Measuring body for verifying geometrical deviations of a 3-axis machine tool, 3-axis machine tool, and method for compensating geometrical deviations of a 3-axis machine tool

Abstract

The invention relates to a measuring body for verifying geometrical deviations in a 3-axis machine tool (1), comprising a base plate (8), a first wall (10) which is arranged on the base plate (8) and projects perpendicularly from the base plate (8), a second wall (20) which is arranged on the base plate (8) and projects perpendicularly from the base plate (8) and which is arranged perpendicularly to the first wall (10), wherein: a first row of holes (101) and a second row of holes (102) are formed in the base plate (8); the first wall (10) is a stepped triangular structure and has, in an upper, exposed region (11), a staircase-like region (12) with a plurality of steps (13); the second wall (20) is a quadrilateral structure and has, in an upper, exposed region (21) parallel to the base plate (8), a first wall-side row of holes (22); and the first row of holes (101) is arranged in parallel to the step-side row of holes (14) and the second row of holes (102) is arranged in parallel to the first wall-side row of holes (22).

Description

[0001] Measuring body for checking geometric deviations of a 3-axis machine tool, 3-axis machine tool and method for compensating geometric deviations of a 3-axis machine tool

[0002] Description

[0003] The present invention relates to a measuring body for checking geometric deviations of a 3-axis machine tool and a 3-axis machine tool with improved geometric accuracy as well as a method for checking and compensating geometric deviations of a 3-axis machine tool.

[0004] A well-known problem area in machine tools is the geometric accuracy of the machine tool. The geometric accuracy of a machine tool is determined by the relative deviation of the actual position and orientation of the tool to the workpiece from the target position and orientation. This error is therefore the cause of deviations from the ideal workpiece geometry and thus of the working accuracy of a machine tool. To improve geometric accuracy, individual axis deviations as well as the position and alignment of the individual axes relative to each other are usually considered.

[0005] Assuming a rigid body model, a 3-axis machine tool exhibits three linear deviations (one in the axial direction and two perpendicular to the axial direction) and three rotational deviations (yaw, pitch, and roll). This results in six deviations for each linear axis, resulting in 18 deviations for the three linear axes. In addition, three perpendicularity deviations of the linear axes must be considered. Thus, a 3-axis machine tool exhibits a total of 21 possible geometric errors. The individual deviations can overlap and then lead to a large overall error, which has an undesirable impact on the geometric accuracy of the machine tool.It is an object of the present invention to provide a measuring body for checking geometric deviations of a 3-axis machine tool, a 3-axis machine tool and a method for checking and compensating geometric deviations of a 3-axis machine tool, wherein the measuring body and the 3-axis machine tool are constructed as simply and cost-effectively as possible and the method can be carried out as cost-effectively and quickly as possible.

[0006] This object is achieved by a measuring body having the features of claim 1, a 3-axis machine tool having the features of claim 10, and a method having the features of claim 12. The subclaims each show preferred developments of the invention.

[0007] The measuring body according to the invention for checking geometric deviations of a 3-axis machine tool with the features of claim 1, however, has the advantage that geometric deviations of the 3-axis machine tool can be compensated with the help of the measuring body, so that the 3-axis machine tool exhibits no linear deviations, no rotational deviations, and no perpendicularity deviations. Thus, workpieces can subsequently be machined using the 3-axis machine tool with the highest precision. The correction data determined using the measuring body can be used directly for error compensation of the 3-axis machine tool. The measuring body is particularly suitable for machine tools for ultra-precision machining.Furthermore, the measuring body is particularly suitable for the inspection, correction and long-term evaluation of machine tools, which can thus be used for ultra-precision machining throughout their entire service life.

[0008] This is achieved according to the invention in that the measuring body has a base plate, a first wall and a second wall. The first wall is arranged on the base plate, which is in particular a square wall, and projects perpendicularly from the base plate. The first wall is a stepped triangle and has a stair-step-shaped area with a plurality of steps on an upper, exposed area. The second wall is also square and likewise projects perpendicularly from the base plate and is arranged perpendicular to the first wall. Furthermore, a first row of holes and a second row of holes are formed in the base plate. Thus, the first wall is stair-step-shaped with a plurality of steps on the side facing away from the base plate. The second wall is a square wall, in particular a rectangular wall, and has an upper, exposed area parallel to the base plate, in which a first row of wall holes is formed.The stair-shaped area of ​​the first wall is thus located at the upper, exposed area of ​​the first wall. Thus, the upper, exposed area of ​​the first wall forms a staircase, at which different positions can be recorded in the Z direction, with the base plate spanning a ground plane in the X and Y directions. Due to the upper, exposed stair-shaped area of ​​the first wall, the first wall essentially has a triangular shape.

