JP2019045485A - Temperature-correction method, temperature-correction program, and coordinate measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature correction method, a temperature correction program, and a coordinate measuring machine capable of reducing a scale error more easily. SOLUTION: When the thermal expansion coefficient of the scale is as, the temperature of the scale is ts, and the scale error is Ec, the nominal dimension L with a known thermal expansion coefficient is measured at a reference temperature (20 ° C ± 0.5 ° C). The step of calculating the scale offset error dts0 using the following equation (1) based on the value Lw1 and the scale error Ec1 of the measured value Lw1 and the nominal dimension L whose thermal expansion coefficient is known under a temperature environment different from the reference temperature. A plurality of different measurement values Lw2 and a step of calculating the equivalent scale temperature coefficient error dKs by using the equation (2) based on the scale error Ec2 of the measurement value Lw2. dts0 = Ec1 / asLw1 ... (1), dKs = (Ec2-asdtts0Lw2) / as (ts-20) Lw2 ... (2) [Selection diagram] FIG.

Description

  The present invention relates to a temperature correction method, a temperature correction program, and a coordinate measuring machine.

ISO 1 defines a standard reference temperature for geometric characteristic specification and verification of a workpiece, and the standard reference temperature is 20 ° C. If there is a deviation between the temperature at the time of measurement and the standard reference temperature, an error occurs in the measured length even if the temperatures of the workpiece and the measuring machine are equal. As a coordinate measuring machine for measuring the length of such a work, for example, in a three-dimensional measuring machine (CMM; Coordinate Measuring Machine), temperature correction is performed to maintain measurement accuracy (for example, Patent Document 1) ). To perform temperature correction, know the coefficient of thermal expansion (CTE) and the temperature of the scale and the work piece to be measured that are arranged along each axis that composes a three-dimensional space in a three-dimensional measuring machine There is a need. For example, when measuring a 1000 mm steel workpiece at 23 ° C., the CTE of the workpiece is about (10 ± 1) × 10 ⁻⁶ / ° C., but the CTE uncertainty is about ± 1 × 10 ⁻⁶ / ° C. Do. Therefore, the uncertainty of the measurement dimension due to the CTE uncertainty is 3 μm. This uncertainty can not be corrected as long as it is measured at 23 ° C., and becomes larger as the deviation from 20 ° C. becomes larger.

  Patent Document 1 discloses a temperature correction method for calculating an error of scale based on scale errors of a plurality of workpieces having different nominal dimensions L.

JP 2017-37068 A

  At a manufacturing site, as the precision of a product is increased, a more accurate three-dimensional measuring machine capable of evaluating the product is required.

  An object of the present invention is to provide a temperature correction method, a temperature correction program, and a coordinate measuring machine capable of reducing a scale error more easily.

The temperature correction method of the coordinate measuring machine according to the present invention is performed at a reference temperature (20 ° C. ± 0.5 ° C.), where the thermal expansion coefficient of the scale is a _s , the temperature of the scale is t _s , and the scale error is E _c . Calculated scale offset error dt _s0 using the following equation (1) from measured value L _w1 of nominal dimension L with known thermal expansion coefficient and calibration error E _c1 of measured value L _w1 or calibrated temperature _Setting the difference between the temperature of the scale measured by the gauge and the temperature measured by the thermometer of the scale as the scale offset error dt s 0, and the thermal expansion coefficient is known under a temperature environment different from the reference temperature measurement of the nominal dimension L _{L w2,} and this and a step of calculating the equivalent scale temperature coefficient errors dK _s using the following equation (2) by the scale error _{E c2} measurements _{L w2} The features.
dt _s0 = E _c1 / a _s L _w1 (1)
dK _s = (E _c2 −a _s dt _s0 L _w2 ) / a _s (t _s −20) L _w2 (2)

The temperature correction program of the coordinate measuring machine according to the present invention, when the computer uses the thermal expansion coefficient of the scale as _s , the temperature of the scale as t _{s, and the} scale error as E _c , the reference temperature (20 ° C. ± 0 The scale offset error dt _s0 is calculated using the above equation (1) from the measured value L _w1 of the nominal dimension L whose thermal expansion coefficient is known and the scale error E _c1 of the measured value L _w1 at 5 ° C.) Or setting the difference between the temperature of the scale measured by the calibrated thermometer and the temperature measured by the thermometer of the scale as the scale offset error dt _s0 , under a temperature environment different from the reference temperature measurements _{L w2} of thermal expansion coefficient is a known nominal dimension L, and an equivalent scale temperature coefficient errors dK _s by using equation (2) by the scale error _{E c2} measurements _{L w2} Characterized in that and a step of leaving.

