JP3380123B2 - Machine tool movement error measurement system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is, ISO230- 2
Oh Rui relates measurement system to measure using the laser measurement device a movement error of a machine tool as defined in ANSI / ASME B5,54 like.

[0002]

2. Description of the Related Art Regarding the accuracy of NC machine tools, ISO
230- 2 Oh Rui the test items and test method standards such as ANSI / ASME B5,54 are defined. The items specified here are error in the amount of movement in each movement axis direction or diagonal direction (diagonal), backlash, yawing, and the like. For example, in the method of testing the movement amount error in each movement axis direction, after performing an operation of moving a predetermined amount for each movement axis direction, a similar operation of returning in the opposite direction is repeated a predetermined amount, and at each movement point, A method for calculating the maximum error value and the mean square value is defined.

A usual contact type gauge, a magnetic scale or the like is used for the measurement of the test items as described above, but a laser length measuring machine is most commonly used. FIG. 1 is a diagram showing a conventional arrangement example for measuring the accuracy of an NC machine tool (machining center) using a laser length measuring machine. As shown in FIG. 1, a machine tool 91 includes a machining tool unit 92 that holds and drives a machining tool, a worktable 93 on which a workpiece is placed, and an NC controller 9 that controls these.
7 is provided. Machining tool section 92 is vertical (Z-axis direction)
The stage 93 is movable in two mutually perpendicular directions within a plane perpendicular to the Z-axis direction, and the movement is controlled by the NC controller 97. ISO23 above
According to the regulations concerning the measurement of the movement amount error of 0-2 and the backlash, how much the movement actually occurs when these NC controllers 97 instruct to move by a predetermined movement amount in each axial direction is measured. The figure shows the case where the movement amount error and the backlash in the direction indicated by the arrow (X-axis direction) are measured. First, the optical axis of the laser light emitted from the laser light source 11 coincides with the X-axis direction. The laser light source 11 whose optical axis is aligned is arranged as described above. Next, the interference optical unit 1 of the laser interferometer is attached to the tip of the processing tool section 92.
3 is attached so that the laser light is incident, and a reflecting mirror (corner cube) is arranged at the end of the stage 93.

FIG. 2 is a diagram showing the structure of the interference optical unit 13. The laser light source 11 is a laser light source that outputs laser light with good coherence (long interference distance), such as a He—Ne laser, and the laser light output from the laser light source is
It is split into two laser beams by the polarization beam splitter 131. At this time, the optical axis of the polarization beam splitter 131 is adjusted to be 45 ° with respect to the polarization plane of the incident laser light. In this case, the polarization beam splitter 1
Laser light transmitted through 31 is called P-polarized light, and laser light reflected by the polarization beam splitter 131 is called S-polarized light, and their polarization directions are orthogonal to each other. One of the laser beams (P-polarized) is the corner cube 1 arranged at the end of the stage 93.
7, the light is reflected in the opposite direction and again enters the polarization beam splitter 131. The other laser beam (S
The polarized light enters the reference corner cube 132 provided in the interference optical unit 13, where it is reflected in the opposite direction and then enters the polarization beam splitter 131 again. The laser beam incident on the polarization beam splitter 131 from the corner cube 17 and the laser beam incident on the polarization beam splitter 131 from the reference corner cube 132 are overlapped by the polarization beam splitter 131, pass through the polarizing plate 138, and then pass through the photodetector 133. Incident. These two laser beams interfere with each other to generate interference fringes. The intensity of the interference fringes becomes maximum when the optical path difference between the two laser beams is an integral multiple of the wavelength of the laser beam, and the optical path difference is an integral multiple of the wavelength. It becomes the smallest when the difference is 1/2. Therefore, when the stage 93 moves and the corner cube 17 arranged at the end moves, the photodetector 133 moves.
Output intensity changes periodically. Specifically, when the corner cube 17 moves by ½ wavelength, an optical path difference of wavelength is generated in a round trip, so the value obtained by multiplying the number of cycles by which the output intensity of the photodetector 133 changes by ½ wavelength is a corner. The moving distance of the cube 17, that is, the stage 93.

