Method for calibrating a gear cutting machine

Abstract

To provide an improved calibration method for a gear cutting machine.SOLUTION: Determining at least one first calibration value by measuring the workpiece at a first workpiece width position, determining at least one second calibration value by measuring the workpiece at a second workpiece width position, and determining at least one third calibration value for a relative orientation of the first linear movement axis Z of the machining head with respect to the first rotational axis C1 of the workpiece holder from the at least one first calibration value and the at least one second calibration value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for calibrating a gear cutting machine by measuring a workpiece held in a workpiece holder of the gear cutting machine. [Background technology]

[0002] Gear cutting machines are used to inspect the workpieces they produce, for example, for tooth thickness, pitch, profile, and flank line inspections. When sensors are installed, particularly in the form of measuring sensors, minute deformations can occur in the machine due to external factors such as temperature fluctuations, which can reduce the accuracy of these inspections. Therefore, to ensure consistently good inspection results, it is necessary to periodically identify and correct any changes in the sensor's position relative to the tooth profile.

[0003] The position of the sensor required for calibration can be determined using a measuring object such as a gauge block. However, there are advantages to directly determining (measuring) a workpiece clamped in the machine, especially a gear. In particular, it saves the operator the trouble of introducing a gauge block (calibration sphere / calibration standard) into the machine (gear cutting machine) and then removing it again after calibration. In the case of gear cutting machines used to manufacture large workpieces, the displacement path of the measuring sensor may not be sufficient to reach the gauge block. This can also be prevented by measuring the workpiece.

[0004] A method for calibrating a measuring sensor of a gear cutting machine using a workpiece is known from Patent Document 1, in which the outer diameter of the workpiece is measured twice in different measurement steps. In the first measurement step, the measuring sensor is moved in a tangential direction while the workpiece is rotating, and in the second measurement step, it is moved in a non-tangential direction, for example, in the radial direction. Based on the difference in the gradient error of the tooth outer diameter measured in each measurement step, the position error of the measuring head is determined and used for calibration.

[0005] A method for calibrating a measuring sensor of a gear cutting machine using a workpiece is known from US Pat. No. 5,649,999, in which the center point of the tip of the measuring sensor moves on a circular orbit (selectively independent of the measured deviation).

[0006] Both methods are used to calibrate the X and V / Y axes along which the measurement sensor can move in a plane perpendicular to the rotation axis C1 of the workpiece holder, and thus the position of these axes relative to the rotation axis C1 of the workpiece holder.

[0007] Furthermore, methods are known in the prior art for determining and, if necessary, correcting workpiece clamping errors, but these methods assume that all axes of the gear cutting machine have already been calibrated relative to one another.

[0008] In this case, US Pat. No. 5,629,999 discloses a gear machining method in which the workpiece is not accurately aligned on the machining device, so that the wheel guide axis, which should later become the rotation axis of the gear, does not coincide with the rotation axis of the machining device, with the result that in the case of a rotating table or a rotating workpiece spindle, the wheel guide axis F oscillates around the rotation axis D of the machining device. In this case, by sampling a corresponding flange on the workpiece, the position of the wheel guide axis F relative to the rotation axis D of the machining device is determined, and the inaccurate alignment of the workpiece during machining is corrected by further movement of the axis, so that a tooth profile is formed about the wheel guide axis F. Similar methods are known from US Pat. No. 5,629,999, US Pat. No. 5,629,999 and US Pat. No. 5,629,999.

[0009] No. 6,299,333 discloses a method for correcting inaccurate clamping of a workpiece by means of an adjustment device provided on the workpiece holder.

[0010] The aim of US Pat. No. 5,629,644 is to compensate for temperature-induced changes in specific workpiece variables such as face width by correcting the feed rate. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] European Patent No. 2554938 [Patent Document 2] German Patent Application Publication No. 102019104891 [Patent Document 3] European Patent Application Publication No. 1319457 [Patent Document 4] European Patent No. 2596892 [Patent Document 5] DE 3712454 A1 [Patent Document 6] DE 19631620 [Patent Document 7] European Patent Application Publication No. 1952927 [Patent Document 8] European Patent No. 3274776 Summary of the Invention [Problem to be solved by the invention]

[0012] The object of the present invention is to improve the calibration method for gear cutting machines.

