Measuring machine and method for positioning a workpiece in the measuring machine

Abstract

The invention relates to a measuring machine (10) and a method for positioning a workpiece (11) in the measuring machine (10). For this purpose, a workpiece carrier (13) holding the workpiece (11) is driven about a machine rotation axis (D), and an optical sensor (23), preferably designed as a camera (24) or matrix camera (25), is positioned in a measuring position parallel to the machine rotation axis (D). In this measuring position, measurement data (M), for example images (B), are acquired from the workpiece (11) and provided to a control unit (30). In the control unit (30), an offset (s) and / or an inclination (α) of a workpiece longitudinal axis (L) relative to the machine rotation axis (D) is determined from the measurement data (M) of at least two measurement points on the workpiece (11) and subsequently reduced or eliminated by controlling a position correction arrangement of the measuring machine (10), so that a predetermined positioning condition is met.The position correction arrangement (17) is designed to tilt and / or move the workpiece carrier (13) relative to the machine axis of rotation (D).

Description

[0001] The invention relates to a measuring machine configured to measure a workpiece, in particular a shape and / or contour on a workpiece. The measuring machine is also configured to place the workpiece in a desired or predetermined position in the measuring machine before the measurement is performed. The invention also relates to a method for positioning the workpiece in the measuring machine before the measurement.

[0002] Such a measuring machine and method are known, for example, from EP 3 255 378 A1. There, a profile or tactile section of a workpiece surface is measured along a measuring plane defined in a machine coordinate system using a non-contact or tactile sensor at different rotational positions. This can then be used to determine the inclination and offset of a workpiece's longitudinal axis relative to a machine rotational axis of the measuring machine.

[0003] DE 10 2019 120 553 A1 discloses a device and a method for measuring the roundness of a workpiece. The workpiece can be arranged on a workpiece carrier and initially moved into a desired position. For this purpose, the workpiece is captured using a video camera and displayed to an operator. The display serves to assist the operator in positioning the workpiece on the workpiece carrier. Within this context, the workpiece can also be automatically positioned and aligned on the workpiece carrier based on the video capture. The video camera is part of a system provided separately from the measuring machine.

[0004] An inductive rotary transformer for the wireless transmission of electrical energy is known from DE 10 2015 100 233 A1.

[0005] Based on the prior art, it can be considered the object of the present invention to provide a measuring machine and a method that enables both fast and very precise positioning of the workpiece in the measuring machine.

[0006] This object is achieved by a measuring machine having the features of patent claim 1 and a method having the features of patent claim 16.

[0007] The measuring machine is designed to measure a shape and / or contour on a workpiece. It has a workpiece carrier on which the workpiece can be positioned. For this purpose, the workpiece carrier can have a clamping device, such as a chuck with multiple clamping jaws or a holding mandrel that interacts with a counter-holding mandrel, with the workpiece being held between the holding mandrel and the counter-holding mandrel. The workpiece carrier can also have a surface for setting down or supporting the workpiece on an underside of the workpiece.

[0008] The measuring machine is specifically designed for measuring workpieces that are rotationally symmetrical with respect to a workpiece's longitudinal axis. Depending on the measuring task, it can also measure workpieces that are not rotationally symmetrical with respect to a workpiece's longitudinal axis, for example, workpieces with an external thread or external helical gearing.

[0009] The measuring machine has a rotary drive that can rotate the workpiece carrier around a machine axis, for example, continuously at a constant speed. An optical sensor is assigned to the workpiece carrier. The detection range of the optical sensor is directed toward a work area in which at least a portion of the workpiece is located when it is mounted on the workpiece carrier.

[0010] A sensor positioning device on the measuring machine is designed to move the optical sensor parallel to the machine's rotational axis to a desired measuring position and position it there. Using the sensor positioning device, the optical sensor can be positioned at one or more suitable measuring positions to record measurement data on the workpiece.

[0011] In particular, in each measuring position, only a contour of a longitudinal section of the workpiece is arranged in the detection range of the optical sensor and not the complete workpiece or a complete contour in the direction parallel to the workpiece longitudinal axis.

[0012] The measuring machine also features a position correction device that tilts and / or translates the workpiece carrier relative to the machine's rotational axis. This allows the workpiece's longitudinal axis to be brought into the desired alignment and position relative to the machine's rotational axis.

[0013] The measuring machine has a control unit that controls its operation. To position the workpiece in the measuring machine, the control unit can perform or initiate the following steps:

[0014] The control unit controls the rotary drive so that the workpiece carrier rotates about the machine's axis of rotation. In doing so, a workpiece arranged on the workpiece carrier also rotates about the machine's axis of rotation. Before or at the same time, the optical sensor is moved to a desired measuring position using the sensor positioning device. In this measuring position, measurement data is then recorded on a contour of the workpiece while the workpiece rotates about the machine's axis of rotation and provided by the optical sensor to the control unit. In a single measuring position of the optical sensor, the measurement data is recorded in particular only on a longitudinal contour section of the workpiece, which is only a section or partial area of ​​the entire contour of the workpiece extending parallel to the workpiece's longitudinal axis.