The output signal of the photodetector 133 is the amplifier 13
After being amplified by 4, it is compared with the intermediate level of the output signal by the comparator 135 and converted into a binary signal, which is converted into a counter 1
Count at 36. The length measurement value calculation unit 137 uses the counter 13
The moving distance is calculated from the value of 6. A procedure for measuring the movement amount in each axial direction with the conventional arrangement shown in FIGS. 1 and 2 will be described.

After the operator completes the arrangement for measuring the movement amount error in the X-axis direction as shown in FIG. 1, the NC controller 9
7 is operated to instruct to move the stage 93 in the X-axis direction by the movement amount corresponding to the test method defined in ISO230-2 or the like. Then, the measurement value of the laser length measuring device corresponding to this movement is recorded. Such measurement is performed by moving to a prescribed number of target positions a prescribed number of times. Number More specifically, the ISO230- 2, it is necessary to take five target positions per meter distance traveled to 2m, it is necessary to further move more than 5 times each direction to each target position, to make measurements Is huge. Moreover, a plurality of cycles such as a linear cycle and a folding cycle are specified depending on the order in which each target position is measured, and it is necessary to select either one for each target machine tool to perform measurement. is there. The input of each target position to the NC controller 97 may be performed for each measurement, or may be input collectively at the beginning and sequentially moved by button operation. In any case, it is necessary to input each target position. Therefore, there is a problem that the work is time-consuming and the work is very complicated and error-prone. Further, it is also necessary to perform a prescribed calculation process on the measured value to calculate the evaluation value.

Further, in NC machine tools such as machining centers and milling machines, there are usually three moving axes, and it is necessary to measure the moving amount error in all of these moving axis directions. Therefore, when the measurement in the X-axis direction is completed, the laser light source 11, the interference optical unit 13, and the corner cube 1
It is necessary to change the arrangement of No. 7 to an arrangement for measuring the movement amount error in the Y-axis direction, measure the Y-axis direction, and then measure the Z-axis direction. Therefore, it is necessary to change the arrangement in which the laser beam from the laser light source 11 shown in FIG. 1 is output in the X-axis direction to the arrangement in which the laser beam is output in the Y-axis direction and the Z-axis direction. Moreover, it is not easy to dispose it so as to pass through the processing tool portion 92. Therefore, the direction of the laser beam is changed by combining a reflecting mirror (mirror) and the like, but the adjustment work becomes more complicated because the number of elements for adjusting the arrangement increases.

[0008] In order to solve such a problem, Japanese Utility Model Application No. 6
No. 2-52869 proposes a separation type laser interferometer in which a laser beam is transmitted from a laser light source to an interference optical unit by an optical fiber, thereby greatly improving the degree of freedom of arrangement. Although the setting of each axis can be easily done by using this separation type laser interferometer, even if such a separation type laser interferometer is used, the direction cannot be changed automatically, and the operator can Currently, it is necessary to set the axis.

Further, in the above arrangement of the laser light source 11, the interference optical unit 13 and the corner cube 17, it is necessary that the laser beam be output parallel to the direction of the moving axis to be measured, and if not parallel. The value measured as is a cosine (cos) value of the angle difference from the parallel and causes an error. If the angle difference is small, the error is small, but the measurement value measured by using the laser length measuring machine requires extremely high accuracy, so the laser beam and the moving axis must be parallel so that the angle difference is sufficiently small. There is a problem in that it is necessary to adjust the degree sufficiently, a skilled worker needs to perform it, and even if a skilled worker does it, it is a complicated task.

Further, FIG. 6 shows ANSI / ASME B5.
It is a figure which shows the conventional example of arrangement | positioning which measures the movement amount error of the diagonal direction prescribed | regulated by 54. As shown, the stage 93
The interference optical unit 13 is arranged at the end of 2, and the corner cube 17 is attached to the tip of the processing tool part so that the laser light emitted from the interference optical unit 13 enters the corner cube 17. Then, the mounted objects 931 and 932 and the processing tool are moved so that the interference optical unit 13 is controlled so as to move on the broken line in the figure relative to the corner cube 17, and the interference optical unit 13 and the corner are moved. The change in the distance between the cubes 17 is detected. Figure 6
It is easy to understand that the setting for measuring the displacement error in the diagonal direction as shown in (3) is more complicated.

