METHOD AND COORDINATE MEASURING MACHINE

Abstract

Procedure, with the procedural steps: - moving a measuring probe of a coordinate measuring machine by moving at least one machine axis of the coordinate measuring machine assigned to the measuring probe; characterized by - Monitoring a vibration behavior of the measuring probe during movement of the measuring probe, wherein a vibration excitation in the direction of at least one measuring probe axis of the measuring probe is detected and compared with an axis-specific natural frequency of the measuring probe in the direction of the at least one measuring probe axis; - Adjustment of a dynamic influencing factor that influences the vibration behavior of the measuring probe, such as a measuring speed, a mass of the measuring probe or the like, provided that the vibration excitation is detected in the range of the axis-specific natural frequency.

Description

[0001] The present invention relates to a method comprising moving a measuring probe of a coordinate measuring machine by moving at least one machine axis of the coordinate measuring machine associated with the measuring probe. Furthermore, the invention relates to a coordinate measuring machine for implementing such a method.

[0002] Measuring probes for tactile coordinate measurement can be excited to vibrate during measurement in the range of their natural frequencies. Especially during tactile gear measurement, these natural frequencies can be close to the waviness of the tooth flanks to be measured, e.g., in the range of 6 Hz. Vibration excitation of the measuring probe can affect the measurement result. It may therefore be impossible to determine which portion of the measured waviness results from vibration excitation of the measuring probe and which portion of the measured waviness reflects the actual waviness of the tooth flank surface.

[0003] Against this background, the present invention is based on the technical problem of providing a method that enables reliable tactile measurement. Furthermore, a coordinate measuring machine for implementing such a method is to be provided.

[0004] The technical problem described above is solved by the features of the independent claims. Further embodiments of the invention emerge from the dependent claims and the following description.

[0005] According to a first aspect, the invention relates to a method comprising the following method steps: moving a measuring probe of a coordinate measuring machine by moving at least one machine axis of the coordinate measuring machine assigned to the measuring probe; monitoring a vibration behavior of the measuring probe during the movement of the measuring probe, wherein a vibration excitation in the direction of at least one measuring probe axis of the measuring probe is detected and compared with an axis-specific natural frequency in the direction of the at least one measuring probe axis; and adapting a dynamic influencing factor that influences the vibration behavior of the measuring probe, such as a measuring speed, a mass of the measuring probe, or the like, provided that the vibration excitation is detected in the range of the axis-specific natural frequency.

[0006] It is therefore possible to detect, in particular, whether a critical excitation of the measuring probe occurs during a measurement, which could result in a falsified measurement result. Conversely, it is possible to detect, in particular, whether a critical excitation of the measuring probe occurs during a measurement, and thus the measurement results have not been falsified as a result of an excitation of the measuring probe.

[0007] If a possible falsification of a measurement result is detected, the measurement can be repeated, for example, with adapted dynamic conditions, by adjusting travel speeds and / or travel accelerations, or by adding weight to the measuring probe or by using a stylus and / or a stylus ball of a different mass.

[0008] To adapt the dynamic conditions or to adapt a dynamic influencing factor, damping in the direction of the corresponding probe axis can be used.

[0009] Alternatively, a preload can be changed in the direction of the probe axes and / or the probe suspensions to adapt the dynamic conditions.

[0010] According to one embodiment of the method, it can be provided that, before the measuring probe is moved, a reference run is carried out to measure the axis-specific natural frequency in the direction of the at least one measuring probe axis, wherein the measuring probe is set into vibration by acceleration and braking, in particular sudden braking, and the vibration is evaluated by means of a frequency analysis, in particular that the measuring probe vibrates freely during the reference run and does not rest against an object to be measured or the like.

[0011] It can be provided that the monitoring of the vibration behavior of the measuring probe includes a continuous axis-specific FFT analysis of a measurement signal from at least one measuring probe axis. Thus, the FFT analysis is performed continuously, in particular, while the measuring probe is moving, i.e., in particular, during an entire measuring cycle. Alternatively, it can be provided that the FFT analysis is only performed when the measuring probe is in contact with an object to be measured or is in tactile measuring contact.

[0012] According to one embodiment of the method, it can be provided that three orthogonal probe axes are assigned to the measuring probe for recording measured values ​​in three orthogonal spatial directions, wherein the probe has an axis-specific natural frequency in the direction of each of the three probe axes, which is compared with the vibration excitation during the monitoring of the vibration behavior of the probe during the movement of the probe, wherein an adaptation of the dynamic influencing factor or several dynamic influencing factors takes place if a vibration excitation in the range of the axis-specific natural frequency is detected for the probe in the direction of at least one of the probe axes, in particular that the probe has three orthogonal parallelogram suspensions.

[0013] Three-dimensional measuring probes with orthogonal parallelogram suspensions are known, for example, from the documents DE 197 21 015 C1 and EP 1 589 317 B1.