[0013] This problem is solved by the method according to claim 1. The dependent claims relate to preferred embodiments of the invention. [Means for solving the problem]

[0014] The present invention includes a method for calibrating a gear cutting machine, the method comprising: a workpiece holder rotatable around a first rotation axis C1; a machining head having a tool holder; and a sensor for measuring a workpiece held in the workpiece holder of the gear cutting machine, the sensor being disposed in the machining head of the gear cutting machine; and the machining head being movable in a width direction of the workpiece relative to the workpiece holder via a first linear motion axis Z of the gear cutting machine, the method comprising: determining at least one first calibration value by determining a tooth profile of the workpiece at a first workpiece width location; determining at least one second calibration value by determining a tooth profile of the workpiece at a second workpiece width location; and The method includes determining at least one third calibration value relating to the relative orientation of the first linear movement axis Z of the machining head with respect to the first rotation axis C1 of the workpiece holder from the at least one first calibration value and the at least one second calibration value.

[0015] In this case, the inventors have found that determining calibration values ​​at two different workpiece width positions also allows for calibration of the relative alignment of the first linear motion axis Z of the machining head with respect to the first rotation axis C1 of the workpiece holder, and in particular allows for recording deviations of the two axes from a desired parallel alignment. Thus, in particular the at least one third calibration value is representative of deviations of the two axes from a desired parallel alignment and / or allows for correction of such deviations.

[0016] A preferred embodiment of the method according to the invention is described below.

[0017] According to a possible embodiment, the first and second calibration values ​​are determined by measuring the same tooth profile at the first workpiece width position and the second workpiece width position. However, the first and second calibration values ​​can alternatively be determined by measuring a first and a second tooth profile of the workpiece. Whenever "tooth profile" is referred to below, this always includes the possibility that two different tooth profiles are measured.

[0018] According to a possible embodiment, the gear cutting machine comprises at least one second linear axis X1 and / or one third linear axis V1 / Y1 for moving the machining head relative to the workpiece holder, and at least one first calibration value and at least one second calibration value relate to the calibration of the position of the second linear axis X1 and / or the third linear axis V1 / Y1, respectively, relative to the first rotation axis C1. In particular, in this case, the first calibration value and the second calibration value, respectively, describe the position of the machining head in a plane perpendicular to the first rotation axis C1 of the workpiece holder.

[0019] In a possible embodiment, the calibration values ​​are determined by measuring the tooth profiles of workpieces produced in the same clamping operation on the gear cutting machine, respectively, which ensures that the measured contours are not influenced by clamping errors of the workpiece in the workpiece holder and that the rotation axis of the workpiece contour coincides with the rotation axis of the workpiece holder.

[0020] However, in an alternative embodiment, the tooth profile is already present before clamping the workpiece in the gear cutting machine, and no machining of the tooth profile is carried out on the gear cutting machine before measuring the tooth profile.

[0021] However, in this case, clamping errors of the workpiece in the workpiece holder cannot be excluded, as a result of which the contact point during measurement may be located slightly inside or outside the assumed involute, but in any case in certain embodiments of the invention this does not significantly affect the determination of the calibration value.

[0022] However, to form the tooth profile surface, it is preferable to machine the tooth profile in a separate clamping operation (e.g., on a separate gear cutting machine) before measurement or to machine it in the same clamping operation. In particular, it is preferable to perform hard precision machining of the tooth profile to prevent feed marks from previous soft machining from adversely affecting the calibration.

[0023] In a possible embodiment, the determination of the at least one first and second calibration value is performed by determining at least one relative position of the workpiece and the machining head, each determined by a sensor at at least one measurement point, and comparing the determined result with a target relative position to determine a correction value for the position of the machining head relative to the rotation axis C1 of the workpiece holder in a plane extending perpendicular to the rotation axis C1.

[0024] In one possible embodiment, determining the at least one first calibration value and the at least one second calibration value is performed by rotating the workpiece around the rotation axis C1 of the workpiece holder for measurement and by moving the sensor through at least one axis of the gear cutting machine to measure the tooth profile.

[0025] In one possible embodiment, the sensor is guided on at least one predetermined path relative to a point on the surface of the workpiece for measurement of the workpiece, which path can be partially predetermined by the expected movement of the point on the workpiece surface when the workpiece undergoes a rotational movement about the rotation axis C1 of the workpiece holder.

[0026] In this case, according to a first variant, the measuring point of the sensor is guided in two measurement runs (two measurement paths) along two different trajectories along the tooth profile surface, and a first or second calibration value is determined from the deviations (deviations) of the measurement results. In particular, in this case, in the first measurement run, the measuring sensor can be moved tangentially while the workpiece is rotating, whereas in the second measurement run, it can be moved in a non-tangential direction, for example, radially. Based on the difference in the gradient error of the tooth profile determined in each measurement path, a position error of the machining head is determined and used to determine the first and second calibration values. This can be done, in particular, as described in patent document 1.