[0009] Particularly preferably, the stepped first wall has a row of stair holes, with a hole formed in each step. This makes it possible to detect positions in the X and Y directions at different heights in addition to determining a position in the Z direction.

[0010] More preferably, the measuring body further comprises a third wall, which is arranged on the base plate and positioned perpendicular to the second wall. Like the second wall, the third wall is a rectangular wall with an upper, exposed region that runs parallel to the base plate and has a second row of wall holes. Thus, the third wall is arranged on the base plate parallel to the first wall. Furthermore, the first row of wall holes and the second row of wall holes are thus arranged perpendicular to one another. The first, second, and third walls form a U-shaped arrangement.

[0011] Further preferably, the measuring body comprises a third row of holes on the base plate, which is parallel to the second row of holes on the third wall.

[0012] Preferably, the first, second, and third rows of holes on the top side of the base plate each run along an edge of the base plate, and are particularly preferably rectangular in shape. Thus, the first row of holes is preferably parallel to a first edge of the base plate, the second row of holes is parallel to a second edge of the base plate, and the third row of holes is parallel to a third edge of the base plate.

[0013] Particularly preferably, the first row of holes is parallel to the first wall and / or the second row of holes is parallel to the second wall and / or the third row of holes is parallel to the third wall. This makes it possible for yaw errors, pitch errors, and roll errors, in particular, to be detected by the measuring body.

[0014] The first, second and third row of holes particularly preferably have the same number of holes, the same hole spacing and the same hole diameter.

[0015] According to a further preferred embodiment of the invention, the first, second, and third walls each have a predetermined distance from the first, second, and third edges. Further preferably, the step surfaces of the steps of the stepped triangle, which are parallel to the base plate, are ground or otherwise finely machined to provide high flatness. Preferably, the upper, exposed regions of the second and / or third walls are also ground or finely machined to provide high flatness. This can significantly improve the accuracy of the measurement using the measuring body.

[0016] Further preferably, the regions in which the first and / or second and / or third row of holes is formed in the base plate and / or regions adjacent to the rows of holes are provided as ground regions.

[0017] Further preferably, the measuring body comprises a reinforcing element on an underside of the base plate to improve the stability of the measuring body. The reinforcing element is preferably a cross bar with two bars, each bar connecting two opposite corners of the base plate to the underside of the base plate. The reinforcing element is preferably also used for clamping the measuring body in the machine tool.

[0018] Further preferably, the first, second and third row of holes in the base plate are arranged such that, in the case of a square base plate, a hole for a measuring process is formed at each corner region of the base plate.

[0019] The base plate is preferably rectangular, in particular square. Further preferably, each row of holes in the base plate, the row of stair holes, and the first and second row of wall holes each have at least one reference hole. The area around each reference hole is preferably ground, so that the ground surface is used as a reference element for determining a Z coordinate. A center point of each reference hole can be used as a reference element for an X and Y coordinate.

[0020] Further preferably, the holes of the first, second and third row of holes are arranged in a straight line.

[0021] The measuring body is preferably made of Invar. Invar has a very low coefficient of thermal expansion, making it particularly well-suited for the production of the measuring body. Further preferably, the thickness of the first, second, and third walls and the thickness of the base plate are the same.

[0022] Furthermore, the present invention relates to a 3-axis machine tool comprising a tool spindle, a measuring device, in particular a 3D measuring probe that can be clamped into the tool spindle, and a control unit for controlling the 3-axis machine tool. Furthermore, the 3-axis machine tool comprises a measuring body according to the invention, wherein the control unit is configured to correct the geometric data of the 3-axis machine tool based on a target-actual comparison of predetermined geometric target dimensions of the measuring body with actual geometric dimensions of the measuring body determined by the measuring device in the 3-axis machine tool. Thus, the control unit has a memory in which the geometric target dimensions of the measuring body, which were determined in a previous step in a measuring machine, are stored.To determine the actual geometric dimensions of the measuring body in the 3-axis machine tool, the control unit preferably starts an NC program for measuring the measuring body in order to determine the actual values ​​of the measuring body. By comparing the target values ​​with the actual values, the geometric data of the 3-axis machine tool can be corrected, significantly improving the accuracy of workpiece machining by the 3-axis machine tool. Thus, geometric errors of the 3-axis machine tool can be easily compensated. The target values ​​are preferably stored in a memory.

