METHOD FOR MACHINING A WORKPIECE BY MEANS OF A CHIP-REMOVING TOOL ON A NUMERICALLY-CONTROLLED MACHINE TOOL

Abstract

The invention relates to a method for machining a workpiece by means of a chip-removing tool on a numerically-controlled machine tool, in which the tool is moved relative to the workpiece along tool paths that are formed by means of a sequence of supporting points N, wherein the bounding volume that is produced during the rotation of the tool essentially comprises a point contact in a point of contact with the desired surface of the workpiece when machining the workpiece, and that in addition to the data relating to the supporting point N the data relating to the respective point of contact of the bounding volume with the desired surface of the workpiece are determined and that the tool path is optimized on the basis of the data relating to the point of contact.

Claims

1. A method for machining a workpiece using a chip-removing tool on a numerically-controlled machine tool, the method comprising: forming tool paths on the workpiece with a sequence of supporting points spaced from a desired surface of the workpiece to be machined; moving the tool relative to the workpiece along tool paths, wherein a bounding volume that is produced during the rotation of the tool comprises a point of contact with the desired surface of the workpiece to be machined; determining data relating to the point of contact of the bounding volume with the desired surface of the workpiece to be machined; and optimizing the tool path on the basis of the data.

2. The method of claim 1, further comprising correcting data relating to the supporting points along or parallel to a surface normal to the point of contact.

3. The method of claim 1, further comprising: determining further data relating to the desired surface of the workpiece to be machined in the point of contact; and calculating a course of the tool path for the respective supporting point.

4. The method of claim 3, wherein the further data includes one or more of: the curvature of the desired surface of the workpiece and/or of the tool path, and a tangential direction of the desired surface of the workpiece and of the tool path.

5. The method of claim 1, further comprising reading geometric surface data relating to a geometry of the workpiece to be produced from a CAD system by a CNC controller in order to calculate a correction of the supporting points.

6. The method of claim 5, further comprising: adding at least one additional supporting point along the tool path on a connecting line of two supporting points; and subsequently correcting the additional supporting point with reference to the geometric surface data.

7. The method of claim 5, further comprising: adding additional tool paths that are initially predetermined with reference to supporting points of adjacent tool paths; and correcting the supporting points of the additional tool paths using the geometric surface data.

8. The method of claim 1, further comprising correcting the data relating to the supporting points using a CNC controller of the tool machine.

9. The method of claim 1, further comprising calculating the data relating to the supporting points using a CAM system.

10. The method of claim 1, wherein the tool is a spherical tool, a parabolic tool, or a toric tool.

11. The method of claim 5, wherein the geometric surface data relating to the workpiece is in the form of free-form surface data.

12. The method of claim 2, further comprising: determining further data relating to the desired surface of the workpiece to be machined in the point of contact; and calculating a course of the tool path for the respective supporting point.

13. The method of claim 12, wherein the further data includes one or more of the curvature of the desired surface of the workpiece and/or of the tool path, and a tangential direction of the desired surface of the workpiece and of the tool path.

14. The method of claim 13, further comprising reading geometric surface data relating to a geometry of the workpiece to be produced from a CAD system by a CNC controller in order to calculate a correction of the supporting points.

15. The method of claim 14, further comprising: adding at least one additional supporting point along the tool path on a connecting line of two supporting points; and subsequently correcting the additional supporting point with reference to the geometric surface data.

16. The method of claim 15, further comprising correcting the data relating to the supporting points using a CNC controller of the tool machine.

17. The method of claim 16, further comprising calculating the data relating to the supporting points using a CAM system.

18. The method of claim 17, wherein the tool is a spherical tool, a parabolic tool, or a toric tool.

19. The method of claim 18, wherein the geometric surface data relating to the workpiece is in the form of free-form surface data.

