Method and device for measuring a numerically controlled machine tool, control device, numerically controlled machine tool and computer program product

Abstract

Method for measuring a numerically controlled machine tool (100), wherein the machine tool (100) has at least a first controllable rotary axis (C) with a machine part (130) rotatably mounted about a first rotation axis (C) and a second controllable rotary axis (B) for rotating the machine part (130) about a second rotation axis (B) oriented transversely or perpendicularly to the first rotation axis (C), and wherein a workpiece is clamped on the machine part (130) and a measuring object (300) is positioned on the machine part (130) at a radial distance from the first axis of rotation (C), the method comprising: - Determining spatial positions of the measuring object (300) on the workpiece-carrying machine part (130), wherein the respective spatial position of the measuring object (300) is determined in at least three different angular positions of the first rotary axis (C) with respect to the first rotation axis (C) for at least one measuring plane corresponding to an angular position of the second rotary axis (B) with respect to the second rotation axis (B), - Determining one or more coordinate reference parameters of the first rotary axis (C) in the measuring plane corresponding to the angular position of the second rotary axis (B) on the basis of the determined spatial positions of the measuring object (300) as a function of the workpiece weight of the workpiece clamped on the machine part (130).

Description

[0001] The present invention relates to a method and a device for measuring a numerically controlled machine tool, machine kinematics or a numerically controlled machine tool, in particular a numerically controlled machine tool with at least two controllable rotary axes.

[0002] In particular, the present invention relates to a method and a device for measuring and / or correcting kinematic errors or kinematic reference parameters of the machine coordinate system or the kinematic description of the machine tool in the numerical control on a numerically controlled machine tool, in particular a numerically controlled machine tool with at least two controllable rotary axes.

[0003] Furthermore, the present invention relates to a control device of a machine tool and a numerically controlled machine tool.

[0004] Furthermore, the present invention relates to a computer program product for the computer-implemented execution of a method for measuring machine kinematics of a numerically controlled machine tool and / or a method for measuring and / or correcting kinematic errors on a numerically controlled machine tool on or by a numerical control device of such a machine tool. background

[0005] Numerically controlled machine tools with a tool-carrying work spindle are known in the state of the art. These are now mostly equipped with numerical controls and are known, for example, as milling machines, milling centers, universal milling machines, or CNC machining centers with four, five, or sometimes more than five numerically controllable linear and / or rotary axes (e.g., rotary or swivel axes). See, for example, the machine tool according to DE 10 2010 064 271 A1.

[0006] Measurement methods on machine tools are known, for example, from EP 1 696 289 A1 and DE 10 2010 038 783 A1. Disadvantages of the teachings of these documents and the advantages of the invention and some exemplary embodiments that offset them are described below.

[0007] Furthermore, a method and a program for detecting mechanical errors are known from DE 10 2010 038 783 A1 and a method for measuring a rotation axis of a machine tool system is known from US 2013 / 253871A1.

[0008] DE 10 2011 102 810 A1 describes a numerical control for controlling a multi-axis machine that performs compensation using a translation compensation amount and a rotation compensation amount.

[0009] DE 29 40 633 A1 presents a method with which the rotational axis of a rotary table can be determined by means of a multi-coordinate measuring device equipped with at least one probe.

[0010] EP 1 559 990 A2 presents a method by means of which a coordinate correction of coordinates of a coordinate measuring machine can be carried out.

[0011] Furthermore, EP 2 735 928 A1 describes a method for adjusting a multifunctional machining center for milling, drilling and / or turning using a deformation model that describes the workpiece-supporting assembly. Summary of the invention

[0012] It is an object of the present invention to further develop the measuring methods on machine tools according to the prior art, in particular based on EP 1696 289A1 and DE 10 2010 038 783 A1.

[0013] It is a further object of the present invention to provide a measuring method and / or position error correction method that is as simple, cost-effective, accurate, easy to carry out and mathematically less complicated as possible for error compensation of the errors in the axis positions of rotary and / or linear axes on machine tools with four, five or even more drive axes and sometimes complex machine kinematics.

[0014] According to one aspect of the invention, to achieve the above-mentioned object, a method for measuring a numerically controlled machine tool according to claim 1, a device for measuring a numerically controlled machine tool according to claim 19, a control device according to claim 21, a machine tool according to claim 22, and a computer program product according to claim 23 are proposed. The dependent claims or combinations of the dependent claims relate to preferred embodiments.

[0015] EP 1 696 289 A1 describes a method for measuring a rotary axis on a machine tool. In this method, a measuring sphere is probed in two measuring positions (two-point measurement), which result from the further pivoting of a rotary axis on which the measuring sphere is attached. Since the radius of the measuring sphere is known, the spatial position of the respective sphere center of the measuring sphere (or of another measuring sphere reference point) at the respective measuring position can be determined, e.g. in relation to the machine coordinate system, by scanning three points on the measuring sphere surface (in each of the two measuring positions of the measuring sphere) and determining the coordinates of the three surface points. According to EP 1 696 289 A1, a center point position of the rotary axis is determined from the pivot angle of the rotary axis between the two measuring positions and the respective determined spatial positions.

[0016] The coordinates of the two measurements are used to determine the pivot point of the rotary axis to which the measuring ball is attached. To calculate a linear axis, the described two-point measurement can be repeated at a different height above the rotary axis, and a pivot point can be calculated for this height from the two-point measurement. The connection between the two pivot points is used to determine the direction of the rotary axis.

[0017] A disadvantage of this method according to EP 1696 289 A1 is that errors in the machine geometry and kinematics are reflected in the measurement and subsequent calculation results and can lead to incorrect determination of the pivot points and the rotary axis in space.

[0018] DE 10 2010 038 783 A1 describes a method in which the movement of a rotary axis is determined by probing several positions of a gauge on the circumference of the rotary axis through the movement of the linear machine axes. The measured values ​​thus obtained are used to mathematically determine a circular path that runs through the coordinates of the probed points. It is also described that the measurement results can be used to determine a relative inclination error between the rotary axis and the probing linear axes.

[0019] In contrast, the embodiments described later differ significantly in that the measured points can be used to determine a plane of a rotational movement and / or the rotation axis or a rotation axis vector (e.g., table axis vector). This approach is mathematically much simpler and thus more efficient, and also delivers more accurate results.

[0020] DE 10 2010 038 783 A1 describes that the measurements on a machine with more than two successive rotary axes can be used to determine the circular arc of the rotary axis for several positions of the swivel axis on which the rotary axis is based.

[0021] In the sense of the invention, a further significantly different aspect compared to DE 10 2010 038 783 A1 is, in the embodiments described later, in addition to the simpler and more precise calculation of the rotary axis errors via planes and axes or axis vectors, in particular the use of the determined error values ​​or correction values ​​to correct the machine kinematics in the internal calculation model of the control or in the internal kinematics description of the numerical control, e.g. by converting the measured errors into correction values ​​for the machine kinematics, which can be entered into the numerical control.

[0022] A further, significantly different proposed aspect is that, according to exemplary embodiments, the proposed method can measure and compensate for changes in the machine kinematics that arise during or as a result of the operation of the machine. These are, on the one hand, thermally induced changes, which can be measured, for example, after the machine has been operated under defined conditions and which are correlated, for example, with a likewise measured temperature signal. Based on the temperature signal, the machine kinematics can then be intervened in according to the measured deviations and the determined geometry and kinematic changes.

[0023] On the other hand, changes in the machine geometry and kinematics, which occur, for example, as a result of the weight of the workpiece or the machining forces at different swivel angles, can also be advantageously measured in the manner described. These can then also be advantageously compensated, particularly preferably in the machine control system or by reference parameters in the kinematic description of the machine tool that are compensated or adjusted in the machine kinematics depending on the workpiece weight.

[0024] In the following, aspects and preferred embodiments of the invention are described, each of which can be provided individually or in any combination with one another.

[0025] According to a first aspect, a method is proposed for measuring a numerically controlled machine tool which has at least a first controllable rotary axis with a machine part mounted so as to be rotatable about a first axis of rotation and a second controllable rotary axis for rotating the machine part about a second axis of rotation oriented transversely or perpendicularly to the first axis of rotation, and wherein a workpiece is clamped on the machine part and a measuring object (e.g. a measuring block, a measuring plate, or a measuring sphere with a previously known size and shape, or known dimensions or size parameters) is positioned (or fastened) on the machine part at a radial distance from the first axis of rotation.

[0026] The method according to a general aspect comprises: - Determining spatial positions of the measuring object on the machine part carrying the workpiece, wherein the respective spatial position of the measuring object is determined in at least three different angular positions of the first rotary axis with respect to the first rotation axis for at least one measuring plane corresponding to an angular position of the second rotary axis with respect to the second rotation axis; and - Determining one or more coordinate reference parameters of the first rotary axis (in particular with regard to a reference position of the first rotary axis and / or a reference orientation of the first rotary axis) in the measuring plane according to the angular position of the second rotary axis on the basis of the determined spatial positions of the measuring object as a function of the workpiece weight of the workpiece clamped on the machine part, and in this case particularly preferably determining a center point position and / or an axis alignment of the rotatably mounted machine part in the measuring plane according to the angular position of the second rotary axis on the basis of the determined spatial positions of the measuring object.

[0027] Preferably, the method may further comprise adapting machine data of the numerical control of the machine tool, which specify a kinematic description of the machine tool, on the basis of the determined coordinate reference parameters, and / or calculating correction values ​​for axis positions of the machine tool for adapting axis positions when processing numerical machining data for controlling the machine tool by the numerical control of the machine tool on the basis of the numerical machining data.

[0028] In preferred embodiments, the determined coordinate reference parameters can include, for example, a center of rotation of the first rotary axis or a center of rotation of the machine part corresponding to the angular position of the second rotary axis and / or an orientation of the first rotary axis or an axis vector of the machine part corresponding to the angular position of the second rotary axis.

[0029] In preferred embodiments, the respective spatial positions of the measurement object can be determined in exactly three different angular positions of the first rotary axis according to a three-point measurement with respect to the first axis of rotation for at least one measuring plane corresponding to an angular position of the second rotary axis with respect to the second axis of rotation; or the respective spatial positions of the measurement object can be determined in exactly four different angular positions of the first rotary axis according to a four-point measurement with respect to the first axis of rotation for at least one measuring plane corresponding to an angular position of the second rotary axis with respect to the second axis of rotation.

[0030] This has the advantage that a high level of accuracy can be achieved at the same time, which is significantly superior to the pure two-point measurement according to EP 1 696 289 A1, while at the same time providing an extremely precise measuring method that is simple and efficient to carry out and yet requires less computational effort, and wherein a simpler mathematical calculation method can be used than with a 12-point measurement of a first rotary axis in two angular positions of a second rotary axis and a further multi-point measurement of the second rotary axis in a single angular position of the first rotary axis according to DE 102010038 783 A1.

[0031] In preferred embodiments, the at least one measuring plane can be oriented perpendicular to a spindle axis of a work spindle of the machine tool and / or horizontally, parallel to the spindle axis of the work spindle of the machine tool and / or vertically, or obliquely to the spindle axis of the work spindle of the machine tool and / or at an angle greater than 0 degrees and less than 90 degrees, in particular greater than or equal to 30 degrees and less than or equal to 60 degrees, to a horizontal plane.

[0032] In preferred embodiments, the respective spatial positions of the measurement object can be determined in at least three different angular positions of the first rotary axis relative to the first rotation axis for at least three different measuring planes corresponding to at least three different angular positions of the second rotary axis relative to the second rotation axis. In preferred embodiments, the method is carried out for exactly three, four, five, or six different measuring planes corresponding to exactly three, four, five, or six different angular positions of the second rotary axis.

[0033] In preferred embodiments, a first measuring plane of the at least three different measuring planes can be aligned perpendicular to a spindle axis of a work spindle of the machine tool, a second measuring plane of the at least three different measuring planes can be aligned obliquely to the spindle axis of the work spindle of the machine tool, and / or a third measuring plane of the at least three different measuring planes can be aligned parallel to the spindle axis of the work spindle of the machine tool.

[0034] In preferred embodiments, a first measuring plane of the at least three different measuring planes can be aligned horizontally, a second measuring plane of the at least three different measuring planes can be aligned at an angle greater than 0 degrees and less than 90 degrees, in particular greater than or equal to 30 degrees and less than or equal to 60 degrees, to a horizontal plane, and / or a third measuring plane of the at least three different measuring planes can be aligned vertically.