[0015] The control unit is configured to determine, based on the measured data, an offset and / or inclination of a workpiece's longitudinal axis relative to the machine's rotational axis. The determined offset and / or inclination represent a positional deviation of the workpiece's longitudinal axis relative to the machine's rotational axis. The positional deviation is adjusted by means of the position correction arrangement while continuing to rotate the workpiece about the machine's rotational axis such that the offset and / or inclination fulfills a predefined positioning condition.

[0016] It is preferred if the position correction arrangement defines a reference plane that is aligned, for example, at right angles to the machine's rotational axis. The offset is determined in this reference plane. The at least one measuring position of the optical sensor is arranged in a direction parallel to the machine's rotational axis at a distance from the reference plane. The reference plane is preferably a plane that is neutral with respect to the inclination of the workpiece carrier set by the position correction arrangement. In particular, the offset determined in the reference plane can be independent of the inclination of the workpiece carrier or the workpiece's longitudinal axis relative to the machine's rotational axis.

[0017] Using the measuring machine, for example, fast and accurate positioning of the workpiece in the measuring machine can be achieved in a single measuring position of the optical sensor. To increase positioning accuracy, it is also possible to arrange the optical sensor in two measuring positions parallel to the machine's rotational axis and spaced from each other, and to record measurement data in both measuring positions. This allows the offset and / or inclination (i.e., the position deviation) of the workpiece's longitudinal axis relative to the machine's rotational axis to be determined more precisely, and more accurate positioning of the workpiece can be achieved. Regardless of how many measuring positions measurement data are recorded at, the rotary drive can continuously rotate the workpiece carrier or the workpiece mounted on it around the machine's rotational axis, eliminating the need to stop and restart the rotary movement.

[0018] The optical sensor is preferably a camera, in particular a line scan or matrix camera. When using a matrix camera, measurements can be taken at multiple measurement locations on the contour of the workpiece, particularly in a single measurement position of the matrix camera. When using a camera, the measurement data is provided in the form of at least one image of a contour (in particular only a longitudinal section of the contour) of the workpiece, which image is recorded at one or more measurement positions.

[0019] It is advantageous if the measuring machine has a buffer memory that is communicatively connected to the optical sensor and, in particular, the camera. The buffer memory serves to temporarily store measurement data, particularly images, which can then be provided to the control unit. This allows the optical sensor to capture the measurement data regardless of the processing speed of the measurement data or images in the control unit.

[0020] The buffer memory can be part of the control unit or implemented as a separate data memory. In either case, the buffer memory is communicatively connected to the control unit or a computing device within the control unit.

[0021] To check the positioning condition, the control unit can instruct the optical sensor to again record and provide measurement data at the – preferably unchanged – measurement position. The provided measurement data can then be compared with reference data. The reference data can, for example, contain one or more limit values. The comparison result indicates whether the positioning condition is met or not. For example, based on the measurement data, a positional deviation between the workpiece's longitudinal axis and the machine's rotational axis can be detected at one or more measurement locations on the workpiece's contour, and it can be checked whether this positional deviation is smaller than at least a specified limit value.

[0022] As part of checking the positioning condition, in one embodiment, measurement data can be recorded at a single measuring position of the optical sensor. The optical sensor is preferably configured to acquire measurement data at multiple measuring locations along the contour of the workpiece. The measuring locations are arranged, in particular, parallel to the machine's rotational axis and spaced apart from one another along the contour of the workpiece.

[0023] In a further embodiment, the optical sensor is arranged at at least two different measuring positions as part of the positioning condition check, and measurement data is acquired on the contour of the workpiece in each measuring position. This embodiment increases the accuracy of determining the positional deviation between the workpiece's longitudinal axis and the machine's rotational axis, and allows for more precise positioning of the workpiece in the measuring machine. The measuring positions are spaced apart in a direction parallel to the machine's rotational axis. Perpendicular to the machine's rotational axis, the measuring positions are preferably identical. The optical sensor is preferably moved exclusively parallel to the machine's rotational axis between the measuring positions.

[0024] The distance between two measuring positions in the direction parallel to the machine rotation axis is, for example, at least 10% or at least 25% or at least 50% of the length of the workpiece in the direction parallel to the workpiece longitudinal axis.

[0025] It is particularly advantageous if the positioning of the workpiece in the measuring machine takes place in a multi-stage and in particular two-stage process. First, the optical sensor is moved to a first measuring position and measurement data is recorded there on the contour of the workpiece. The control unit is then used to check whether a first positioning condition based on first reference data (e.g. first limit values) is met. If necessary, the position of the workpiece's longitudinal axis is corrected using the position correction arrangement until the first positioning condition is met. For this check, the optical sensor remains in the first measuring position and makes measurement data available for testing. Once the first positioning condition has been met, the optical sensor can be moved to a second measuring position using the sensor positioning device and record measurement data on the contour of the workpiece there.Measurement data from the first and second measurement positions are then available, acquired after the first test condition was met. Based on this measurement data, it is then checked whether a second positioning condition based on second reference data is met. The second reference data underlying the second positioning condition (e.g., second limit values) may differ from the first reference data (e.g., first limit values) and, in particular, may permit a smaller positional deviation of the workpiece's longitudinal axis from the machine's rotational axis than the first positioning condition based on the first reference data.

[0026] In a preferred embodiment, the communication connection between the control unit and the position correction arrangement can be wireless. The position correction arrangement can also receive electrical energy wirelessly, for example, by means of inductive energy transmission.