[0027] According to a second variant, the sensor is moved such that the measuring point on the tooth flank remains unchanged in the case of a perfect calibration, and the first or second calibration value is determined from the deviation between the sensor displacement behavior expected in the case of a perfect calibration and / or the sensor value expected in the case of a perfect calibration and the actual sensor displacement behavior and / or the actual sensor value at the time of determination. In particular, the machining head with the sensor moves in a circular orbit around the rotation axis C1 (excluding the measured deviation).

[0028] According to a possible embodiment, a measurement sensor can be used as the sensor.

[0029] According to a first embodiment of the second variant, the determination of the first calibration value and / or the second calibration value, respectively, comprises: moving the measurement sensor and / or the workpiece to a relative position where the tip of the measurement sensor contacts the tooth flank of the workpiece; rotating the workpiece about the rotation axis of the workpiece holder and moving the measurement sensor through the second linear movement axis and the third linear movement axis of the gear cutting machine so that the contact point of the tip of the measurement sensor on the tooth surface remains unchanged in the case of a complete calibration and the deviation or the magnitude of the deviation of the tip of the measurement sensor takes or maintains at least one predetermined value in the case of a complete calibration; determining, at at least one measurement point, a deviation of the tip of the measurement sensor from at least one predetermined value; and determining at least one first or second calibration value based on the deviation; This is done by:

[0030] According to a second embodiment of the second variant, the determination of the first calibration value and / or the second calibration value, respectively, comprises: moving the measurement sensor and / or the workpiece to a relative position where the tip of the measurement sensor contacts a tooth flank of the workpiece; rotating the workpiece about the rotation axis of the workpiece holder and moving the measurement sensor through the second linear movement axis and the third linear movement axis of the gear cutting machine so that the contact point of the tip of the measurement sensor on the tooth surface remains unchanged in the case of a perfect calibration and the deviation or the magnitude of the deviation of the tip of the measurement sensor takes or maintains at least one predetermined value; Determining the deviation (deviation) of the actual position of the rotation axis of the workpiece holder and / or the actual positions of at least two movement axes of the gear cutting machine from the positions that these axes would occupy in the case of a complete calibration at at least one measuring point, and determining at least one first or second calibration value based on the deviation; This is done by:

[0031] In particular, the first calibration value and / or the second calibration value can be determined by the method described in Patent Document 2, respectively.

[0032] The sensor may be a measurement sensor, regardless of the particular method used to determine the first calibration value and / or the second calibration value.

[0033] According to one possible embodiment, the third calibration value is referenced to correct the displacement kinematics of the machining head and / or to correct the measurement values ​​and / or actuation values ​​(control values) in subsequent measurements and / or machining.

[0034] Therefore, in a first possible embodiment, in subsequent measurements and / or processing, while the processing head is displaced along the first linear axis Z according to the widthwise position of the workpiece, the third linear axis X and / or the third linear axis V / Y also move according to the third calibration value.

[0035] In a second embodiment, in subsequent measurements and / or machining, the measured target flank line angle and / or the target flank line angle on which the actuation (control) is based is corrected in accordance with the third calibration value, in particular by an offset that depends on the calibration value. As a result, the method can also be implemented with conventional controllers without changing the actuation (control) of the operating axes of the gear cutting machine.

[0036] According to one possible embodiment, the calibration is performed before the machining of the workpiece, between two machining steps of the workpiece, or after a machining step of the workpiece has been performed. In particular, in this case, the correction of the machining based on the third calibration value can be performed before the last machining step of the workpiece, in particular before the final finishing cut, so that errors in the alignment of the rotary axis C1 and the first linear axis Z1 do not affect the machining quality.

[0037] On the other hand, in one possible embodiment, calibration is performed only after machining of a workpiece, and corrections can be incorporated into measurements of this or other workpieces and / or machining of other workpieces.

[0038] According to a possible embodiment, calibration is performed at three or more workpiece width positions to determine the at least one third calibration value. In this way, the accuracy of determining the at least one third calibration value can be increased. In this case, the at least one third calibration value can be determined by interpolation of values ​​obtained from three or more calibration positions or can be determined in the form of a calibration curve that depends on the position in the workpiece width direction.

[0039] The present invention also provides a gear cutting machine comprising a workpiece holder rotatable about a first axis of rotation C1, a machining head with a tool holder, and a sensor for measuring a workpiece held in the workpiece holder of the gear cutting machine, the sensor being arranged in the machining head of the gear cutting machine, the machining head being movable relative to the workpiece holder in a workpiece width direction about a first linear motion axis Z of the gear cutting machine, the gear cutting machine comprising a specially programmed controller configured to perform the above-mentioned method on the gear cutting machine, in particular the controller automatically executing the individual steps of the method and / or having operator guidance for executing said steps.