In the coordinate measuring machine with temperature correction function according to the present invention, when the thermal expansion coefficient of the scale is a _s , the temperature of the scale is t _{s, and the} scale error is E _c , at the reference temperature (20 ° C. ± 0.5 ° C.) A thermometer that calculates or calibrates the scale offset error dt _s0 using the above equation (1) from the measured value L _w1 of the nominal dimension L whose thermal expansion coefficient is known and the scale error E _c1 of the measured value L _w1 The difference between the temperature of the scale measured by the scale and the temperature measured by the thermometer of the scale is the scale offset error dt _s0, and under a temperature environment different from the reference temperature, the nominal dimension L whose thermal expansion coefficient is known measurements L _w2, and, characterized in that it comprises a control device that calculates an equivalent scale temperature coefficient errors dK _s by using equation (2) by the scale error E _c2 measurements L _w2.

  According to the present invention, a scale error immediately at the reference temperature (20 ± 0.5 ° C.) or a scale immediately from the difference between the temperature of the scale measured by the calibrated thermometer and the temperature measured by the thermometer of the scale Since the offset error is calculated, the scale error can be more easily reduced.

It is a perspective view which shows typically the structure of the measuring machine main body which concerns on this embodiment. It is a block diagram showing composition of a control device concerning this embodiment. It is a perspective view which shows typically the structure of the measuring machine main body which concerns on the modification of this embodiment. It is a graph which shows the positioning error computed based on the measured value measured by the laser interference length measuring device. It is the graph which took out the measured value of 19.65 degreeC from the graph shown in FIG. It is a graph which shows the positioning error which corrected the scale offset error in the measured value of 16.50 ° C and 26.44 ° C. It is a graph which shows the result of having calculated the positioning error at 20 ° C based on the result of FIG. It is a graph which shows the positioning error computed by substituting temperature t _s of a scale by temperature t _{s -corr} after amendment. It is a graph which shows the correlation of the result measured by the workpiece | work thermometer attached to a three-dimensional measuring machine, and the calibrated temperature sensor. It is a graph which shows the result of having performed temperature correction of a scale and work thermometer. It is a graph which shows the correlation of the result measured by the scale thermometer attached to a three-dimensional measuring machine, and the temperature sensor calibrated. It is a graph which shows the positioning error which corrected the scale offset error in the measured value of 16.50 ° C and 26.44 ° C. It is a graph which shows the result of having calculated the positioning error at 20 ° C based on the result of FIG. It is a graph which shows the positioning error computed by substituting temperature t _s of a scale by temperature t _{s -corr} after amendment. It is a graph which shows the result of having performed temperature correction of a scale and work thermometer.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1. Embodiment (1) Overall Configuration A three-dimensional measuring device as a coordinate measuring device includes a measuring device main body 10 shown in FIG. 1 and a control device described later. The measuring machine main body 10 includes a base 12, a Y-axis rail 14, a Y-axis moving body 16, an X-axis moving body 18, and a Z-axis moving body 19. The Y-axis rail 14 is provided along the Y-axis on the base 12. The Y-axis movable body 16 has a pair of legs 15 and a beam 17 bridged between the upper ends of the legs 15, and the legs 15 travel along the Y-axis rail 14 to obtain a base. The table 12 can be moved in the Y-axis direction. The X-axis moving body 18 is supported by the beam portion 17 of the Y-axis moving body 16 so as to be movable in the X-axis direction orthogonal to the Y-axis. The Z-axis mobile unit 19 is supported by the X-axis mobile unit 18 so as to be movable in the Z-axis direction orthogonal to the X-axis and the Y-axis. The Z-axis moving body 19 holds the probe 20 at its tip.

  The measuring machine body 10 has a Y-axis scale 22 for measuring the amount of movement of the probe 20 in the Y-axis direction, an X-axis scale 24 for measuring the amount of movement of the probe 20 in the X-axis direction, and a movement of the probe 20 in the Z-axis direction And a Z-axis scale 26 for measuring the quantity. The Y-axis scale 22 is provided on the Y-axis rail 14, the X-axis scale 24 is provided on the beam portion 17, and the Z-axis scale 26 is provided on the Z-axis moving body 19. In practice, the measuring machine main body 10 is provided with a detector (not shown) for reading the values of the X axis scale 24, the Y axis scale 22, and the Z axis scale 26, respectively. The said detector outputs the coordinate signal which shows the read result to the control apparatus mentioned later.

