Method and device for optically measuring a thread

Abstract

A method and a device can be used for optically measuring a thread on an end of a metal pipe by at least one measuring head which is fastened to a manipulator. The measuring head is preferably freely positionable in relation to the metal pipe and has at least one optical measuring path for measuring the thread and at least one position detector. The method includes at least the following method steps: A) providing the metal pipe in a measurement position; B) determining the spatial position of a longitudinal axis of the metal pipe by means of the at least one position detector before and/or while the measuring head is positioned in a measurement position; C) aligning the measuring head parallel to the longitudinal axis of the metal pipe before and/or while the measuring head is positioned in the measurement position; and D) carrying out the optical thread measurement.

Claims

1.-22. (canceled)

23. A method for optically measuring a thread on an end of a metal pipe (3) by a measuring head (10) which is fastened to a manipulator and freely positionable in relation to the metal pipe (3), the measuring head (10) having an optical measuring path (16) for measuring the thread and a position detector, the method comprising: A) providing the metal pipe (3) in a measurement position; B) determining a spatial position of a longitudinal axis (2) of the metal pipe (3) by the position detector before and/or while positioning the measuring head (10) in a measurement position; C) aligning the measuring head (10) parallel to the longitudinal axis (2) of the metal pipe (3) before and/or while positioning the measuring head (10) in the measurement position; and D) optically measuring the thread, wherein determining the spatial position of the longitudinal axis (2) of the metal pipe (3) is carried out during a linear movement of the measuring head (10) along a target course of the longitudinal axis (2) of the metal pipe (3) of the measuring head (10), wherein the position detector is a first line laser (6). wherein determining the spatial position of the longitudinal axis (2) of the metal pipe (3) and/or a fine aligning the measuring head (3) and/or the optical measuring path (16) is carried out using a second line laser (7) on the measuring head, the second line laser (7) being aligned parallel to a target course of the longitudinal axis (2) of the metal pipe.

24. The method according to claim 23, further comprising: fine aligning the measuring head (10) and/or the optical measuring path (16) of the measuring head (10) in the measurement position at a specific and given angle and or in a certain axial position in relation to the longitudinal axis (2) of the metal pipe (3).

25. The method according to claim 23, wherein the first line laser (6) on the measuring head (10) is aligned at a right angle to the target course of the longitudinal axis (2) of the metal pipe (3).

26. The method according to claim 23, further comprising: determining a roundness of the metal pipe during a rotation of the measuring head over a predetermined target course of the longitudinal axis of the metal pipe.

27. The method according to claim 23, further comprising: measuring a deviation of an actual thread depth from a target thread depth over a circumference of the metal pipe (3) by the optical measuring path (16) during a rotation of the measuring head (10) of at least 180? about a target course of the longitudinal axis (2) of the metal pipe (3).

28. The method according to claim 27, further comprising: calculating an angular offset of the actual course of the longitudinal axis of the metal pipe from the target course of the longitudinal axis (2) of the metal pipe (3) from the deviation of the thread depth over the circumference of the metal pipe (3).

29. The method according to claim 23, wherein the measuring head (10) and/or the optical measuring path (16) is adjustable relative to a carrier (11) for fine alignment.

30. The method according to claim 23, wherein the measuring head (10) has a further optical measuring path (16) extending at a distance from the optical measuring path (16), the distance being adjustable in relation to the longitudinal axis (2) of the metal pipe (3), wherein method further comprises: adjusting the distance as a function of a determined and/or calculated diameter of the metal pipe (3).

31. The method according to claim 23, further comprising: manually or automatically adjusting the optical measuring path (16) about an axis perpendicular to a target course of the longitudinal axis (2) of the metal pipe (3) for adapting the measuring head to a specified pitch angle of the thread.

32. The method according to claim 23, further comprising: detecting a possible collision of the measuring head (10); and blocking further movement of the measuring head (10) and/or the manipulator.

33. The method according to claim 23, further comprising: detecting a degree of contamination of the optical measuring path (16); and initiating a cleaning process or a functional interruption of the measuring as a function of the detected degree of contamination.

34. A device for optically measuring a thread on an end of a metal pipe (3), comprising: a measuring head (10) guided on a manipulator and freely positionable in relation to the metal pipe (3), the measuring head (10) having an optical measuring path (16) for measuring the thread and a position detector, wherein the measuring head (10) is mounted so as to be linearly adjustable and/or pivotable about an axis relative to a carrier (11) fastened to the manipulator, and wherein the optical measuring path (16) extends approximately perpendicularly to a linear adjustment path of the measuring head (10), wherein the device further comprises means for adjusting and/or calibrating the measuring head and/or the optical measuring path (16) of the measuring head (10) in a measurement position, wherein the position detector comprises a first line laser (6) that extends approximately at a right angle to the linear adjustment path of the measuring head (10), and a second line laser (7) that extends approximately parallel to the linear adjustment path of the measuring head (10).

