METHOD AND MACHINING MACHINE FOR DETERMINING THE CONDITION OF A PINION-RAW DRIVE FOR A MOVABLE AXLE

Description

[0001] The invention relates to a method for determining the state of a pinion-rack drive for a movable axis in a machine tool and to a machine tool.

[0002] Machining machines are used to process workpieces. These machines have at least one movable axis along which a machining head can travel to direct a machining tool, such as a punch or a laser beam, onto the workpiece. Such axes in machining machines can be supported and driven on one or both sides. A rack and pinion drive is used to power these axes. For precision in workpiece machining, the backlash between the pinion and the rack of the drive, as well as monitoring of its condition, is necessary to ensure that the machining positions are precisely reached by the at least one axis. The adjustment of the rack and pinion drive, as well as other influencing factors, is measured manually at individual measuring points using separate measuring instruments.

[0003] From DE 10 2016 222 660 A1 a technique for detecting deviations and / or changes in at least one operating state of an electrically, in particular electromotor, operated drive - for example a rack and pinion drive - has become known.

[0004] The present invention is based on the objective of proposing a method and a machining machine that are improved compared to the prior art, so that an automated determination of the condition of a rack and pinion drive is made possible for the precise machining of workpieces.

[0005] This task is solved by a method for determining the state of a rack and pinion drive for a movable axis in a machine tool, in which at least one measurement run of a movable axis is performed across the entire working range of a linear axis, in which the measurement run is controlled by a traversing movement of the axis at a constant feed rate in at least one direction of movement of the linear axis, in which the signals are acquired as a function of the axis positions during the measurement run, and in which the acquired signals are evaluated as a function of the axis positions in a data processing unit and analyzed using a mathematical method, such as an image processing algorithm. This can also be done using image processing.This method not only allows for measurements at randomly selected positions within the working range of the movable axis along the linear axis, but also captures the condition of the rack and pinion drive across the entire working range of the movable axis in relation to the linear axis. Furthermore, the at least one measurement run at a constant feed rate offers the advantage that the same conditions regarding the feed rate prevail along the entire working range during this run. This allows individual deviations from an actual or ideal state to be detected by a corresponding signal change and displayed in a readout for the respective axis position. This enables a standardized and rapid measurement method that provides information about the condition of the rack and pinion drive across the entire working range.Furthermore, the acquired signals and the resulting conclusions are reproducible across the entire working range. In particular, the components and data already present in the machining center can be used and processed to determine its condition.

[0006] According to the invention, during a measurement run, the movable axis is moved in both directions of movement of the linear axis across its entire working range. Thus, the movable axis is fully traversed along the entire length of the linear axis in both directions. The signals are acquired synchronously with the axis positions. Furthermore, the measurement signals acquired from both directions of movement are compared. This measurement run enables further analysis of conditions or errors that, for example, occur only in one direction but not in the opposite direction. This can be the case, for instance, with an incorrectly installed bellows that causes jamming in one direction of movement but not in the other.Furthermore, during such a test run, backlash, especially its qualitative change, between the pinion and the rack of the pinion-rack drive can be evaluated more effectively, since a comparison of the recorded measurement data from both directions of travel is possible.

[0007] Furthermore, several measurement runs are preferably performed consecutively, with each run using a different feed rate than the previous one. This allows for further information about the condition of the rack and pinion drive, such as vibrations or natural frequencies occurring at different axis speeds, which can arise during machining a workpiece or between two machining steps.

[0008] During at least one measurement run, a torque-generating operating current from a motor driving a pinion of the rack-and-pinion drive is preferably recorded as a signal dependent on the axis position. A gearbox inserted between the motor and pinion can also be taken into account. This drive current allows for direct feedback on the state of the rack-and-pinion pairing.

[0009] In particular, in addition to the drive current, the motor speed is recorded synchronously with the axis position. This speed can serve as a further evaluation parameter for condition monitoring. Furthermore, at least one additional measurement signal can be acquired, for example, using an accelerometer, a direct displacement measuring system, or similar.