[0027] Any embodiment of the measuring machine explained above can be used to carry out a method for positioning a workpiece in the measuring machine.

[0028] Advantageous embodiments of the invention will become apparent from the dependent claims, the description, and the drawings. Preferred embodiments of the invention are explained in detail below with reference to the accompanying drawings. The drawings show: Fig. 1 a block diagram of an embodiment of a measuring machine, Fig. 2 a highly schematic representation of essential components of the measuring machine from Fig. 1 in the form of a block diagram to explain their function, Fig. 3 the alignment of a workpiece longitudinal axis of a workpiece parallel to a machine rotation axis of the measuring machine from the Fig. 1 and Fig. 2 by means of a position correction arrangement of the measuring machine and Fig. 4 the translational movement of the workpiece by means of the position correction arrangement of the measuring machine to reduce or eliminate an offset between the workpiece longitudinal axis and the machine rotation axis, Fig. 5 a flowchart of an embodiment of a method according to the invention and Fig. 6a and Fig. 6b a flowchart of a further embodiment of a method according to the invention.

[0029] Fig. 1 shows a block diagram as an embodiment of a measuring machine 10. In the block diagram according to Fig. 2 only parts of the measuring machine 10 are shown which are essential for explaining the functional principle of the measuring machine 10 and a method V1, V2 which can be carried out by means of the measuring machine 10.

[0030] The measuring machine 10 is configured to measure the shape and / or contour of a workpiece 11. It has a machine base 12 on which a workpiece carrier 13 is arranged. In the exemplary embodiment, the workpiece carrier 13 is designed in the form of a table. The workpiece carrier 13 serves to position the workpiece 11 in the measuring machine 10. For this purpose, suitable holding or clamping devices 14 can be arranged on the workpiece carrier 13 or directly or indirectly connected to the workpiece carrier 13. The clamping device 14 can be, for example, a chuck.

[0031] A machine coordinate system Km is defined immovably relative to the machine base 12, which, for example, is a Cartesian coordinate system and has a first coordinate axis xm, a second coordinate axis ym, and a third coordinate axis zm. A position correction coordinate system Kw is defined immovably relative to the workpiece carrier 13 or the workpiece 11 arranged on the workpiece carrier 13, which, for example, is a Cartesian coordinate system and has a first coordinate axis xw, a second coordinate axis yw, and a third coordinate axis zw.

[0032] The workpiece carrier 13 is indirectly connected to the machine base 12 via a position correction arrangement 17. The position correction arrangement 17 is configured to change or adjust the position of the workpiece carrier 13 relative to the machine base 12. For this purpose, the position correction arrangement 17 can incline the workpiece carrier 13 about the first and second coordinate axes xw, yw of the position correction coordinate system Kw. The first and second coordinate axes xw, yw of the position correction coordinate system Kw are aligned at right angles to one another, for example within a plane which, in an ideal arrangement of the workpiece 11 on the workpiece carrier 13, is aligned at right angles to the workpiece longitudinal axis L. The third coordinate axis zw of the position correction coordinate system Kw would in this case extend parallel to the workpiece longitudinal axis L or congruently along the workpiece longitudinal axis L.If the workpiece 11 is not ideally aligned, the third coordinate axis zw of the position correction coordinate system Kw and the workpiece longitudinal axis L are inclined to each other at an acute angle.

[0033] The position correction arrangement 17 has a linear drive arrangement 18, by means of which the workpiece carrier 13 can be moved translationally, for example in the direction of the first coordinate axis xw and the second coordinate axis yw of the position correction coordinate system Kw. For this purpose, the linear drive arrangement 18 has a first linear drive 18x for the translational movement in the direction of the first coordinate axis xw of the position correction coordinate system Kw and a second linear drive 18y for the translational movement of the workpiece carrier 13 in the direction of the second coordinate axis yw of the position correction coordinate system Kw.

[0034] The position correction arrangement 17 also has a tilt drive arrangement 19 for tilting or inclining the workpiece carrier 13 relative to the machine coordinate system Km. In the exemplary embodiment, the tilt drive arrangement has a first tilt drive 19x for a tilting movement about the first coordinate axis xw of the position correction coordinate system Kw and a second tilt drive 19y for a tilting movement about the second coordinate axis yw of the position correction coordinate system Kw. To tilt the workpiece carrier 13, the tilt drives 19x, 19y can, for example, adjust the distance of the workpiece carrier 13 from the machine base 12 differently at different locations, which then results in the inclined position or inclination of the workpiece carrier 13. For this purpose, for example, movable wedge surfaces can be used, on which the workpiece carrier 13 is supported at an assigned location.

[0035] The measuring machine 10 also has a rotary drive 22 configured to rotate the workpiece carrier 13 about a machine rotation axis D. In the exemplary embodiment illustrated here, the machine rotation axis D is aligned parallel to the coordinate axis zm of the machine coordinate system Km. The rotary drive 22 can, for example, be arranged on the machine base 12 and drive the position correction arrangement 17 together with the workpiece carrier 13 in rotation about the machine rotation axis D. When a workpiece 11 is arranged on the workpiece carrier 13, the workpiece 11 is driven together with the workpiece carrier 13 in rotation about the machine rotation axis D.

