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

Description

[0001] 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.

[0002] 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.

[0003] 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 a total of 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 actually lead to a large overall error, which has an undesirable impact on the geometric accuracy of the machine tool.

[0004] DE 19 507 806 A1 describes a test specimen for testing coordinate measuring machines and machine tools, consisting of a plate with an incomplete grid of probing elements, which is characterized in that the grid consists only of closely adjacent rows (X-direction) and closely adjacent columns (Y-direction).

[0005] 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 9, and a method having the features of claim 11. 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 has no linear deviations and no perpendicularity deviations. This allows workpieces to be machined with the highest precision using the 3-axis machine tool. The correction data determined using the measuring body can be used directly for error compensation of the 3-axis machine tool. This is achieved according to the invention in that the measuring body has a square base plate, a first wall, and a second wall. The first wall is arranged on the base plate and protrudes perpendicularly from the base plate. The second wall is also arranged protruding perpendicularly from the base plate.Here, a first row of holes and a second row of holes are formed in the base plate. Furthermore, the first wall is designed in the shape of a step with a plurality of steps on the side facing away from the base plate. In the same way, the second wall is also designed in the shape of a step with a plurality of steps on the side facing away from the base plate. The step-shaped region of the first and second wall thus lies in each case on the upper, exposed region of the first and second wall. Thus, the upper, exposed region of the first and second wall forms a staircase on which different positions in the Z direction can be detected, with the base plate spanning a base plane in the X and Y directions. Due to the upper, exposed step-shaped region of the first and second walls, the first and second walls have a substantially triangular shape.

[0008] The first wall is arranged along a first edge of the base plate, and the second wall is arranged along a second edge of the base plate. Furthermore, the first row of holes is arranged along a third edge of the base plate, and the second row of holes is arranged along a fourth edge of the base plate. Thus, the quadrangular, preferably square, base plate has the first and second walls on two edges and the first and second rows of holes on the other two edges.

[0009] The first and second walls are arranged such that they adjoin one another at a corner of the base plate or form a corner region. The first and second walls can be arranged on the base plate, or alternatively, the first and second walls can be arranged on lateral regions of the base plate, and the corner of the base plate lies in a corner line of the contacting first and second walls.

[0010] Each step of the measuring body has a reference hole.

[0011] To simplify the manufacture of the measuring body, the first wall and the second wall are preferably identical. Further preferably, each step surface of the stepped region of each wall has a reference hole. The reference hole is preferably formed centrally in the step surface. Further preferably, each step surface is ground or milled. The reference holes are preferably bores. This makes it possible for the bore and the ground surface to each be used as a reference element, with the ground surface of the step being used to determine the Z coordinate and a center point of a bore being used as the X and Y coordinate.

[0012] Further preferably, a first reference surface is formed on the base plate next to the first row of holes, and a second reference surface is formed on the base plate next to the second row of holes. The two reference surfaces are thus also reference elements and are each configured to determine Z coordinates.

[0013] To simplify the measurement process as much as possible, the holes in the first row are arranged along a first straight line, and the holes in the second row are arranged along a second straight line. The first straight line is preferably perpendicular to the second straight line.

[0014] Further preferably, the first and second reference surfaces are arranged in strips next to the rows of holes and parallel to the rows of holes. Particularly preferably, the first and second reference surfaces are ground or milled surfaces. Further preferably, the first and second reference surfaces run parallel to the edge of the base plate.

[0015] The first and second rows of holes particularly preferably have the same number of holes, the same hole spacing and the same hole diameter.

[0016] The measuring body is preferably made of Invar. Invar has a very low coefficient of thermal expansion, making it particularly well-suited for manufacturing the measuring body. Further preferably, the thickness of the first and second walls and the thickness of the base plate are the same.

[0017] 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 ​​and the actual values, the geometric data of the 3-axis machine tool can be corrected, thereby significantly improving the accuracy of workpiece machining by the 3-axis machine tool. Accordingly, geometric errors of the 3-axis machine tool can be easily compensated. The target values ​​are preferably stored in a memory. The measuring body further preferably comprises a three-point support with which it is placed or clamped on the machine table. This means that the measuring body stands on three feet, which are arranged as far apart as possible below the base plate.

[0018] 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: Clamping a measuring device, in particular a 3D measuring probe, into a spindle of the 3-axis machine tool, arranging a measuring body in a working space of the 3-axis machine tool, moving the measuring device to a plurality of different positions of the measuring body in order to record actual geometric data on the measuring body, carrying out a target-actual comparison between the recorded actual data and predetermined target data of the measuring body in order to determine geometric deviations and compensating for 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.