[0023] Furthermore, the present invention relates to a method for checking and compensating geometric deviations of a 3-axis machine tool, the method comprising the steps:

[0024] Clamping a measuring device, in particular a 3D measuring probe, into a spindle of the 3-axis machine tool,

[0025] - Arranging a measuring body according to the invention in a working space of the 3-axis machine tool, in particular by clamping it to a reinforcing element,

[0026] - Moving the measuring device to a number of different positions of the measuring body in order to record actual geometric data on the measuring body, performing a target-actual comparison between the recorded actual data and predetermined target data of the measuring body in order to determine geometric deviations, in particular linear and rotational and perpendicularity deviations, and

[0027] Compensating the geometric deviations of the 3-axis machine tool in a control unit of the 3-axis machine tool in order to increase the working accuracy of the 3-axis machine tool.

[0028] The method according to the invention can be carried out relatively quickly and reliably. In particular, the method according to the invention can be carried out within a short time even after delivery of a 3-axis machine tool to a customer, so that prevailing conditions at the customer's site, in particular temperature conditions, no longer have a negative influence on the geometric accuracy of the 3-axis machine tool during operation.

[0029] Of course, it is also possible for the procedure to be carried out at the manufacturer of the 3-axis machine tool in order to optimize manufacturing processes at the manufacturer of the 3-axis machine tool if necessary.

[0030] Preferably, the target values ​​of the measuring body are determined in advance in a coordinate measuring machine and the measuring body is then arranged in the working space of the 3-axis machine tool in such a way that a coordinate system of the measuring body corresponds to a coordinate system of the 3-axis machine tool.

[0031] Further preferred is the measurement of the measuring body in the 3-axis machine tool, which involves recording the temperature of the work area, and then correcting the actual data based on the recorded temperature of the work area. This further improves the accuracy of compensating for geometric deviations.

[0032] The method according to the invention is preferably used for the inspection, correction, and long-term evaluation of a three-axis machine tool. The method according to the invention preferably determines twenty-one possible geometric errors:

[0033] - one position deviation each (translational movement of each axis (three possible errors, since there are three axes)),

[0034] - two straightness deviations per axis (translational movement transverse to the axis direction), ie a total of six possible geometric errors,

[0035] - and three rotational deviations: yaw, pitch, roll in each of the three axes (i.e. nine geometric deviations),

[0036] - three perpendicularity deviations of the linear axes X, Y, Z to each other (XY-

[0037] Perpendicularity deviation, XZ perpendicularity deviation, YZ

[0038] Perpendicularity deviation).

[0039] It should be noted that, depending on the design and kinematics of the three-axis machine tool, individual errors can be neglected. Preferably, a pitch error of the Y-axis is corrected by the Y-positioning error, the straightness error of the Y-axis in the X-direction, and the perpendicularity error between the Y-axis and the X-axis. The prerequisite for this is that the X-distance between the spindle and the machine tool table is constant. More preferably, a roll error of the Z-axis is neglected, since the tool rotates in this axis. More preferably, if a tool length is constant, a pitch error of the Z-axis and a yaw error of the Z-axis can be neglected. Both errors can be corrected by the straightness and perpendicularity errors of the Z-axis. Thus, these measures can reduce the measurement effort.

[0040] A preferred embodiment of the invention will be described below with reference to the accompanying drawings. In the drawing:

[0041] Fig. 1 is a schematic perspective view of a measuring body in a 3-axis machine tool according to a preferred embodiment of the invention,

[0042] Fig. 2 is a schematic perspective view of the measuring body of Figure 1 from a different perspective,

[0043] Fig. 3 is a schematic plan view of the measuring body of Figure 2,

[0044] Fig. 4 is a schematic side view of the measuring body showing the exemplary determination of a pitch error of the X-axis,

[0045] Fig. 5 is a partial side view of the measuring body showing an exemplary determination of a rolling error of the X-axis, and

[0046] Fig. 6 is a schematic diagram for determining a yaw error of the X-axis.

[0047] In the following, a 3-axis machine tool 1 and a measuring body 2 for checking geometric deviations of the 3-axis machine tool are described in detail with reference to Figures 1 to 6.

[0048] Furthermore, with reference to Figures 1 to 6, a method for checking and compensating geometric deviations of a 3-axis machine tool is also described.

[0049] As can be seen from Figures 1 and 5, the 3-axis machine tool 1 comprises a working space 3, a spindle 4 and a control unit 9.

[0050] As can be seen from Figure 1, a measuring body 2 is arranged on a machine table 6 of the 3-axis machine tool 1.