[0040] The controller preferably includes a microcontroller and a software program for controlling the gear cutting machine stored in a non-volatile memory, the software program having commands that, when executed by the microcontroller, cause the gear cutting machine to implement the method as described above. The controller is preferably communicatively connected to the sensors and motion axes of the gear cutting machine, drives the motion axes of the gear cutting machine, and evaluates the sensor signals.

[0041] The present invention further includes a gear cutting machine control software program having commands that, when executed on a microcontroller, cause the gear cutting machine to implement the method as described above.

[0042] In particular, the gear cutting machine may be operated by a software program to automatically carry out the individual steps of the method and / or may have an operator guide for carrying out the steps.

[0043] The invention will now be explained in more detail with reference to embodiments and drawings. [Brief explanation of the drawings]

[0044] [Figure 1] FIG. 1 shows an embodiment of a gear cutting machine according to the present invention. [Figure 2] FIG. 2 shows an embodiment of a machining head with a sensor, which is inserted into a gear cutting machine. [Figure 3] FIG. 3 is a schematic diagram illustrating an embodiment of the method according to the invention, showing the circular path that the contact point between the tip of the measuring sensor and the flank of the tooth profile must describe when the workpiece rotation axis rotates and the measuring sensor is displaced synchronously. [Figure 4] FIG. 4 is a perspective view of a workpiece ready to measure the tooth profile of the workpiece at three different workpiece width locations. [Figure 5] Figure 5 is a schematic diagram showing the calculated contact point (41, 41') and the actual trajectory of the contact point in the presence of position errors (43, 43') between the measurement sensor tip and the tooth profile flank at two different workpiece width positions. [Figure 6] FIG. 6 is a schematic diagram showing the relative positions of the tooth profile flank and the sensor on the first linear motion axis of the gear cutting machine, which is inclined with respect to the rotation axis C1 of the workpiece holder, and / or the first and / or second calibration values ​​dV (or dY) obtained at each workpiece width position Z. [Figure 7]FIG. 7 shows a table showing the first and second calibration values ​​determined at three different workpiece width positions, and two graphs for determining the third calibration value from the first and second calibration values. DETAILED DESCRIPTION OF THE INVENTION

[0045] An embodiment of the structure and mode of operation of a gear cutting machine according to the invention is shown in Figure 1. Figure 2 shows an embodiment of a machining head 13 with a measuring sensor 14 that can be inserted into the gear cutting machine.

[0046] In this embodiment, the gear cutting machine comprises a workpiece holder 11 and a tool holder 12. The workpiece holder and the tool holder are drivable by corresponding drives about rotation axes C2 and B1, respectively.

[0047] The tool holder is arranged in a machining head 13, which is movable relative to the workpiece holder via a movement axis. In this embodiment, a first linear axis Z1 is provided, by which the tool holder 12 can be moved in a direction extending parallel to the rotation axis C1 of the workpiece holder with perfect calibration. A second linear axis X1 is also provided, by which the tool holder 12 can be moved in a direction perpendicular to the rotation axis C1 of the workpiece holder, thereby changing the axial distance. A third linear axis V1 is also provided, by which the tool holder 12 can be moved in a direction parallel to its own rotation axis B1. The orientation of the linear axis V1 and the tool holder 12 can be changed via a swivel axis A1, which extends parallel to the X1 axis.

[0048] In this embodiment, the workpiece holder 11 is arranged on a tool bench 15. The machine bed 15 supports a tool stand 16 that is linearly movable along the X1 axis. A carriage that is movable along the Z1 axis is arranged on the tool stand, and a machining head equipped with a tool holder 12 is arranged on this carriage via the A1 axis and the V1 axis.

[0049] The gear cutting machine may be, for example, a gear hobbing machine and / or a gear grinding machine, but the invention may also be applied to any other gear cutting machine.

[0050] 2 shows an embodiment of the processing head 13. A measuring sensor 14 is arranged in the processing head as a sensor. This measuring sensor has a measuring sensor base 23, and the deviation (deviation) of the measuring sensor tip of the measuring sensor 14 relative to the measuring sensor base 23 can be measured by at least one sensor.

[0051] The measurement sensor 14 is arranged on a pivoting arm 21 via a measurement sensor base 23 and can be pivoted by a drive 22 from an idle position to a measurement position and from the measurement position back to the idle position.