[0019] 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 period of time even after delivery of a 3-axis machine tool to a customer, so that prevailing conditions, in particular temperature conditions at the customer's site, no longer have a negative influence on the geometric accuracy of the 3-axis machine tool during operation.

[0020] 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 production processes at the manufacturer of the 3-axis machine tool if necessary.

[0021] 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.

[0022] Further preferably, when measuring the measuring body in the 3-axis machine tool, the temperature of the work area is recorded, and the actual data is corrected based on the recorded temperature of the work area. This further improves the accuracy for compensating for geometric deviations.

[0023] The method according to the invention preferably determines position deviations of the respective axes in the X-direction, Y-direction, and Z-direction, as well as two straightness deviations of the respective axes. This allows a total of nine different geometric error sources to be detected.

[0024] More preferably, perpendicularity errors are calculated between the three axes, ie the X-axis, the Y-axis and the Z-axis, whereby the accuracy for compensating geometric deviations is further improved and a total of twelve geometric deviations can be detected.

[0025] A preferred embodiment of the invention will now be described with reference to the accompanying drawings. In the drawing: 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, Fig. 2 is a schematic, perspective view of the measuring body of Figure 1 from a different perspective, Fig. 3 a schematic top view of the measuring body of Figure 2 and Fig. 4 a schematic, perspective overall view of the 3-axis machine tool of Figure 1 .

[0026] The following is based on the Figures 1 to 4 a 3-axis machine tool 1 with a measuring body 2 for checking geometric deviations of the 3-axis machine tool is described in detail.

[0027] Furthermore, with reference to the Figures 1 to 4 A method for checking and compensating geometric deviations of a 3-axis machine tool is also described.

[0028] As can be seen from the Figures 1 and 4 As can be seen, the 3-axis machine tool 1 comprises a working space 3, a spindle 4 and a control unit 10.

[0029] As from Figure 1 and Figure 4 As can be seen, a measuring body 2 is arranged on a machine table 6 of the 3-axis machine tool 1.

[0030] The measuring body 2 is shown in detail in the Figures 2 and 3The measuring body 2 is designed to check geometric deviations of the 3-axis machine tool. 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.

[0031] The measuring body 2 comprises a flat base plate 20, which defines a base plane in an X-direction and a Y-direction. Furthermore, the measuring body 2 comprises a first wall 21 and a second wall 22. The first wall 21 and the second wall 22 are arranged on the base plate 20 and protrude perpendicularly from the base plate 20.

[0032] As from Figure 2 As can be seen, the first wall 21 and the second wall 22 are arranged on the base surface of the base plate 20.

[0033] The first wall 21 and the second wall 22 are arranged along edges of the base plate 20. More specifically, the first wall 21 is arranged along a first edge 20a of the base plate 20, and the second wall 22 is arranged along a second edge 20b of the base plate 20.

[0034] The first and second walls 21, 22 are arranged on the base plate 20 such that the first and second walls touch at a corner of the base plate. This creates a corner line 27 (see. Figure 1 ), which is perpendicular to the base surface of the base plate 20.

[0035] As can be seen from the Figures 1 and 2 As can be seen, the first wall 21 and the second wall 22 are triangular, with steps being formed at an upper free end of the first and second walls. This creates a stepped triangle, with a step-shaped area 25 exposed on each wall. As can be seen from Figure 2As can be seen, each step 25a has a reference hole 26 and a ground or milled step surface 26a. The thickness of the first and second walls is preferably chosen to be the same. Further preferably, the thickness of the base plate 20 is also the same as the wall thicknesses of the walls 21, 22.

[0036] Furthermore, the measuring body 2 comprises a first row of holes 23 and a second row of holes 24 in the base plate 20. The first row of holes 23 comprises a plurality of holes 23a arranged on a first straight line 31. The second row of holes 24 comprises a plurality of second holes 24a arranged on a second straight line 32. The centers of the holes 23a, 24a are each arranged on the straight lines 31, 32. The first and second straight lines 31, 32 intersect at a right angle.

[0037] How to continue Figure 2As can be seen, a first strip-shaped reference surface 28 is arranged next to the first row of holes 23. A second strip-shaped reference surface 29 is arranged next to the second row of holes 24. The reference surfaces are each located between the rows of holes and a third edge 20c or fourth edge 20d (cf. Figure 2 ).