[0051] The measuring body 2 is shown in detail in Figures 1, 2, and 3. The measuring body 2 is designed to check geometric deviations of the 3-axis machine tool, whereby all linear, rotational, and perpendicularity errors, a total of twenty-one errors, can be determined in one setup of the measuring body. In particular, the measuring body 2 can be used to very precisely determine coordinates for positioning a tool of the 3-axis machine tool 1.

[0052] The measuring body 2 comprises a flat base plate 8, which defines a base plane in an X-direction and a Y-direction. Furthermore, the measuring body 2 comprises a first wall 10, a second wall 20, and a third wall 30. The first wall 10, the second wall 20, and the third wall 30 are arranged on the base plate 8 and protrude perpendicularly from the base plate 8, forming a U-shape.

[0053] As shown in Figure 2, a Z direction is perpendicular to the X direction and perpendicular to the Y direction.

[0054] As can be seen from Figure 2, the first wall 10 and the second wall 20 and the third wall 30 are arranged on the base surface of the base plate 8.

[0055] The base plate 8 is square and comprises a first edge 81, a second edge 82, a third edge 83 and a fourth edge 84.

[0056] The three walls 10, 20, 30 are geometrically different, as can be seen particularly from Figures 1 and 2. The first wall 10 is a stepped triangle with an upper, exposed region 11, on which a stair-step-shaped region 12 is formed. The stair-step-shaped region 12 has a plurality of steps 13.

[0057] A hole 15 is formed in each step 13. The holes 15 form a row of stair holes 14. In this embodiment, the step triangle formed as the first wall 10 has seven steps.

[0058] The second wall 20 is a rectangular wall with an upper exposed area 21. In the upper exposed area 21, a first row of wall holes 22 with a plurality of holes 23 is formed.

[0059] The third wall 30 is also a rectangular wall and has an upper, exposed area 31. A second wall hole row 32 with a plurality of holes 33 is formed in the upper, exposed area 31.

[0060] As can be seen in particular from Fig. 2, a size of the second wall 20 is smaller than a size of the third wall 30.

[0061] The holes 23 of the second wall 20 lie in a straight line. The holes 33 of the third wall 30 also lie in a straight line. The holes of the second and third walls are arranged such that the straight lines formed by the holes 23 and 33 intersect at right angles. As can be seen particularly from Fig. 2, the first wall 10 is arranged at a right angle to the second wall 20. The second wall 20 is also arranged at a right angle to the third wall 30. As a result, the first wall 10 and the second wall 30 are parallel to one another.

[0062] Furthermore, the first, second, and third walls 10, 20, and 30 are arranged along their longitudinal sides at a distance from the respective edges 81, 82, 83 of the base plate 8. Only one end region of the third plate 30 extends to the fourth edge 84 (see Fig. 2).

[0063] To reduce weight, the base plate 8 has a larger central opening and several longitudinal openings (without reference numerals).

[0064] On the underside of the base plate 8, a reinforcing element 7 is arranged, which has a first bar 71 and a second bar 72. The two bars 71, 72 are arranged in a cross shape and stiffen the base plate 8 and thus the measuring body 2. The reinforcing element 7 also makes it possible for the measuring body 2 to be easily clamped onto the machine table 6. This prevents, in particular, undesired stresses from being introduced into the base plate or the three walls 10, 20, 30 during the clamping process, which could lead to falsified measurement results.

[0065] Furthermore, the measuring body 2 comprises in the base plate on the upper side a first row of holes 101, a second row of holes 102 and a third row of holes 103. The first row of holes 101 comprises a plurality of holes 101a, which are arranged on a first straight line 111. The first straight line 111 runs parallel to the first edge 81. The second row of holes 102 comprises a plurality of holes 102a, which are arranged on a second straight line 112. The second row of holes 102 is parallel to the second edge 82. The third row of holes 103 comprises a plurality of holes 103a, which are arranged on a third straight line 113. The third row of holes 103 is parallel to the third edge 83 (cf. Fig. 3). For better clarity, not all holes in the first, second and third rows of holes are provided with a reference symbol in Fig. 3.

[0066] As can be further seen from Fig. 3, the first row of holes 101 is parallel to the stair hole row 14. The second row of holes 102 is parallel to the first wall hole row 22 of the second wall 20. The third row of holes 103 is parallel to the second wall hole row 32.

[0067] The number of holes in the first, second and third row of holes is preferably the same, as are the geometric dimensions, in particular the hole spacing.