[0052] The definitions of the directions X, Y, and Z chosen in this description are also shown in Figure 1, where Z is orthogonal to X and Y, and the three axes form a Cartesian coordinate system. In a fully calibrated system, the Z axis runs parallel to the gear's rotation axis (the workpiece's rotation axis). In this case, the C1 axis of the machine represents the rotation axis of the workpiece holder, which rotates the workpiece around the workpiece's rotation axis. The X, Y, and Z axes represent the machine axes that move the measurement sensor in the X, Y, and Z directions relative to the gear. In this case, the axes do not necessarily have to be physical axes. Therefore, this movement can also be achieved by interpolating two or more axes.

[0053] In particular, movement in the X direction in this embodiment can be achieved by the X1 direction, and movement in the Y direction in this embodiment can be achieved by the V1 axis alone at the position of the A1 axis where the V1 axis is parallel to the Y direction, and can be achieved by superimposing the movements of the V1 and Z1 axes at other positions. However, in other embodiments of the gear cutting machine, for example, a Y1 axis may be provided that is always parallel to the Y direction so that the Y1 axis does not rotate with the A1 axis by supporting the A1 axis.

[0054] The measurement sensor tip 1 at the end of the tracer pin 2 of the measurement sensor 14 is preferably a sphere (measurement sensor sphere), for example a ruby ​​sphere.

[0055] However, the invention is also applicable to other embodiments of the gear cutter or sensor.

[0056] When determining the first and second calibration values ​​(sensors on the workpiece), the relative position between the workpiece and the machining head is determined in each case in a plane perpendicular to the rotation axis C1 of the workpiece holder. The measuring sensor for the calibration is attached to the same point / axis as the machining tool, as described above. The determination result is compared with the target position, resulting in a calibration value in the form of an offset (x- and y / v-offset), which can be added to the actual position, for example. As a result, the selected position corresponds to the target position of the machine (gear cutting machine) and can be used by this machine during machining and measurement / tooth profile inspection.

[0057] In the prior art, such calibration is performed at only one position across the width of the workpiece. However, if the Z1 and / or C1 axes are not perpendicular to the X and Y directions but are tilted in a different direction so that they are no longer parallel, the relative positions of the workpiece and tool / sensor will change across the width of the workpiece.

[0058] Performing calibration at at least two different workpiece width positions z1 and z2 results in different first and second calibration values ​​(x and y / v directions) for different first and second workpiece width positions z1 and z2. Measurement and determination of calibration values ​​can also be performed at three or more workpiece width positions to increase accuracy. In this case, Figure 4 shows measurements of the tooth profile of workpiece 5 at three different workpiece width positions z1 to z3.

[0059] According to the present invention, a third calibration value for tilt between the C1 and Z1 axes can be determined from at least two calibration values ​​at different workpiece width positions.

[0060] According to the present invention, calibration is performed at different workpiece width positions on the tooth profile of the workpiece, and the inclinations of the C1 and Z1 axes are determined from the calibration values ​​identified in this case.

[0061] The workpiece is preferably machined (on a gear cutting machine) to form the tooth profile before the calibration values ​​are determined. This ensures that the workpiece's rotation axis coincides with the workpiece holder's rotation axis C1. This procedure also ensures that any axial tilt between the machine's Z1 and C1 axes is reflected in the workpiece. A tilt in the X direction results in a conical shape of the workpiece, while a tilt in the V direction (for small angles) results in a change in the workpiece of approximately the pitch height.

[0062] However, the method of the present invention is also applicable to workpieces processed with other machines or other clamping operations. The exact circularity (roundness) of the workpiece, or the tilt between the Z1 and C1 axes reflected in the workpiece, is not essential to implementing the method of the present invention. Rather, when determining the first and second calibration values, the distance between the sensor and therefore the Z1 and C1 axes is determined, thereby calibrating the machine axes. As long as this calibration is performed according to the detailed description below, workpiece clamping errors will only have a small effect on the calibration results.

[0063] In this case, if a calibration is performed on a workpiece at two workpiece width locations to determine the axial tilt of the Z1 and C1 axes, it will not matter to the calibration result whether there is a slightly tilted Z1 axis or a slightly tilted C1 axis (or both), as this will make only a small difference at most.

[0064] According to a possible embodiment of the invention, the determination of the first and second calibration values ​​(x-direction and y / v-direction) is performed at two workpiece width positions z1 and z2, for example as follows:

[0065] The processing head is moved along the Z1 axis so that the measurement sensor is located at the first or second workpiece width position z1 and z2, respectively.