[0038] The base plate 20 is square, so that the number of holes in the first and second rows 23, 24 is the same. In the corner opposite the corner where the wall sections touch, a common hole 30 for both rows is provided.

[0039] As in Figure 2 As shown, a Z direction is perpendicular to the X direction and perpendicular to the Y direction.

[0040] 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.

[0041] The 3-axis machine tool 1 further comprises the control unit 10, which is configured to control the 3-axis machine tool. The control unit 10 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.

[0042] 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.

[0043] 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.

[0044] By means of the method according to the invention, a check and correction of position deviations, straightness deviations and perpendicularity deviations of the 3-axis machine tool can be carried out, as in Figure 4 shown, which is a portal machine.

[0045] 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 10 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 20. 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. The ground step surfaces 26a and the first and second reference surfaces 28, 29 for the Z positions serve as reference elements, for example.The holes in rows 23 and 24 as well as holes 26 in the steps serve as reference elements for the X and Y positions.

[0046] 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.

[0047] 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.

[0048] After the measuring body 2 is fixed in the working space 3 of the 3-axis machine tool, the control unit 10 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.

[0049] 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.

[0050] After completing the measurement of the measuring body 2 in the 3-axis machine tool 1 and, if necessary, thermally adjusting 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 and position deviations P.

[0051] For example, a position deviation of the X-axis can first be determined by evaluating the differences between actual positions and target positions in the X-direction of the measured reference elements on the base plate 20 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 10.

[0052] 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.

[0053] 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.

[0054] In the same way, straightness deviations G of the X-axis are determined. 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 rows of holes 23, 24 and the reference holes 26 on the stepped area 25. The differences between the actual positions and the target positions in the Z-direction result from the reference surfaces 28, 29 on the base plate 20 and the ground step surfaces 26a. Mathematical preprocessing or approximation is also possible here.

[0055] Once the correction data for the positional 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 positional 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 preferably assumed that the adjusted actual positions no longer exhibit any errors in the X-direction. This allows the errors in the Z-direction to be calculated in the further evaluation without these Z-errors being influenced by the errors in the X-direction. This is because, with the wall 21 arranged in the X-direction, the X-axis must be moved so that the reference holes 26 can be measured at different Z-axis positions.

[0056] 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 2 along the X-direction and their position deviations in the Y-direction. The second best-fit line results from the Y-axis positions of the reference elements on the base plate 2 along the Y-direction and their position deviations in the X-direction. An angle α is then calculated between the two best-fit lines (see Figure 3 ). The determined deviation can be used directly as a correction value for error compensation in the control unit 10.

[0057] 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 XY perpendicularity error.

[0058] Subsequently, the position deviations and straightness deviations of the Y-axis are 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 base plate 2 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 directly transferred to the control unit 10 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 to define the entire workspace 3.

[0059] 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 preferable to assume that the adjusted actual positions no longer exhibit any errors in the Y-direction. This allows the errors in the Z-direction to be calculated in the further evaluation without these errors being influenced by the errors in the Y-direction. This is because, for the second wall 22 arranged in the Y-direction, the Y-axis must be moved so that the holes 26 can be measured at different Z-axis positions.

[0060] 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 2 along the X-direction and their positional deviations in the Z-direction. The second best-fit line results from the Z-axis position of the reference elements on the first wall 21 (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 10.

[0061] 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 20 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 22 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.

[0062] 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 error or YZ perpendicularity error.

[0063] In the final step, the geometric deviations of the Z-axis are calculated. The reference elements (reference holes 26 and ground step surfaces 26a) of the two triangular walls 21, 22 are used for this purpose. 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 process in the X-direction or Y-direction, which is necessary to measure the steps, does not affect the geometric deviations of the Z-axis.

[0064] 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 both walls 21, 22. 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.

[0065] 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.

[0066] In this way, all geometric errors except yaw, pitch, and roll can be checked and corrected using measuring body 2. This method is particularly suitable for correcting a 3-axis machine tool geometry after a change in thermal conditions, since in this case, linear errors usually occur that can be easily extrapolated. Additionally, 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.