35. The device according to claim 34, wherein the manipulator is an industrial robot with an articulated arm (9) having a plurality of degrees of freedom.

36. The device according to claim 34, further comprising a collision detector which blocks the adjustment of the measuring head (10) and/or movement of the manipulator if the measuring head (10) or parts of the measuring head (10) may collide with the metal pipe (3).

37. The device according to claim 34, wherein the measuring head (10) comprises a second optical measuring path (16), wherein the optical measuring path and the second optical measuring path both extend approximately perpendicularly to the linear adjustment path of the measuring head (10).

38. The device according to claim 34, wherein the measuring head (10) has two legs (19) arranged at a distance from one another and adjustable relative to one another, wherein an optical sensor and a light source are arranged in each of the two legs (19).

39. The device according to claim 34, wherein the optical measuring path (16) is pivotable relative to a further optical measuring path (16) transversely to the linear adjustment path of the measuring head (10).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG. 1 is a perspective illustration of the measuring head during thread measurement,

[0043] FIG. 2 is a schematic illustration as a side view with the lasers provided on the measuring head for position detection,

[0044] FIG. 3a is an illustration of the optical measuring principle as a view in the direction of the longitudinal axis of the metal pipe,

[0045] FIG. 3b a side view of the optical measuring principle with an additional light section sensor for measuring undercut thread flanks and

[0046] FIG. 3c a schematic illustration of the measuring principle for the measurement of undercut thread flanks.

DETAILED DESCRIPTION

[0047] A device for optically measuring a thread is shown schematically in FIG. 1. This comprises as a manipulator a robot 8, with a rotatable and pivotable robot arm 9 with preferably five degrees of freedom, at the free end of which a measuring head 10 is arranged. The measuring head 10 comprises a carrier 11 with optical measuring means provided thereon for optical measurement of an external thread 4 provided on a metal pipe 3. The external thread 4 of the metal pipe 3 was previously cut in a machine tool (not shown), for example in the form of a CNC milling machine or a machining center. The metal pipe 3 was then fixed in a defined measurement position, as shown in FIG. 1. The measurement position may be defined, for example, as shown schematically in FIG. 1, by a centrally constricted position roller (diabolo roller) 13 on a roller table 12, wherein the constriction of the position roller 13 determines the position of the metal pipe 3. Alternatively, a lateral stop may be provided to fix the position of the metal pipe 3 to be measured. In the measurement position of the metal pipe 3, the carrier 11 of the measuring head 10 is moved, if necessary after a diameter calibration of the metal pipe 3, into a measurement position, in which the measuring head 10 is aligned relative to the metal pipe.

[0048] The diameter calibration of the measuring head 10 serves to position the measuring means of the measuring head 10 relative to the carrier 11 in such a manner that the metal pipe 3 is positioned between the measuring means, such that the measuring head 10 does not collide with the metal pipe 3 during the pre-alignment. For this purpose, a gauge may be arranged in the measurement station as a reference component, on the basis of which the measuring head 10 may be calibrated before the measurement process is carried out.

[0049] For positioning or pre-alignment, as the case may be, of the measuring head 10, at least one position detector may be provided on the measuring head 10, which position detector determines the spatial position of the longitudinal axis 2 of the metal pipe 3 before and/or while the measuring head 10 is moved into the measurement position shown in FIG. 1. The actual course of the longitudinal axis 2 of the metal pipe 3 may deviate from a target course of the longitudinal axis 2. To detect the actual course of the longitudinal axis 2 of the metal pipe 3, the measuring head 10 comprises a first and a second line laser 6,7 as position detectors, with the aid of which the position of the measuring head 10 relative to the metal pipe 3 fixed in the measurement position may be checked and, if necessary, corrected.

[0050] The arrangement of the first and second line lasers 6, 7 on the measuring head is shown schematically in FIG. 2. The first line laser 6 extends at approximately a 90? angle relative to a target course of the longitudinal axis 2 of the metal pipe 3, or at a 90? angle in relation to a linear adjustment path of the measuring head 10. The second line laser 7 extends approximately parallel to a target course of the longitudinal axis 2 of the metal pipe 3 or parallel to a target course of the longitudinal axis of the second metal pipe 3, as the case may be, or parallel to the linear adjustment path of the measuring head 10. The second line laser 7 is arranged at the level of the target position of the longitudinal axis 2 of the metal pipe 3 on a non-pivotable leg 19 of the measuring head 10.