[0035] In preferred embodiments, the determined coordinate reference parameters may include angular errors between orientations of machine axes of the machine tool.

[0036] In preferred embodiments, the respective spatial positions of the measurement object can be determined in N different angular positions of the first rotary axis with N > 2 according to an N-point measurement with respect to the first rotation axis for at least one measuring plane corresponding to an angular position of the second rotary axis with respect to the second rotation axis, wherein preferably the respective angular positions of the first rotary axis each have an angular distance of 360 / N degrees (or less).

[0037] In preferred embodiments, the adaptation of the machine data of the numerical control of the machine tool may comprise a calculation of correction values ​​for reference parameters of the kinematic description of the machine tool on the basis of a target / actual comparison of the spatial positions of the measuring object or machine coordinate parameters calculated therefrom.

[0038] This can include target-actual comparisons of coordinate values ​​or coordinate vectors, wherein the respective actual values ​​are preferably calculated from the measurement(s) and / or the determined spatial positions and / or based on the kinematics description of the numerical control, and wherein the respective target values ​​are preferably calculated based on the specified target spatial positions and / or specified axis positions and / or based on the kinematics description of the numerical control. Furthermore, correction values ​​of the kinematics description for modifying the specified reference parameters of the kinematics description of the machine tool in the numerical control can preferably be calculated based on the target-actual comparison.

[0039] In preferred embodiments, the target-actual comparison for each of the at least one measuring planes can comprise a comparison of an actual orientation of the respective measuring plane with a target orientation of the respective measuring plane of the corresponding angular position of the second rotary axis and / or a comparison of an actual orientation of the rotational axis of the first rotary axis with a target orientation of the rotational axis of the first rotary axis with respect to the corresponding angular position of the second rotary axis.

[0040] In preferred embodiments, the target-actual comparison for each of the at least one measuring planes may comprise a comparison of an actual position of a rotation center of the first rotary axis with a target position of the rotation center of the first rotary axis in a machine coordinate system.

[0041] In preferred embodiments, the method can be repeated on the basis of the adjusted machine data, preferably until the correction values ​​are essentially zero or the absolute values ​​of the calculated correction values ​​fall below a respective adjustable or preset limit value and / or until the target / actual comparison shows that the target and actual values ​​are each equal or their difference falls at least below a predetermined limit value.

[0042] In preferred embodiments, the machine data, the kinematic description of the machine tool, may be suitable to be used as a basis for kinematic transformations between a workpiece coordinate system and a machine coordinate system by the numerical control of the machine tool.

[0043] In preferred embodiments, the method may further comprise: clamping a first test weight with a predetermined weight on the machine part of the machine tool, wherein, for example, the determination of the respective spatial position of the measurement object is carried out in at least three different angular positions of the first rotary axis with respect to the first axis of rotation for at least one measuring plane corresponding to an angular position of the second rotary axis with respect to the second axis of rotation, optionally preferably with the first test weight clamped on the machine part of the machine tool.

[0044] In preferred embodiments, the method may further comprise: clamping a second test weight with a predetermined weight and / or preferably a weight different from the weight of the first test weight on the machine part of the machine tool, wherein the determination of the respective spatial position of the measurement object is preferably carried out again in at least three different angular positions of the first rotary axis with respect to the first axis of rotation for at least one measuring plane corresponding to an angular position of the second rotary axis with respect to the second axis of rotation, preferably with the second test weight clamped on the machine part of the machine tool.

[0045] In preferred embodiments, the determination of the respective spatial position of the measurement object can be carried out in at least three different angular positions of the first rotary axis with respect to the first rotation axis for at least one measuring plane corresponding to an angular position of the second rotary axis with respect to the second rotation axis, preferably once without and once with the first (and / or second) test weight clamped on the machine part of the machine tool.

[0046] The above-mentioned embodiments are particularly useful when heavy workpieces are to be machined at possibly high swivel angles of the machine part, since the weight force acting on the workpiece can possibly generate large torques acting on the machine part, which can influence the alignment of the axes and thus impair the accuracy of the machining of heavy workpieces.

[0047] It is extremely advantageous if a calibration procedure is carried out with a test weight (or, if necessary, with the workpiece to be machined) by carrying out the machine measurement with the workpiece weight and storing it in the machine control system.

[0048] In particularly expedient embodiments, a respective measuring method with different test weights with different weight values ​​could be carried out for a respective machine type of a machine tool, wherein workpiece weight machine data could then preferably be stored in the machine control system with correction values ​​of the kinematics description calculated for different test workpieces with different weight values.

[0049] If a machine tool operator later wishes to machine a workpiece of a certain weight on the machine tool, he can simply enter the respective workpiece weight into the numerical control, which then automatically modifies the kinematics description of the machine tool for the respective machining operation with the (possibly interpolated) correction values ​​based on the correction values ​​of the pre-stored workpiece weight machine data stored as a function of the workpiece weight.

[0050] According to this aspect, it is particularly advantageous and possible as an independent aspect to provide a machine tool control device (and / or a machine tool with such a machine tool control device) comprising: - a storage device for storing machine kinematics or machine data of the machine tool specifying machine kinematics and workpiece weight machine data specifying correction values ​​for the machine kinematics of the machine tool as a function of a workpiece weight and / or correction values ​​for reference parameters, in particular axis positions, as a function of a workpiece weight, - a data processing device of a numerical control of the machine tool for controlling the machine tool on the basis of numerical processing data and the machine kinematics of the machine tool and for transforming coordinate data between a relative coordinate system and a machine coordinate system of the machine tool on the basis of the machine kinematics of the machine tool, and - an input unit which enables an operator to enter a workpiece weight of a workpiece to be machined, wherein the data processing device is configured to adapt the machine kinematics or the machine data specifying the machine kinematics for machining the workpiece on the machine tool by means of correction values ​​of the machine kinematics on the basis of the input workpiece weight and / or to adapt reference parameters, in particular axis positions, when processing numerical machining data for controlling the machine tool by the numerical control of the machine tool on the basis of the numerical machining data by means of correction values ​​of the reference parameters on the basis of the input workpiece weight.

[0051] According to a second aspect, a device for measuring a numerically controlled machine tool is proposed, wherein the machine tool preferably has at least a first controllable rotary axis with a machine part mounted for rotation about a first axis of rotation and / or a second controllable rotary axis for rotating the machine part about a second axis of rotation oriented transversely or perpendicularly to the first axis of rotation; and wherein preferably a workpiece is clamped on the machine part and a measuring object is fastened or can be fastened on the machine part of the machine tool at a radial distance from the first axis of rotation.

[0052] The device preferably comprises means for determining spatial positions of the measuring object on the machine part carrying the workpiece, wherein the respective spatial position of the measuring object is determined in at least three different angular positions of the first rotary axis with respect to the first axis of rotation for at least one measuring plane corresponding to an angular position of the second rotary axis with respect to the second axis of rotation; and / or means for determining a center point position of the rotatably mounted machine part in the measuring plane corresponding to the angular position of the second rotary axis on the basis of the determined spatial positions of the measuring object as a function of the workpiece weight of the workpiece clamped on the machine part.

[0053] Particularly preferably, the device is a numerical control device of a machine tool or is integrated into a numerical control device of a machine tool.

[0054] According to a third aspect, a control device of a machine tool is provided, which comprises a device according to one of the preceding aspects for carrying out one or more of the preceding aspects. Furthermore, the control device comprises a memory device for storing machine kinematics orof machine data of the machine tool specifying machine kinematics and workpiece weight machine data, which specify correction values ​​for the machine kinematics of the machine tool as a function of a workpiece weight and / or correction values ​​for reference parameters, in particular axis positions, as a function of a workpiece weight, a data processing device of a numerical control of the machine tool for controlling the machine tool on the basis of numerical machining data and the machine kinematics of the machine tool and for transforming coordinate data between a relative coordinate system and a machine coordinate system of the machine tool on the basis of the machine kinematics of the machine tool, and an input unit which enables an operator to enter a workpiece weight of a workpiece to be machined. The data processing device is designed toto adapt the machine data specifying the machine kinematics for machining the workpiece on the machine tool by means of correction values ​​of the machine kinematics on the basis of the entered workpiece weight and / or to adapt reference parameters, in particular axis positions, when processing numerical machining data for controlling the machine tool by the numerical control of the machine tool on the basis of the numerical machining data by means of correction values ​​of the reference parameters on the basis of the entered workpiece weight.

[0055] According to a fourth aspect, a numerically controlled machine tool is proposed, preferably comprising at least a first controllable rotary axis with a machine part mounted for rotation about a first axis of rotation and a second controllable rotary axis for rotating the machine part about a second axis of rotation oriented transversely or perpendicularly to the first axis of rotation; and a device according to one of the preceding aspects for carrying out one or more of the preceding aspects.

[0056] Finally, according to a fifth aspect, a computer program product is proposed with a computer program stored on a computer-readable data storage medium, which is executable in a numerical control device of a machine tool and / or in a computer connectable to a numerical control device of a machine tool.

[0057] The executable computer program is designed to carry out a method according to one or more of the above aspects on the machine tool, which has at least a first controllable rotary axis with a machine part mounted rotatably about a first axis of rotation and a second controllable rotary axis for rotating the machine part about a second axis of rotation oriented transversely or perpendicularly to the first axis of rotation, and wherein a workpiece is clamped on the machine part and a measuring object is fastened or can be fastened on the machine part of the machine tool at a radial distance from the first axis of rotation.

[0058] In summary, the invention provides the simplest, most cost-effective, most accurate, most easily implemented and mathematically less complicated measuring methods and / or position error correction methods for compensating the errors in the axis positions of rotary and / or linear axes on machine tools with four, five or even more drive axes and sometimes complex machine kinematics. Short description of the characters Fig. 1 shows an exemplary perspective view of a machine tool according to an embodiment of the invention; Fig. 2 shows an exemplary perspective view of another machine tool according to another embodiment of the invention; Fig. 3A to 3C schematically show an exemplary three-point measurement according to an embodiment of the invention in an exemplary horizontally oriented first measuring plane; Fig. 4A to 4C schematically show an exemplary three-point measurement according to an embodiment of the invention in an exemplary obliquely oriented second measuring plane; Fig. 5A to 5C schematically show an exemplary three-point measurement according to an embodiment of the invention in an exemplary vertically oriented third measuring plane; Fig. 6A illustrates an example of an adverse influence of a perpendicularity error in a two-point measurement according to EP 1696 289A1; Fig. 6B illustrates an example of a detrimental influence of a straightness error of an axis in a two-point measurement according to EP 1696 289 A1; Fig. 6C illustrates an example of an advantage of a three-point measurement according to embodiments of the invention in the event of a possible perpendicularity error; Fig. 7 schematically illustrates a possible machining error on a workpiece due to the weight of the workpiece; Fig. 8A to 8C schematically show an exemplary three-point measurement according to an embodiment of the invention in an exemplary horizontally oriented first measuring plane with a clamped test weight; Fig. 9A to 9C schematically show an exemplary three-point measurement according to an embodiment of the invention in an exemplary obliquely aligned second measuring plane with a clamped test weight; Fig. 10A to 10C schematically show an exemplary three-point measurement according to an embodiment of the invention in an exemplary vertically oriented third measuring plane with a clamped test weight; Fig. 11 shows a schematic exemplary representation of a part of a machine kinematics description according to an embodiment of the invention; and Fig. 12 shows a schematic exemplary representation of a control device according to an embodiment. Detailed description of the figures and preferred embodiments of the present invention

[0059] Examples and embodiments of the present invention are described in detail below with reference to the accompanying figures. Identical or similar elements in the figures may be designated by the same reference numerals, although sometimes different reference numerals may be used.

[0060] It should be emphasized, however, that the present invention is in no way limited or restricted to the exemplary embodiments and their embodiment features described below, but further comprises modifications of the exemplary embodiments, in particular those which are encompassed by modifications of the features of the described examples or by combination of one or more of the features of the described examples within the scope of protection of the independent claims. 1. Example machine tools

[0061] Fig. 1 shows an exemplary perspective view of a machine tool 100 according to an embodiment of the invention. The machine tool 100 comprises, for example, a machine bed 110 on which, for example, a pivotably mounted swivel table 120 is arranged, with a rotary table 130, for example, rotatably mounted on the swivel table 120, on which, for example, a workpiece WS is clamped for machining on the machine tool 100.