[0036] To measure measurement data M on the workpiece 11, and in particular on a contour of the workpiece 11, the measuring machine 10 has an optical sensor 23. In the exemplary embodiment, a camera 24, and in particular a matrix camera 25, is used as the optical sensor 23.

[0037] By means of a sensor positioning device 26, the optical sensor 23 can be arranged parallel to the machine rotation axis D in a desired measuring position P, wherein Fig. 2 schematically illustrates a first measuring position P1 and a second measuring position P2. The sensor positioning device 26 can, for example, comprise a carriage 28 movable along a column 27. The column 27 can be arranged on the machine base 12. The optical sensor 23 is connected to the carriage 28 via a suitable holding device.

[0038] In the exemplary embodiment, an illumination device 29 is optionally present in order to emit light in the direction of the working area of ​​the measuring machine 10 or of a workpiece 11 arranged on the workpiece carrier 13. The illumination device 29 is particularly advantageous if a camera 24 (e.g. matrix camera 25) is used as the optical sensor 23. With respect to the workpiece 11 or with respect to the machine rotation axis D, the camera 24 and the illumination device 29 are arranged on opposite sides or opposite one another. The illumination device 29 emits light in the direction of the camera 24. The light can be partially shaded by the workpiece 11 so that the light captured by the camera 24 and emitted by the illumination device 29 can image the contour of at least a section of the workpiece 11. The camera 24 and the illumination device 29 are thus designed as a transmitted-light system.

[0039] The illumination device 29 can be moved together with the camera 24 by means of the sensor positioning device 26. In addition to the translational movement parallel to the machine rotation axis D, the sensor positioning device 26 can also be configured to pivot the optical sensor 23 and, for example, the camera 24 about an axis oriented perpendicular to the machine rotation axis D. This can be advantageous, for example, when measuring helical workpiece contours, such as threads.

[0040] As it is in the Fig. 1 and Fig. As can also be seen schematically in Figure 2, the measuring machine 10 has a control unit 30. The control unit 30 is communicatively connected to the optical sensor 23, the sensor positioning device 26, the rotary drive 22, and the position correction arrangement 17. The communication connections can be wired and / or wireless. In particular, the communication connection to the position correction arrangement 17 can be wireless, since the position correction arrangement 17 is rotatable about the machine rotation axis D together with the workpiece carrier 13.

[0041] In the Fig. In the embodiment illustrated in Figure 1, the control unit 30 is also communicatively connected to the lighting device 29, provided a lighting device 29 is present. Alternatively, this communication connection can be omitted, and the optical sensor 23 can be communicatively connected to the lighting device 29 for controlling it.

[0042] The control unit 30 has a computing device 31, for example a microcontroller. In a preferred embodiment, the control unit 30 is communicatively connected to a buffer memory 32 ( Fig. 2). In particular, there is a communication connection between the computing device 31 and the buffer memory 32. In the Fig. In the embodiment shown in Figure 2, the buffer memory 32 is part of the control unit 30. Alternatively, the buffer memory 32 can also be designed as a data memory separate from the control unit 30.

[0043] The optical sensor 23 can acquire measurement data M of a contour on the workpiece 11 in each measurement position P and provide it to the control unit 30. When configured as a camera 24, images B captured by the camera 24 represent the measurement data M.

[0044] If the camera 24 has several pixel elements, as is the case with the matrix camera 25, measurements can be taken at several measuring locations O on the workpiece 11 in each measuring position P, for example at a first measuring location O11 and at a second measuring location O12 in the first measuring position P1 and at a first measuring location O21 and a second measuring location O22 in the second measuring position P2 ( Fig. 2). At each measuring position P1, P2, the measuring locations O11, O12 and O21, O22 that can be recorded there are arranged at a distance from each other in the direction of the machine's rotation axis D.

[0045] In the matrix camera 25, the pixel elements are arranged and aligned parallel to a zm-ym plane of the machine coordinate system Km. This zm-ym plane is defined by the second coordinate axis ym and the third coordinate axis zm of the machine coordinate system Km.

[0046] The measurement data M can thus, for example, represent coordinate values ​​determined from images B in the directions xm, ym, zm and D. In the transmitted-light method, the light-dark transition in a line describes the position of the workpiece in the machine coordinate system Km. Coordinate values ​​zm, ym and xm of the machine coordinate system Km are assigned to the camera pixels, with the position determined for the light-dark transition taking into account the sensor positioning device 26. The sensor positioning device 26 can position the optical sensor 23 (here: camera 24) along one spatial direction or in several spatial directions using several (e.g. combined or stacked) axes of movement of the measuring machine 10. In addition, the corresponding coordinate value of the rotational position of the machine rotational axis D and thus the corresponding workpiece rotational position is recorded for each image B.

[0047] When a workpiece 11 is arranged on the workpiece carrier 13, a workpiece longitudinal axis L of the workpiece 11 can have a position deviation relative to the machine rotation axis D. If a rotation about the machine rotation axis D is caused by the rotary drive 22, the workpiece 11 performs an eccentric rotational movement about the machine rotation axis D. The eccentricity depends on an offset s and an inclination α of the workpiece longitudinal axis L relative to the machine rotation axis D.