[0014] It can be provided that, before moving the probe, a reference run is performed for each of the probe axes to measure the axis-specific natural frequency. If the probe is a three-dimensional measuring probe, a reference run can be performed in each of the three orthogonal spatial directions to determine the axis-specific natural frequencies.

[0015] According to one embodiment of the method, it can be provided that the movement of the measuring probe comprises a tactile measurement of a component to be measured, wherein the measuring probe in contact with the component to be measured detects measured values ​​tactilely, wherein the component to be measured has in particular a toothing which is measured tactilely by means of the measuring probe.

[0016] It can be provided that the coordinate measuring machine has a rotary table for receiving the component to be measured in order to rotate the component to be measured about a rotation axis of the component, wherein measuring movements of the coordinate measuring machine have an at least partial rotation of the component to be measured about its own axis.

[0017] According to one embodiment of the method, the coordinate measuring machine can issue a warning if vibration excitation is detected in the range of the axis-specific natural frequency of the measuring probe. Following the warning, an operator can repeat the measurement with adjusted dynamic conditions to exclude any influence of the vibration excitation on the measurement result.

[0018] According to a second aspect, the invention relates to a coordinate measuring machine having a measuring probe, having at least one machine axis assigned to the measuring probe and having a controller configured to carry out the method according to the invention.

[0019] It can be provided that the coordinate measuring machine is a gear measuring machine which has a rotary table for rotating a gear to be measured about its rotation axis.

[0020] The invention is explained in more detail below with reference to a drawing illustrating exemplary embodiments. The drawings schematically show: Fig. 1 a coordinate measuring machine according to the invention; Fig. 2 a touch probe system with a measuring probe; Fig. 3 a flow chart of a method according to the invention.

[0021] Fig. Figure 1 shows a coordinate measuring machine 2 according to the invention. The coordinate measuring machine 2 is a gear measuring machine. The coordinate measuring machine 2 has a rotary table 4, which is designed to hold and rotate a component 6 to be measured about its own axis. In this case, the component 6 to be measured is a gear.

[0022] The coordinate measuring machine 2 has a measuring probe 8 for tactile gear measurement, which is mounted on a touch probe system 12. The coordinate measuring machine 2 also has an optical measuring device 10 for optical gear measurement. The coordinate measuring machine 2 has a controller 11 configured to execute a method according to the invention described below.

[0023] The measuring probe 8 can be moved in three mutually orthogonal spatial directions X, Y, and Z by means of controlled machine axes of the coordinate measuring machine. The reference symbols X, Y, and Z therefore denote equally controlled numerical axes of the coordinate measuring machine 2, which enable the measuring probe 8 to be moved according to the aforementioned degrees of freedom in the X, Y, and Z directions. Rotation around the C axis by means of the rotary table 4 represents a further degree of freedom for executing measuring movements.

[0024] Fig.2 shows an exemplary and schematic view of the touch probe system 12 on which the measuring probe 8 is held. The measuring probe 8 can, in particular, be detachably and replaceably attached to the touch probe system 12, for example, by means of a magnetic attachment. The touch probe system 12 has three parallelogram suspensions 14, 16, 18, which enable mutually orthogonal movements of the measuring probe 8 in the MX direction, MY direction, and MZ direction. The structure and operation of such a three-dimensional measuring touch probe system 12 are well known, in particular from documents DE 197 21 015 C1 and EP 1 589 317 B1, the relevant disclosures of which are incorporated by reference into the disclosure of the present application.

[0025] The axes MX, MY, MZ are also referred to as measuring probe axes.

[0026] In a first method step (A) of the method according to the invention, the measuring probe 8 of the coordinate measuring machine 2 is first moved by moving at least one machine axis X, Y, Z of the coordinate measuring machine 2 assigned to the measuring probe 8. Moving the measuring probe 8 equally means moving the entire touch probe system 12, since the measuring probe 8 is held on this touch probe system 12 and the touch probe system 12 is held on the movable machine axes X, Y, Z of the coordinate measuring machine 2 via a base plate 20.

[0027] The movement of the measuring probe 8 can comprise measuring movements for carrying out a gear measurement, wherein the measuring movements comprise both movements in contact with the component 6 to be measured and movements that do not take place in contact with the component 6 to be measured.

[0028] During the movement of the measuring probe 8, in a method step (B), which thus takes place simultaneously with method step (A), a monitoring of a vibration behavior of the measuring probe 8 is carried out, wherein a vibration excitation in the direction of each of the three measuring probe axes MX, MY, MZ is recorded and compared with an axis-specific natural frequency of the measuring probe 8 in the direction of the respective measuring probe axis MX, MY, MZ.