[0010] According to a further advantageous embodiment of the method, when evaluating the signals from the measurement run at a constant feed rate, the signals from an acceleration phase and a braking phase at the beginning and end of the axis range are not recorded. Due to the transient acceleration or braking phase, non-reproducible signals can arise, which adversely affect or at least significantly complicate the condition monitoring.

[0011] During a measurement run, instantaneous measured values ​​of the drive current of the pinion-rack drive motor are preferably acquired and recorded as a function of the axis position. The individually acquired segments can be combined into a complete measurement. The analysis can be performed for individual segments only or for the complete measurement comprised of the segments. A detailed resolution of the signals along the linear axis is possible. Preferably, the engagement of a pinion tooth with the rack is detected and recorded by its local periodicity corresponding to the axis position. This enables the detection of the condition of each individual tooth as well as the detection of the pinion's runout through a periodic mapping around its circumference.

[0012] In particular, the periodic pattern around the circumference of the drive pinion, preferably in the form of amplitudes resulting from one rotation of the pinion, is displayed in a color that differs from the previous one. This allows a multitude of color patterns to be displayed during a measurement run, making it easy to see visually whether and to what extent a rotation of the pinion, corresponding to the respective axis position, deviates from the adjacent or subsequent rotations. For example, an increased amplitude within a sequence of amplitudes recorded for one rotation of the pinion, such as the third amplitude, can indicate that the third tooth is subject to wear, is otherwise damaged, or may even have a tooth fracture. This corresponds to a spatial arrangement of the measured values ​​around the circumference of the drive pinion.

[0013] Furthermore, by examining the entire working range of the linear axis, it is possible to identify whether there is increased wear, damage, or misalignment of consecutive rack segments in individual sections or working areas, provided that several consecutive amplitudes exhibit a different value than their neighboring values. This localized or area-specific increased wear can occur when workpieces are machined over an extended period using the same travel distance and thus the same reversal points, as is the case, for example, in series production or mass manufacturing.

[0014] Another preferred embodiment of the method provides that the mathematical procedure determines an envelope from the upper and lower measured values ​​of the recorded amplitudes of the drive current and displays this envelope, for example. Preferably, an upper and lower straight line is formed from the statistical parameters of the extreme values ​​of the upper and lower measured amplitudes, which are also displayed for comparison with the envelope. This allows individual events along the entire working range to be directly identified and / or mathematically quantified. These events can, for example, indicate that there are local defects between the pinion and the rack that are outside the specified tolerance range and would no longer guarantee the required machining accuracy.This allows the location of the pinion-rack pair to be checked to be immediately identified and further suitable repair measures to be taken.

[0015] To determine wear or to predict when unacceptable wear will occur, the first and at least one subsequent measurement run can be carried out at regular intervals, particularly daily, weekly, monthly, and / or annually. By comparing the amplitudes across the entire operating range, changes in condition can be detected and predicted. This allows, for example, for proactive maintenance to be indicated and carried out in order to prevent a malfunction during a production phase.

[0016] Preferably, in the above method, a tooth fracture, runout error, backlash, an assembly error at the transition of two adjacent racks, and / or an assembly error on another component are detected and evaluated as a condition or change of condition. This detection of conditions or changes of condition can preferably be implemented in the data processing unit of the machine tool. Preferably, the measurement data can be interpolated into a predefined path grid for data analysis. This allows a measurement run to determine the condition to be carried out even during downtimes of the machine tool. Furthermore, such condition monitoring can serve as a digital / smart service for the operator. Remote diagnostics are also possible.