[0048] The inclination α can have inclination angle components in several directions, for example an inclination angle component in the plane spanned by the first coordinate axis xm and the third coordinate axis zm of the machine coordinate system Km and an inclination angle component spanned by the second coordinate axis ym and the third coordinate axis zm of the machine coordinate system Km.

[0049] In addition or alternatively to the inclination α, the workpiece longitudinal axis L can have an offset s in a direction perpendicular to the machine rotation axis D. Analogous to the inclination α, the offset s can have several offset components, for example an offset component in a plane spanned by the first coordinate axis xm and the third coordinate axis zm of the machine coordinate system Km and an offset component in a plane spanned by the second coordinate axis ym and the third coordinate axis zm in the machine coordinate system Km.

[0050] Thus, the inclination α and the offset s can be two-dimensional vectors.

[0051] The offset s is determined by means of the control unit 30, for example, in a reference plane E, which is defined by the construction of the position correction arrangement 17 ( Fig. 2). In this reference plane E, the inclination adjustment of the workpiece carrier 13 about the first and second coordinate axes xw, yw of the position correction coordinate system Kw has no influence on an offset s between the machine rotational axis D and the workpiece longitudinal axis L. The reference plane E can be referred to as a tilt-neutral plane. It is preferably located outside the working area of ​​the measuring machine 10, in which a workpiece 11 is located, which is held on the workpiece carrier 13.

[0052] The position of the reference plane E can, for example, be determined from the design data of the position correction arrangement 17 and stored as a position value relative to the machine coordinate system Km (e.g. position of the reference plane parallel to the third coordinate axis zm).

[0053] It is particularly advantageous to measure and save the exact position of the reference plane E once after the manufacturing or final assembly of the measuring machine 10. A known workpiece or standard can be measured in one or more measuring positions P, P1, P2. Then, assuming a theoretical initial value for the position of the reference plane E—e.g., determined based on the design data—correction values ​​for the drives of the position correction arrangement 17 can be determined and set. Subsequent measurement in P1 and P2 and determination of the offset s and inclination α still present enables the actual position of the reference plane E for the individual measuring machine 10 to be determined by comparing the target and actual values. This two-stage method for determining the position of the reference plane E can be performed once or multiple times, particularly iteratively.The position of the reference plane E determined after the first process can be used as a theoretical starting value for the position of the reference plane E in the next process run.

[0054] In order to reduce or eliminate any offset s and / or any inclination α that may be present after the workpiece 11 has been arranged on the workpiece carrier 13, the measuring machine 10 can execute a method for positioning or position correction of the workpiece 11 under the control of the control unit 30. In Fig. 5 shows an embodiment of the method in the form of a flow chart, which can be referred to as the first method V1.

[0055] After starting the first method V1, the control unit 30 causes the workpiece 11 to rotate about the machine's rotational axis D by controlling the rotary drive 22 (first step S11 of the first method V1). In a second step S12 of the first method V1, the camera 24 is positioned in a measuring position P. For this purpose, the control unit 30 can, if necessary, control the sensor positioning device 26 if the camera 24 is not yet in the desired measuring position P. The second step S12 can be performed simultaneously with or before the first step S11.

[0056] The measuring position P has a determinable distance from the reference plane E, which can be measured, for example, by means of suitable position sensors of the sensor positioning device 26.

[0057] While the workpiece 11 is rotated about the machine rotation axis D, the camera 24 takes pictures B in the measuring position P (third step S13 of the first method V1), wherein in each image, for example, two or more measuring locations O are recorded, which are arranged parallel to the machine rotation axis D at a distance from each other. Fig. 2 in the first measuring position P1, the first measuring location O11 and the second measuring location O12 and in the second measuring position P2 the first measuring location O21 and the second measuring location O22 are shown schematically.

[0058] Alternatively, the camera can detect only a single measuring location in each measuring position P and is moved to several measuring positions to measure at several measuring locations.

[0059] At each measuring location, a circular profile (especially the contour in the circumferential direction) can be recorded and its center or center of gravity determined. Two spaced-apart center points define an axis whose inclination α and an offset s relative to the machine's rotational axis D can be determined.

[0060] Measurements at at least two measurement locations are required to determine the inclination α and the offset s. In particular, all measurement locations are located outside the reference plane E. In all embodiments, the offset s can also be determined from measurements at a single measurement location.

[0061] The images B represent measurement data M if the optical sensor 23 is configured as a camera 24 or matrix camera 25. The images B are provided to the control unit 30 and preferably temporarily stored in the buffer memory 32. This allows the control unit 30 to evaluate the images B independently of the acquisition speed of the camera 24 or matrix camera 25.

[0062] After capturing images in the third step S13, the offset s within the reference plane E and the inclination α of the workpiece longitudinal axis L relative to the machine rotation axis D are determined by means of the control unit 30 in a fourth step S14 of the first method V1. The offset s in the reference plane E can be determined from the measurement data acquired in the measurement position P depending on the distance of the measurement position P from the reference plane E.

[0063] Subsequently, in a fifth step S15 of the first method V1, it can be checked whether a positioning condition is met. For this purpose, for example, the inclination can be compared with an assigned inclination limit value and the offset s with an assigned offset limit value, and it can be checked whether the inclination α is smaller than the inclination limit value and the offset s is smaller than the offset limit value. If this is the case, the positioning condition in the fifth step S15 of the first method V1 is met, and the positioning or position correction of the workpiece is complete (branch OK from the fifth step S15). Otherwise (branch NOK from the fifth step S15), the first method V1 continues in a sixth step S16.

