result because the abrasive becomes hot with increasing machining time and the viscosity or flow rate of the abrasive changes as a result. [0007] Based thereon, it is an object of the present invention to provide a novel apparatus for surface machining a workpiece and a corresponding method. [0008] The apparatus has at least two opposite pressure devices, such that the workpiece to be machined is arranged between the opposite pressure devices and an abrasive can be moved past the workpiece to be machined. According to the invention, the opposite pressure devices are pressurized with a defined pressure, such that a uniform pressure is established in the entire abrasive on every side of the workpiece to be machined. The movement of the abrasive relative to the workpiece to be machined can be adjusted by a movement of the opposite pressure devices in the same direction while maintaining the uniform pressure in the abrasive. The uniform pressure on all sides of the workpiece to be machined causes a uniform removal of material on all sides of the workpiece. The machining of the surface is thereby improved. [0009] According to an advantageous further refinement of the invention, the apparatus has two opposite pressure devices, between which the workpiece is clamped by means of a mechanism. The first, upper pressure device is mounted to a first horizontally extending cross member and another, lower pressure device to a second horizontally extending cross member. The two cross members are interconnected. The two pressure devices can be displaced relative to the mechanism by a vertical movement of the two cross members. This vertical movement of the two cross members can be used to adjust the movement of the abrasive relative to the workpiece to be machined. [0010] Preferably, the or each cross member is a controllable drive unit for ensuring a uniform flow rate of the abrasive relative to the workpiece to be machined. By maintaining a constant flow rate of the abrasive, it is possible to improve the surface machining result. [0011] According to another advantageous further refinement of the invention, a controllable cooling and/or heating device for the abrasive is provided to ensure a uniform temperature of the abrasive. By maintaining a constant temperature of the abrasive, the surface machining result can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS [0012] Exemplary embodiments of the invention, which shall not be construed as a limitation thereof, will now be described with reference to the drawings, in which: [0013] FIG. 1: is a highly schematic representation of an apparatus for surface machining a workpiece according to the prior art, [0014] FIG. 2: is a highly schematic representation of the apparatus for surface machining a workpiece according to the invention, and [0015] FIG. 3: is an enlarged detail of the arrangement shown in FIG. 2 with additional guide elements. DETAILED DESCRIPTION OF THE DRAWINGS [0016] FIG. 1 shows a highly schematic representation of the apparatus 10 for abrasive flow machining according to the prior art. In the prior art apparatus 10, two pressure cylinders 11, 12 are disposed vertically one above the other. A workpiece 13 to be machined is clamped between these two pressure cylinders 11, 12. In the arrangement depicted in FIG. 1, the workpiece 13 has a borehole, the inner surface of which is to be machined. To this end, an abrasive 14 is pushed back and forth between the pressure cylinders 11, 12, which are arranged vertically one above the other. The movement of the abrasive 14 is effected by the pressure pistons 15, 16 associated with the pressure cylinders 11, 12. [0017] FIG. 2 shows an apparatus 17 for abrasive flow machining according to the invention. The inventive apparatus 17 has two opposite pressure devices 18, 19, i.e., a first upper pressure device 18 and a second lower pressure device 19. The two pressure devices 18, 19 are designed as cylinder-piston systems. [0018] A workpiece to be machined 21 is positioned and clamped between the two pressure devices 18, 19 by means of a mechanism 20. In the exemplary embodiment shown in FIG. 2, the workpiece 21 is a gas turbine assembly. FIG. 2 shows three blades 22 of this gas turbine assembly. [0019] According to FIG. 2, the first upper pressure device 18 is connected to a first horizontally extending cross member 23. The second lower pressure device 19 is connected to a second, likewise horizontally extending cross member 24. The two horizontally extending cross members 23, 24 are interconnected at opposite ends by vertically extending supports 25, 26. The two pressure devices 18, 19 can be pressurized with a defined pressure, such that a uniform pressure is established in the entire abrasive and thus on every side of the workpiece to be machined 21 or the blades to be machined 22. By moving the entire unit which consists of the cross members 23 and 24, the supports 25 an 26 and the pressure devices 18 and 19 connected to the cross members 23, 24 relative to the mechanism 20, the movement of the abrasive 27 in relation to the workpiece to be machined 21, or the blades to be machined 22, can be adjusted while maintaining the uniform pressure of the abrasive. This makes it possible to achieve a uniform removal of material along the surfaces of the workpiece 21, even if the surfaces of the workpiece to be machined 21 are curved. [0020] The cross members 23, 24 and the supports 25, 26 are associated with a controllable drive unit. The drive unit is used to realize the movement of the unit which consists of the cross members 23 and 24, the supports 25 and 26 and the pressure devices 18 and 19 connected to the cross members 23, 24 relative to the mechanism 20. This controllable drive unit makes it possible to adjust a uniform flow rate of the abrasive 27 relative to the workpiece to be machined 21. [0021] A further characteristic of the invention is that the apparatus 17 has a controllable cooling and/or heating device (not depicted) for the abrasive 27. This cooling and/or heating device for the abrasive 27 is used to adjust a uniform temperature for the abrasive 27. Continue reading... Full patent description for Device and method for surface machining a workpiece Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Device and method for surface machining a workpiece patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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