[0017] The invention, as well as further advantageous embodiments and developments thereof, are described and explained in more detail below with reference to the examples shown in the drawings. The features that can be derived from the description and the drawings can be applied individually or in any combination. (The following are shown:) Figure 1 is a perspective view of a machine tool for machining plate-shaped workpieces; Figure 2 is a schematically enlarged view of an axis movable by a drive device; Figure 3 is a diagram illustrating a motor current over the entire working range of a linear axis along which the movable axis can be controlled; Figure 4 is a section of the illustration according to Figure 3in higher resolution, Figure 5 is a diagram showing the motor current over a section of the working area during the commissioning of the machine tool, Figure 6 is a diagram showing the motor current over a section of the working area after a longer operating time of the machine tool, Figure 7 is a schematic representation of the motor current over the entire working area with a local fault, Figure 8 is another diagram of the motor current over the entire working area showing another fault, and Figure 9 is another diagram of the motor current over the entire working area showing a backlash fault.

[0018] In Figure 1A system 1 for the machining of plate-shaped workpieces 8, made of metal for example, is shown in perspective. System 1 comprises a machining center 2. This machining center 2 is enclosed by a housing 4. Inside the housing 4, a machining station 5 is provided, in which a linear axis arrangement 6 accommodates at least one machining head 7, which is controlled to be movable within a horizontal plane of motion. Outside the housing 4, a loading and unloading station 10 is provided, for example. This station includes at least one movable pallet 11, on which the plate-shaped workpiece 8 is placed for machining in order to feed it to the machining station 5. After machining, the machined plate-shaped workpiece 8 is moved back into the loading and unloading station 10 by means of the pallet 11 in order to unload the pallet 11.

[0019] The processing machine 2 can, for example, be configured as a laser cutting system. Alternatively, the processing machine 2 can also be configured as a plasma cutting machine, a laser punching machine, a laser welding machine, or a punching machine.

[0020] In Figure 2 is a schematically enlarged view of detail X in Figure 1The linear axis arrangement 6 comprises, as a machine component, a movable axis 14, which is controlled to move along a linear axis 15 in and against an X-direction on a machine base 16. The machining head 7 is controlled to move along the axis 14 in the Y-direction. A drive device 21, in particular a rack and pinion drive, is provided to control a traversing movement along the machine base 16. This rack and pinion drive 21 allows the axis 14 to move along a guide 17 of the linear axis 15 arranged on the machine base 16 in and against the X-direction. This guide 17 is attached to the machine base 16. A rack 23 is aligned adjacent to the guide 17. The rack 23 is also attached to the machine base 16.A motor 22 and a pinion 24 of the rack and pinion drive 21, arranged on the motor shaft, are moved together with the axle 14 along the guide 17. Bellows 18 are schematically provided on the left and right sides of the rack and pinion drive 21 to protect the rack 23 and the guide 17 from contamination.

[0021] This pinion-rack drive 21 can alternatively control the movable axis 14 or also control other machine components movable relative to the machine base 16.

[0022] Alternatively, the linear axis arrangement 6 in a machine tool (not shown in detail) can be designed by a movable axis 14 supported on one side, on which the machining head 7 is provided. This movable axis 14 can be moved in and against the X-direction along the guide 17, as already described above.

[0023] A data processing unit 9 is provided for controlling the system 1. This unit comprises a mathematical procedure or operations for analyzing signals for status monitoring of the processing machine 2 and preferably displaying them on a display 12. This display 12 can be located on the housing 4. Alternatively, it can be located separately from the housing 4 on a control column. Furthermore, other mobile display devices, such as mobile phones, tablets, or the like, can be provided. These communicate with the data processing unit 9, particularly wirelessly, and include the display 12. The data processing unit 9 can also be located outside the actual machine control system, for example, in the form of a cloud-based system.

[0024] To determine the state of the rack and pinion drive 21, data or signals from the machine tool 2 are acquired and processed and evaluated in the data processing unit 9. These signals can be, for example, the drive current or motor current, in particular the torque-generating drive current, of the motor 22 of the rack and pinion drive 21. Additionally, the rotational speed of the motor 22 can be acquired as a further signal, or any other signal suitable for analysis (e.g., synchronously recorded values ​​from an external sensor, such as an accelerometer). This recording can also be performed with a separate data acquisition unit by subsequently assigning the signals to the respective axis position or, optionally, interpolating them. These signals are acquired across the entire working range or travel range of the linear axis 15.The entire working area encompasses the length of the linear axis 15, along which the rack and pinion drive 21 can travel within the housing 4, in particular the machine tool 2. One or more racks are arranged in series along the length of the linear axis 15. The signals received by the data processing unit 9 are recorded and processed synchronously and spatially, so that each signal is assigned to a defined position along the linear axis 15.

