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  Compensation for a fluid cutting apparatusRelated Patent Categories: Abrading, Machine, Sandblast, Sandblast Nozzle StructureThe Patent Description & Claims data below is from USPTO Patent Application 20070037496. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application is based on and claims the benefit of U.S. provisional patent applications Ser. No. 60/705,684, filed Aug. 4, 2005, and Ser. No. 60/815,032, filed Jun. 20, 2006, the contents of which are hereby incorporated by reference in their entirety. BACKGROUND [0002] The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. [0003] Systems using fluid such as water to cut material precisely are well known. Typically, such systems place the fluid under extreme pressure (e.g. 30,000 psi or higher) and force the fluid through an aperture or orifice so as to be discharged at a high velocity upon the material to be cut through an erosion process. In many applications, an abrasive is also introduced into the fluid stream and discharged with the fluid to improve the efficiency of the cutting action by enhancing the erosion process. [0004] Using a fluid stream to cut material produces cuts with characteristics different than those made with conventional cutters. Both FIGS. 1 and 2 illustrate a fluid stream 10 exiting an orifice 12 of a nozzle 14 to cut a workpiece 16. Typically, more than a hole is desired in the workpiece 16 so the nozzle 14 and hence the fluid stream 10 are moved along a desired path 15 relative to the workpiece 16. In FIG. 1, the nozzle 14 moves in and out of the page, while in FIG. 2 the nozzle 14 moves in the direction indicated by arrow 15. [0005] Referring to FIG. 1, the resulting cut 20 made by the fluid stream 10 has a width on a top surface 22 (facing the nozzle 14) that differs in width from the bottom surface 24 (facing away from the nozzle 14). The resulting taper 28 due to the difference in widths is referred to as the "Kerf angle" 30. Stated another way, the Kerf angle 30 is the angle the cut face 32 is out of parallel from the fluid stream axis (the stream is often not normal to the material surface by design). The taper 28 is a function of material thickness, but also is a function of cutting speed or movement of the nozzle 14. In general, the taper 28 becomes less as cutting speed slows, and then as cutting speed further slows beyond a point, the taper 28 reverses from that illustrated in FIG. 1 becoming narrower toward the surface 22. Compensation for the taper 28 typically includes tilting the nozzle 14 relative to the workpiece 16 about the axis of motion of the nozzle 14. [0006] In addition to the taper 28 present in the cut, a "lag" is present due again to the thickness of the material and movement of the nozzle 14. Referring to FIG. 2, the faster the nozzle 14 moves, the more the fluid stream 10 is deflected by the material of the workpiece 16. As illustrated, a deflection distance 32 is defined as the difference in length between the point where the fluid stream 10 impinges the top surface 22 and where the stream 10 exits the bottom surface 24, whereas a "Kerf lag" can be defined as an angle 34 using a straight line 36 formed between these points. Typically, the Kerf lag 34 does not affect cutting accuracy when cutting a straight line since the exiting portion of the fluid stream 10 follows the impact point. However, on corners, for example, the deflection of the fluid stream 10 can cause cutting errors as it flares to the outside of a corner leaving behind or cutting undesirable deflection tapers. Furthermore, the finish of even straight line cuts is affected by the speed of the nozzle 14. However, unlike the taper 28, the lag 34 may be reduced by slowing the motion of the nozzle 14 across the workpiece 16. Like the taper 28, tilting of the nozzle 14, in this case, about an axis transverse to the direction of motion can also provide some compensation for the lag 34. [0007] Systems have been advanced using compensation for Kerf errors, nevertheless improvements are desired. SUMMARY [0008] This Summary and the Abstract are provided to introduce some concepts in a simplified form that are further described below in the Detailed Description. The Summary and Abstract are not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. In addition, the description herein provided and the claimed subject matter should not be interpreted as being directed to addressing any of the short-comings discussed in the Background. [0009] A system and method for positioning a fluid stream for cutting a double contour workpiece includes a compensation module configured to receive information regarding a contour path in at least five degrees of freedom for cutting the double contour workpiece and a velocity of movement of the fluid stream during cutting and configured to provide as an output a modified contour path of said at least five degrees of freedom based on Kerf compensation errors. A motion controller is adapted to receive the modified contour path of said at least five degrees of freedom and the velocity and is configured to provide control signals. A positioner is configured to receive the control signals and position a fluid stream adjacent the workpiece accordingly. BRIEF DESCRIPTION OF THE DRAWINGS [0010] FIG. 1 is schematic illustration of a taper present in fluid stream cutting of the prior art. [0011] FIG. 2 is schematic illustration of fluid stream lag present in fluid stream cutting of the prior art. [0012] FIG. 3 is a flow diagram illustrating exemplary operation of a fluid stream cutting system. [0013] FIG. 4 is a pictorial representation of a cutting path provided with compensation. [0014] FIGS. 5A, 5B and 5C are pictorial representation of a polynomial based compensation for an exemplary material. [0015] FIG. 6 is an exemplary schematic illustration of a taper present in fluid stream cutting of the present invention. [0016] FIG. 7 is an exemplary schematic illustration of fluid stream lag present in fluid stream cutting of the present invention. DETAILED DESCRIPTION [0017] FIG. 3 is a block/flow diagram illustrating exemplary operation of a fluid stream cutting system 100. Generally, material is cut using a fluid stream cutting apparatus (also commonly referred to as a water jet system although other types of "fluids", which is defined herein as including liquids, plasma, particles, gases or combinations thereof, can be used) 102, which are well known and therefore is shown schematically. Referring to FIGS. 6 and 7, apparatus 102 includes nozzle 14'. At this point it should be noted prime numbers are used to indicated similar concepts above; however, the workpiece to be cut and the cutting process itself is different in that a complex workpiece that can have double contours and/or varying thickness is cut. [0018] In the present embodiment, the cutting nozzle 14' of cutting apparatus 102 is moved relative to the material to be cut or workpiece by a multi-axis positioner (e.g. 5 or 6 axis control) 104. Like the cutting apparatus 102, such positioners are well known and need not be discussed in detail for purposes of understanding the concepts herein described. [0019] Briefly, the typical technique for fluid stream cutting is to mount the workpiece (sometimes also referred to as the "material being cut") in a suitable jig. The fluid stream or fluid-jet is typically directed onto the workpiece to accomplish the desired cutting to produce a target piece having a shape and is generally under computer or robotic control. The cutting power is typically generated by means of a high-pressure pump connected to the cutting head through high-pressure tubing, hose, piping, accumulators, and filters. It is not necessary to keep the workpiece stationary and to manipulate the fluid-jet cutting tool. The workpiece can be manipulated under a stationary cutting jet, or both the fluid-jet and the workpiece can be manipulated to facilitate cutting. As will be described below, specifications of the desired workpiece to be cut are received by system 100 wherein cutting parameters such as but not limited to a cutting velocity or speed of the nozzle, its cutting path including orientation of the nozzle are determined in order to generate the desired workpiece with requisite compensation taking into account characteristics of the cutting process. Continue reading... Full patent description for Compensation for a fluid cutting apparatus Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Compensation for a fluid cutting apparatus 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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