[0062] By way of example, the machine tool 100 thus comprises two rotationally controllable rotary axes for rotating the workpiece WS clamped on the rotary table 130, for example about a pivot axis (driven / driven pivot axis B - B axis) which is oriented horizontally with respect to the machine bed 110, about which the pivot table 120 can be pivoted on the machine bed 110, and about a rotation axis (driven / driven rotation axis C - C axis) which is oriented vertically with respect to the pivot table 120, about which the rotary table 130 can be rotated on the pivot table 120.

[0063] In this exemplary embodiment, the rotation axis of the rotary table 130 is designed as a rotary axis that is not absolutely fixed in relation to the machine bed 110, but the rotation axis of the rotary axis of the rotary table 130 pivots with the pivoting of the pivot table 120, since the rotary table 130 mounted on the pivot table 120 pivots with the pivot table 120.

[0064] In further embodiments of the invention, it is possible to provide two pivot axes, two rotation axes, only one, or more than two rotation or pivot axes. Furthermore, in further embodiments, it is possible to provide independent pivot or rotation axes, e.g., by having one or more rotation or pivot axes rotate the workpiece and one or more other rotation or pivot axes rotate the tool or spindle head.

[0065] The machine tool 100 according to Fig. 1 further comprises, by way of example, an axis slide assembly with a first axis slide 140, which is arranged on a rear machine stand of the machine bed 110 and is guided on longitudinal axis slide guides fastened to the machine stand. On the longitudinal axis slide guides, the first axis slide 140 is movable, for example, horizontally and linearly in the direction of a Y-axis of the machine tool 100 (in Fig. 1 (exemplarily in a horizontal direction from front to back).

[0066] At the front side of the first axis slide 140, horizontally aligned cross-axis slide guides are arranged, for example, on which a second axis slide 150 can be moved linearly, for example in the direction of an X-axis of the machine tool 100, for example horizontally and transversely or perpendicularly to the direction of the Y-axis of the first axis slide 140 (in Fig. 1 in a horizontal direction from left to right).

[0067] At the front of the second axis slide 150, a spindle head with a spindle head housing is held on a third axis slide 160. The spindle head is, for example, vertically linearly movable in the direction of a Z-axis of the machine tool 100 (vertically movable third axis slide 160), ie, in particular, for example, transversely or perpendicularly to the directions of the X and Y axes.

[0068] On the underside of the spindle head with the spindle head housing on the third axis slide 160, a work spindle 170 of a spindle device is arranged, the spindle axis of which is oriented vertically, for example, and in particular parallel to the direction of the Z-axis, for example.

[0069] In the embodiment according to Fig. 1, three independently controllable linear axes are therefore provided by way of example (e.g. controllable by a control device (not shown) of a numerical machine tool control, possibly with a CNC control unit and / or PLC control unit, possibly on the basis of NC programs and / or control commands entered manually on a control panel of the machine tool 100).

[0070] For example, all three linear axes can actively move the tool mounted on the work spindle 170 of the spindle device independently of one another or simultaneously with respect to the position of the workpiece WS clamped on the rotary table 130.

[0071] In further embodiments, one, two or more than three independently movable linear axes may be provided, or one, two, three or more linear axes may be provided for moving the workpiece or the rotary table 130 and / or the swivel table 120.

[0072] Furthermore, the machine tool 100 includes, for example, a tool magazine 180 configured to store a plurality of tools, tool interfaces, and / or tools with tool interfaces. For example, the tool magazine 180 is configured as a chain magazine, but other types of tool magazines may also be provided, such as shelf magazines or wheel magazines, etc.

[0073] In addition, the machine tool 100 comprises, for example, a tool changing device 190 which is linearly movable between a tool changing position of the work spindle 170 of the spindle device and a tool removal or tool insertion position of the tool magazine 180. The tool changing device 190 is configured to remove a tool from the tool magazine 180 at the tool removal or tool insertion position of the tool magazine 180 in order to feed it to the work spindle in a tool change, and to feed a tool removed from the work spindle 170 of the spindle device in the tool change at the tool changing position to the tool magazine 180.

[0074] Preferably, the tool changing device 190 optionally comprises a pivotable double gripper for holding or receiving two tools or tool interfaces, optionally with one gripper section for receiving a tool from the spindle or the tool magazine and another gripper section with a tool to be inserted in the work spindle or the tool magazine.

[0075] Fig. Figure 2 shows an exemplary perspective view of another machine tool 100 according to another embodiment of the invention. The basic structure is similar to Fig. 1, by the machine tool 100 according to Fig. 2 also comprises a machine bed 110 on which, for example, a pivotably mounted swivel table 120 is arranged, with a rotary table 130 which is, for example, rotatably mounted on the swivel table 120 and on which, for example, a workpiece WS is clamped for machining on the machine tool 100.

[0076] In this exemplary embodiment, the rotation axis of the rotary table 130 is designed as a rotary axis that is not absolutely fixed in relation to the machine bed 110, but the rotation axis of the rotary axis of the rotary table 130 pivots with the pivoting of the pivot table 120, since the rotary table 130 mounted on the pivot table 120 pivots with the pivot table 120.

[0077] While in Fig. 1 the swivel table 120 is held and supported on both sides of the machine bed 110 with a horizontally aligned rotation axis, the swivel table 120 is according to Fig. 2, for example, only held or pivotably mounted on one side of the machine bed 110, wherein the rotation axis of the swivel table 120 in Fig. 2 is oriented, for example, at an angle of 45 degrees to a horizontal plane.

[0078] In further embodiments of the invention, it is possible to provide two pivot axes, two rotation axes, only one, or more than two rotation or pivot axes. Furthermore, in further embodiments, it is possible to provide independent pivot or rotation axes, e.g., by having one or more rotation or pivot axes rotate the workpiece and one or more other rotation or pivot axes rotate the tool or spindle head.

[0079] The machine tool 100 according to Fig. 2 also includes, by way of example, an axis slide assembly with a first axis slide 140, which is arranged on a rear machine stand of the machine bed 110 and is guided on cross-axis slide guides fastened to the machine stand. On the cross-axis slide guides, the first axis slide 140 is movable, for example, horizontally and linearly in the direction of an X-axis of the machine tool 100 (in Fig. 2 (exemplarily in a horizontal direction from left to right).

[0080] On the upper side of the first axis slide 140, for example, horizontally aligned longitudinal axis slide guides are arranged, on which a second axis slide 150 can be moved linearly, for example in the direction of a Y-axis of the machine tool 100, for example horizontally and transversely or perpendicularly to the direction of the X-axis of the first axis slide 140 (in Fig. 2 in a horizontal direction from diagonally left-front to diagonally right-back).

[0081] At the front of the second axis slide 150, a spindle head with a spindle head housing is held on a third axis slide 160. The spindle head is, for example, vertically linearly movable in the direction of a Z-axis of the machine tool 100 (vertically movable third axis slide 160), ie, in particular, for example, transversely or perpendicularly to the directions of the X and Y axes.

[0082] On the underside of the spindle head with the spindle head housing on the third axis slide 160, a work spindle 170 of a spindle device is arranged, the spindle axis of which is oriented vertically, for example, and in particular parallel to the direction of the Z-axis, for example.

[0083] In the embodiment according to Fig. 2, three independently controllable linear axes are therefore provided by way of example (e.g. controllable by a control device (not shown) of a numerical machine tool control, possibly with a CNC control unit and / or PLC control unit, possibly on the basis of NC programs and / or control commands entered manually on a control panel of the machine tool 100).

[0084] For example, all three linear axes can actively move the tool mounted on the work spindle 170 of the spindle device independently of one another or simultaneously with respect to the position of the workpiece WS clamped on the rotary table 130.

[0085] In further embodiments, one, two or more than three independently movable linear axes may be provided, or one, two, three or more linear axes may be provided for moving the workpiece or the rotary table 130 and / or the swivel table 120.

[0086] In further embodiments, it is therefore possible for each of the machine tools described above to omit one or more of the provided axes or to provide one or more further linear and / or pivoting or rotary axes, e.g. also one or more linear and / or pivoting or rotary axes for moving the tool.

[0087] It should be mentioned here that the difference between a rotary axis and a swivel axis is that a rotary axis can be rotated in both directions about its axis of rotation, whereby a rotation of 360 degrees or more or possibly 720 degrees or more or possibly without angular restriction is possible, and that a pivot axis can be rotated in both directions about its axis of rotation between a first and a second angular position, whereby the angular positions are fixed, possibly with an angular distance of 360 degrees or less, e.g. as 90 degrees, 120 degrees, 180 degrees (e.g. +90 degrees and -90 degrees), 240 degrees (e.g. +120 degrees and -120 degrees), 270 degrees or 360 degrees (e.g. +180 degrees and -180 degrees).

[0088] In the following, the term “rotary axis” is generally used as a generic term for rotary or swivel axes, i.e. a respective rotary axis can be designed as a swivel axis or as a rotary axis.

[0089] Furthermore, the machine tool can comprise a numerical machine control (e.g. NC or CNC control, possibly with one or more NC and PLC control units) and / or a machine control panel (not shown), and possibly have a machine tool housing (not shown).

[0090] Five-axis machine tools, for example, have, according to the machine tools according to Fig. 1 and Fig. 2 three linear motion axes and two rotary axes. For example, the workpiece WS is mounted on one of the rotary axes (e.g., on the rotary table 130) – the so-called rotary axis or C-axis – which can, for example, rotate continuously.

[0091] The second rotary axis—e.g., the so-called swivel axis or B-axis—is used to swivel either the workpiece WS or the spindle 170° in space to make the workpiece WS accessible for machining the sides. On some machine tools, the swivel axis has a limited swivel range of, for example, 0° to 90° or even from, for example, -120° to +120°.

[0092] Geometric errors in the machine tool components and errors in the alignment of the machine tool components, as well as thermal expansion and deformation of the machine components, e.g. due to weight forces, may result in the movement axes of the machine tools not moving in an ideally straight line and that they may not be at exactly the right angle to each other.

[0093] These errors lead to dimensional errors during workpiece machining. Particularly in five-axis machining, they can be amplified by the movement of the rotary axes. For example, the error may be the same magnitude on one side of the workpiece, but in the opposite direction on the opposite side, which can double the total error defined by both machining operations (this is also referred to as "reversion errors").

[0094] Also, the position of the center of rotation and the axis of rotation of a rotary axis in machine assembly cannot always be determined without errors - especially when both rotary axes are located one above the other (rotary axes that build on one another, e.g. as a rotary table 130 rotatably mounted on a swivel table 120, see e.g. Fig. 1 and Fig. 2) and the possibly limited swivel range of the swivel axis prevents rotation by 180°, which facilitates many measurements.

[0095] It is preferable to consider that, even with extremely precise machine tools, there are usually limits to the alignment of the straightness and angularity of the axes relative to each other. These limits are defined by the machining accuracy of the machine components and the accuracy of the measuring instruments.

[0096] In practice, this usually means that a very precise machine geometry is achieved when the individual axes are straight in the range of preferably less than or equal to 10µm and are perpendicular to each other in the range of preferably less than or equal to 10µm.

[0097] These small errors in the individual axes can add up to larger values ​​in five-axis machining with swiveling of the spindle and / or workpiece in space. The magnitude of the errors may then depend on the relative spatial position of the axes.

[0098] This means that even a machine whose individual axes are geometrically adjusted and adjusted with extreme precision can still make errors during spatial positioning, the magnitude of which can generally significantly exceed the residual errors. Added to this may be the effects that thermal expansion and deformation, for example, due to (workpiece) weight forces, have on the machine structure, which can lead to the adjusted machine geometry changing slightly during operation.

[0099] Thus, a fully assembled five-axis machine tool usually exhibits undesirable residual errors in which the actual machine kinematics deviate from the kinematic description stored in the control system. This is especially true because many control systems do not have the ability to model all errors of a machine axis, such as roll, pitch, and yaw, in their kinematic model. Instead, the usual kinematic descriptions in the control systems calculate with axes that are ideally straight and ideally perpendicular to each other.

[0100] Thus, the residual errors of the real machine kinematics in the state of the art lead to undesirable positioning errors because the control system calculates with an idealized model of the machine kinematics that does not take the real errors into account.

[0101] To reduce or prevent this limitation, control system manufacturers have introduced state-of-the-art compensation methods, such as so-called sag compensation. These compensation options often have the disadvantage that the entered compensation values ​​are not part of the machine's kinematic description and are therefore not "carried along" during movements of the swivel axis, for example, in which the spindle and / or the workpiece change their spatial position.