[0068] It should be noted that, for example, strip-shaped, ground reference surfaces (not shown in Fig. 3) can be provided parallel to the three rows of holes. Furthermore, the first, second, and third rows of holes 101, 102, 103 are arranged such that a hole is provided in each corner of the base plate 8.

[0069] Further preferably, a thickness of the base plate 8 is the same as the wall thicknesses of the walls 10, 20, 30.

[0070] The measuring body 2 is fixed on the machine table 6 of the 3-axis machine tool 1. Furthermore, a 3D measuring probe is arranged in the spindle 4, by means of which the actual coordinates of the 3-axis machine tool are determined using the measuring body 2.

[0071] The 3-axis machine tool 1 further comprises the control unit 9, which is configured to control the 3-axis machine tool. The control unit 9 is further configured to correct the geometric data of the 3-axis machine tool 1 based on a target-actual comparison of the geometric dimensions of the measuring body 2.

[0072] As already explained above, the 3-axis machine tool has three linear axes, namely a first axis in the X direction, a second axis in the Y direction and a third axis in the Z direction.

[0073] In total, the three linear axes result in twenty-one deviations, three of which are perpendicularity deviations between the linear axes. This results in a total of twenty-one error parameters for the three-axis machine tool.

[0074] By means of the method according to the invention, a check and correction of all straightness deviations, rotation deviations and perpendicularity deviations of the 3-axis machine tool can be carried out.

[0075] For this purpose, the measuring body 2 must first be measured using a coordinate measuring machine (not shown) in order to generate target values. These target values ​​are then fed to the control unit 9 of the 3-axis machine tool 1 and stored in a memory. To measure the measuring body 2, a coordinate system is spanned such that an XY plane is parallel to the base plate 8. Based on repeatedly determined Z positions, X positions, and Y positions of various reference elements of the measuring body 2, the geometry of the measuring body 2, which is preferably made of Invar, is thus determined. At the same time, a zero point of the coordinate system of the measuring body 2 is also defined. Examples of reference elements include the ground step surfaces or the ground reference surfaces for the Z positions.The holes of the rows of holes 101, 102, 103 as well as the holes 15 in the steps 13 and the holes 23, 33 in the exposed areas 11, 21 serve as reference elements for the X-positions and Y-positions.

[0076] In order to record the geometric deviations of the 3-axis machine tool, the measuring body 2 is placed on the machine table 6 in the workspace 3 of the 3-axis machine tool. The measuring body 2 can be clamped or attached to a machine table in some other way. The XYZ coordinate system of the measuring body should generally be aligned parallel to the XYZ coordinate system of the 3-axis machine tool. The measurement of the measuring body 2 in the 3-axis machine tool 1 is then carried out using the 3D measuring device 5, e.g., a 3D measuring probe. Modern 3-axis machine tools usually have such a 3D measuring probe, for example, for recording component positions and component geometries.

[0077] Before the measurement, the coordinate system of the 3-axis machine tool is aligned identically to the coordinate system of the coordinate measuring machine in which the measuring body 2 was previously measured.

[0078] After the measuring body 2 is fixed in the working space 3 of the 3-axis machine tool, the control unit 9 can preferably run a fully automatic NC program in order to measure the measuring body 2 by means of the 3D measuring probe 5 and thereby determine the actual values ​​of the 3-axis machine tool 1.

[0079] Preferably, when measuring the measuring body 2 in the work area of ​​the 3-axis machine tool 1, the temperature of the work area 3 of the 3-axis machine tool 1 is also recorded and stored. If this work area temperature differs from a reference temperature, e.g., 20 °C, a thermal expansion coefficient of the workpieces to be machined on the 3-axis machine tool must be taken into account during workpiece machining. In this case, the actual values ​​of the 3-axis machine tool must be corrected accordingly.

[0080] After completing the measurement of the measuring body 2 in the 3-axis machine tool 1 and, if necessary, a thermal adjustment of the actual values, the actual values ​​of the 3-axis machine tool are determined and can be compared with the target values ​​of the measuring body. By comparing the target and actual values, the geometric deviations of the 3-axis machine tool in the form of position deviations, straightness deviations, and perpendicularity deviations can be calculated and thus checked and corrected. Figure 3 shows, in a top view of the measuring body 2, examples of straightness deviations G, a perpendicularity deviation R (angle α), and position deviations P.