[0011]

SUMMARY OF THE INVENTION In order to solve such a problem, the present applicant has proposed in Japanese Patent Application No. 8-56082.
Disclosed is a laser length measuring device that can switch the emission direction of a measurement laser beam output from an interference optical unit in three axial directions. By using this, the emission direction of the measurement laser beam can be automatically switched. However, the conventional laser length measuring device in which the emitting direction of the measuring laser beam cannot be switched is widely used, and the movement error of the machine tool can be easily measured by using such a conventional laser length measuring device. A measurement system is desired.

Further, if the emission direction of the laser beam can be switched to the three-axis directions, the setting for the measurement in the diagonal direction shown in FIG. 6 will not be easy, and there is a problem that complicated work is still required. there were. The present invention is to realize such a demand, and an object of the present invention is to realize a machine tool movement error measuring system that can easily measure a machine tool movement error and can be applied to automation of measurement work.

[0013]

In order to achieve the above object, the movement error measuring system for a machine tool according to the present invention is provided with an interferometer.
The optical unit is separated from the laser light source or the light reception processing unit.
Laser measurement, separated and connected with optical fiber between them
Equipped with a rotation mechanism that rotates the interference optical unit in response to an external signal, even if a conventional laser length measuring device that cannot switch the emitting direction of the measurement laser beam is used,
The emitting direction of the measuring laser beam is switched.

[0014] That is, the machine tool movement error measurement system of the present invention, the movement error of each moving axis of the machine tool, a machine tool movement error measurement system to measure using the laser measurement device, mobile Measurement corner fixed to the part
Interference that emits a measuring laser beam towards the cube
The optical unit is a laser light source or a measurement laser beam
Of interference fringes from the interference light composed of
Generate the same electric signal and count the number of changes in interference fringes
It is provided separately from the light receiving processing unit, and between each
Laser length measurement with an optical fiber for transmitting a laser beam
And a rotation mechanism for rotating the interference optical unit according to an external signal.

In order to measure the movement error in the three-axis directions, it is desirable that the rotating mechanism is a two-axis rotating mechanism that can independently rotate around two orthogonal axes. Since the laser light source for emitting From boss was laser beam having a considerable size and weight,
It is difficult to rotate the laser light source together with the interference optical unit. Therefore, a light receiving processing unit that generates an electric signal according to the interference fringes from the laser light source and the interference light and counts the number of changes in the interference fringes is provided separately from the interference optical unit, and an optical fiber is connected between them. that use separate type laser measurement device.

[0016]

FIG. 3 is a diagram showing the configuration of a fully automatic measuring system for a vertical machining center according to the first embodiment of the present invention. As shown in FIG. 3, the NC machine tool is the same as the conventional one, and includes a machining tool unit 92, a mounting table 93, and an N.
The C controller 97 and the like are provided. The NC controller 97 of the conventional NC machine tool generally has a data input / output port such as a terminal for RS-232C. The NC controller 97 of the NC machine tool to which the present invention is applied is also required to have such a data input / output port.

The laser length measuring device used in this embodiment is a separation type laser interferometer described in Japanese Patent Application No. 62-52869. This separable laser interferometer eliminates the need for alignment adjustment between the laser light source and the interference optical unit by connecting the laser light source and the interference optical unit with an optical fiber such as a single mode fiber or a polarization-maintaining fiber. In addition, the laser length measuring device has a high degree of freedom in arrangement between them. Furthermore, the signal processing unit can be separated from the interference optical unit, and a photodetector is provided in the interference optical unit to convert the signal of the interference fringes into an electric signal and send it to the signal processing unit with an electric signal cable. Although it is also possible, a type in which a photodetector is provided in the signal processing unit and an optical signal of an interference fringe is transmitted to the photodetector in the signal processing unit via an optical fiber is used here. As a result, the interference optical unit can be made smaller.

