Method and device for monitoring the wear condition of a tool

• US 20020017139A1
• Filed: 05/15/2001
• Published: 02/14/2002
• Est. Priority Date: 05/15/2000
• Status: Active Grant

• Current Assignee: Prometec GmbH (Sandvik AB)
• Original Assignee: Prometec GmbH (Sandvik AB)
• Inventors: Reuber, Martin Josef, Kluft, Werner Wilhelm, Kratz, Heinz-Hubert
• Granted Patent: US 6,732,056 B2
• Time in Patent Office: Days
• US Class Current: 73/593
• CPC Class Codes: B23Q 17/0971 by measuring mechanical vibrations of parts of the machine arrangements for measuring vibrations B23Q17/12
• CPC Class Codes: G05B 19/4065 Monitoring tool breakage, life or condition
• CPC Class Codes: G05B 2219/50325 As function of measured vibrations

Abstract

In a method for monitoring the wear condition of a tool (2) during machining of a metal workpiece (4) by means of a machine tool (1) by detecting measuring signals generated during the machining process with the aid of at least one sensor (6) and by transforming said measuring signals detected by said sensor (6) into wavelet coefficients by means of a wavelet function, wherein the resultant wavelet coefficients are used for calculating wear condition parameters for the tool (2), it is provided that the vibrations, which are generated during the machining process, of a vibration system comprising at least the tool (2) and the metal workpiece (4) are detected by at least one vibration sensor (6).

Claims

1. Method for monitoring the wear condition of a tool (2) during machining of a metal workpiece (4) by means of a machine tool (1) by detecting measuring signals generated during the machining process with the aid of at least one sensor (6) and by transforming said measuring signals detected by said sensor (6) into wavelet coefficients by means of a wavelet function, the resultant wavelet coefficients being used for calculating wear condition parameters for the tool (2),

wherein the vibrations, which are generated during the machining process, of a vibration system comprising at least the tool (2) and the metal workpiece (4) are detected by at least one vibration sensor (6), and in the case of varying cutting, engagement and/or contact conditions between tool (2) and workpiece (4) the wear condition is evaluated on the basis of changes in the wear condition parameter at given measuring locations with comparable cutting, engagement and/or contact conditions on similar or different workpieces (4).

2. Method according to claim 1, wherein the vibration signal is detected in the three-dimensional space in at least on space axis.

3. Method according to claim 1, wherein the vibration signal is detected in the three-dimensional space in all space axes.

4. Method according to claim 3, wherein the three-dimensional vibration signal is individually evaluated in each space axis and results in a direction-oriented vibration signal such that by means of the wavelet function respective wear condition parameters are defined from the respective wavelet coefficients.

5. Method according to claim 3, wherein the three-dimensional vibration signal is individually evaluated in each space axis, and after transformation of the three direction-oriented vibration signals wavelet coefficients forming a wear condition parameter are determined from the respective wavelet coefficients by means of the wavelet function, e. g. by addition, ratio formation, multiplication or vector addition.

6. Method according to claim 3, wherein the three-dimensional vibration signal is individually evaluated in each space axis, and after transformation of the three direction-oriented vibration signals three wear condition parameters are determined from the respective wavelet coefficients by means of the wavelet function, the three wear condition parameters being combined, e. g. by addition, ratio formation or multiplication, to form a single wear condition parameter.

7. Method according to claim 3, wherein the three-dimensional vibration signal is individually evaluated in each space axis, and, prior to transformation, combined by means of the wavelet function to form a resultant vibration signal, e. g. by addition, ratio formation, multiplication or vector addition, and the resultant vibration signal is transformed by means of the wavelet function to determine a wear condition parameter from the wavelet coefficients.

8. Method according to claim 1, wherein the vibration signal is detected on the tool (2), the tool receiving means or the machine components directly or indirectly supporting the tool receiving means.

9. Method according to claim 1, wherein the vibration signal is detected on the workpiece (4), the workpiece receiving means or the machine tool (1) components directly or indirectly supporting the workpiece receiving means.

10. Method according to claim 1, wherein an acceleration sensor, a vibration velocity sensor, a vibration path sensor or, in the higher-frequency range, a solid-borne sound sensor or a sound emission sensor is used as a vibration sensor.

11. Method according to claim 1, wherein the wear condition of a tool (2) is monitored during machining with interrupted cut.

12. Method according to claim 11, wherein the wear condition of a milling tool is monitored.

13. Method according to claim 12, wherein the wear condition monitoring of the milling tool is performed during free-form milling.

15. Method according to claim 1, wherein the given measuring locations with comparable cutting, engagement and/or contact conditions between tool (2) and workpiece (4) are determined from the data contained in the NC production program of the machine tool (1).

16. Method according to claim 1, wherein the given measuring locations with comparable cutting, engagement and/or contact conditions between tool (2) and workpiece (4) are determined as a function of one or a plurality of the following parameters, namely workpiece blank geometry, workpiece finished part geometry, intermediate cut surfaces, machining parameters and tool geometry.