[0102] The methods described here according to embodiments of the invention can be used to measure the actual machine kinematics using simple means and / or to use these measured values: e.g., to determine deviations from the kinematics calculation model and to use these deviations as compensation values ​​to correct the errors of the actual movements compared to the target movement; and / or to determine the deviations of the actual kinematics from the kinematics calculation model and to use these deviations to correct the kinematics calculation model of the machine control.

[0103] This can successfully and advantageously achieve a significant reduction in the errors that occur during positioning in space, so that the positioning accuracy of the machine in space can be improved. 2. Advantages of position measurement at at least three rotary axis positions

[0104] EP 1 696 289 A1 describes a method for measuring a rotary axis in a machine. A measuring ball is probed in two positions (two-point measurement) resulting from the further pivoting of the rotary axis to which the measuring ball is mounted. The coordinates of the measurements can be used to determine the pivot point of the rotary axis to which the measuring ball is mounted.

[0105] The disadvantage of this method is that errors in the machine geometry and kinematics are also reflected in the measurement and subsequent calculation results and lead to an incorrect determination of the pivot points M and the axis of rotation in space.

[0106] Fig. Figure 6A illustrates, by way of example, the adverse impact of a perpendicularity error in a two-point measurement according to EP 1696 289 A1. In the example shown, the center point determined by the measurement is off by half the perpendicularity error of the axes. A perpendicularity error occurs when at least two axes of the machine tool are not exactly perpendicular to each other.

[0107] Fig. Figure 6B illustrates an example of a detrimental influence of a straightness error of an axis in a two-point measurement according to EP 1 696 289 A1. In the example according to Fig. 6B, an arc in one axis also leads to an error in the determination of the rotation axis in a two-point measurement according to EP 1 696 289 A1. Depending on the shape and position of the arcs, these errors lead to a similar error in the determination of the center point M.

[0108] One of the differences between the method proposed in EP 1 696 289 A1 and embodiments of the invention is that it is proposed to measure at least 3 points per measuring plane, e.g. three-point measurement, four-point measurement or N-point measurement when N > 2.

[0109] In this way, the influence of the machine's geometric and kinematic errors on the calculation of the pivot point can be avoided or reduced. This is because the additional information provided by measuring the third point or the additional points N > 2 can be used to advantageously calculate any perpendicularity errors between the measuring axes or any straightness errors of one or more axes.

[0110] The lower susceptibility of the three-point measurement or N-point measurement with N > 2 compared to the two-point measurement of EP 1 696 289 A1 can also be demonstrated with the help of the Fig. 6C will be explained. Fig. 6C illustrates an example of an advantage of a three-point measurement according to embodiments of the invention in the event of a possible perpendicularity error;

[0111] If the first measuring point "1" is taken as the starting point for determining the pivot point, one of the other two points ("2") lies on the same side of the table relative to the measuring axes. However, the third point "3" lies on the other side of the table – at least if the three measuring points lie on a fairly evenly divided circumference of the flight circle of the measuring sphere 300.

[0112] The center point "M1" determined by measuring the first two points "1" and "2" is distorted by the perpendicularity error, as described above. However, if the center point "M2" is determined between points "1" and "3," the determined pivot point lies on the other side of the table center. Thus, both errors cancel each other out.

[0113] In other words: By measuring at least three measuring points “1”, “2” and “3” (in the example at 0 degrees, 120 degrees and 240 degrees of the C-axis), preferably evenly distributed around the circumference of the flight circle of the measuring sphere 300, the influence of the geometric and kinematic errors of the measuring machine axes on the accuracy of the rotation center determination can be completely excluded (if the perpendicularity error is calculated), or at least greatly reduced (if two pivot points are determined and calculated from the three measurements).

[0114] If the results are used to compensate for the movements or to correct the kinematic calculation model of the machine, the result is also the elimination of the errors to which EP 1696 289 is still susceptible.

[0115] Measuring at least three points also offers the advantage that the position of the rotary axis can be easily determined, since the three points span a plane (measuring plane) on which the rotary axis is perpendicular and runs through the center of rotation.

[0116] It is thus clearly evident that the method proposed here according to embodiments of the invention is superior to the method from EP 1 696 289 A1, especially since, as will be presented in the following sections in connection with embodiments, it enables significantly more extensive compensation of the machine errors, e.g. by integrating further measuring steps and / or including further parameters. 3. First exemplary surveying procedure

[0117] In a first exemplary sub-method, the errors described above in determining the center of rotation and the axis of rotation of a rotary axis are preferably avoided by probing at least three points in space, ie in a three-point measuring method.

[0118] This is done in exemplary embodiments by, for example, attaching or positioning a measuring ball 300 with a known diameter on the machine table (rotary table 130) away from the center of the rotary table 130.

[0119] The position of the measuring sphere 300 is recorded, for example, with the aid of a measuring probe or also by means of a laser measuring unit, if necessary by repeatedly probing or measuring the measuring sphere 300 at different points on the surface of the measuring sphere 300 while maintaining the same positioning of the rotary table 130.

[0120] The rotary table 130 is then indexed by, for example, 120° (generally preferred by an angle of 360 / N degrees for an N-point measurement), and the new position of the measuring sphere 300 is again recorded by probing. Finally, the measuring sphere 300 is indexed another time by, for example, 120°, and the new position is again recorded (example 3-point measurement at C = 0 degrees, C = 120 degrees, and C = 240 degrees).

[0121] Since the probing of two points is theoretically sufficient to determine a rotation center of the rotary table 130, the measurement of the third point provides additional information which - as described above - can be used according to the invention to determine the perpendicularity or the perpendicularity error between the two rotary axes.

[0122] Measuring the third point also allows - as also described above - the determination of the rotational axis of the rotary table 130 by calculating a plane between them to which the rotational axis (first rotary axis) should be perpendicular. This is theoretically possible with the measurement of two points, even if the rotary axis angle between the first and second points was not rotated by exactly 180 degrees, but, for example, only by 90 degrees or 120 degrees.

[0123] However, the accuracy of the axis calculation is many times higher when measuring three (or more) points relatively evenly distributed around the circumference of a circle, because the plane used for the calculation covers a much larger area.

[0124] To increase the accuracy, the number of measurements can be increased to, for example, four, whereby the measuring points are then preferably rotated by, for example, 90 degrees.

[0125] In a second sub-method, the machine tool kinematics of a five-axis machine are measured according to the invention by measuring the real center of the machine table and the real plane of the machine table for at least two and preferably three or more angular positions of the machine swivel axis offset by an angle.

[0126] The rotation centers and rotation axes determined in this way will potentially deviate from the position that they would or should assume according to the machine kinematics model stored in the machine control system due to residual errors in the individual components of the machine, residual errors in the measuring systems, residual errors in the machine kinematics, i.e. the deviations of the machine axes from ideal straightness and angularity, heat-induced expansion of the machine components, and / or force-induced expansion of the machine components.

[0127] These deviations can now be calculated using the measurement results from outside and / or inside the machine control system and stored as correction values ​​in the control system or in the control system's kinematics description. The machine then performs additional movements with one, several, or all axes (including, if necessary, the rotary axes) to compensate for the measured errors based on the correction values. These additional movements allow the machine to position itself significantly more precisely in space.

[0128] If the measurement is repeated more than twice for different positions of the swivel axis (e.g. in steps of 15° swivel angle), not only the deviation of the position of the center and the axis orientation of the first rotary axis but also the center and the axis orientation of the second rotary axis (e.g. swivel axis) of the machine can be calculated and compared with the target positions according to the description of the machine kinematics stored in the control system.

[0129] The measurement in the swivel angle steps also allows the description of the deviation of the real path described by the center of the first rotary axis and the deviation of the orientation of the real rotation axis of the rotary axis from the corresponding target values ​​according to the kinematics description of the machine control over the swivel range of the swivel axis.

[0130] This measurement preferably includes all described errors of the involved axes—preferably all four, five, or more machine axes. Since the deviation between the target and actual path of the turning center and the deviation between the target and actual orientation of the rotation axis are known after the measurement is completed, the errors can be compensated by performing compensating movements on one, several, or preferably all, linear and rotary axes of the machine tool.

[0131] This makes it possible, for example, to correct the movement of the rotary or swivel axis and to correct the other machine axes relative to the rotary or swivel axis in space, which leads to a significant increase in the accuracy of the workpiece positioning.

[0132] The determined correction values ​​can be used in different ways to carry out the desired correction in the machine control or the NC control.

[0133] One practical option is to overlay the path specification of the NC program with one or more compensation values ​​that reduce the motion errors. However, this approach would be disadvantageous in that it would interfere with the control system on the "program side."

[0134] A much more practical approach is to use the measured path deviations to determine the geometric errors causing the path deviations. The effects of these geometric errors—for example, a possible angular error between two of the machine tool's axes, or the deviating length of a console—on the machine's movement can be advantageously reduced by changing or correcting the machine's kinematic description.

[0135] Another efficient and easy-to-implement third option with very good accuracy is the storage or saving of correction values ​​- e.g. in matrix form, data list, or table form - in the control system and the preferred automatic modification, e.g. by adding the correction values ​​to the axis position(s) of the linear and / or rotary axes.

[0136] With the help of a subroutine provided by the control system or a subroutine programmed for this purpose, the axis positions of the machine can be read out, the correction values ​​suitable for the axis positions can be taken from the tables or calculated and preferably returned to the control system in the controller cycle and added to the axis position as a correction value.

[0137] An exemplary measuring method according to an embodiment of the invention is described below with reference to the Fig. 3A to 5C. This relates, for example, to a three-point measuring method at, for example, three angular positions of the second rotary axis or, for example, in this embodiment, at three angular positions of the swivel axis.

[0138] Fig. 3A to 3C schematically show an exemplary three-point measurement according to an embodiment of the invention in an exemplary horizontally oriented first measuring plane.

[0139] In Fig. 3A to 3C schematically illustrate a rotary table 130 of a machine tool 100, which is rotatable or rotatably movable by means of a C-axis (e.g., configured as a rotary axis) about a rotation axis axially aligned with the rotary table 130. During workpiece machining on the machine tool 100, a workpiece can, for example, be clamped to or on the rotary table 130.

[0140] By way of example, a test object, here for example a measuring sphere 300 with a preferably previously known diameter, is positioned on the rotary table 130 at a radial distance from the axis of rotation of the rotation axis C.

[0141] By repeatedly probing the surface of the measuring sphere 300 at different surface points of the measuring sphere 300 by means of a measuring probe tip 210 of a measuring probe device 200 mounted on the work spindle 170 of the machine tool 100, a reference position of the measuring sphere 300, such as the spatial position of the sphere center point of the measuring sphere 300, can be determined or preferably triangulated.

[0142] If the diameter of the measuring sphere 300 is known, it is sufficient to determine three surface points of the measuring sphere 300 by scanning and to determine the reference position of the measuring sphere 300, such as the spatial position of the sphere center of the measuring sphere 300, using the known diameter or radius of the measuring sphere 300.

[0143] If more than three surface points of the measuring sphere 300 are measured, the reference position of the measuring sphere 300, such as the spatial position of the sphere center of the measuring sphere 300, can even potentially be determined without knowledge of the diameter, since if more than three surface points of the measuring sphere 300 are measured, the system of equations to be solved would be overdetermined if the measuring sphere diameter were known.

[0144] For example, it is assumed that the Fig. 3A, the angular position of the C-axis is at 0 degrees, i.e., C = 0 degrees. Since this is merely an example of a rotational axis that can rotate continuously, it would be unimportant whether the angular position is designated as 0 degrees or 360 degrees, or as a positive or negative integer multiple of 360 degrees, i.e., C = 0 degrees = 360 degrees.

[0145] However, if the rotary table 130 were designed as a swivel axis with, for example, a swivel range of 0 degrees to 360 degrees, the 0-degree and 360-degree positions would have to be differentiated, since in each case, movement would only be possible in a clockwise or counterclockwise direction. However, in this case, a different rotary table coordinate system would preferably be selected, one in which, for example, from an angular position of 0 degrees, it would be possible to swivel in both directions up to +180 degrees and down to -180 degrees.