[0025] In Figure 3A schematic representation of a diagram is shown, in which the travel distance of the entire working range of the linear axis 15 is plotted along the X-axis. The drive current in amperes of the motor 22 is plotted along the Y-axis. The amplitudes shown there, arranged sequentially, present a homogeneous pattern across the entire working range. This diagram displays a multitude of amplitudes in sequence, subdivided, for example, into individual sequences 27, 28, 29. These sequences may, for instance, be represented by different colors. Each sequence 27, 28, 29 shows one complete revolution of a pinion 24, which is moved along the rack 23.

[0026] In Figure 4For example, sequence 27 is shown enlarged. Each amplitude within sequence 27 represents a tooth of the pinion 24, with each amplitude being assigned to a defined axis position along the working area. This allows an evaluation of the state of each individual tooth of the pinion 24 with respect to the rack 23 at the respective location.

[0027] The recording of the amplitudes according to Figure 3 The entire working range shows that an acceleration phase 31 and a deceleration phase 32 at the beginning and end of the working range are not recorded. In between, the traversing motion of the movable axis is controlled with a constant feed rate. Provided that the amplitudes remain constant across the entire working range, it follows that there is no or uniform wear in the rack and pinion drive 21.

[0028] To acquire the signals, especially amplitudes, a measurement run of the movable axis 14 across the entire working range along the linear axis 15 is controlled in the plus-X direction and in the opposite direction in the minus-X direction, or vice versa. In the representation in Figure 3 The signals from the measurement run in and against the linear axis 15 are shown overlapping across the entire working range.

[0029] Figure 5 shows a schematically enlarged representation of sequence 27 in Figure 4 The upper and lower amplitude measurements are very homogeneous and lie within a very narrow band. This evaluation of the recorded signals shows, for example, that there is no discernible runout error of the pinion 24 relative to the rack 23 during one revolution of the pinion. This condition of the machine tool 2 can be detected particularly during initial commissioning.

[0030] In comparison, according to Figure 6 a diagram regarding the same axis position in the work area Figure 5 The analog sequence 27 from the recorded signals is also shown. Based on the upper and lower recorded amplitude measurements, it is evident that these differ from those in Figure 5 exhibit greater dispersion. These in Figure 6 The measurement shown was taken after a prolonged period of operation of the processing machine 2. Due to the deviations, for example the scatter of the amplitudes, compared to the amplitudes in Figure 5 An error in the concentricity of the pinion 24 relative to the rack 23 is detected. This condition can be identified, for example, by comparing the sequence 27 in Figure 5 and sequence 27 in Figure 6This can be achieved, for example, by calculating an average of the upper and lower amplitude measurements and defining a range for each of these upper and lower averages, within which the upper and lower amplitude measurements must lie for proper circularity. In sequence 27 according to... Figure 6 Individual upper and lower measured values ​​of the respective amplitude lie outside such a scatter range. This allows the determination that the concentricity is outside the tolerance.

[0031] Figure 7This diagram shows a further evaluation of the acquired signals for determining the condition of the rack and pinion drive 21. In this representation, the measurement run in and against the direction of movement of the linear axis 15 is plotted on a common characteristic curve along a zero axis in the Y direction. The individual amplitudes are plotted with positional accuracy relative to the X-axis across the entire working range. For example, this diagram shows two local errors 35, 36, where the amplitude is a multiple of that of the adjacent areas. These could, for example, be local geometric deviations at the transition from one rack to the adjacent rack. Due to the precise positional indication of the errors 35, 36, it can be seen that the distance between the first and second errors 35, 36 corresponds to the length of the rack 23, which is used in this machine tool 2 to form the rack and pinion drive 21.Therefore, based on these two errors 35, 36, it can be determined that there is an error in the transition area between two racks 23 and that there is a backlash which is outside a tolerance range.