  The measuring machine main body 10 is provided with an X-axis scale 24, a Y-axis scale 22, a Z-axis scale 26, and a temperature sensor 28 as a thermometer for measuring the temperature of the workpiece W. The temperature sensor 28 x is provided on the X axis scale 24, the temperature sensor 28 y is provided on the Y axis scale 22, the temperature sensor 28 z is provided on the Z axis scale 26, and the temperature sensor 28 w is provided on the work W. Each temperature sensor 28 outputs the detected temperature signal to a control device described later.

  FIG. 2 is a block diagram showing the configuration of the control device 30. As shown in FIG. The control device 30 includes a temperature calculation unit 32, a temperature correction unit 34, a displacement calculation unit 36, and a basic temperature correction unit 35. The control device 30 reads various programs such as a basic program and a temperature correction processing program stored in advance, and controls the whole according to the various programs.

  Each temperature sensor 28 and the measuring machine main body 10 are electrically connected to the control device 30. The control device 30 receives the temperature signal output from each temperature sensor 28 and the coordinate signal output from the measuring instrument main body 10. As shown to this figure, the three-dimensional measuring machine 1 is provided with the measuring machine main body 10, the control apparatus 30, and each temperature sensor 28. As shown in FIG. The temperature correction device 38 further includes temperature sensors 28, a temperature calculation unit 32, a temperature correction unit 34, and a basic temperature correction unit 35.

The temperature calculation unit 32 converts the input temperature signal into temperature data, and calculates the temperature t _{s of} the scale and the temperature t _{w of the} work W. The displacement calculation unit 36 calculates the displacement amount of the probe 20, that is, the length (hereinafter, also referred to as “scale reading”) L _s based on the input coordinate signal. For example, when measuring the length in the X-axis direction of the work W, ie, the distance between two points, when the contact portion at the tip of the probe 20 contacts the work W, a coordinate signal related to the coordinates of the contact portion is measured The main unit 10 outputs. The control device 30 calculates the length in the X-axis direction of the workpiece W, which is the displacement amount of the probe 20, based on the coordinate signals of the two points obtained in this manner.

As the temperature t _s of the scale, the temperature measured by the temperature sensor 28 installed in the measuring machine main body 10 can be used.

The basic temperature correction unit 35 performs basic temperature correction processing on the reading L _{s of} the scale based on the temperature data of each portion obtained by the temperature calculation unit 32. Base temperature correction process is calculated for scale reading L _s, the thermal expansion coefficient of a _s, a measured value L _w of the length of the workpiece W subjected to basic temperature correction based on a _w. Measurements L _w of the length of the workpiece W, the thermal expansion coefficient of the scale a _s, a thermal expansion coefficient of the workpiece W a _w, a temperature scale t _s, the temperature of the workpiece W and t _w, the following formula It can be expressed by (10).

L _w = L _s (1 + a _s (t _s -20) -a _w (t _w -20)) (10)

The temperature correction unit 34 corrects the temperature sensor 28 based on the temperature data of each portion obtained by the temperature calculation unit 32. First, the temperature correction unit 34 is a temperature sensor provided on each scale from scale errors E _c in a plurality of lengths of a step gauge having a small thermal expansion coefficient (hereinafter referred to as a “low thermal expansion coefficient step gauge”) as the work W The correction of 28x, 28y and 28z is performed, and then the temperature sensor 28w of the workpiece W is corrected using a separately prepared calibrated temperature sensor.

First, the case of correcting the temperature sensors 28x, 28y, and 28z will be described. Assuming that the calibration value of the length of the work W is L _c , the scale error E _c can be expressed by the following equation (11).

_{E c = L w -L c =} L s (1 + a s (t s -20) -a w (t w -20)) - L c ··· (11)

In this embodiment, the error included in the measured value L _w is provided as an error of the X-axis scale 24, Y-axis scale 22, and Z-axis scale 26, the error of each scale intrinsic thermal expansion coefficient a _s, in each scale temperatures sensors 28x, 28y, the error of the temperature _{t s} measured by 28z, believed to include the magnification error of each scale reading _{L s.} Furthermore, the error of the measured temperature t _s of each scale is composed of a magnification error and an offset error.

The error of the work W is considered to include the error of the thermal expansion coefficient a _w of the work W, the error of the temperature t _w measured by the temperature sensor 28 _w provided on the work W, and the error of the calibration value L _c . Furthermore, the error of the measured temperature t _w of the workpiece W is composed of a magnification error and an offset error.