[0146] Show examples Fig. 3A to 3C a three-point measurement, in which the rotary table 130 is, for example, after measuring the measuring ball 300 in Fig. 3A by 120 degrees to the angular position C = 120 degrees of the C-axis (ie into a second angular position of the C-axis or the first rotary axis, compared to the first angular position of the C-axis or the first rotary axis according to Fig. 3A) with the same angular position of the B-axis (second rotary axis) is further rotated, see e.g. Fig. 3B, in order to again scan the measuring sphere 300 with the measuring probe tip 210 of the measuring probe device 200 to determine the corresponding reference position of the measuring sphere 300, such as the spatial position of the sphere center of the measuring sphere 300, and in which the rotary table 130, for example, after measuring the measuring sphere 300 in Fig. 3B by a further 120 degrees to the angular position C = 240 degrees of the C-axis (ie into a third angular position of the C-axis or the first rotary axis, compared to the second angular position of the C-axis or the first rotary axis according to Fig. 3B) with the same angular position of the B-axis (second rotary axis) is further rotated, see e.g. Fig. 3C, in order to scan the measuring sphere 300 again - a third time according to the three-point measurement - with the measuring probe tip 210 of the measuring probe device 200 in order to determine the corresponding reference position of the measuring sphere 300, such as the spatial position of the sphere center point of the measuring sphere 300.

[0147] After determining the three reference positions of the measuring ball 300 in the angular positions C = 0 degrees, C = 120 degrees and C = 240 degrees according to Fig. 3A to 3C, based on the three reference positions of the measuring sphere 300, the center of rotation of the rotation axis of the rotary table 130 or, if the height of the measuring sphere 300 above the rotary table 130 is known, the position of the rotary table center point can be determined or triangulated. This results in the previously described advantages of the three-point measurement over the previously known two-point measurement.

[0148] In addition, a first measuring plane can be determined, which describes the plane in which all three determined reference positions of the measuring ball 300 in the angular positions C = 0 degrees, C = 120 degrees and C = 240 degrees according to Fig. 3A to 3C.

[0149] In this case, an orientation of the rotation axis of the C-axis or of the rotary table 130 (e.g. table axis vector) can be determined as a straight line perpendicular to the determined first measuring plane or as a normal vector of the first measuring plane.

[0150] Thus, the three-point measurement according to Fig. 3A to 3C both an accurate, efficient and simple determination of the rotation center and the rotation axis direction of the C-axis of the rotary table 130 can be carried out.

[0151] For example, Fig. 3A to 3C, the C-axis is each indexed by 120 degrees from one measuring point position to the next measuring point position of the three measuring point positions (e.g. corresponding to 360 / N degrees with N = 3), although other indexing is also possible.

[0152] In particular, the respective angular distances do not have to be equal or regular. As soon as three different measuring points are measured at different angular positions of the first rotary axis with the same angular position of the second rotary axis (swivel axis), they always lie in one plane (first measuring plane), so that it is possible to draw exactly one circular arc through the three measuring points. Therefore, the center of rotation can be clearly determined, as can the orientation of the rotation axis of the first rotary axis perpendicular to the definable plane (first measuring plane).

[0153] Furthermore, it is possible in further embodiments to carry out a four-point measurement or an N-point measurement with N > 2, wherein, for example, angular positions can preferably, but not necessarily, be further clocked by 360 / N degrees.

[0154] Fig. 4A to 4C schematically show an exemplary three-point measurement according to an embodiment of the invention in an exemplary obliquely aligned second measuring plane.

[0155] In Fig. 3A to 3C, the angular position of the second rotary axis was oriented horizontally. The angular position of the second rotary axis is shown in Fig. 4A to 4C are moved forward by 45 degrees, for example, or rotated, so that a second measuring plane of the Fig. 4A to 4C at 45 degrees to the first measuring plane of the Fig. 3A to 3C.

[0156] Show examples Fig. 4A to 4C thus show a further three-point measurement in a second angular position of the second rotary axis at 45 degrees, for example, compared to Fig. 3A to 3C, in which the rotary table 130 is shown as an example after measuring the measuring ball 300 in Fig. 4A by 120 degrees to the angular position C = 120 degrees of the C-axis (ie into a second angular position of the C-axis or the first rotary axis, compared to the first angular position of the C-axis or the first rotary axis according to Fig. 4A) with the same (second) angular position of the B-axis (second rotary axis) is further rotated, see e.g. Fig. 4B, in order to again scan the measuring sphere 300 with the measuring probe tip 210 of the measuring probe device 200 to determine the corresponding reference position of the measuring sphere 300, such as the spatial position of the sphere center of the measuring sphere 300, and in which the rotary table 130, for example, after measuring the measuring sphere 300 in Fig. 4B by a further 120 degrees to the angular position C = 240 degrees of the C-axis (ie into a third angular position of the C-axis or the first rotary axis, compared to the second angular position of the C-axis or the first rotary axis according to Fig. 3B) with the same (second) angular position of the B-axis (second rotary axis), see e.g. Fig. 4C, in order to scan the measuring sphere 300 again - a third time according to the three-point measurement - with the measuring probe tip 210 of the measuring probe device 200 in order to determine the corresponding reference position of the measuring sphere 300, such as the spatial position of the sphere center point of the measuring sphere 300.

[0157] After determining the three reference positions of the measuring ball 300 in the angular positions C = 0 degrees, C = 120 degrees and C = 240 degrees according to Fig. 4A to 4C, based on the three reference positions of the measuring sphere 300, for the second angular position of the second rotary axis, the center of rotation of the rotation axis of the rotary table 130 or, if the height of the measuring sphere 300 above the rotary table 130 is known, the position of the rotary table center point can be determined or triangulated. This results in the already described advantages of the three-point measurement over the previously known two-point measurement.

[0158] In addition, a second measuring plane can be determined for the second angular position of the second rotary axis, which describes the plane in which all three determined reference positions of the measuring ball 300 in the angular positions C = 0 degrees, C = 120 degrees and C = 240 degrees according to Fig. 4A to 4C.

[0159] In this case, an orientation of the rotation axis of the C-axis or of the rotary table 130 (e.g. table axis vector) can be determined as a straight line perpendicular to the determined second measuring plane or as a normal vector of the second measuring plane.

[0160] Thus, the three-point measurement according to Fig. 4A to 4C, both the center of rotation and the direction of rotation of the C-axis of the rotary table 130 for the second angular position of the second rotary axis can be determined accurately, efficiently and easily.

[0161] For example, Fig. 4A to 4C, the C-axis is each indexed by 120 degrees from one measuring point position to the next of the three measuring point positions (e.g., corresponding to 360 / N degrees with N = 3), although other indexing cycles are also possible. Furthermore, it is again possible to perform a four-point measurement or an N-point measurement with N > 2 in further embodiments, whereby, for example, angular positions can be indexed by 360 / N degrees each, preferably but not necessarily.

[0162] Fig. 5A to 5C schematically show an exemplary three-point measurement according to an embodiment of the invention in an exemplary vertically oriented third measuring plane.

[0163] An example is the angular position of the second rotary axis in Fig. 5A to 5C are moved further by an example of a further 45 degrees, or given away or rotated, so that a third measuring plane of the Fig. 5A to 5C exemplarily vertically and in particular exemplarily at 45 degrees to the second measuring plane of the Fig. 4A to 4C or, for example, at 90 degrees to the first measuring plane of the Fig. 3A to 3C.

[0164] Show examples Fig. 5A to 5C thus show a further three-point measurement in a third angular position of the second rotary axis at 90 degrees as an example compared to Fig. 3A to 3C, in which the rotary table 130 is shown as an example after measuring the measuring ball 300 in Fig. 5A by 120 degrees to the angular position C = 120 degrees of the C-axis (ie into a second angular position of the C-axis or the first rotary axis, compared to the first angular position of the C-axis or the first rotary axis according to Fig. 4A) with the same (third) angular position of the B-axis (second rotary axis) is further rotated, see e.g. Fig. 5B, in order to again scan the measuring sphere 300 with the measuring probe tip 210 of the measuring probe device 200 to determine the corresponding reference position of the measuring sphere 300, such as the spatial position of the sphere center of the measuring sphere 300, and in which the rotary table 130, for example, after measuring the measuring sphere 300 in Fig. 5B by a further 120 degrees to the angular position C = 240 degrees of the C-axis (ie into a third angular position of the C-axis or the first rotary axis, compared to the second angular position of the C-axis or the first rotary axis according to Fig. 5B) with the same (third) angular position of the B-axis (second rotary axis), see e.g. Fig. 5C, in order to scan the measuring sphere 300 again - a third time according to the three-point measurement - with the measuring probe tip 210 of the measuring probe device 200 in order to determine the corresponding reference position of the measuring sphere 300, such as the spatial position of the sphere center point of the measuring sphere 300.

[0165] After determining the three reference positions of the measuring ball 300 in the angular positions C = 0 degrees, C = 120 degrees and C = 240 degrees according to Fig. 5A to 5C, based on the three reference positions of the measuring sphere 300, for the third angular position of the second rotary axis, the center of rotation of the rotation axis of the rotary table 130 or, if the height of the measuring sphere 300 above the rotary table 130 is known, the position of the rotary table center point can be determined or triangulated. This results in the previously described advantages of the three-point measurement over the previously known two-point measurement.

[0166] In addition, a third measuring plane can be determined for the third angular position of the second rotary axis, which describes the plane in which all three determined reference positions of the measuring ball 300 in the angular positions C = 0 degrees, C = 120 degrees and C = 240 degrees according to Fig. 5A to 5C.

[0167] In this case, an orientation of the rotation axis of the C-axis or of the rotary table 130 (e.g. table axis vector) can be determined as a straight line perpendicular to the determined third measuring plane or as a normal vector of the third measuring plane.

[0168] Thus, the three-point measurement according to Fig. 5A to 5C, both the center of rotation and the direction of rotation of the C-axis of the rotary table 130 for the third angular position of the second rotary axis can be determined accurately, efficiently and easily.

[0169] For example, Fig. 5A to 5C, the C-axis is each indexed by 120 degrees from one measuring point position to the next of the three measuring point positions (e.g., corresponding to 360 / N degrees with N = 3), although other indexing cycles are also possible. Furthermore, it is again possible to perform a four-point measurement or an N-point measurement with N > 2 in further embodiments, whereby, for example, angular positions can be indexed by 360 / N degrees each, preferably but not necessarily.

[0170] In addition, it can be advantageously utilized that a respective rotary table position, such as the rotation center of the first rotary axis or a table center point of the rotary table 130, was determined in each three-point measurement of the three angular positions of the second rotary axis, which each lie in a (fourth) measuring plane.

[0171] By triangulating the three rotary table positions, a rotation center position of the second rotary axis can be determined. Based on the (fourth) measurement plane, the perpendicular orientation of the rotation axis of the second rotary axis can be determined. This can then be used, in comparison with the respective determined orientations of the rotation axis of the first rotary axis, to determine a perpendicularity error between the first and second rotary axes.

[0172] Consequently, Fig. 3A to 5C, a simple method is proposed by way of example, in which the rotation centers and alignments of both rotary axes as well as any perpendicularity error can be determined efficiently, accurately, simply and cost-effectively.

[0173] In summary, the invention provides the simplest, most cost-effective, most accurate, most easily implemented and mathematically less complicated measuring methods and / or position error correction methods for compensating the errors in the axis positions of rotary and / or linear axes on machine tools with four, five or even more drive axes and sometimes complex machine kinematics. 4. Second exemplary surveying procedure

[0174] In a separately available measuring method or, in further embodiments, as a further sub-method of the embodiments mentioned under point 3, the method according to the invention can be used to determine the position and path deviations that occur due to changes to the machine. Causes of such changes can be, for example, the influence of a workpiece weight, especially with relatively heavy workpieces.

[0175] Despite the high but finite rigidity of the machine and its components, the weight of the workpiece may lead to possible elastic deformations, particularly in angular positions of the rotary axis(es), where, for example, a rotary table or machine table on which the workpiece is clamped is aligned obliquely or even vertically and is exposed to a potentially large torque due to the weight of the workpiece.

[0176] These deformations potentially change the dimensions, straightness and / or angularity of the machine components and may therefore also lead to a change in the machine kinematics.

[0177] This can be explained using the example of a two-axis machine table in which the console—i.e., a pivoting part—twist due to the influence of the workpiece weight. The torsion and sag of the pivoting part, as well as the spring action of the rotary table bearing, can lead to an inclination error of the workpiece relative to the linear machine axes. In one calculated example, this error is approximately 20 µm, which can therefore well exceed the machining accuracy requirements.