[0081] For example, a position deviation of the X-axis can first be determined by evaluating the differences between the actual positions and the target positions in the X-direction of the measured reference elements on the base plate 8 along the X-axis. Since the zero point of the measuring body 2 and the position of the reference elements relative to the zero point are known, the determined differences can be assigned to X-axis positions of the 3-axis machine tool. This results in a table of X-axis positions of the 3-axis machine tool and position deviations in the X-direction at these X-axis positions. These position deviations can be stored and used directly as correction data for error compensation of the 3-axis machine tool in the control unit 9.

[0082] Alternatively, the deviations could also be preprocessed mathematically. For example, the deviations can also be approximated using various mathematical functions. Especially for small measuring bodies 2 with few reference elements, an approximation of the differences with a straight line (best-fit line) is conceivable. In this case, only a scaling error is corrected.

[0083] Since the measuring body 2 only covers a portion of the working area 3 of the 3-axis machine tool, the recorded actual values ​​are preferably extrapolated using a corresponding mathematical function. This yields deviations for the entire working area 3 of the 3-axis machine tool 1.

[0084] Straightness deviations G of the X-axis are determined in the same way. The position deviations P in the Y-direction and Z-direction are assigned to the X-axis positions. The differences between the actual position and the target positions in the Y-direction result from the determined centers of the holes in the three rows of holes 101, 102, 103 and the reference holes on the first, second, and third walls 10, 20, 30. The differences between the actual positions and the target positions in the Z-direction result, for example, from the reference surfaces on the base plate 8 and the ground surfaces of the steps 13. Mathematical preprocessing or approximation is also possible here.

[0085] Once the correction data for the position deviation and straightness deviation of the X-axis have been calculated, all measurement data of the actual positions of the reference elements are adjusted for further evaluation based on the correction data for the position deviation of the X-axis, the straightness deviation of the X-axis in the Y direction, and the straightness deviation of the X-axis in the Z direction. At this point, it is preferable to assume that the adjusted actual positions no longer exhibit any errors in the X-direction. This allows the errors in the X-direction to be neglected in the further evaluation.

[0086] In the next step, a perpendicularity error R between the X-axis and the Y-axis can be calculated. For this purpose, two best-fit lines are calculated. The first best-fit line results from the X-axis position of the reference elements on the base plate 8 along the X-direction and their positional deviations in the Y-direction. The second best-fit line results from the Y-axis positions of the reference elements on the base plate 8 along the Y-direction and their positional deviations in the X-direction. An angle α between the two best-fit lines is then calculated (see Figure 3). The determined deviation can be used directly as a correction value for error compensation in the control unit 9.

[0087] The actual positions of all reference elements in the measurement data are then adjusted according to their Y position using the perpendicularity error so that the measurement data no longer contains any X-Y perpendicularity error.

[0088] The position deviations and straightness deviations of the Y-axis are then calculated in the same way as for the X-axis. For this purpose, the differences between the actual and target positions of the reference positions on the base plate 8 along the Y-axis are evaluated (see Figure 3). Together with the zero point, this results in a table containing the Y-axis positions of the 3-axis machine tool and the position deviations in the X, Y, and Z directions at these Y-axis positions. The data can be further processed as for the X-axis or transferred directly to the control unit 9 as correction data for error compensation of the 3-axis machine tool. Here, too, the correction data should be extrapolated using an appropriate mathematical function in order to define the entire workspace 3.

[0089] Subsequently, all actual positions of the reference elements are adjusted for further evaluation based on the correction data for the position deviation and the two straightness deviations of the Y-axis. At this point, it is preferably assumed that the adjusted actual positions no longer exhibit any errors in the Y-direction. This allows the errors in the Y-direction to be neglected in the further evaluation. Figures 4, 5, and 6 show, as examples, the determination of a pitch error in the X-axis (Fig. 4) and the determination of a roll error in the X-axis (Fig. 5), as well as the determination of a yaw error in the X-axis (Fig. 6).

[0090] To determine a yaw error of the X-axis (Fig. 6), geometric features must be present in the X-direction whose X-position can be measured with the measuring probe. To determine the error independently of other errors, the Y and Z positions of the features must be identical. To measure the influence of the X-yaw error, measurements must be taken at a different Y-position than the first X-feature row. Furthermore, the Y-distance d to the first X-feature row must be known (see Fig. 6).

[0091] In the next step, the pitch error of the X-axis is calculated. To determine the pitch error of the X-axis (Fig. 4), geometric features must be present in the X-direction whose X-position can be measured with the measuring probe. To determine the error independently of other errors, the Y and Z positions of the features must be identical. To measure the influence of the X-pitch error, measurements must also be taken at a different Z-position than the first X-feature row. Furthermore, the Z-distance d to the first X-feature row must be known.