In FIG. 3, reference numeral 11 is He-Ne.
A laser light source that outputs a laser beam having a long coherence length, such as a laser, 14 is an interference optical unit, 15 is a rotating mechanism, 16 is a signal processing unit, and 32 is an operation of the rotating mechanism 15. And a reference numeral 31 denotes a notebook personal computer (PC) corresponding to a measurement control unit. The notebook PC is an ordinary computer, and the description of the configuration is omitted. The laser light source 11 and the interference optical unit 14 are connected by an optical fiber 121 such as a single mode fiber or a polarization-maintaining fiber, and the interference optical unit 14 and the signal processing unit 16 are connected by an optical fiber 122. .
An electric cable 35 connects the rotating mechanism 15 and the direction switching controller 32. Also, a notebook PC
31 and NC controller 97, signal processing unit 16,
A data communication cable is connected between the direction switching controller 32 and the direction switching controller 32, and control signals and data can be transmitted and received. The signal processing unit 16 includes a photodetector and a counter that counts the number of interference fringes based on changes in the output thereof.

FIG. 4 is a perspective view showing the interference optical unit 14 and the rotating mechanism 15. As shown in FIG.
A spindle 921 extends from the machining tool portion 92 of the C machine tool, and a tool chuck 922 for attaching a cutting tool such as an end mill is provided at the tip thereof. The rotating mechanism 15 is attached to the tool chuck 922. Rotating mechanism 15
Is a pole 151 attached to the tool chuck 922.
And the first support member 154 fixed to the pole 151.
And the motor 15 attached to the first support member 154.
2 and a second support member 155 rotatably supported by the first support member 154 and rotated by the motor 152.
And the motor 15 attached to the second support member 155.
3, a rotation shaft 156 rotatably supported by the second support member 155 and rotated by the motor 153, and a third support member 157 fixed to the rotation shaft 156.
The interference optical unit 14 is fixed to the third supporting member 157.

The direction of the main shaft 921 is the Z-axis direction, and the two directions in the plane perpendicular to the Z-axis direction are the X-axis direction and the Y-axis direction.
In this state, it is assumed that the measurement laser beam is emitted from the interference optical unit 14 in the X-axis direction. By rotating the motor 152, the direction of the measuring laser beam emitted from the interference optical unit 14 changes in the XY plane.
Therefore, if it is rotated by 90 ° from the state of FIG. 4, the measuring laser beam is emitted in the Y-axis direction. Further, by rotating the motor 153, the direction of the measurement laser beam emitted from the interference optical unit 14 changes in the XZ plane. Therefore, if it is rotated 90 ° from the state shown in FIG. 4, the measurement laser beam is emitted in the Z-axis direction. Motors 152 and 1
53 is a direction switching controller 32 and a cable 35.
, And operates according to a drive signal from the direction switching controller 32. Also, the motors 152 and 1
Reference numeral 53 is a motor provided with an encoder for detecting the rotation amount, and the direction switching controller 32 can detect the rotation amount via the cable 35. Therefore,
It is also possible to rotate by any desired value other than 90 °.

FIG. 5 is a diagram showing the internal construction of the interference optical unit 14. As described above, the interference optical unit 14 is the separation type laser interferometer described in Japanese Patent Application No. 62-52869, and the difference from the conventional configuration shown in FIG. Optical fiber 1
The point is that a collimator lens 139 that makes the laser beam transmitted by the laser beam 21 parallel to the parallel beam and a collimator lens 140 that focuses the interference beam that has passed through the polarizing plate 138 on the end face of the optical fiber 122 are provided. Therefore, detailed description is omitted.

The interference optical unit 14 shown in FIGS. 4 and 5.
A procedure for measuring the movement error of the NC machine tool 91 shown in FIG. 3 by using the and rotation mechanism 15 will be briefly described. First, make sure that the direction of the laser beam is parallel to each axis when switching the direction, and place all corner cubes used for measurement of each axis at the specified positions. Then, after setting the measurement laser beam to be emitted in the axial direction to be measured first, the NC machine tool 91
The mounting table 93 or the processing tool section 92 is moved, and the amount of movement at that time is measured by the laser length measuring device. When the measurement in one axial direction is completed, the interference optical unit 14 is rotated so that the measurement laser beam is emitted in the axial direction to be measured next, the movement amount is measured, and the remaining movement axes are also measured. The same scan is performed.