[0064] Subsequently, in a sixth step S16 of the first method V1, the offset s and the inclination α are corrected. Such a correction is described in a greatly simplified manner in the Fig. 3 and Fig. 4. To correct the offset s and the inclination α, the control unit 30 controls the position correction arrangement 17, by means of which the workpiece carrier 13 can be tilted and moved translationally relative to the machine rotational axis D. For example, the inclination α can first be reduced and ideally completely eliminated, so that the workpiece longitudinal axis L and the machine rotational axis D are aligned parallel to each other. Subsequently, the offset s can be reduced or eliminated with the aim of aligning the workpiece longitudinal axis L along the machine rotational axis D ( Fig. 4). These corrections can also be performed in reverse order or simultaneously. After the sixth step S16, the first method V1 is continued in the third method step S13.

[0065] In a Fig. In the modified embodiment of the first method V1 shown in dashed lines in Figure 5, the camera 24 (or generally the optical sensor 23) can be arranged not only at a single, but also at at least two different measuring positions P1, P2 and can record images B in each of these measuring positions P1, P2. Due to the greater distance between the measuring locations O11, O12, O21, O22, the accuracy in determining inclination α and offset s can be increased.

[0066] A further embodiment of the method, which is referred to as the second method V2, is described in the Fig. 6a and Fig. 6b.

[0067] The first six steps S21 to S26 of the second method V2 are analogous to the first method V1 (steps S11 to S16), so reference can be made to the above description of the first method V1. In this part of the second method V2, the measuring position P is the first measuring position P1.

[0068] Following the fifth step S25 of the second method V2, a seventh step S27 of the second method V2 follows if a first positioning condition was met in the fifth step S25 (branch OK from the fifth step S25 of the second method V2). In this seventh step S27, the camera 24 or matrix camera 25 is positioned in a second measuring position P2, which differs from the first measuring position P1 in which the camera 24 was previously located. The two measuring positions P1, P2 are arranged at a distance from each other in a direction parallel to the machine rotation axis D ( Fig. 2).

[0069] After the seventh method step S27, images B of a contour of the workpiece 11 are again taken by the camera 24 or matrix camera 25 in the second measuring position P2 (eighth step S28 of the second method V2) and then the offset s in the reference plane E and the inclination α of the workpiece longitudinal axis L relative to the machine rotation axis D are determined.

[0070] Subsequently, in a tenth step S210 of the second method V2, it is checked whether a second positioning condition is met. Analogous to the check of the first positioning condition in the fifth step S25 of this second method V2, the offset s and the inclination α of the workpiece's longitudinal axis L relative to the machine's rotational axis D can be determined and compared with a respective assigned limit value. The limit values ​​of the second positioning condition can be equal to or smaller than the limit values ​​of the first positioning condition in order to achieve greater positioning accuracy of the workpiece 11 in the measuring machine 10.

[0071] If the second positioning condition is met, the process for positioning or position correction of the workpiece 11 in the measuring machine 10 ends (branch OK from the tenth step S210 of the second process V2). If the second positioning condition is not met (branch NOK from the tenth step S210 of the second process V2), the second process V2 continues in the eleventh step S211.

[0072] The determined position deviation (inclination α and offset s) are then corrected in the eleventh step S211 of the second method V2, analogously to the sixth step S16 in the first method V1 and to the sixth step S26 in the second method V2. In a subsequent twelfth method step, the camera 14 is positioned successively in the second measuring position P2 and the first measuring position P1 (or alternatively vice versa), and images B are recorded in each measuring position P2, P1. The second method V2 then continues in the ninth method step V29.

[0073] The second method V2 is, so to speak, two-stage compared to the single-stage first method V1. Initially, a less precise positioning of the workpiece 11 in the measuring machine 10 is achieved because the camera 24 only records images B at a first measuring position P1. Subsequently, in a further process step, a more precise position of the workpiece 11 in the measuring machine 10 is achieved because the camera 24 then records images B at two spaced-apart measuring positions P1 and P2, so that the actual position and orientation of the workpiece longitudinal axis L in the machine coordinate system Km can be determined more accurately. It is also advantageous to use the second positioning condition to specify stricter specifications for the permissible position deviation of the workpiece longitudinal axis L relative to the machine rotational axis D.

[0074] For example, the first method V1 and the first method part of the second method V2 can be set up to achieve rapid positioning of the workpiece 11. In this case, the optical sensor 23 and, for example, the camera 24 or matrix camera 25 remain in a single measuring position P, e.g., in the first measuring position P1. The offset s and the inclination α can be determined by measuring at multiple measuring locations O11 and O12 in the first measuring position P1. The distance between the measuring locations O11, O12 or O21, O22 in a single measuring position P is limited and, in the exemplary embodiment, depends on the size of the camera sensor, i.e., in particular, the number of pixel elements in the direction parallel to the machine rotation axis D.