[0092] To determine a roll error in the X-axis (Fig. 5), geometric features must be present in the X-direction whose Y-position can be measured with the measuring probe. To determine the error independently of other errors, the Y- and Z-positions of the features must be identical. To measure the influence of the X-roll error, measurements must also be taken at a Z-position other than the first X-row of features. Furthermore, the Z-distance d to the first X-row of features must be known (see Fig. 5).

[0093] According to the measurement described in Fig. 4 and Fig. 5, the roll error and the yaw error of the Y-axis are determined.

[0094] In the next step, the perpendicularities between the X-axis and the Z-axis are calculated. For this purpose, two best-fit lines are calculated. The first best-fit line results from the X-axis positions of the reference elements on the base plate 8 along the X-direction and their positional deviations in the Z-direction. The second best-fit line results from the Z-axis positions of the reference elements on the first wall 10 (step triangle) in the X-direction and their positional deviations in the X-direction. The angle α between the two best-fit lines is then calculated. The determined deviation can be used directly as a correction value for error compensation in the control unit 9.

[0095] The perpendicularity between the Y-axis and the Z-axis is calculated in the same way. The first best-fit line results from the Y-axis positions of the reference elements on the base plate 8 along the Y-direction and their positional deviations in the Z-direction. The second best-fit line results from the Z-axis positions of the reference elements on the second wall 20 in the Y-direction and their positional deviations in the Y-direction. The perpendicularity deviations between these two lines can, in turn, be used directly as a correction value for error compensation.

[0096] The actual position of all reference elements in the measurement data is then adjusted according to their Z position using the perpendicularity errors so that the measurement data no longer contains any XZ perpendicularity errors and no YZ perpendicularity errors.

[0097] In a further step, the geometric deviations of the Z-axis are calculated. For this purpose, the reference elements (reference holes and ground step surfaces) of the three walls 10, 20, and 30 are used. Since the X-axis and Y-axis errors, as well as the three perpendicularity errors, were already calculated from the measured data in the previous evaluation, it is assumed in this step that a procedure in the X- or Y-direction, which is necessary for measuring the steps, does not affect the geometric deviations of the Z-axis.

[0098] Thus, the position deviation of the Z-axis is determined by evaluating the differences between the actual position and the target position of the reference position in the Z direction on the first wall 10. Since the zero point of the measuring body 2 and the position of the reference elements relative to the zero point are known, the determined differences can be assigned to Z-axis positions of the 3-axis machine tool. This results in a table of Z-axis positions, which can then be used directly as correction data for error compensation of the 3-axis machine tool. The data can be further processed as with the X-axis and Y-axis or used directly as correction data. Here, too, the correction data can be extrapolated using an appropriate mathematical function.

[0099] As with the other axes, the straightness deviations of the Z-axis are determined in the same way. The position deviations in the Y- and X-directions are assigned to the Z-axis positions. The differences between the actual and target positions are determined from the determined center points of the holes. Further processing of the straightness deviations can be carried out in the same way as the position deviation of the Z-axis.

[0100] In this way, all relevant geometric errors, including yaw, pitch, and roll, can be checked and corrected using the measuring body 2. This method is particularly suitable for correcting a 3-axis machine tool geometry after a change in thermal conditions, as linear errors typically occur in this case and can be easily extrapolated. In addition, this method can also be used to adapt the geometry of the 3-axis machine tool to materials with different thermal expansion coefficients if the temperature in the work area deviates from the reference temperature.

[0101] In addition to the above written description of the invention, reference is hereby explicitly made to the graphic representation of the invention in Figs. 1 to 6 for its supplementary disclosure.

[0102] List of reference symbols

[0103] 1 3-axis machine tool

[0104] 2 measuring bodies

[0105] 3 Workspace

[0106] 4 spindle

[0107] 5 Measuring device (3D measuring probe)