[0178] If a workpiece is manufactured on a machine with these weight-related positioning errors, a truncated pyramid is potentially created. This is an example with regard to Fig. 7 explained. Fig. 7 schematically illustrates a possible machining error on a workpiece WS due to the weight of the workpiece WS.

[0179] For example, the workpiece WS is clamped on a rotary table 130 of the machine tool 100, which is vertically aligned, for example, according to an angular position of the second rotary axis or exemplary pivot axis, so that a torque acts on the rotary table 130 due to the workpiece weight, which can lead to the rotation axis of the rotary axis of the rotary table 130, which theoretically should ideally be aligned horizontally according to the target value, being slightly inclined downwards (this also leads to the rotation axis of the workpiece WS being inclined downwards with the rotary table center axis.

[0180] For example, a tool WZ is used on the work spindle 170 for machining the workpiece WS. If the spindle 170 now moves by means of one of the horizontal axes in a horizontal plane for a traversing movement of a horizontally aligned machining path (dashed line at the base of the tool WZ in Fig. 7) for the removal of material from the workpiece WS, an undesirable truncated cone is potentially created, as shown for example on the right side of the Fig. 7 is shown.

[0181] If the measurements of the position of the center of rotation and the axis of rotation of the machine table relative to the machine axes described above are carried out not only without but also with workpiece weight, the difference in the measured deviations advantageously shows the errors in the machine kinematics that arise from the workpiece weight.

[0182] Since the deformations of the machine components to which these kinematic changes are due are caused by elastic deformations of the machine components, the resulting deviations can be related to the workpiece weight and advantageously used for a workpiece weight-dependent correction of the errors in the machine kinematics caused by the workpiece weight.

[0183] In addition to the workpiece weight, such deformations can also be caused by cutting forces or machine overheating, for example. The resulting deviations can be related to the applied cutting forces and advantageously used to correct the machine kinematic errors caused by the workpiece weight based on the cutting force.

[0184] Put simply, a comparison measurement with a test workpiece (or test weight), e.g. on an inclined or vertically aligned machine table / rotary table, can on the one hand determine position errors when machining a workpiece with the same or a similar weight to the test workpiece on the inclined or vertically aligned machine table / rotary table or can be used to compensate for these errors in the calculation of correction values ​​or changes to the machine kinematics description, and on the other hand the comparison measurement with the test workpiece (or test weight), e.g. on the inclined or vertically aligned machine table / rotary table, can determine position errors when machining a comparatively light workpiece on the inclined or vertically aligned machine table / rotary table, whereby cutting forces arise that exert a torque analogous to the torque caused by the weight of the test workpiece.to compensate for them when calculating correction values ​​or changes to the machine kinematics description.

[0185] A basic idea of ​​the exemplary third method or sub-method according to embodiments is to measure these deformations with the method described above as a function of the triggering parameters - i.e. weight, force and / or temperature - and to use them to generate correction values ​​that are stored in the machine kinematics or that are used by the machine control to calculate corrective movements.

[0186] In both cases, the aim is to correct the deformations by compensating movements of the machine axes and thus improve the dimensional accuracy of the workpiece,

[0187] An exemplary measuring method according to an embodiment of the invention is described below with reference to the Fig. 8A to 10C. This relates, for example, to a three-point measuring method at, for example, three angular positions of the second rotary axis or, for example, in this embodiment, at three angular positions of the swivel axis.

[0188] Fig. 8A to 8C schematically show an exemplary three-point measurement according to an embodiment of the invention in an exemplary horizontally oriented first measuring plane with a clamped test weight TG; Fig. 9A to 9C schematically show an exemplary three-point measurement according to an embodiment of the invention in an exemplary obliquely aligned second measuring plane with a clamped test weight TG; and Fig. 10A to 10C schematically show an exemplary three-point measurement according to an embodiment of the invention in an exemplary vertically aligned third measuring plane with a clamped test weight TG.

[0189] The process steps are analogous to the descriptions of the Fig. 3A to 5C, with the only difference that in Fig. 8A to 10C, for example, a test workpiece or test weight TG with preferably a known weight is clamped on the rotary table 130. 5. Exemplary aspects according to embodiments of the invention

[0190] The aspects below can be combined to form further methods according to further embodiments.

[0191] According to a first exemplary embodiment, a method for determining the center point and the axis of rotation of a rotary axis of a machine tool, in particular a machine tool with at least one and preferably at least two rotary axes, can be determined.

[0192] For example, more than two and at least three measuring points - preferably evenly distributed around the circumference of the rotary axis and thus offset by 120° each, for example - can be recorded by rotating the rotary axis (ie at least three-point measurement or N-point measurement with N > 2), the coordinates of which are used to determine the center of rotation of the rotary axis, to determine the perpendicularity of the machine axes moved for measurement and / or to calculate the axis of rotation of the machine rotary axis.

[0193] For example, the errors determined can be used to change the description of the machine kinematics in the machine control system, so that the errors determined from the measured values ​​can be corrected by the corrections in the machine kinematics description and by corresponding additional movements that the machine control system calculates and executes.

[0194] According to a second exemplary embodiment, a method for measuring and correcting the machine kinematics of a five-axis machine tool can be provided.

[0195] For example, the position of the center of rotation and the axis of rotation of the rotary axis or the rotatable machine table (rotary table 130) can be measured by probing at least three measuring points offset by an angle using a measuring probe attached to the spindle for one or more, and preferably for at least two, positions of the swivel axis of the machine.

[0196] For example, the deviations of the positions of the turning center and rotation axis measured in this way from the target positions that the machine table would have assumed according to the kinematic description stored in the machine control system can be used to store correction values ​​in the machine control system and to overlay the machine's travel commands in all machine axes - e.g. also the rotary axes - in order to achieve greater positioning accuracy between the machine table and the machine spindle.

[0197] By way of example, a method for measuring and / or correcting the machine kinematics of a five-axis machine tool can be provided, which determines the real spatial position of the turning center and / or the rotation axis of the rotary table / machine table, for example by probing at least three measuring points offset by an angle (e.g. using a measuring probe attached to the spindle) for at least two orpreferably three positions of the swivel axis of the machine are measured, and / or the deviations of the spatial positions measured in this way from the center of rotation and / or axis of rotation to the target positions that the rotary table / machine table should have assumed according to the kinematics description stored in the machine control (target positions) are used to change and / or correct the kinematics description stored in the machine control by the measured deviations, preferably in order to achieve greater positioning accuracy between the machine table and the machine spindle.

[0198] By way of example, a method for measuring and / or correcting the machine kinematics of a five-axis machine tool can be provided, in which the actual spatial position of the center of rotation and / or the axis of rotation of the rotary table / machine table is not only measured for two positions of the swivel axis, but for several positions of the swivel axis that are spaced apart by a smaller angular step over the entire swivel range of the swivel axis, and the deviations of the positions of the center of rotation and / or the axis of rotation measured in this way from the target positions that the rotary table / machine table should have assumed according to the kinematic description stored in the machine control system can be used to store correction values ​​in the machine control system over the entire swivel range, which, depending on the swivel position, are assigned to the travel commands of the machine in one, several or all axes - e.g.Linear and / or rotary axes - can be superimposed and thus an improvement in the positioning accuracy between the machine table and the machine spindle can be achieved for the entire swivel range of the swivel axis.

[0199] By way of example, a method for measuring and / or correcting the machine kinematics of a five-axis machine tool can be provided, wherein for a machine kinematics in which the rotation axis is located on the swivel axis (e.g. according to Fig. 1 or Fig. 2), compensation values ​​for the swivel and rotary axes are determined, which ensure that the table plane of the rotary axis assumes the swivel angle in all spatial positions that it should have according to the positioning command of the machine (nominal orientation and actual orientation of the table axis vector).

[0200] By way of example, a method for measuring and / or correcting the machine kinematics of a five-axis machine tool can be provided, wherein several or all measuring and calculation steps are carried out with and without a workpiece weight or test weight, and the difference in the position deviations with and without a workpiece weight or test weight is used to determine correction values ​​related to the workpiece weight or test weight as a function of the weight for the movement of the machine axes, with the aid of which correction values ​​can be corrected which arise on the machine components due to the workpiece weight and which in turn change the machine kinematics. 6. Calculation basis

[0201] A method according to some embodiments is preferably based on the comparison of a measured actual vector with a desired vector according to the kinematics description in the machine control.

[0202] Rotation matrices can be used here. The rotation of a vector around the principal axes of a coordinate system can be described as follows: Around the X axis: Rφ,ex→=[1000cos(φ)−sin(φ)0sin(φ)cos(φ)] Around the Y axis: Rφ,ey→=[cos(φ)0−sin(φ)010sin(φ)0cos(φ)] Around the Z axis: Rφ,ez→=[cos(φ)−sin(φ)0sin(φ)cos(φ)0001].

[0203] A rotation around the axis normalized to length 1 (e.g. around a unit vector parallel to the axis) n→=[n1n2n3] around the angle φ in space can be described by: Rφ,n→=[n12(1−cos(φ))+cos(φ)n1n2(1−cos(φ))−n3 sin(φ)n1n3(1−cos(φ))+n2 sin(φ)n2n1(1−cos(φ))+n3 sin(φ)n22(1−cos(φ))+cos(φ)n2n3(1−cos(φ))−n1 sin(φ)n3n1(1−cos(φ))−n2 sin(φ)n3n2(1−cos(φ))−n1 sin(φ)n32(1−cos(φ))+cos(φ)] Description of an exemplary procedure

[0204] The calculation of the target movement and the correction values ​​by means of a target-actual comparison can, in exemplary embodiments, depend on the respective kinematics of the machine to be measured and may need to be adapted to the respective kinematics.

[0205] The further calculation method according to an example calculation is exemplary for a machine with a kinematics with a rotary table 130 (C-axis) rotatably mounted on a swivel table 120 (B-axis), e.g. corresponding to the machine tool according to Fig. 2, wherein the exemplary machine according to Fig. 1 can be calculated analogously.

[0206] Fig. 11 shows a schematic exemplary representation of a part of a machine kinematics description according to an embodiment of the invention.

[0207] The kinematics of the machine are described in the control system by the vector from the axis zero point (0,0,0) of the machine to the table center point of the rotary table 130 at B = 0 degrees (i.e. with horizontally aligned rotary table 130 or vertically aligned rotation axis of the C-axis): (mTABLE,B0°→), the in Fig. 11 is designated as v1 by way of example, and further by the vector from the table center to the axis intersection point of B (swivel) axis and C (rotation) axis: vACP→, the in Fig. 11 is designated as v2, and further by the two angles ϑConsole,z and ϑConsole,x, which in Fig. 11 are designated as a1 and a2, and which describe, by way of example, the inclination of the rotation axis of the B axis around the directions of the X and Z axes of the machine coordinate system. The term "console" is an exemplary designation for a swivel part or swivel table of the machine tool.

[0208] According to the exemplary position of the turntable 130 in Fig. 11 is the table axis vector v2 (or vector in the direction of the rotation axis of the C-axis) axial to the vector v2 (vAKP→ at B=0). If the rotary table 130 is pivoted about the rotation axis of the B-axis (swivel axis), this vector v2 pivots along with it, since it remains aligned from the table center to the axis intersection point of the B-(swivel) axis and the C-(rotation) axis.

[0209] The change in vector v2 when the table is swiveled can be calculated as the target table axis vector based on the kinematics description of the numerical control and the swivel angle (setpoint) of the C-axis and compared with a table axis vector calculated from the measurement (actual table axis vector), whereby one or more correction values ​​can be calculated for the machine control, provided that the target and actual table axis vectors are calculated to the same value (or the difference does not exceed a preset limit).

[0210] Likewise, the position of the table center changes when the rotary table 130 is pivoted, so that the direction and magnitude of the vector v1 change with respect to the vector stored in the kinematics description (mTABLE,B0°→) change.

[0211] The change in vector v1 when the table is swiveled (and / or during linear movements with one or more of the linear axes) can be calculated as the target table center vector based on the kinematics description of the numerical control and the swivel angle (setpoint) of the C-axis (and, if applicable, the axis positions of the linear axes) and compared with a table center vector calculated from the measurement (actual table center vector), whereby one or more correction values ​​can be calculated for the machine control, provided that the target and actual table center vectors are calculated to the same value (or the difference does not exceed a preset limit).