  Here, the magnification error and the offset error will be described. In the case of an ideal temperature sensor without error, the result measured by the temperature sensor provided in the three-dimensional measuring device 1 corresponds to the result measured by the calibrated temperature sensor, so the measurement result passes through the origin The slope is a straight line of 1. On the other hand, when there is an error in the temperature sensor provided in the three-dimensional measuring device 1, the measurement result is a straight line with different inclination or a straight line not passing the origin. The error appearing in the slope of the straight line is called a magnification error. Also, an error that appears in the deviation of the origin is called an offset error. The actual error is a combination of the magnification error and the offset error.

X-axis scale 24, Y-axis scale 22, and out of the error in the Z-axis scale 26, error and magnification error in temperature t _s of the scale of the thermal expansion coefficient a _s of each scale when the temperature changes, in the same way It can not be distinguished because it occurs. The magnification error of each scale reading L _s and the offset error of each scale temperature t _s are likewise indistinguishable. Among the errors relating to the work W, an error of the thermal expansion coefficient a _w of the work W, a magnification error of the temperature t _w of the work W, and an error of the calibration value L _c and an offset error of the temperature t _w of the work W can not be distinguished. In addition, when the calibration value _Lc and the value of the thermal expansion coefficient _aw of the work W can be regarded as known with high accuracy, it can be assumed that there is no error, and the following four errors of the temperature sensor can be considered. That is, an error dK _s (hereinafter referred to as “equivalent scale temperature coefficient error”) composed of a magnification error of each scale temperature t _{s and} an error of the thermal expansion coefficient a _s of each scale, temperature t _s of each scale An error dt _s0 (hereinafter referred to as “scale offset error”) composed of an offset error and a magnification error of each scale, a magnification error of the temperature t _w of the workpiece W and an error of the thermal expansion coefficient a _w of the workpiece W Error dk _w (hereinafter referred to as “equivalent work temperature coefficient error”), error dt _w0 composed of an offset error of the temperature t _w of the work W and an error of the calibration value L _c of the work W It is called "error").

Assuming that the temperature t _s of each scale and the temperature t _w of the work W are the correct temperature of each scale and the work W, the measurement temperature t _s ^* of each scale and the measurement temperature t _w ^* of the work W are represented by the following equation (12), It can be represented by (13).

^{_{t s * = (1 + dK}} s) t s + dt s0 ··· (12)
^{_{t w * = (1 + dk}} w) t w + dt w0 ··· (13)

When a step gauge with a low thermal expansion coefficient is used as the workpiece W, the thermal expansion coefficient a _w of the workpiece W is 0, so that the scale error E _c represented by the above equation (11) corresponds to L _w Then, it can be represented by the following formula (14).

_{E c = L w -L c =} L s (1 + a s (t s * -20)) - L c
_{≒ a s dt s0 L w +} a s dK s (t s -20) L w ··· (14)

Here, in the case of t _s = 20 ± 0.5 ° C., since a _s dK _s (t _s −20) L _w is less than 0.3, a _s dK _s (t _s − of the above equation (14) can be obtained. 20) Ignore L _w . Then, the scale offset error dt _s0 can be expressed by the following equation (15) by the scale error E _c1 calculated from the measured value L _w1 measured at the reference temperature (20 ± 0.5 ° C.).

dt _s0 = E _c1 / a _s L _w1 (15)

The scale error E _c1 calculated from the measured value L _w1 measured at the reference temperature (20 ± 0.5 ° C.) can be expressed by the following equation (16).

E _c1 = L _w1 -L _c (16)

Incidentally, the measured value _{L w1} and multiple measurements _{L w1L1, L w1L2,} replacing the scale error _{E c1} and a plurality of graduation errors _{E c1L1, E c1L2,} that equation (15) is expressed by the following formula (17) it can.

dt _s0 = (E _c1 L ₁ -E _c1 L ₂ ) / (L _{w 1} L ₁ -L _{w 1} L ₂ ) a _s (17)

Under the temperature environment different from the reference temperature, the equivalent scale temperature coefficient error dK _s can be expressed by the following equation (18) based on the measured value L _w2 of the nominal dimension L whose thermal expansion coefficient is known.

dK _s = (E _c2 −a _s dt _s0 L _w2 ) / a _s (t _s −20) L _w2 (18)

Under the temperature environment different from the reference temperature, the scale error E _c2 calculated from the measured value L _w2 of the nominal dimension L whose thermal expansion coefficient is known can be expressed by the following equation (19).