[0108] 6 Machine table

[0109] 7 Reinforcing element

[0110] 8 Base plate

[0111] 9 Control unit

[0112] 10 first wall

[0113] 11 upper, exposed area

[0114] 12 stair-shaped area

[0115] 13 steps

[0116] 14 stair hole row

[0117] 15 holes

[0118] 20 second wall

[0119] 21 upper, exposed area

[0120] 22 first row of wall holes

[0121] 23 holes

[0122] 30 third wall

[0123] 31 upper, exposed area

[0124] 32 second row of wall holes

[0125] 33 holes

[0126] 71 first bar

[0127] 72 second bar

[0128] 81 first edge

[0129] 82 second edge

[0130] 83 third edge

[0131] 84 fourth edge

[0132] 101 first row of holes

[0133] 101a Holes

[0134] 102 second row of holes

[0135] 102a holes

[0136] 103 third row of holes

[0137] 103a Holes

[0138] 111 first straight 112 second straight

[0139] 113 third straight line d distance

[0140] G Straightness deviation R Perpendicularity error

[0141] P Position deviation

[0142] X X-axis

[0143] Y Y-axis

[0144] Z Z-axis a Perpendicularity deviation

Claims

Claims 1. Measuring body for checking geometric deviations in a 3-axis machine tool (1) comprising: - a base plate (8), - a first wall (10) which is arranged on the base plate (8) and projects perpendicularly from the base plate (8), - a second wall (20) which is arranged on the base plate (8) and projects perpendicularly from the base plate (8) and is arranged perpendicular to the first wall (10), - wherein a first row of holes (101) and a second row of holes (102) are formed in the base plate (8), - wherein the first wall (10) is a stepped triangle and has a stair-shaped area (12) with a plurality of steps (13) at an upper, exposed area (11), - wherein the second wall (20) is a square wall and has a first row of wall holes (22) at an upper, exposed area (21) which runs parallel to the base plate (8), and - wherein the first row of holes (101) is arranged parallel to the stairwell row of holes (14) and the second row of holes (102) is arranged parallel to the first wall row of holes (22).

2. Measuring body according to claim 1, wherein the step-shaped area (12) has a row of steps (14), wherein in particular a hole (15) and a ground reference surface are formed in each step (13).

3. Measuring body according to one of the preceding claims, further comprising a third wall (30) which is arranged on the base plate (8) and projects perpendicularly from the base plate (8), wherein the third wall (30) is arranged perpendicular to the second wall (20) and wherein the second wall (30) has a second wall hole row (32) with holes (33) at an upper, exposed area (31).

4. Measuring body according to claim 3, wherein the first wall (10), the second wall (20) and the third wall (30) are arranged in a U-shape on the base plate.

5. Measuring body according to claim 3 or 4, further comprising a third row of holes (103) in the base plate (8) which runs parallel to the second row of wall holes (32).

6. Measuring body according to claim 4 or 5, wherein the first row of holes (101), the second row of holes (102) and the third row of holes (103) each extend along an edge of the base plate (8) such that a hole of one of the rows of holes is arranged at each corner of the base plate (8). Measuring body according to any one of claims 4 to 6, wherein the first wall (10), the second wall (20), and the third wall (30) are arranged on the base plate (8) at a distance from the first edge (81), the second edge (82), and the third edge (83), the distance being greater than or equal to twice the diameter of the holes of the first, second, and third rows of holes. Measuring body according to any one of the preceding claims, wherein ground surfaces are provided next to the holes in the steps (13), and / or wherein ground surfaces are formed next to the holes of the first and / or second and / or third rows of holes (101, 102, 103). Measuring body according to any one of the preceding claims, further comprising a reinforcing element (7) which is arranged under the base plate (8) for mechanical reinforcement of the base plate (8) and / or as a clamping aid on the machine tool.A 3-axis machine tool comprising a tool spindle (4), a measuring body (2) according to one of the preceding claims, a measuring device (5) which can be clamped into the tool spindle (4) and is configured to acquire actual values ​​of the measuring body (2) fixed in the 3-axis machine tool (1), and a control unit (9) configured to control the 3-axis machine tool (1), wherein the control unit (9) is further configured to perform a target-actual comparison based on the geometric target values ​​of the dimensions of the measuring body (2) and the actual values ​​of the measuring body (2) fixed in the 3-axis machine tool (1) determined for the 3-axis machine tool (1) by means of the measuring device (5), and to make a correction of geometric data of the 3-axis machine tool (1) in the control program of the control unit (9) if deviations occur between the target values ​​and the actual values.3-axis machine tool according to claim 10, wherein the control unit (9) has a memory in which the target values ​​of the measuring body (2) are stored. Method for checking and compensating geometric deviations of a 3-axis machine tool comprising the following steps: Clamping a measuring device (5) into a tool spindle (4) of the 3-axis machine tool, - Arranging a measuring body (2) according to one of claims 1 to 9 in a Working area (3) of the 3-axis machine tool, Moving to a large number of positions of the measuring body (2) in order to acquire geometric actual data of the 3-axis machine tool using the measuring body (2), Performing a target-actual comparison of the geometric actual data with the stored target data of the measuring body (2) to determine geometric deviations and Compensating for geometric deviations in a control unit (9) of the 3-axis machine tool.

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