In the machine tool, not only the movement axis direction but also A
In some cases, it is necessary to measure a diagonal movement error, which is a movement error when moved in a direction forming an angle with respect to the movement axis as specified in NSI / ASME B5, 54 and the like. In such a case, after rotating the interference optical unit by the rotating mechanism and setting the measurement laser beam to be emitted in the diagonal movement direction,
You just have to measure. In the movement error measuring system of the present invention, after measuring the movement error in each axial direction, even when continuously measuring the diagonal movement error, it is possible to set the measurement laser beam to be automatically emitted in the diagonal movement, It is possible to measure continuously.

[0024]

As described above, according to the present invention,
It becomes possible to easily perform the complicated work of measuring the movement error of the machine tool, which reduces the man-hours and makes it possible to greatly automate the measurement work.

[Brief description of drawings]

FIG. 1 is a diagram showing a conventional arrangement example for measuring a movement error in a movement axis direction of an NC machine tool.

FIG. 2 is a diagram showing a configuration of a conventional interference optical unit.

FIG. 3 is a diagram showing a configuration of a movement error measuring system for a vertical machining center according to an embodiment of the present invention.

FIG. 4 is a perspective view showing an interference optical unit and a rotation mechanism of the embodiment.

FIG. 5 is a diagram showing a configuration of an interference optical unit of an example.

FIG. 6 is a diagram showing a conventional setting example for measuring a movement error in a diagonal direction.

[Explanation of symbols]

11 ... Laser light sources 13, 14 ... Interference optical unit 16 ... Signal processing units 170, 171, 172 ... Corner cube 31 ... Measurement control means (notebook personal computer) 91 ... Machine tool 92 ... Machining tool section 93 ... Mounting table 97 ... NC controller

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-183042 (JP, A) JP-A-6-114684 (JP, A) JP-A-63-56385 (JP, A) JP-A-1- 191002 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B23Q 17/24 G01B 9 / 02,11 / 00

Claims (4)

(57) [Claims] 1. A movement error measuring system for a machine tool, wherein a movement error of each movement axis of a machine tool (91) is measured using a laser length measuring machine, wherein the laser length measuring machine is a laser light source ( 11) is a measurement corner cube (170, 17) fixed to the moving part.
1, 172) and is provided separately from the interference optical unit (14) that emits the measurement laser beam.
From the laser light source (11) to the interference optical unit (1
4) is provided with an optical fiber (121) for transmitting a laser beam, and the interference optical unit (14) has at least a beam scanning unit.
Plitter (131) and reference corner cube (13
2), including the beam splitter (131) and a reference corner cube.
The interference optical unit (14) including a tube (132)
Rotation mechanism (15) for rotating the whole according to an external signal
A machine tool movement error measuring system comprising: 2. The movement error measuring system for a machine tool according to claim 1, wherein the laser length measuring device is the interference optical unit (14).
A light receiving processing unit (16) that counts the number of changes in the interference fringes by generating an electrical signal corresponding to the interference fringes from the interference light obtained by combining the measurement laser beam and the reference laser beam.
And the interference optical unit (1
4) A movement error measuring system for a machine tool, comprising an optical fiber (122) for transmitting a laser beam from the light receiving processing unit (16) to the light receiving processing unit (16). 3. A machine tool movement error measuring system for measuring a movement error of each movement axis of a machine tool (91) using a laser length measuring machine, wherein the laser length measuring machine is provided in a moving part. Interference optical unit (14) for emitting a measurement laser beam toward a fixed measurement corner cube (170, 171, 172).
A light receiving processing unit (16) that counts the number of changes in the interference fringes by generating an electrical signal corresponding to the interference fringes from the interference light obtained by combining the measurement laser beam and the reference laser beam.
And the interference optical unit (1
4) is provided with an optical fiber (122) for transmitting a laser beam from the light reception processing unit (16), and the interference optical unit (14) includes at least a beam splitter.
Plitter (131) and reference corner cube (13
2), including the beam splitter (131) and a reference corner cube.
The interference optical unit (14) including a tube (132)
Rotation mechanism (15) for rotating the whole according to an external signal
A machine tool movement error measuring system comprising: 4. The movement error measuring system for a machine tool according to claim 1, wherein the rotation mechanism (15) is capable of independently rotating about two orthogonal axes. A system for measuring the movement error of a machine tool that is a shaft rotation mechanism.