20. A method for machining a workpiece using a chip-removing tool on a numerically-controlled machine tool, the method comprising: forming tool paths on the workpiece with a sequence of supporting points spaced from a desired surface of the workpiece to be machined; moving the tool relative to the workpiece along tool paths, wherein a bounding volume that is produced during the rotation of the tool comprises a point of contact with the desired surface of the workpiece to be machined; determining data relating to the point of contact of the bounding volume with the desired surface of the workpiece to be machined; optimizing the tool path on the basis of the data; reading geometric surface data relating to a geometry of the workpiece to be produced from a CAD system by a CNC controller in order to calculate a correction of the supporting points; adding at least one additional supporting point along the tool path on a connecting line of two supporting points; and subsequently correcting the additional supporting point with reference to the geometric surface data.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The invention is described hereinunder with reference to an exemplary embodiment in connection with the drawing. In the drawing:

[0024] FIG. 1 illustrates a schematic view of a workpiece that is to be machined showing tool paths long which a tool is moved,

[0025] FIG. 2 illustrates a schematic view of the allocation of the movement path of the tools to the desired surface of the workpiece with corrections, and

[0026] FIG. 3 illustrates a view, similar to FIG. 2, so as to illustrate adding additional supporting points.

DETAILED DESCRIPTION

[0027] FIG. 1 illustrates the schematic view of a workpiece 1 that is machined using a spherical tool 2. The centre point path of this tool centre point M is described for the machining procedure in the machining program and said tool centre point M, as is illustrated in FIG. 1, ensures that the tool 2 moves in a line-shaped path on the surface of the workpiece 1. In the geometric data relating to the workpiece (the form), the desired surface of the workpiece 1 is contained as free-form surface data. This geometric information can be transmitted in a standard format, for example STEP, to the controller as a file. Moreover, for the machining procedure, a numerically-controlled program is transmitted to the controller and said numerically-controlled program describes the line-shaped tool path of the spherical tool 2 relative to the form by means of a sequence of supporting points.

[0028] FIG. 2 is illustrated as a 2D view of a section of the tool path 3 relative to the desired surface of the workpiece 1 that is to be produced showing the supporting points of the centre point path N−1, N, N+1 and N+2. The spherical tool 2 is referred to as the bounding volume 4 for the supporting point N. It is evident that the supporting point has been calculated as too close to the desired surface of the workpiece 1 that is to be produced and when approaching the supporting point N the tool 2 would have damaged the workpiece 1, in other words would have removed too much material. With the aid of the geometric data relating to the workpiece 1 that is to be produced, it is possible to calculate the shortest distance of the supporting point N to the desired surface of the workpiece 1. The point 6 of the desired surface at which the supporting point N of the tool path 3 comprises the shortest distance is simultaneously the base point for the surface normal 7 that describes the shortest distance between the desired surface 5 of the workpiece and the supporting point N. After calculating the surface normal 7, the surface point N can be displaced along this surface normal 7, in the illustrated case away from the desired surface 5 of the workpiece 1, in such a manner until a tool 2 that is approaching the displaced, new supporting point NK makes contact with the desired surface 5 of the workpiece 1 only in the base point 6 of the surface normal 7. The position of the tool 2 for the displaced, new supporting point NK is illustrated by a dashed line. It is reversed for the supporting point N+1. The supporting point lies too far from the desired surface 5 of the workpiece 1 that is to be produced and must be moved closer to said desired surface 5 by means of the method in accordance with the invention so that the new corrected supporting point N+1k is produced for the tool 2 that is indicated by the dashed line.

[0029] FIG. 3 likewise illustrates a 2D view of the tool path 3 for the supporting points N−1, N, N+1 and N+2. The supporting points N and N+1 are already precisely calculated so that the tool 2 that is approaching these supporting points in each case only makes contact in one point with the desired surface 5 of the workpiece 1. Since the supporting points N and N+1 are relatively far away from one another, the auxiliary points H1 and H2 are added on the connecting line 8 of the tool path 3 between N and N+1. It is clearly evident that owing to the convex desired surface 5 of the workpiece 1, the tool 2 would have been too close to the desired surface 5 of the workpiece 1 at the auxiliary points H1 and H2 and would consequently have damaged said workpiece 1. It is therefore possible with the method in accordance with the invention to correct the position of the auxiliary points H1 and H2 in such a manner that said auxiliary points become precise supporting points in the tool path 3. For this purpose, said supporting points are displaced slightly in the direction of the drawn normal vector. The machining procedure of the workpiece 1 is consequently considerably more precise.

[0030] Various features of the invention are set forth in the following claims.