[0029] If a vibration excitation is detected for the measuring probe in the direction of one of the measuring probe axes MX, MY, MZ in the range of the respective axis-specific natural frequency, an adjustment of a dynamic influencing factor which has an influence on the vibration behavior of the measuring probe 8 takes place in a process step (C).

[0030] An adjustment of the dynamic influencing factor can, for example, be a change in the speed of the machine axes of the coordinate measuring machine 2 during the execution of the measuring movements or the movement of the measuring probe. Adjusting the dynamic influencing factor can, for example, mean adjusting the damping in the direction of the relevant measuring probe axis. The preload of a suspension of the parallelograms can also be changed. Furthermore, the mass of the measuring probe 8 can be changed by replacing components of the measuring probe, such as a probe ball, a stylus, or the like.

[0031] It can be provided that before moving the measuring probe 8, a reference run is carried out to measure the axis-specific natural frequency of the measuring probe 8 in the direction of each of the measuring probe axes MX, MY, MX.

[0032] For each reference run, it can be provided that the measuring probe 8 is accelerated and decelerated in the corresponding spatial directions, in particular, decelerated abruptly, in order to cause the measuring probe 8 to oscillate, and this oscillation is evaluated by means of a frequency analysis. During each reference run, the measuring probe can, in particular, oscillate freely and is not in contact with an object to be measured or the like.

[0033] Monitoring the vibration behavior of the measuring probe 8 according to method step (B) can comprise a continuous axis-specific FFT analysis of a measurement signal for each of the measuring probe axes MX, MY, MX. Therefore, during the movement of the measuring probe 8, i.e., in particular during a measuring process, a continuous check is performed for each of the measuring probe axes MX, MY, MX to determine whether vibration excitation of the measuring probe 8 occurs in the range of one of the natural frequencies.

Claims

[1] Procedure, with the following steps: - Moving a measuring probe of a coordinate measuring machine by moving at least one machine axis of the coordinate measuring machine assigned to the measuring probe; characterized by - Monitoring a vibration behavior of the measuring probe during movement of the measuring probe, wherein a vibration excitation in the direction of at least one measuring probe axis of the measuring probe is detected and compared with an axis-specific natural frequency of the measuring probe in the direction of the at least one measuring probe axis; - Adjustment of a dynamic influencing factor that influences the vibration behavior of the measuring probe, such as a measuring speed, a mass of the measuring probe or the like, provided that the vibration excitation is detected in the range of the axis-specific natural frequency. [2] Method according to claim 1, characterized bythat before moving the measuring probe, a reference run is carried out to measure the axis-specific natural frequency in the direction of at least one measuring probe axis, wherein the measuring probe is set into vibration by acceleration and braking, in particular jerky braking, and the vibration is evaluated by means of a frequency analysis, in particular that the measuring probe vibrates freely during the reference run and does not rest against an object to be measured or the like. [3] Method according to one of the preceding claims, characterized by that the monitoring of the vibration behavior of the measuring probe comprises a continuous axis-specific FFT analysis of a measuring signal in the direction of at least one measuring probe axis. [4] Method according to one of the preceding claims, characterized bythat three orthogonal probe axes are assigned to the measuring probe for recording measured values ​​in three orthogonal spatial directions, wherein the probe has an axis-specific natural frequency in the direction of each of the three probe axes, which is compared with the vibration excitation during the monitoring of the vibration behavior of the probe during the movement of the probe, wherein an adjustment of the dynamic influencing factor or several dynamic influencing factors takes place if a vibration excitation in the range of the axis-specific natural frequency is detected for the probe in the direction of at least one of the probe axes, in particular that the probe has three orthogonal parallelogram suspensions. [5] Method according to claim 4, characterized by that before moving the probe, a reference run is carried out for each of the probe axes to measure the axis-specific natural frequency. [6] Method according to one of the preceding claims, characterized by that the movement of the measuring probe comprises a tactile measurement of a component to be measured, wherein the measuring probe in contact with the component to be measured detects measured values ​​tactilely, wherein the component to be measured in particular has a toothing which is measured tactilely by means of the measuring probe. [7] Method according to claim 6, characterized by that the coordinate measuring machine has a rotary table for receiving the component to be measured in order to rotate the component to be measured about a rotation axis of the component, wherein measuring movements of the coordinate measuring machine comprise an at least partial rotation of the component to be measured about its own axis. [8] Method according to one of the preceding claims, characterized by that the coordinate measuring machine issues a warning if the vibration excitation is detected in the range of the axis-specific natural frequency of the measuring probe. [9] Coordinate measuring machine, - with a measuring probe, - with at least one machine axis assigned to the measuring probe, and - with a controller which is arranged to carry out a method according to one of the preceding claims. [10] Coordinate measuring machine according to claim 9, characterized by that the coordinate measuring machine is a gear measuring machine which has a rotary table for rotating a gear to be measured around its rotation axis.

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