[0075] To achieve greater accuracy (for example, in the second process step of the second process V2), the optical sensor 23 or the camera 24 can additionally measure in a second measuring position P2, which is spaced apart from the first measuring position P1 in the direction of the machine rotation axis D. This enables a more precise determination of the offset s and the inclination α of the workpiece longitudinal axis L relative to the machine rotation axis D.

[0076] In all embodiments, to check the relevant positioning condition, measurement data M can be acquired from at least two measuring locations in at least one measuring position P, and the resulting position deviation (offset s and inclination α) between the workpiece longitudinal axis L and the machine rotation axis D can be compared with predetermined limit values. For example, in the second method V2, after a correction of the offset s and the inclination α in the tenth step S210 of the second method V2, measurement data M (here: images B) can be acquired again both in the first measuring position P1 and in the second measuring position P2, and then the remaining offset s and the remaining inclination α can be determined and compared with the respectively assigned limit values ​​of the second positioning condition.

[0077] For example, the first positioning condition is met if: α<α1lim s <s1lim

[0078] The second positioning condition is met if: α<α2lim≤α1lim s <s2lim≤s1lim

[0079] In equations (1) to (4) α1 lim a first tilt angle limit, α2 lim a second tilt angle limit, S1 lim a first offset limit and S2 lim a second offset limit.

[0080] In all embodiments, the workpiece carrier 13 and thus the workpiece 11 are rotated continuously (preferably at a constant speed) about the machine rotation axis D without stopping during the positioning or position correction of the workpiece 11 in the measuring machine 10 and in particular during the recording of the images B at the measuring positions P1, P2 and the control of the position correction arrangement 17. Stopping and re-acceleration of the rotary drive 22 is avoided. The rotary movement caused by the rotary drive 22 can in particular only be stopped when the first method V1 or the second method V2 has been completed, i.e. when the desired positioning of the workpiece 11 in the measuring machine 10 has been achieved.

[0081] Because the optical sensor 23—in particular camera 24 or matrix camera 25—measures a contour of the workpiece 11 either exclusively in a single measuring position P or in multiple measuring positions P1, P2, depending on the application, very rapid positioning of the workpiece 11 or—if necessary or desired—very precise positioning of the workpiece 11 in the measuring machine 10 can be achieved. Positioning the optical sensor 23 in a single measuring position P (e.g., first measuring position P1) or two different measuring positions P1, P2 is sufficient.

[0082] The invention relates to a measuring machine 10 and a method for positioning a workpiece 11 in the measuring machine 10. For this purpose, a workpiece carrier 13 holding the workpiece 11 is driven about a machine rotation axis D and an optical sensor 23, preferably designed as a camera 24 or matrix camera 25, is positioned in a measuring position parallel to the machine rotation axis D. In this measuring position, measurement data M, for example images B, are recorded on the workpiece 11 and provided to a control unit 30. In the control unit 30, an offset s and / or an inclination α of a workpiece longitudinal axis L relative to the machine rotation axis D is determined from the measurement data M from at least two measurement locations on the workpiece 11 and then reduced or eliminated by controlling a position correction arrangement of the measuring machine 10, so that a predetermined positioning condition is met.The position correction arrangement 17 is designed to incline and / or move the workpiece carrier 13 relative to the machine rotation axis D in a translational manner. List of reference symbols: 10 measuring machine 11 Workpiece 12 Machine base 13 workpiece carriers 14 Clamping device 17 Position correction arrangement 18 Linear drive arrangement 18x first linear drive 18y second linear drive 19 Tilt drive arrangement 19x first tilt drive 19y second tilt drive 22 Rotary drive 23 optical sensor 24 Camera 25 matrix camera 26 Sensor positioning device 27 Column 28 sleds 29 Lighting equipment 30 Control unit 31 computing device 32 buffer storage α inclination B Image D Machine rotation axis E Reference plane Km machine coordinate system Kw position correction coordinate system L Workpiece longitudinal axis M measurement data O Measuring location O11 first measuring location in the first measuring position O12 second measuring location in the first measuring position 021 first measuring location in the second measuring position O22 second measuring location in the second measuring position P measuring position P1 first measuring position P2 second measuring position s offset S11 first step of the first procedure S12 second step of the first procedure S13 third step of the first procedure S14 fourth step of the first procedure S15 fifth step of the first procedure S16 sixth step of the first procedure S21 first step of the second procedure S22 second step of the second procedure S23 third step of the second procedure S24 fourth step of the second procedure S25 fifth step of the second procedure S26 sixth step of the second procedure S27 seventh step of the second procedure S28 eighth step of the second procedure S29 ninth step of the second procedure S210 tenth step of the second procedure S211 eleventh step of the second procedure S212 twelfth step of the second procedure V1 first procedure V2 second procedure xm first coordinate axis of a machine coordinate system xw first coordinate axis of a position correction coordinate system ym second coordinate axis of a machine coordinate system yw second coordinate axis of a position correction coordinate system zm third coordinate axis of a machine coordinate system zw third coordinate axis of a position correction coordinate system QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3 255 378 A1

[0002] DE 10 2019 120 553 A1

[0003] DE 10 2015 100 233 A1

[0004]