[0212] In the example according to Fig. 1 are exemplary a1 = 90 degrees and exemplary a2 = 0, and in the example according to Fig. 2 are for example a1 = a2 with for example a1 = a2 = 45 degrees.

[0213] Preferably, the coordinates or reference parameters (such as the reference parameters described above) (vAKP→,mTISCH,B0°→,ϑKonsole,z and ϑKonsole,x) In exemplary embodiments, the machine kinematics description specifies the machine coordinate system relative to a machine zero point with coordinate axes aligned parallel to the linear axes X, Y, and Z. However, it is also possible to select other reference coordinate systems, whereby a different or further three-dimensional coordinate transformation could be performed.

[0214] Since the workpiece can be clamped on the rotary table 130 during machining, only a vector from the center of the machine table to the workpiece zero point would have to be specified for the conversion / transformation between the workpiece coordinate system and the machine coordinate system, and a workpiece orientation would have to be specified by an alignment vector for rotationally symmetrical workpieces and two alignment vectors for non-rotationally symmetrical workpieces with respect to the table axis vector.

[0215] This has the advantage that the spatial position and orientation of a clamped workpiece does not have to be measured or specified in relation to the machine coordinate system, but can simply be specified in relation to the rotary table / machine table or a relative coordinate system of the rotary table / machine table. NC data, NC programs, NC subprograms, or numerical machining data for workpiece machining can then be specified in the workpiece coordinate system, with the machine control transforming values ​​of the workpiece coordinate system or workpiece reference parameters specified in the machining data into the machine coordinate system based on the workpiece coordinate data in the rotary table coordinate system and the reference parameters stored in the kinematics description.The correction of the reference parameters stored in the kinematics description in embodiments of the invention thus enables more precise machining of the workpiece, since the accuracy of the coordinate system transformations of the machine control can be carried out more precisely. General kinematic correction

[0216] With a method according to some embodiments of the invention, the deviations between the target position and the actual position of one, several or all machine axes can be measured and / or corrected.

[0217] Since the measured kinematic errors may be machine-specific, it is preferable that the method can be performed on each individual machine or machine type whose kinematics are to be improved. It is conceivable to calibrate the machine tool after production and / or repeatedly during recalibration or maintenance work.

[0218] It is also conceivable that a calibration process cycle is stored in the control system of the machine tool, which enables an operator to have a calibration or machine tool measurement carried out automatically by the machine control system when required or desired. Calculation of actual table axis vector and actual table center point:

[0219] By cycling the rotation axis by 120 degrees each (for example, with three position measurements per measuring plane), three points are measured for each position of the swivel axis. p1→,p2→,p3→∈ℝ3 measured.

[0220] The center of rotation (=table center) of the rotary table 130 is then: m→(b)=13⋅∑i=13pι→;<@P_MID> certainly.

[0221] The normal vector on the measured plane (measurement plane) is calculated as follows: ne,IST→(b)Sp−KS=(p3→−p1→)×(p2→−p1→).

[0222] The vector is then converted to a unit vector if necessary.

[0223] By applying this calculation, a unit normal vector (ie the actual table axis vector) can be determined for each swivel axis position of the swivel table.

[0224] The actual table center point of the rotary table 130 can be calculated from the measured values ​​using the known height of the measuring plane above the table top - this height results, for example, from the sum of the measuring probe length and the measuring ball height: mTABLE,IST→(b)SP−KS=m→(b)−Rb,eVob→∗[00hmess]

[0225] This includes Rb,eVob→ the general rotation matrix around the B-axis of the machine by the angle b.

[0226] The vector of the B-axis eVob→=Rϑconsole,x,ex→⋅Rϑconsole,z,ez→⋅(−ey→) is also known from the kinematics of the machine, where it is determined by means of the angle ϑ Konsole,z and ϑ Konsole,x described. Calculation of the target table axis vector and the target table center point:

[0227] The theoretically ideal normal vector or target table axis vector no,SHALL→ can be obtained by transforming the ideal unit vector e→=

[001] around the swivel axis of the swivel table 120 with the known swivel angle b.

[0228] The following applies, for example: ne,TARGET→(b)SP−KS=Rb,eVob→ e→

[0229] The target table center point can again be determined using the kinematic description of the machine: mTISCH,TARGET→(b)SP−KS=mTISCH,B0°→−vAKP→+Rb,eVob→∗vAKP→

[0230] This includes mTABLE,B0°→ For example, the coordinates of the table center at B = 0 degrees taken from the kinematics description and vAKP→ the vector from the table center to the axis intersection point, see Fig. 11: Vectors v1 and v2. These values ​​are provided as examples in the kinematic description of the machine. Calculation of the angular deviations between the actual and target table axis vector

[0231] The angular deviations between the actual and the nominal table axis vector in the spindle coordinate system can be determined as follows: angledw(b)SP−KS=[∝βγ]= =[sin−1((ne,ACTUAL→×ne,TARGET→)⋅ex→)sin−1((ne,ACTUAL→×ne,TARGET→)⋅ey→)sin−1((ne,ACTUAL→×ne,TARGET→)⋅ez→)] Calculation of the position deviations between the actual and target table axis vector

[0232] The position difference in the spindle coordinate system is given, for example, by: mTABLE,DIFF→(b)SP−KS=mTABLE,ACTUAL→(b)−mTABLE,TARGET→(b)

[0233] Thus, the actual and target table axes and table center and the deviations between the two in all six degrees of freedom are known as examples. Calculation of the values ​​for correcting the machine kinematics

[0234] The two difference vectors, which contain the errors between the nominal and actual kinematics, can be transformed into the individual axes according to the machine's kinematic transformation, for example, to determine the required correction movement in the local coordinate system of the respective axis. This applies in particular to the correction of the rotary axes.

[0235] First, the angular deviation can be transformed into the B-axis coordinate system: angular devi→(b)B−KS=[∝BβBγB]B−KS= =Rϑx,ex→⋅Rϑz,ez→⋅angular devi→(b)Sp−KS

[0236] The angular deviation β B corresponds directly to the required angle correction around the B-axis.

[0237] The correction movement of the B or swivel axis may, for example, cause a rotation of the C or rotary axis located on it. This can be undone as an unintended consequence of the correction movement around B. It can be calculated, for example, by shifting the actual table axis vector around B by the correction value. ne corr_B→(b)Konsol−KS=Rϑconsole,x,ex→⋅Rϑconsole,z,ez→⋅R(b−βB),eVob→⋅ne IST→(b)SP−KS

[0238] The target table axis vector can also be moved into this coordinate system. ne SOLL→(b)Konsol−KS=Rϑconsole,x,ex→⋅Rϑconsole,z,ez→⋅R(b−βB),eVob→⋅ne SOLL→(b)SP−KS

[0239] The angle difference between both vectors angle abw→(b)Konsol−KS=[∝KonsolβKonsolγKonsol]=[sin−1((ne,corr_B→Konsol−KS×ne,SET→Konsol−KS)⋅ex→)s in−1((ne,korr_B→Konsol−KS×ne,SOLL→Konsol−KS)⋅ey→)sin−1((ne,korr_B→Konsol−KS×ne,SOLL→Konsol−KS)⋅ez→)] contains in the form of γ Konsolthe potential correction value for the C or rotary axis of the machine.

[0240] The correction movement of the B-axis may also cause an inclination of the rotary axis relative to the spindle. This can be superimposed on the original error of the rotary axis. This error can be calculated by adjusting the table axis vector in the spindle coordinate system by β. B is twisted. ne corr_B→(b)SP−KS=⋅R(−βB),eVob→⋅ne IST→(b)SP−KS

[0241] Now the twist between the β B corrected table axis vector can be calculated: winklabw→(b)corrB,SP−KS=[∝Corr_BβKorr_BγKorr_B]=[sin−1((ne,corr_B→SP−KS×ne,SET→SP−KS)⋅e x→)sin−1((ne,corr_B→SP−KS×ne,SET→SP−KS)⋅ey→)sin−1((ne,corr_B→SP−KS×ne,SET→SP−KS)⋅ez→)]

[0242] The angle γ Korr_Bcorresponds, for example, to the angle by which the table plate of the rotary table 130 is / can be rotated about the Z axis relative to the spindle coordinate system due to the original error and the correction rotation about B.

[0243] This value can be applied to the spindle's coordinate system as a virtual rotation around the spindle axis and can thus be corrected.

[0244] The correction(s) in X, Y, or Z may consist, on the one hand, of the original error, which is expressed by the vector. On the other hand, the corrective movement of the B-axis may result in a shift of the table center in X, Y, or Z, which can also be corrected.

[0245] This displacement can be calculated, for example, by imposing the correction B rotation on the table center: mTable:Corr_B→(b)=[vAKP,DIFF1vAKP,DIFF2vAKP,DIFF3]=R(b−βB),eVob→[vAKP,TARGET1vAKP,TARGET2vAKP,TARGET3]−[vAKP,TARGET1vAKP,TARGET2vAKP,TARGET3]

[0246] The total correction is therefore, for example, as follows: mTABLE,totalCorr→(b)SP−KS=mTABLE,DIFF→(b)+mTABLE,Corr_b→(b) Correction of errors caused by weight

[0247] The weight of a workpiece can cause deflections, bends, or inclinations in the machine structure. These effects may also be a source of deviations between the actual kinematics and the desired kinematics, because the relative positions of the machine axes can change or be changed.

[0248] Since the mechanical stiffness of the machines is comparable within narrow tolerances, the weight force effects on different machines of the same type are also comparable due to the same weight force.

[0249] Thus, the weight-dependent kinematic correction is not machine-specific, but can be performed as a calibration measurement on a machine of a particular type, e.g., during the machine's development phase or at the beginning of series production. The results can then be applied to all machines of that type and, if necessary, stored as standard in the machine control system.

[0250] For example, it is conceivable that correction values ​​are stored as functions or interpolation data depending on a workpiece weight, so that later during processing on the machine only the weight of the workpiece can be measured or entered in another way, so that the weight-dependent correction can be carried out automatically on the basis of the workpiece weight information input on the control system. Measurement of the actual table axis vector and the actual table center point without weight load

[0251] By cycling the rotary axis of the rotary table by 120° each (for example with three position measurements), three points are measured for each position of the swivel axis of the swivel table 120 p1→,p2→,p3→∈ℝ3 measured.

[0252] The center of rotation (=table center) of the rotary table 130 is then: m→oG(b)=13⋅∑1=13pι→;<@P_MID> certainly.

[0253] The normal vector (=table axis vector) on the measured plane is calculated as follows: ne,IST,oG→(b)Sp−KS=(p3→−p1→)×(p2→−p1→).

[0254] The vector is then converted to a unit vector. Applying this calculation operation determines a unit normal vector—the actual table axis vector—for each swivel axis position.

[0255] The actual table center point is calculated from the measured values ​​using the known height of the measuring plane above the table top - this height results from the sum of the measuring probe length and the measuring ball height: mTABLE,ACTUAL,oG→(b)SP−KS=m→(b)−Rb,eVob→∗[00hmess]

[0256] This corresponds to the calculations according to (8), (9) and (10) of an exemplary procedure according to the example calculation above (see e.g. Fig. 3A to 5C). Measurement of the target table axis vector and the target table center point with weight load

[0257] The measurements according to (25), (26) and (27) can be repeated with weight (e.g. with test weight TG clamped on the turntable): m→mG(b)=13⋅∑i=13pι→;<@P_MID> ne,IST.mG→(b)Sp−KS=(p3→−p1→)×(p2→−p1→). mTABLE,ACTUAL,MG→(b)SP−KS=m→(b)−Rb,eVob→∗[00hmess]

[0258] This corresponds to the calculations according to (8), (9) and (10) of an exemplary procedure according to the above example calculation, but with the workpiece or test weight TG clamped on the turntable 130 (see e.g. Fig. 8A to 10C). Calculation of corrective movements

[0259] The corrective movements of the machine axes can be calculated analogously to the general kinematic correction. However, in preferred embodiments, the vectors without weight can be used instead of the target vectors. 7. Control device

[0260] Fig. 12 shows a schematic exemplary representation of a control device 400 according to an embodiment. This can be used, for example, in connection with a machine tool, for example according to Fig. 1 or 2 or a machine tool with preferably at least two rotary axes.

[0261] For example, the control device 400 may be configured to control or perform a method on the machine tool according to one or more of the exemplary aspects described above.