[0032] From this diagram, it can further be seen, based on the smaller amplitudes 37, 38, 39 compared to errors 35, 36, that these deflections repeat at regular intervals – i.e., with each revolution of the pinion 24 – at larger amplitudes. From this, it can be determined that a defect must be present in the pinion 24, since this defect repeats periodically with the circumference of the drive pinion. If the respective sequence for a complete revolution of a pinion 24 is enlarged, it can then be observed that the amplitudes 37, 38, 39 always occur at the same point within the sequence, for example, the third amplitude. Therefore, it can be determined that this change of state is always caused by the same tooth of the pinion 24.

[0033] In Figure 8Figure 1 shows another schematic representation for determining the state of a rack and pinion drive 21 for a movable axis 14 in the machine tool 2. In this representation, the drive current for a first direction of travel along the axis is shown separately from the direction of travel in the opposite direction. The lower characteristic curve 34 shows the direction of travel, for example, in the X-direction. The upper characteristic curve 33 shows the direction of travel, for example, opposite to the X-direction. The lower characteristic curve 34 exhibits a homogeneous profile over the entire working range with the exception of an event 41. The upper characteristic curve 33 also shows a homogeneous profile with the exception of an event 42. Events 41 and 42 occur at the same position within the working range, but differ in their amplitude.This representation allows for an evaluation showing that wear or impairment in a rack and pinion drive 21 is not affected by the differing individual events regarding potential damage. In the present example, it can be determined that, for instance, an assembly error exists, particularly with the bellows 18, which behaves differently in opposite directions due to the connection of the bellows around the drive carriage 25 or to an adjacent bellows 18 along the linear axis 15.

[0034] In Figure 9A further schematic representation of measurement runs along the entire working range is shown. In this representation, the forward and return movements along the axis are again shown separately in the lower and upper characteristic curves 33, 34. The upper and lower characteristic curves 33, 34 show two identical errors 45, 46 at the same position within the working range. These indicate that, also due to the distance between the two errors, the adjacent racks 23 are offset from each other, and a backlash error is present. A backlash error results in an increase in noise, such as impacts or vibrations in the machine tool 2. This leads to inaccurate machining, causing contours on the workpieces to be damaged or rounded. This backlash error therefore reduces precision. The pinion-rack drive 21 is set to a predetermined tolerance range for the backlash.The in . Figure 9 The deviation shown for errors 45 and 46 lies outside this tolerance range. This is determined by the data processing unit 9. Errors 45 and 46 can be visually highlighted in the display 12.

[0035] The rack and pinion drive 21 allows for backlash compensation within a tolerance range. In the area of ​​errors 45 and 46, an operator can make an adjustment to compensate for these detected deviations. Subsequently, one or more test runs are performed again, and the upper and lower characteristic curves 38 and 39 are re-evaluated. If errors 45 and 46 remain outside the tolerance range, this indicates that component replacement is necessary.

[0036] Furthermore, it can preferably be provided that, after a measurement run along the entire working area, preferably along a round trip, the method outputs measurement positions as a result, at which a local measurement procedure is to be carried out in order to determine an exact value of the backlash of the pinion-rack drive 21. This can, for example, be the potentially best and worst positions in the working area.

[0037] In comparison, according to Figure 6 a diagram regarding the same axis position in the work area Figure 5 The analog sequence 27 from the recorded signals is also shown. Based on the upper and lower recorded amplitude measurements, it is evident that these differ from those in Figure 5 exhibit greater dispersion. These in Figure 6The measurement shown was taken after a prolonged period of operation of the processing machine 2. Due to the deviations, for example the scatter of the amplitudes, compared to the amplitudes in Figure 5 An error in the concentricity of the pinion 24 relative to the rack 23 is detected. This condition can be identified, for example, by comparing the sequence 27 in Figure 5 and sequence 27 in Figure 6, by, for example, averaging the upper and lower amplitude measurements and defining a range for each of these upper and lower averages, within which the upper and lower amplitude measurements must lie for proper concentricity. In sequence 27 according to Figure 6 Individual upper and lower measured values ​​of the respective amplitude lie outside such a scatter range. This allows the determination that the concentricity is outside the tolerance.