[0051] The method comprises both a pre-alignment of the measuring head 10 or a positioning of the measuring head 10, as the case may be, in the measurement position shown in FIG. 1 by a corresponding control of the robot arm 3 and a fine alignment of the measuring head 10 in the measurement position by adjusting the measuring head 10 relative to the carrier 11. The fine alignment comprises aligning at least one measuring path 16 in relation to the longitudinal axis 2 of the metal pipe 3 by pivoting the measuring head about a pivot axis 1 extending approximately transversely to the longitudinal axis 2 of the metal pipe.

[0052] As mentioned above, the measuring head 10 is linearly movable relative to the carrier and preferably pivotable about at least one axis. The linear adjustment can be achieved, for example, by means of at least one driven recirculating ball screw or by means of at least one lantern pinion. The adjustment about the pivot axis 1 can be accomplished, for example, by means of an electric rotary drive, which is not shown.

[0053] The measuring means for measuring the external thread 4 are each arranged in legs 19 of the measuring head 10. The legs 19 of the measuring head 10 are linearly adjustable in their distance relative to one another. The legs 19 of the measuring head 10 form a U-shaped enclosure of the metal pipe 3. These may both be formed independently and adjustable relative to one another. With the described exemplary embodiment, it is provided that one leg 19 of the measuring head 10 is arranged in a stationary manner, whereas the other leg 19 of the measuring head 10 is adjustable relative to the opposite leg 19 of the measuring head 10. For the purpose of adjusting the measuring head 10 to different thread pitches, it is provided that the legs 19 of the measuring head 10 may be pivoted relative to one another about an axis transverse to the linear adjustment path of the measuring head 10.

[0054] In each of the legs 19 of the measuring head 10, a camera 14 with telecentric optics and a light source 15 positioned opposite the camera are provided as measuring means, as shown for example in FIG. 3a. The camera 14 and the light source 15 are each arranged opposite one another at a distance from one another, forming a measuring path 16, wherein the measuring path 16 may be formed as a straight measuring path 16. The beam path between the camera 14 and the light source 15 may alternatively be deflected via mirrors.

[0055] The measuring principle is explained below with reference to FIGS. 3a, 3b and 3c. Each measuring path 16 detects a part of the external thread profile on one side of the metal pipe, wherein the projection of a part of the external thread 4, generated by a light source 15, appears by means of telecentric optics on a light-sensitive sensor, for example a CMOS or a CCD sensor, arranged in a camera 14. The use of telecentric lenses on the cameras 14 ensures that the projection detected by the respective sensor can be recorded undistorted and true to scale. The measured data of the external thread 4 detected in this manner are recorded and compared with the target profile of the external thread 4. The two measuring paths 16 may form a single measuring channel.

[0056] With one variant of the measuring head 10, it is provided that it comprises at least one light section sensor 17, which is formed as a laser section sensor and which is aligned with a thread flank 5 of the external thread 4. The measurement of the thread flanks 18 is illustrated in FIG. 3c.

[0057] In a control unit, which is not shown, the measured data of the external thread profile and/or a sealing lip of the external thread 4 is evaluated, and control commands for controlling the machine tool are derived, in particular in the case of a deviation between the target profile and the actual profile documented by the measured data. The respective target profile can, for example, be freely selectable in an operator interface (HMI) from a catalog of different thread types.

[0058] The measuring head 10 and the controller of the machine tool form a preferably closed control loop. Control commands may be, for example, the readjustment of the tool positions, the selection of the tools, the rotation speed and the torque that is thereby applied of the chuck of the machine tool and of the metal pipe 3, the carrying out of a tool change, the change of the cycle time of the machine tool, etc. The control system may be designed as a self-learning control system (AI) and comprise at least one control algorithm for this purpose. The measurement data determined with respect to a pipe are used not only for feedback with the machine tool and for its control, also for quality data assurance and tracking.

LIST OF REFERENCE SIGNS

[0059] 1 Pivot axis of the measuring head [0060] 2 Longitudinal axis of the metal pipe [0061] 3 Metal pipe [0062] 4 External thread [0063] 5 Thread flanks [0064] 6 First line laser [0065] 7 Second line laser [0066] 8 Robot [0067] 9 Robot arm [0068] 10 Measuring head [0069] 11 Carrier [0070] 12 Roller table [0071] 13 Position roller [0072] 14 Camera [0073] 15 Light source [0074] 16 Measuring path [0075] 17 Light section sensor [0076] 18 Gauge [0077] 19 Leg of the measuring head