[0262] By way of example, the control device 400 comprises an interface 410 to the machine tool; a storage device 420 for storing machining data (e.g. NC programs or NC subprograms and / or cycle programs for the above-mentioned measuring or correction methods), machine kinematics or machine data of the machine tool indicating machine kinematics and / or workpiece weight machine data indicating correction values ​​for the machine kinematics of the machine tool as a function of a workpiece weight; a data processing device 430 of a numerical control of the machine tool for controlling the machine tool on the basis of numerical machining data and the machine kinematics of the machine tool and for transforming coordinate data between a relative coordinate system and a machine coordinate system of the machine tool on the basis of the machine kinematics of the machine tool; and by way of example in Fig.12 also an input unit 440 (e.g. keyboard, computer mouse, control buttons or rotary knobs and / or touch screen) which enables an operator to enter a workpiece weight of a workpiece to be machined; wherein the data processing device 430 is preferably configured to adapt the machine kinematics or the machine data indicating the machine kinematics for machining the workpiece on the machine tool 100 by means of correction values ​​of the machine kinematics on the basis of the entered workpiece weight.

[0263] In summary, the invention provides the simplest, most cost-effective, most accurate, most easily implemented and mathematically less complicated measuring methods and / or position error correction methods for compensating the errors in the axis positions of rotary and / or linear axes on machine tools with four, five or even more drive axes and sometimes complex machine kinematics. List of reference symbols 100 machine tools 110 Machine bed 120 swivel table 130 turntable 140 first axle slide 150 second axle slide 160 third axle slide 170 work spindle 180 tool magazine 190 tool changing device 200 measuring device 210 measuring probe 300 test object (test ball / measuring ball) 400 control device 410 interface 420 storage device 430 Data processing facility 440 input unit WS workpiece WZ tool

Claims

[1] Method for measuring a numerically controlled machine tool (100), wherein the machine tool (100) has at least a first controllable rotary axis (C) with a machine part (130) rotatably mounted about a first rotation axis (C) and a second controllable rotary axis (B) for rotating the machine part (130) about a second rotation axis (B) oriented transversely or perpendicularly to the first rotation axis (C), and wherein a workpiece is clamped on the machine part (130) and a measuring object (300) is positioned on the machine part (130) at a radial distance from the first axis of rotation (C), the method comprising: - Determining spatial positions of the measuring object (300) on the workpiece-carrying machine part (130), wherein the respective spatial position of the measuring object (300) is determined in at least three different angular positions of the first rotary axis (C) with respect to the first rotation axis (C) for at least one measuring plane corresponding to an angular position of the second rotary axis (B) with respect to the second rotation axis (B), - Determining one or more coordinate reference parameters of the first rotary axis (C) in the measuring plane corresponding to the angular position of the second rotary axis (B) on the basis of the determined spatial positions of the measuring object (300) as a function of the workpiece weight of the workpiece clamped on the machine part (130). [2] Method according to claim 1, characterized by - adapting machine data stored on the numerical control of the machine tool, which specify a kinematic description of the machine tool (100), on the basis of the determined coordinate reference parameters, and / or - Calculating correction values ​​for reference parameters, in particular axis positions, of the machine tool (100) for adapting the reference parameters, in particular axis positions, when processing numerical machining data for controlling the machine tool (100) by the numerical control of the machine tool on the basis of the numerical machining data. [3] Method according to claim 2, characterized bythat the adaptation of the machine data of the kinematics description of the numerical control of the machine tool or the calculation of correction values ​​for reference parameters of the machine tool (100) is carried out on the basis of a target / actual comparison of the spatial positions of the measuring object (300) or machine coordinate parameters calculated therefrom. [4] Method according to claim 3, characterized by that the target-actual comparison for each of the at least one measuring planes comprises a comparison of an actual orientation of the respective measuring plane with a target orientation of the respective measuring plane of the corresponding angular position of the second rotary axis (B) or a comparison of an actual orientation of the rotational axis of the first rotary axis (C) with a target orientation of the rotational axis of the first rotary axis (C) in relation to the corresponding angular position of the second rotary axis (B). [5] Method according to claim 3 or 4, characterized bythat the target-actual comparison for each of the at least one measuring planes comprises a comparison of an actual position of a rotation center of the first rotary axis (C) with a target position of the rotation center of the first rotary axis (C) in a machine coordinate system. [6] Method according to one of claims 3 to 5, characterized by that the procedure is repeated on the basis of the adjusted machine data or calculated correction values ​​until deviations from the respective target and actual values ​​of the target-actual comparison disappear or at least fall below a specified limit value. [7] Method according to one of claims 2 to 6, characterized by that the machine data of the kinematic description of the machine tool (100) are suitable for being used as a basis for kinematic transformations between a workpiece coordinate system and a machine coordinate system by the numerical control of the machine tool. [8] Method according to one of the preceding claims, characterized by that the determined coordinate reference parameters comprise a center of rotation of the first rotary axis (C) corresponding to the angular position of the second rotary axis (B) and / or an orientation of the first rotary axis (C) corresponding to the angular position of the second rotary axis (B). [9] Method according to claim 8, characterized by , that the respective spatial positions of the measurement object (300) are determined in exactly three different angular positions of the first rotary axis (C) according to a three-point measurement with respect to the first rotation axis (C) for at least one measuring plane corresponding to an angular position of the second rotary axis (B) with respect to the second rotation axis (B); or the respective spatial positions of the measurement object (300) are determined in exactly four different angular positions of the first rotary axis (C) according to a four-point measurement with respect to the first rotation axis (C) for at least one measuring plane corresponding to an angular position of the second rotary axis (B) with respect to the second rotation axis (B). [10] Method according to one of the preceding claims, characterized by that the at least one measuring plane is oriented perpendicular to a spindle axis of a work spindle (170) of the machine tool and / or horizontally, parallel to the spindle axis of the work spindle (170) of the machine tool and / or vertically, or obliquely to the spindle axis of the work spindle (170) of the machine tool and / or at an angle greater than 0 degrees and less than 90 degrees, in particular greater than or equal to 30 degrees and less than or equal to 60 degrees, to a horizontal plane. [11] Method according to one of claims 1 to 9, characterized bythat the respective spatial positions of the measuring object (300) are determined in at least three different angular positions of the first rotary axis (C) with respect to the first rotation axis (C) for at least three different measuring planes corresponding to at least three different angular positions of the second rotary axis (B) with respect to the second rotation axis (B). [12] Method according to claim 11, characterized by that a first measuring plane of the at least three different measuring planes is aligned perpendicular to a spindle axis of a work spindle (170) of the machine tool, a second measuring plane of the at least three different measuring planes is aligned obliquely to the spindle axis of the work spindle (170) of the machine tool, and a third measuring plane of the at least three different measuring planes is aligned parallel to the spindle axis of the work spindle (170) of the machine tool. [13] Method according to claim 11 or 12, characterized by that a first measuring plane of the at least three different measuring planes is aligned horizontally, a second measuring plane of the at least three different measuring planes is aligned at an angle greater than 0 degrees and less than 90 degrees, in particular greater than or equal to 30 degrees and less than or equal to 60 degrees, to a horizontal plane, and a third measuring plane of the at least three different measuring planes is aligned vertically. [14] Method according to one of claims 11 to 13, characterized by that the determined coordinate reference parameters include angular errors between orientations of machine axes (X, Y, Z, B, C) of the machine tool (100). [15] Method according to one of the preceding claims, characterized bythat the respective spatial positions of the measurement object (300) in N different angular positions of the first rotary axis (C) with N > 2 are determined according to an N-point measurement with respect to the first rotation axis (C) for at least one measuring plane corresponding to an angular position of the second rotary axis (B) with respect to the second rotation axis (B), wherein the respective angular positions of the first rotary axis (C) each have an angular distance of 360 / N degrees. [16] Method according to one of the preceding claims, characterized by - clamping a first test weight with a predetermined weight on the machine part (130) of the machine tool, wherein the determination of the respective spatial position of the measurement object (300) is carried out in at least three different angular positions of the first rotary axis (C) with respect to the first rotation axis (C) for at least one measuring plane corresponding to an angular position of the second rotary axis (B) with respect to the second rotation axis (B) with the first test weight clamped on the machine part (130) of the machine tool. [17] Method according to claim 16, characterized by - clamping a second test weight with a predetermined weight that is different from the weight of the first test weight on the machine part (130) of the machine tool, wherein the determination of the respective spatial position of the measurement object (300) is carried out again in at least three different angular positions of the first rotary axis (C) with respect to the first rotation axis (C) for at least one measuring plane corresponding to an angular position of the second rotary axis (B) with respect to the second rotation axis (B) with the second test weight clamped on the machine part (130) of the machine tool. [18] Method according to claim 16 or 17, characterized bythat the determination of the respective spatial position of the measuring object (300) in at least three different angular positions of the first rotary axis (C) in relation to the first rotational axis (C) for at least one measuring plane is carried out once without and once with the first test weight clamped on the machine part (130) of the machine tool, in accordance with an angular position of the second rotary axis (B) in relation to the second rotational axis (B). [19] Device for measuring a numerically controlled machine tool (100), wherein the machine tool (100) has at least a first controllable rotary axis (C) with a machine part (130) rotatably mounted about a first axis of rotation (C) and a second controllable rotary axis (B) for rotating the machine part (130) about a second axis of rotation (B) oriented transversely or perpendicularly to the first axis of rotation (C), and wherein a workpiece is clamped on the machine part (130) and a measuring object (300) is fastened or positioned on the machine part (130) of the machine tool at a radial distance from the first axis of rotation (C), wherein the device comprises a data processing device, with: - means for determining spatial positions of the measuring object (300) on the workpiece-carrying machine part (130), wherein the respective spatial position of the measuring object (300) is determined in at least three different angular positions of the first rotary axis (C) with respect to the first rotation axis (C) for at least one measuring plane corresponding to an angular position of the second rotary axis (B) with respect to the second rotation axis (B), and - means for determining a center point position of the rotatably mounted machine part (130) in the measuring plane corresponding to the angular position of the second rotary axis (B) on the basis of the determined spatial positions of the measuring object (300) as a function of the workpiece weight of the workpiece clamped on the machine part (130). [20] Device according to claim 19, characterized bythat the device is a numerical control device (400) of a machine tool (100) or is integrated into a numerical control device (400) of a machine tool (100). [21] Control device (400) of a machine tool (100), with - a device according to claim 19 or 20, - a storage device (420) for storing machine kinematics or machine data of the machine tool (100) specifying machine kinematics and workpiece weight machine data specifying correction values ​​for the machine kinematics of the machine tool (100) as a function of a workpiece weight and / or correction values ​​for reference parameters, in particular axis positions, as a function of a workpiece weight, - a data processing device (430) of a numerical control of the machine tool for controlling the machine tool on the basis of numerical processing data and the machine kinematics of the machine tool (100) and for transforming coordinate data between a relative coordinate system and a machine coordinate system of the machine tool (100) on the basis of the machine kinematics of the machine tool (100), and - an input unit (440) which enables an operator to enter a workpiece weight of a workpiece to be machined, wherein the data processing device (430) is configured to adapt the machine kinematics or the machine data specifying the machine kinematics for machining the workpiece on the machine tool (100) by means of correction values ​​of the machine kinematics on the basis of the input workpiece weight and / or to adapt reference parameters, in particular axis positions, when processing numerical machining data for controlling the machine tool (100) by the numerical control of the machine tool on the basis of the numerical machining data by means of correction values ​​of the reference parameters on the basis of the input workpiece weight. [22] Numerically controlled machine tool (100), with: - at least one first controllable rotary axis (C) with a machine part (130) mounted rotatably about a first rotation axis (C) and a second controllable rotary axis (B) for rotating the machine part (130) about a second rotation axis (B) aligned transversely or perpendicularly to the first rotation axis (C), and - a device according to claim 19, 20 or 21. [23] Computer program product comprising a computer program stored on a computer-readable data storage medium, which is executable in a numerical control device of a machine tool or in a computer connectable to a numerical control device of a machine tool, and which is designed to carry out a method according to one of claims 1 to 18 on the machine tool (100), which has at least a first controllable rotary axis (C) with a machine part (130) mounted so as to be rotatable about a first axis of rotation (C) and a second controllable rotary axis (B) for rotating the machine part (130) about a second axis of rotation (B) oriented transversely or perpendicularly to the first axis of rotation (C), and wherein a workpiece is clamped on the machine part (130) and a measuring object (300) is fastened or positioned on the machine part (130) of the machine tool at a radial distance from the first axis of rotation (C).

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