[0067] In addition to the above written description of the invention, for its supplementary disclosure, reference is hereby explicitly made to the graphic representation of the invention in the Fig. 1 to 4 reference is made. List of reference symbols

[0068] 13-axis machine tool 2Measuring body 3Working area 4Spindle 5Measuring device (3D measuring probe) 6Machine table 10Control unit 20Base plate 20aFirst edge 20bSecond edge 20cThird edge 20dFourth edge 21First wall 22Second wall 23First row of holes 23aHoles of the first row of holes 24Second row of holes 24aHoles of the second row of holes 25Step-shaped area 25aSteps 26Reference hole 26aGround step surface 27Corner line 28First reference surface 29Second reference surface 30Common hole 31First straight line 32Second straight line GStraightness deviation RPerpendicularity PPosition deviation XX-axis YY-axis ZZ-axis

Claims

1. A measuring body for checking geometric deviations in a 3-axis machine tool (1) comprising: ▪a quadrangular base plate (20), ▪a first wall (21), which is arranged at the base plate (20) and protrudes perpendicularly from the base plate (20), ▪a second wall (22), which is arranged at the base plate (20) and protrudes perpendicularly from the base plate (20), ▪wherein a first hole row (23) and a second hole row (24) are formed in the base plate (20), ▪wherein the first wall (21) comprises a step-shaped portion (25) with a plurality of steps (25a) at an upper, exposed portion, ▪wherein the second wall (22) comprises a step-shaped portion (25) with a plurality of steps (25a) at an upper, exposed portion, ▪wherein the first wall (21) is arranged along a first edge (20a) of the base plate (20) and wherein the second wall (22) is arranged along a second edge (20b) of the base plate (20), wherein the first hole row (23) is arranged along a third edge (20c) of the base plate (20) and wherein the second hole row (24) is arranged along a fourth edge (20d) of the base plate (20), ▪wherein the first wall (21) and the second wall (22) are adjacent to each other at a corner of the base plate (20), and ▪wherein each step comprises a reference hole (26).

2. The measuring body according to one of the previous claims, wherein the steps (25a) of the first wall (21) and the second wall (22) have equal step heights and / or equal step lengths and / or equal step numbers.

3. The measuring body according to one of the previous claims, wherein each step (25a) comprises a burnished or milled step surface (26a).

4. The measuring body according to one of the previous claims, wherein a first reference surface (28) is arranged adjacent to the first hole row (23) as a reference for a Z direction and a second reference surface (29) is arranged adjacent to the second hole row (24) as a reference for the Z direction, wherein the Z direction is perpendicular to the base plate (20).

5. The measuring body according to one of the previous claims, wherein the holes of the first hole row (23) lie on a first straight line (31) and / or wherein the holes of the second hole row (24) lie on a second straight line (32).

6. The measuring body according to claim 5, wherein the first reference surface (28) and the second reference surface (29) are strip-shaped and arranged parallel to the first hole row (23) and to the second hole row (24).

7. A 3-axis machine tool comprising a tool spindle (4) - a measuring body (2) according to one of the previous claims, - a measuring device (5), which is clampable into the tool spindle (4) and is arranged to detect actual values of the measuring body (2) fixed in the 3-axis machine tool (1), and - a control unit (10) arranged to control the 3-axis machine tool (1), wherein the control unit (10) is further arranged, 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) detected by the measuring device (5) for the 3-axis machine tool (1), to perform a target-actual comparison, and, if deviations occur between the target values and the actual values, to correct geometric data of the 3-axis machine tool (1) in the control program of the control unit (10).

8. The 3-axis machine tool according to claim 7, wherein the control unit comprises a memory, in which the target values of the measuring body (2) are stored.

9. A method for checking and compensating of geometric deviations of a 3-axis machine tool, comprising the 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 6 in a working space (3) of the 3-axis machine tool, - approaching a plurality of positions of the measuring body (2) in order to detect geometric actual data of the 3-axis machine tool by means of 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 of the geometric deviations in a control unit (10) of the 3-axis machine tool.

10. The method according to claim 9, wherein the target values of the measuring body (2) were detected in advance in a coordinate measuring machine and the measuring body (2) is arranged in the working space (3) of the 3-axis machine tool in such a way that the coordinate system of the measuring body (2) coincides with the coordinate system of the 3-axis machine tool.

11. The method according to claim 9 or 10, wherein during the measurement of the measuring body (2) in the 3-axis machine tool (1), a temperature of the working space (3) is detected and a correction of the actual data is performed based on the detected temperature of the working space (3).

12. The method according to one of claims 9 to 11, wherein position deviations of the respective axes and two straightness deviations of the respective axes are determined in the X direction, Y direction, and Z direction, respectively.

13. The method according to one of claims 9 to 12, wherein perpendicularity errors between the X-axis, the Y-axis and the Z-axis are calculated.