Gear cutting – milling – or planing – Milling – Process
Reexamination Certificate
2000-09-20
2004-01-13
Howell, Daniel W. (Department: 3722)
Gear cutting, milling, or planing
Milling
Process
C409S080000, C409S084000, C700S172000, C700S191000
Reexamination Certificate
active
06676344
ABSTRACT:
The present invention relates to the machining of workpieces, for instance during manufacture.
Many types of machine tool exist for machining workpieces by various techniques. Many of these techniques, including those of milling machines and the like, require a tool to move relative to a workpiece to create a cut which removes material from the workpiece. Machines such as CNC machines control this movement automatically, executing a sequence of cuts under automatic control. The time taken to complete the machining of a workpiece will naturally depend on the number of cuts required.
The present invention provides a method for machining a workpiece in which a final shape required for the whole or part of the workpiece is identified, an envelope shape is generated, the envelope shape wholly containing the final shape, and a sequence of one or more machining steps is identified to form the workpiece to the envelope shape, wherein identification of each machining step of the sequence takes account of the previous steps, to minimise tool movement during cutting.
Preferably an image is produced to simulate the performance of the steps of the sequence.
The sequence of machining steps is preferably used to create a tool path by which the steps may be executed. The identification of a sequence of machining steps may be dependent upon parameters such as tool size or type, the number of cuts to be used to create the envelope shape, a maximum depth of cut, and the like.
Preferably an image or sequence of images is produced to simulate the toolpath for consideration prior to machining commencing. Preferably the toolpath is encoded as a set of instructions for a machine tool.
Preferably the method is repeatedly applied to a single workpiece, the initial shape for the second and subsequent cycles being an envelope shape produced by the machine sequence of the previous cycle.
Preferably the envelope shape is three dimensional, surrounding all or part of the workpiece. The envelope shape preferably has one or more planar faces and may consist entirely of planar faces, which may be orthogonal.
The envelope shape may be a prism surrounding all or part of the length of the workpiece and having a constant cross section along an axis. The cross section may be polygonal.
The envelope shape is preferably chosen to optimise the fit of the final shape within the envelope shape. Preferably the optimisation includes the location of a planar face of the envelope shape against a planar or generally planar surface of the final shape. The envelope shape may be optimised by selecting the shape having minimum volume or cross sectional area. The optimisation process may be required to create an envelope shape having a specified number of faces.
Preferably the machining steps are cuts which may be straight cuts of an end cutting milling machine. Alternatively, the cut may be produced by a flank milling operation, during which the workpiece may be turned relative to the tool to produce non linear cutting paths across the workpiece.
The invention also provides a method of creating a sequence of machining steps for machining a workpiece, in which a final shape required for the whole or part of the workpiece is identified, an envelope shape is generated, the envelope shape wholly containing the final shape, and a sequence of one or more machining steps is identified to form the workpiece to the envelope shape wherein identification of each machining step of the sequence takes into account of the previous steps, to minimise tool movement during cutting.
Preferably an image is produced to simulate the performance of the sequence steps.
The sequence of machining steps is preferably used to create a tool path by which the steps may be executed. The identification of a sequence of machining steps may be dependent upon parameters such as tool size or type, the number of cuts to be used to create the envelope shape, a maximum depth of cut, and the like.
Preferably an image or sequence of images is produced to simulate the toolpath for consideration prior to machining commencing. Preferably the toolpath is encoded as a set of instructions for a machine tool.
Preferably the method is repeatedly applied to a single workpiece, the initial shape for the second and subsequent cycles being an envelope shape produced by the machine sequence of the previous cycle.
Preferably the envelope shape is three dimensional, surrounding all or part of the workpiece. The envelope shape preferably has one or more planar faces and may consist entirely of planar faces, which may be orthogonal.
The envelope shape may be a prism surrounding all or part of the length of the workpiece and having a constant cross section along an axis. The cross section may be polygonal.
The envelope shape is preferably chosen to optimise the fit of the final shape within the envelope shape. Preferably the optimisation includes the location of a planar face of the envelope shape against a planar or generally planar surface of the final shape. The envelope shape may be optimised by selecting the shape having minimum volume or cross sectional area. The optimisation process may be required to create an envelope shape having a specified number of faces.
Preferably the machining steps are cuts, which may be straight cuts of an end cutting milling machine. Alternatively, the cuts may be produced by a flank milling operation, during which the workpiece may be turned relative to the tool to produce non linear cutting paths across the workpiece.
The invention also provides apparatus for use in machining a workpiece, comprising final shape identification means operable to record a final shape required for the whole or part of the workpiece, envelope shape generating means operable to generate an envelope shape wholly containing the final shape, and sequence generating means operable to identify one or more machine steps to form the workpiece to the envelope shape.
Preferably the envelope shape is three dimensional, surrounding all or part of the workpiece. The envelope shape preferably has one or more planar faces and may consist entirely of planar faces, which may be orthogonal.
The envelope shape may be a prism surrounding all or part of the length of the workpiece and having a constant cross section along an axis. The cross section may be polygonal.
The envelope shape is preferably chosen to optimise the fit of the final shape within the envelope shape. Preferably the optimisation includes the location of a planar face of the envelope shape against a planar or generally planar surface of the final shape. The envelope shape may be optimised by selecting the shape having minimum volume or cross sectional area. The optimisation process may be required to create an envelope shape having a specified number of faces.
Preferably the machining steps are cuts which may be straight cuts of an end cutting milling machine. Alternatively, the cuts may be flank milling operations, during which the workpiece may be turned relative to the tool to produce non linear cutting paths across the workpiece.
Identification of each machining step of the sequence preferably takes account of the previous steps, to minimise tool movement during cutting.
Preferably an image is produced to simulate the performance of the sequence steps.
The sequence of machining steps is preferably used to create a tool path by which the steps may be executed. The identification of a sequence of machining steps may be dependent upon parameters such as tool size or type, the number of cuts to be used to create the envelope shape, a maximum depth of cut, and the like.
Preferably an image or sequence of images is produced to simulate the toolpath for consideration prior to machining commencing. Preferably the toolpath is encoded as a set of instructions for a machine tool.
Preferably the method is repeatedly applied to a single workpiece, the initial shape for the second and subsequent cycles being an envelope shape produced by the machine sequence of the previous cycle.
The invention also provides apparatus for use in cre
Howell Daniel W.
Pillsbury & Winthrop LLP
Rolls Royce plc
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