[0038] Figure 7This diagram shows a further evaluation of the acquired signals for determining the condition of the rack and pinion drive 21. In this representation, the measurement run in and against the direction of movement of the linear axis 15 is plotted on a common characteristic curve along a zero axis in the Y direction. The individual amplitudes are plotted with positional accuracy relative to the X-axis across the entire working range. For example, this diagram shows two local errors 35, 36, where the amplitude is a multiple of that of the adjacent areas. These could, for example, be local geometric deviations at the transition from one rack to the adjacent rack. Due to the precise positional indication of the errors 35, 36, it can be seen that the distance between the first and second errors 35, 36 corresponds to the length of the rack 23, which is used in this machine tool 2 to form the rack and pinion drive 21.Therefore, based on these two errors 35, 36, it can be determined that there is an error in the transition area between two racks 23 and that there is a backlash which is outside a tolerance range.

[0039] From this diagram, it can further be seen, based on the smaller amplitudes 37, 38, 39 compared to errors 35, 36, that these deflections repeat at regular intervals – i.e., with each revolution of the pinion 24 – at larger amplitudes. From this, it can be determined that a defect must be present in the pinion 24, since this defect repeats periodically with the circumference of the drive pinion. If the respective sequence for a complete revolution of a pinion 24 is enlarged, it can then be observed that the amplitudes 37, 38, 39 always occur at the same point within the sequence, for example, the third amplitude. Therefore, it can be determined that this change of state is always caused by the same tooth of the pinion 24.

[0040] In Figure 8Figure 1 shows another schematic representation for determining the state of a rack and pinion drive 21 for a movable axis 14 in the machine tool 2. In this representation, the drive current for a first direction of travel along the axis is shown separately from the direction of travel in the opposite direction. The lower characteristic curve 34 shows the direction of travel, for example, in the X-direction. The upper characteristic curve 33 shows the direction of travel, for example, opposite to the X-direction. The lower characteristic curve 34 exhibits a homogeneous profile over the entire working range with the exception of an event 41. The upper characteristic curve 33 also shows a homogeneous profile with the exception of an event 42. Events 41 and 42 occur at the same position within the working range, but differ in their amplitude.This representation allows for an evaluation showing that wear or impairment in a rack and pinion drive 21 is not affected by the differing individual events regarding potential damage. In the present example, it can be determined that, for instance, an assembly error exists, particularly with the bellows 18, which behaves differently in opposite directions due to the connection of the bellows around the drive carriage 25 or to an adjacent bellows 18 along the linear axis 15.

[0041] In Figure 9A further schematic representation of measurement runs along the entire working range is shown. In this representation, the forward and return movements along the axis are again shown separately in the lower and upper characteristic curves 33, 34. The upper and lower characteristic curves 33, 34 show two identical errors 45, 46 at the same position within the working range. These indicate that, also due to the distance between the two errors, the adjacent racks 23 are offset from each other, and a backlash error is present. A backlash error results in an increase in noise, such as impacts or vibrations in the machine tool 2. This leads to inaccurate machining, causing contours on the workpieces to be damaged or rounded. This backlash error therefore reduces precision. The pinion-rack drive 21 is set to a predetermined tolerance range for the backlash.The in . Figure 9 The deviation shown for errors 45 and 46 lies outside this tolerance range. This is determined by the data processing unit 9. Errors 45 and 46 can be visually highlighted in the display 12.

[0042] The rack and pinion drive 21 allows for backlash compensation within a tolerance range. In the area of ​​errors 45 and 46, an operator can make an adjustment to compensate for these detected deviations. Subsequently, one or more test runs are performed again, and the upper and lower characteristic curves 38 and 39 are re-evaluated. If errors 45 and 46 remain outside the tolerance range, this indicates that component replacement is necessary.