[0066] The C1 axis is then rotated until the workpiece, excluding the tracer pin, reaches the desired deviation, i.e., the workpiece preferably reaches half of the possible deviation, as shown on the right side of FIG.

[0067] Next, the C1 axis is rotated continuously, and the X and Y axes are moved synchronously. If the calibration is perfect, the point where the tip of the measurement sensor contacts the tooth flank and the magnitude of the sensor deviation (deviation) will remain constant (see Figure 1). The contact point between the tip of the measurement sensor and the tooth profile moves on a circular orbit whose center is located on the gear's rotation axis.

[0068] During this rotation, the deviation of the tracer pin against the rotation angle C1 is plotted, in particular at as many separate points as possible.

[0069] This procedure is repeated on the other flank (tooth surface) to obtain the deviation appearing at the point on the left flank and the deviation appearing at the point on the right flank.

[0070] If the calibration is perfect and there is no inaccuracy in either the measuring sensor or the machine axis, the plotted sensor deviations at all C1 positions for both flanks will be constant at the initial sensor deviations. In this case, the contact points between the tip of the measuring sensor and the two flanks will not change.

[0071] If the calibration is not perfect, the actual contact point (42, 42') of the measurement sensor tip with the flank at the start of the measurement will not coincide with the calculated contact point (41, 41'), as shown in Figure 5. As a result, the calculated C1 angle assumed at the start of the measurement will not be achieved exactly when the desired deflection of the tracer pin is reached. Furthermore, the deflection of the tracer pin and the contact point of the flank will change during the displacement of the calculated motion trajectory (43, 43'). Plotting the deflection of the tracer pin versus the C1 position will result in one curve for each flank.

[0072] From this, first or second calibration values ​​for the X and Y positions of the machining head relative to the rotation axis C1 can be determined for the first or second Z positions z1 and z2 employed, respectively.

[0073] This determination can be carried out in each case in the manner known from US Pat. No. 5,699,499, and it is also possible to carry out an alternative to the procedure described therein. Furthermore, it is also possible instead to determine the first or second calibration values ​​of the X and Y positions of the machining head for the first or second Z positions z1 and z2 about the rotation axis C1 in the manner known from US Pat.

[0074] In either case, calibration at different workpiece width positions provides x and y corrections for each of these different workpiece width positions. In Figure 6, the y correction is shown as dV / dY. This provides information about the relative position of the C1 (workpiece holder) rotation axis and the Z1 (gear cutter axis) axis for the different workpiece width positions.

[0075] In this case, in Figures 4, 6, and 7, calibration is performed at three different workpiece width positions or Z positions, and calibration values ​​for the X1 axis and V1 / Y1 axis are determined for each.

[0076] Using these calibration values, the best approximation straight line for each can be drawn as shown in Figure 7. In this case, the large dots are the calibration values ​​at the measurement points, and the dashed lines are the best approximation straight lines / trend lines.

[0077] The pitch of the best fit line constitutes a third calibration value that represents the tilt of the C1 and Z1 axes relative to each other and can be used to correct for it.

[0078] The best fit straight line can be linearly extrapolated to the entire displacement range of the machine (gear cutter) in the Z direction to obtain the correction curve.

[0079] In the first variant, in order to correct tilts during both machining and measurement / inspection on this machine, when the Z axis is displaced, the X1 axis and V1 / Y1 axis can be moved simultaneously along a correction curve depending on the Z position.

[0080] For example, if the Z1 axis moves from position 110 to position 140 in Figure 7, and you do not want the relative positions in the X1 and V1 / Y1 directions to change in this example, the machine will automatically change the X1 position by +3 and the V1 position by +1 (along the compensation curve) during the displacement.

[0081] This allows the machining tool / measuring sensor to be moved exactly parallel to C1 in the Z1 direction, so no errors due to axis tilt occur during machining or measurement.

[0082] Therefore, all that is required in the final deployment step is to calculate the correction curve from the calibration results and operate the machine accordingly.

[0083] If it is not possible or desirable to shift the compensation curve, such that X1 and V1 are additionally shifted along the compensation curve according to Z1, for example, if this cannot be implemented directly in the machine's (gear cutting machine's) controller, another possible solution is to calculate the flank line angle offsets for the right and left flanks, respectively, from the pitch of the compensation curve when measuring the flank lines on the machine. When measuring the flank lines with a measuring sensor, this offset must be added to fHbeta for the right and left flanks. Similarly, for machining processes, an offset can be calculated to specify the change in fHbeta to correct for axial tilt. The offset for measurement depends on the X position of the measuring sensor when measuring the flank line, while the offset for machining depends on the machining method. Therefore, they are not necessarily the same.