17. Method according to claim 1, wherein, as a function of the wear condition parameters, the wear condition of the tool (2) is indicated in terms of quantity in a two-dimensional or three-dimensional representation of the tool along the cutting edge of the tool.

18. Method according to claim 14, wherein, as a function of the wear condition parameters, the wear condition of the tool (2) is indicated in terms of quantity in a two-dimensional or three-dimensional representation of the tool along the cutting edge of the tool.

20. Device according to claim 19, wherein the tool (2) consists a milling tool.

21. Device according to claim 19, wherein the vibration sensor (6) consists of an acceleration sensor, a vibration velocity sensor, a vibration path sensor or, in the higher-frequency range, a solid-borne sound sensor or a sound-emission sensor.

22. Device according to claim 19, wherein the vibration sensor is arranged on the tool, the tool receiving means or the machine components directly or indirectly supporting the tool receiving means.

23. Device according to claim 19, wherein the vibration sensor is arranged on the workpiece, the workpiece receiving means or the machine tool components directly or indirectly supporting the workpiece receiving means.

24. Device according to claim 19, wherein one vibration sensor is provided for each space axis.

25. Device according to claim 19, wherein the vibration sensor is a three-dimensional sensor generating one vibration signal per space axis.

26. Device according to claim 19, wherein a display unit is provided on which a two-dimensional or three-dimensional representation of the tool can be displayed, and the computer indicates, in terms of quantity and as a function of the wear condition parameters, the wear condition at the the worn locations on the representation of the tool.

28. Device according to claim 27, wherein the tool (2) consists of a milling tool.

29. Device according to claim 27, wherein the vibration sensor (6) consists of an acceleration sensor, a vibration velocity sensor, a vibration path sensor or, in the higher-frequency range, a solid-borne sound sensor or a sound-emission sensor.

30. Device according to claim 27, wherein the vibration sensor is arranged on the tool, the tool receiving means or the machine components directly or indirectly supporting the tool receiving means.

31. Device according to claim 27, wherein the vibration sensor is arranged on the workpiece, the workpiece receiving means or the machine tool components directly or indirectly supporting the workpiece receiving means.

32. Device according to claim 27, wherein one vibration sensor is provided for each space axis.

33. Device according to claim 27, wherein the vibration sensor is a three-dimensional sensor generating one vibration signal per space axis.

34. Device according to claim 27, wherein a display unit is provided on which a two-dimensional or three-dimensional representation of the tool can be displayed, and the computer indicates, in terms of quantity and as a function of the wear condition parameters, the wear condition at the the worn locations on the representation of the tool.

14. Method for monitoring the wear condition of a tool (2) during machining of a metal workpiece (4) by means of a machine tool (1) by detecting measuring signals generated during the machining process with the aid of at least one sensor (6) and by transforming said measuring signals detected by said sensor (6) into wavelet coefficients by means of a wavelet function, the resultant wavelet coefficients being used for calculating wear condition parameters for the tool (2),

wherein the vibrations, which are generated during the machining process, of a vibration system comprising at least the tool (2) and the metal workpiece (4) are detected by at least one vibration sensor (6), and in the case of repeated machining actions on similar workpieces (4) the wear condition of the tool (2) is evaluated on the basis of the change in the wear condition parameter relative to an initial parameter or relative to a given limit parameter at comparable cutting, engagement and/or contact conditions between tool (2) and workpiece (4) on similar or different workpieces (4).

19. Device for monitoring the wear condition of a tool (2) during machining of a metal workpiece (4) by means of a machine tool, the device comprising at least one sensor (6) for detecting measuring signals generated during the machining process, a signal evaluation means performing a wavelet transformation of the measuring signals detected by said sensor (6), and a computer for evaluating the wear condition as a function of the calculated wavelet coefficients,

wherein said sensor (6) is a vibration sensor detecting the vibrations, which are generated during the machining process, of a vibration system comprising at least the tool (2) and the workpiece (4), and the computer evaluates the wear condition of the tool (2) on the basis of the change in the wear condition parameter at given measuring locations with comparable cutting, engagement and/or contact conditions on similar or different workpieces (4).

27. Device for monitoring the wear condition of a tool (2) during machining of a metal workpiece (4) by means of a machine tool (1), the device comprising at least one sensor (6) for detecting measuring signals generated during the machining process, a signal evaluation means performing a wavelet transformation of the measuring signals detected by said sensor (6), and a computer for evaluating the wear condition as a function of the calculated wavelet coefficients,

wherein said sensor (6) is a vibration sensor detecting the vibrations, which are generated during the machining process, of a vibration system comprising at least the tool (2) and the workpiece (4), and the computer evaluates the wear condition of the tool (2) on the basis of the change in the wear condition parameter relative to an initial parameter or relative to a given limit parameter at comparable cutting, engagement and/or contact conditions between tool (2) and workpiece (4) on similar or different workpieces (4).