[0043] Furthermore, it can preferably be provided that, after a measurement run along the entire working area, preferably along a round trip, the method outputs measurement positions as a result, at which a local measurement procedure is to be carried out in order to determine an exact value of the backlash of the pinion-rack drive 21. This can, for example, be the potentially best and worst positions in the working area.

Claims

1. A method for determining the state of a rack and pinion drive (21) for a movable axis (14) in a processing machine (2), - in which at least one measurement run of the movable axis (14) is carried out over the entire working range of a linear axis (15), - in which the measurement run is initiated when the movable axis (14) travels with a constant rate of advancement in both directions of motion over the entire working range of the linear axis (15) in each case, - in which, during the measurement run, signals are detected as a function of the axial positions of the movable axis (14) relative to the linear axis (15), - in which the detected signals as a function of the axial position are evaluated in a data processing device (9) and are analyzed by means of a mathematical method, wherein a comparison takes place of the signals detected from both movement directions.

2. The method according to claim 1, characterized in that a plurality of measurement runs are initiated one after the other, and each of the measurement runs is initiated with its own rate of advancement that differs from the prior measurement run.

3. The method according to any one of the preceding claims, characterized in that during the at least one measurement run a torque-forming drive current of a motor (22) of the rack and pinion drive (21) is detected as the signal as a function of the axial position of the linear axis (15).

4. The method according to claim 3, characterized in that the speed of the motor (22) and / or at least a further measurement signal are detected, in particular by way of an acceleration sensor or a direct path measuring system, as a function of the axial position along the linear axis (15).

5. The method according to any one of the preceding claims, characterized in that, during the measurement run at the constant rate of advancement, signals from an acceleration and braking phase at the beginning and the end of the working range are not detected.

6. The method according to any one of the preceding claims, characterized in that, during the measurement run, instantaneous measured values of the drive current of the motor (22) are detected and represented as a function of the axial positions of the linear axis (15).

7. The method according to claim 6, characterized in that the engagement of a tooth of the pinion (24) in the rack (23) is detected and recorded by way of a periodic assignment over the circumference of the pinion, preferably in the representation of amplitudes corresponding to the axial position.

8. The method according to claim 7, characterized in that for each full rotation of the pinion (24) the periodic assignment is output in a color that differs from the prior color.

9. The method according to any one of the preceding claims, characterized in that the mathematical method forms an enveloping end from the upper and lower measured values, respectively, of the detected amplitudes of the drive current, and these ends are output in the display.

10. The method according to claim 9, characterized in that an upper and lower mean value is formed from the upper measured values of the amplitudes and the lower measured values of the amplitudes, respectively, and the envelope ends and the straight lines formed by the mean values are displayed and correlated for the analysis.

11. The method according to any one of the preceding claims, characterized in that the first and at least one further measurement run is carried out in time intervals, in particular daily, weekly and / or monthly, and at least one state change is detected and preferably determined in advance by comparing the amplitudes detected overall over the entire working range.

12. The method according to any one of the preceding claims, characterized in that the state that is detected and evaluated is a tooth wear, a tooth breakage, a concentricity error, a backlash, an assembly error in the transition between two racks lined up next to one another, a local defect in a toothed rack, an assembly error or a defect in other components of the movable axis (14), in particular the linear guiding system, and / or the linear axis (15).

13. The method according to any one of the preceding claims, characterized in that measurement positions at which the exact values, in particular an exact value of a backlash of the rack and pinion drive (21), is to be determined by a local measuring method, are output as the result of the analysis of the measurement signals by the data processing device (9).

14. A processing machine (2) with a rack and pinion drive (21) for a movable axis (14) along a linear axis (15), wherein the processing machine (2) has at least one data processing device which is configured to carry out a method according to any one of the preceding claims, wherein the data processing device detects and evaluates signals detected during at least one measuring run, as a function of the axial positions along the entire working range, and also analyzes them by means of a mathematical method.