[0084] If further improvements are to be made, for example because the conicity of the workpiece due to axial tilt in the X direction has not been fully taken into account, much more complex calculations can be considered. In the procedure described above, the calibration evaluation calculation only includes calibrations at the profile heights of the right and left flanks, from which the X and V corrections are calculated. An extended calculation / evaluation can also include calibration measurements at different profile heights.

[0085] So, following this procedure, e.g. The first calibration has a contact point on the SAP, a second calibration with contact points on the EAP; By doing this, the mechanical errors when moving (scanning) the entire contour (when calibrating the sensor between SAP and EAP) can be identified and largely eliminated.

[0086] However, what is important to the present invention is the calibration across the width of the workpiece, and further embodiments of the present invention are described below.

[0087] As mentioned above, when measuring the flank line, there is an inherent problem in that the axial parallelism of the lift axis (elevation axis) Z1 relative to the workpiece holder axis C1 has so far only been measured during trial operation and corrected if necessary.

[0088] Therefore, in the present invention, Perform the first calibration in the upper flank line area (e.g., 10% of the workpiece width), Perform a second calibration in the lower flank line area (e.g., 90% of the workpiece width), This identifies and eliminates as much as possible the mechanical errors when moving (scanning) the entire flank line (e.g., calibrating at 50%).

[0089] In this case, each calibration specifies the X and Y offsets of the measurement sensor in absolute values ​​relative to the workpiece rotation axis C1.

[0090] Therefore, by performing calibration at different face width positions, for example near the two end faces, it is possible to identify the mechatronic error from the upper end point to the lower end point of the flank line measurement, thereby correcting the mechatronically "inaccurate" measured fH-β.

[0091] This allows the workpiece inspection accuracy on production machines to approach that of measuring machines, since an additional calibration before the actual measurement records the current geometric state of the machine (gear cutter), which can change especially due to thermal effects.

[0092] Thus, the dependency of the axial position of the lift axis Z1 relative to the workpiece holder axis C1, particularly in measuring the flank line angle, is largely eliminated, allowing new levels of accuracy to be achieved that were previously unthinkable on production machines.

[0093] Calibration involves the gear currently positioned in the workpiece space being Before processing, During processing (between processing periods), After processing Can be used for.

[0094] In this way, the parallelism of the lift axis Z1 (or the position of the sensor) relative to the bench rotation axis C1 is recorded, Correct the kinematics settings before starting machining, Correct the motion settings during processing, Correcting measurements after processing (pre- or post-processing) It is possible.

[0095] The machining of the tooth profile is preferably a hard precision machining with corresponding accuracy requirements, but can also be machining by other methods such as milling, gear skiving or knocking.

[0096] Combining fHbeta calibration with temperature measurements or other corrective measurements (AMC) allows for a better understanding or prediction of the machine's behavior. Corresponding verification is also possible after machining.

[0097] Note: AMC = Automatic X-Compensation after measurement by the measuring sensor of the measuring surface of the workpiece or counter holder.

[0098] The crucial aspect of in-process control calibration is that the thermal (geometric) damage caused by interrupting the machining process does not outweigh the accuracy gains from the calibration. This impact can be better assessed and determined in advance by continuous learning in different machining processes.

[0099] All calibration methods assume that the workpiece rotates. The rotational position can usually be recorded with high precision using integrated transducers. This also applies in the case of helical teeth, where the twist of the workpiece must be superimposed depending on the lift position. The actual position of the sensor relative to the table axis is the sum of the thermal and mechatronic deviations of the involved axes and components. Optionally, different kinematics during calibration can be used to estimate the different degrees of influence of the involved axes and components (e.g., pure tangential movement of V1 combined with C1 compared to the combined movement of V1, X1 and C1).

[0100] If it is possible to determine the position of the sensor relative to the table axis, the displacement of the counterholder relative to the table axis can be determined, which allows a new interpretation of additional calibration measurements such as AMC on the counterholder. If this (displacement) exceeds the tolerance limits of the control calibration during machining, for example, the process can be interrupted to readjust the tip of the counterholder. This prevents rejects, but there is of course a risk that the thermal (geometric) damage caused by interrupting the machining process will not be greater than the accuracy improvement achieved by the calibration / readjustment.