Claims

[1] Measuring machine (10) which is designed to measure a workpiece (11), in particular a shape and / or a contour on a workpiece (11), comprising: - a workpiece carrier (13) on which the workpiece (11) can be arranged, - a rotary drive (22) for rotating the workpiece carrier (13) about a machine rotation axis (D), - an optical sensor (23) which is designed to record measurement data (M) on a contour on the workpiece (11), - a sensor positioning device (26) which is designed to position the optical sensor (23) parallel to the machine rotation axis (D) in at least one measuring position (P), - a position correction arrangement (17) which is designed to incline and / or move the workpiece carrier (13) relative to the machine rotation axis (D) in a translational manner, - a control unit (30) which is designed to control the rotary drive (22), the optical sensor (23) and the sensor positioning device (26) in such a way that, during a rotation of the workpiece (11) about the machine rotation axis (D), measurement data (M) are recorded by the optical sensor (23) in at least one measurement position (P), which describe an offset (s) and / or an inclination (α) of a workpiece longitudinal axis (L) relative to the machine rotation axis (D), and which is also designed to control the position correction arrangement (17) during a rotation of the workpiece (11) about the machine rotation axis (D) in such a way that the offset (s) and / or the inclination (α) fulfills or fulfills a predetermined positioning condition. [2] Measuring machine according to claim 1, wherein the optical sensor (23) is a camera (24). [3] Measuring machine according to claim 2, wherein the camera (24) is a line or matrix camera (25). [4] Measuring machine according to claim 2 or 3, wherein the camera (24) is configured to record at least one image (B) of a contour of at least one portion of the workpiece (11) as measurement data (M). [5] Measuring machine according to one of the preceding claims, further comprising a buffer memory (32) which is communicatively connected to the optical sensor (23) and the control unit (30) and which is arranged for temporarily storing the measurement data (M) provided by the optical sensor (23). [6] Measuring machine according to one of the preceding claims, wherein the control unit (30) for checking the positioning condition is configured to cause the optical sensor (23) to record and provide measurement data (M), and wherein the control unit (30) is further configured to compare the provided measurement data (M) with reference data in order to determine whether the positioning condition is met. [7] Measuring machine according to claim 6, wherein the control unit (30) is arranged to cause the optical sensor (23) to record and provide measurement data (M) in a single measurement position (P). [8] Measuring machine according to claim 6, wherein the control unit (30) is arranged to cause the optical sensor (23) to record and provide measurement data (M) in at least two different measurement positions (P1, P2). [9] Measuring machine according to claim 8, wherein the control unit (30) is arranged to - to cause the sensor positioning device (26) to position the optical sensor (23) in a first measuring position (P1), - to cause the optical sensor (23) to record and provide measurement data (M) in the first measurement position (P1), - the measurement data (M) recorded and provided in the first measurement position (P1) with first reference data (α1 lim, s1 lim) to determine whether a first positioning condition (R1) is met, - to cause the sensor positioning device (26) to position the optical sensor (23) in a second measuring position (P2), - to cause the optical sensor (23) to record and provide measurement data (M) in the second measurement position (P2), - the measurement data (M) recorded and provided in the second measurement position (P2) with second reference data (α2 lim, s2 lim ) to determine whether a second positioning condition (R2) is met. [10] Measuring machine according to claim 8, wherein the positioning of the optical sensor (23) in the second measuring position (P2) only takes place when the first positioning condition (R1) is fulfilled. [11] Measuring machine according to claim 8 or 9, wherein the second reference data is different from the first reference data. [12] Measuring machine according to claim 11, wherein the second reference data (α2 lim, s2 lim ) define a smaller offset (s) and / or a smaller inclination (α) of the workpiece longitudinal axis (L) relative to the machine rotation axis (D) than the first reference data (α1 lim, s1 lim ). [13] Measuring machine according to one of the preceding claims, wherein the communication connection between the control unit (30) and the position correction arrangement (17) is wireless and / or wherein the power supply connection to the position correction arrangement (17) is wireless. [14] Measuring machine according to one of the preceding claims, wherein a reference plane (E) is defined in a position known relative to the machine rotation axis (D), in particular perpendicular to the machine rotation axis (D), wherein the offset (s) and the inclination (α) are determined in this reference plane (E). [15] Measuring machine according to claim 14, wherein the reference plane (E) is defined outside the area in which a workpiece (11) arranged in the measuring machine (10) is located. [16] Method (V1, V2) for positioning a workpiece (11) in a measuring machine (10) before measuring a shape and / or a contour on the workpiece (11), the method (V1, V2) comprising: - arranging the workpiece (11) on a workpiece carrier (13), - Rotating the workpiece carrier (13) around a machine rotation axis (D), - contactless recording of measurement data (M) on a contour of the workpiece (11) by means of an optical sensor (23) in a measuring position (P1, P2) of the optical sensor (23) along the machine rotation axis (D) during the rotation of the workpiece (11) about the machine rotation axis (D), wherein the measurement data (M) describe an offset (s) and / or an inclination (α) of a workpiece longitudinal axis (L) relative to the machine rotation axis (D), - Controlling a position correction arrangement (17) during the rotation of the workpiece (11) about the machine rotation axis (D) until the offset (s) and / or the inclination (α) satisfies a predetermined positioning condition (R1, R2), wherein the position correction arrangement (17) is designed to incline and / or move the workpiece carrier (13) in a translational manner relative to the machine rotation axis (D).

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