Claims

1. A method for calibrating a gear cutting machine, comprising: a workpiece holder rotatable around a first rotation axis C1; a machining head having a tool holder; and a sensor for measuring a workpiece held in the workpiece holder of the gear cutting machine, wherein the sensor is disposed in the machining head of the gear cutting machine, and the machining head is movable in a width direction of the workpiece relative to the workpiece holder via a first linear motion axis Z of the gear cutting machine, determining at least one first calibration value by measuring a tooth profile of the workpiece at a first workpiece width location; determining at least one second calibration value by measuring a tooth profile of the workpiece at a second workpiece width location; and determining at least one third calibration value relating to a relative orientation of a first linear movement axis Z of the machining head with respect to a first rotation axis C1 of the workpiece holder from the at least one first calibration value and the at least one second calibration value; A method having the following.

2. 10. The method of claim 1, the gear cutting machine has at least one second linear axis X1 and / or one third linear axis V1 / Y1 for moving the machining head relative to the workpiece holder, and the at least one first calibration value and the at least one second calibration value relate to calibrating the position of the second linear axis X1 and / or the third linear axis V1 / Y1, respectively, relative to the first rotation axis C1.

3. 3. The method according to claim 1 or 2, A method in which the tooth profile is created before measurement in the same clamping operation on the gear cutting machine, or the tooth profile already exists before clamping the workpiece on the gear cutting machine, and no machining of the tooth profile is performed on the gear cutting machine before measuring the tooth profile.

4. The method according to any one of claims 1 to 3, The method for determining the at least one first calibration value and the at least one second calibration value is performed by determining at least one relative position of the workpiece and the machining head determined by the sensor at at least one measurement point, and comparing the determined result with a target relative position to determine a correction value.

5. 5. The method according to claim 1, wherein The method wherein the determination of the at least one first calibration value and the at least one second calibration value is performed by rotating the workpiece about a rotation axis C1 of the workpiece holder for measurement and by moving the sensor through at least one axis of the gear cutting machine to measure the tooth profile, and the sensor is preferably guided on at least one predetermined path relative to points on the surface of the workpiece for measurement of the workpiece.

6. 6. The method of claim 5, A method in which the measurement point of the sensor is guided in two measurement runs along two different paths along the surface of the tooth profile, and the first calibration value or the second calibration value is determined from the deviation of the measurement results.

7. 6. The method of claim 5, The sensor is moved in such a way that the measurement point on the tooth flank remains unchanged in the case of a perfect calibration, and the first calibration value or the second calibration value is determined from the deviation between the displacement movement of the sensor expected in the case of a perfect calibration and / or the sensor value expected in the case of a perfect calibration and the actual displacement movement of the sensor and / or the actual sensor value at the time of determination.

8. 8. The method according to any one of claims 1 to 7, The method wherein the sensor is a measurement sensor.

9. 9. The method according to any one of claims 1 to 8, A method in which at least the third calibration value is referenced in subsequent measurements and / or processing to correct displacement movements of the processing head and / or to correct measurement values ​​and / or operating values.

10. 10. The method according to any one of claims 1 to 9, In subsequent measurement and / or processing, while the processing head is displaced along the first linear axis Z according to the widthwise position of the workpiece, the second linear axis X and / or the third linear axis V / Y are also moved according to a third calibration value.

11. 11. The method according to any one of claims 1 to 10, In a subsequent measurement and / or processing, the measured target flank line angle and / or the target flank line angle on which the operation is based is corrected according to the third calibration value, in particular by an offset that depends on the calibration value.

12. 12. The method according to any one of claims 1 to 11, A method in which the calibration is performed between two processing steps of said workpiece or the calibration is performed after processing of the workpiece.

13. 13. The method according to any one of claims 1 to 12, The method wherein calibration values ​​are identified at three or more workpiece width locations by measuring the workpiece to determine at least one third calibration value.

14. A gear cutting machine comprising: a workpiece holder rotatable around a first rotation axis C1; a processing head having a tool holder; and a sensor for measuring a workpiece held in the workpiece holder of the gear cutting machine, the sensor being disposed in the processing head of the gear cutting machine, and the processing head being movable in a workpiece width direction relative to the workpiece holder along a first linear motion axis Z of the gear cutting machine; the gear cutting machine comprises a controller configured and / or programmed to perform the method according to any one of claims 1 to 13 on the gear cutting machine; The controller preferably performs the individual steps of the method automatically and / or has operator guidance for performing the steps.

15. A software program for controlling a gear cutting machine, the software program comprising commands which, when executed on a controller, cause the gear cutting machine to implement the method of any one of claims 1 to 13; The gear cutting machine preferably performs the individual steps of the method automatically under the control of the software program and / or comprises an operator guide for performing the steps.

Images