E _c2 = L _w2 -L _c (19)

The measured value _{L w2} and multiple measurements _{L w2L1, L w2L2,} replacing the scale error _{E c2} and a plurality of graduation errors _{E c2L1, E c2L2,} formula (18) can be represented by the following formula (20).

_{dK s = {(E c2L2 -E} c2L1) -a s dt s0 (L w2L1 -L w2L2)} / a s (L w2L1 -L w2L2) (t s -20) ··· (20)

Thus, the temperature correction unit 34 obtains the scale offset error dt _s0 and the equivalent scale temperature coefficient error dK _s from the scale errors E _c1 and E _c2 at different temperatures at the nominal dimension L of the step gauge with the low thermal expansion coefficient. The temperature t _s ^* is calculated from the obtained scale offset error dt _s0 , the equivalent scale temperature coefficient error dK _s , and the above equation (12). The temperature calculated in this manner is called a post-correction temperature t _{s -corr} . By calculating the after-correction temperature t _s -corr for each scale, the temperature sensors 28 x, 28 y and 28 z of each scale can be corrected. Specifically, correction can be made by changing the settings of the temperature sensors 28x, 28y, 28z to the corrected temperature t _s -corr.

Since the error of the thermal expansion coefficient a _w of the workpiece W included in the equivalent workpiece temperature coefficient error dk _w varies depending on the target workpiece W, the equivalent workpiece of the temperature sensor 28 w can not be separated from the magnification error of the workpiece W Correction by temperature coefficient error dk _w is not possible. Therefore, in the case of the present embodiment, the equivalent work temperature coefficient error dk _w is ignored.

The uncertainty of the calibration value L _c of the workpiece W included in the workpiece offset error dt _w0 is 0.3 μm in the case of a 500 mm step gauge (Tamitsu Osawa et al., Synthesiology Vol 2 No. 2 p. 101-112 Jun. 2009) Therefore, the influence on the work offset error dt _w0 is considered to be small. Thus in the present embodiment, the error of the calibration values L _c of the work W is to be ignored. From the above, the temperature correction unit 34 calculates the work offset error dt _w0 , that is, the temperature after correction t _w -corr by comparing the temperature sensor 28 _w that measures the temperature t _{w of the} workpiece W with the calibrated temperature sensor. And correct the temperature sensor 28w.

The control device 30 is a measurement value of the workpiece W obtained by performing temperature correction on the scale reading L _s based on the temperature t _{s of} each scale and the temperature t _{w of the} workpiece W measured by the corrected temperature sensor 28 Calculate L _w .

(2) Operation and effect The temperature sensor 28 x is corrected using the three-dimensional measuring device 1 configured as described above, and the temperature sensor 28 w is corrected using the calibrated temperature sensor, and these corrections are performed. A procedure for performing temperature correction on the scale reading L _s at the temperature measured using each temperature sensor 28 will be described.

First, two or more lengths having different nominal dimensions L of the step gauge having a low thermal expansion coefficient as the workpiece W are measured under a reference temperature (20 ± 0.5 ° C.) and a temperature environment different from the reference temperature. Specifically, the step gauge is installed on the base 12 in parallel with the X axis, and the coordinates of two points in the X axis direction of the step gauge are detected under the above two conditions. The detection result is output from the measuring machine main body 10 to the control device 30 as a coordinate signal. The control device 30 calculates the measurement value L _w in the X-axis direction of the step gauge by performing basic temperature correction based on the obtained two-point coordinate signals. The measurements at the reference temperature _{(20 ± 0.5 ℃) L w1L1} , L w1L2, the measurements at the reference temperature different environments _{L w2L1, L w2L2,} to.

Next, the control device 30 calculates scale errors E _c1L1 and E _C1L2 at the reference temperature (20 ± 0.5 ° C.) according to the above equation (16). Further, the control device 30 calculates the scale offset error dt _{s0 according} to the above equation (17).

Subsequently, the control device 30 calculates scale errors E _c2L1 and E _C2L2 under the temperature environment different from the reference temperature by the above equation (19). Further, control device 30 calculates equivalent scale temperature coefficient error dK _s by the above equation (20).

The resulting equivalent scale temperature coefficient errors dK _s, by calculating the corrected temperature _{t s-corr} from the scale offset error _{dt s0,} and the formula (12), to correct the temperature sensor 28x. Similarly, the temperature sensors 28 y and 28 z are corrected for the Y-axis scale 22 and the Z-axis scale 26.

Then, the control device 30 receives a temperature signal from a calibrated temperature sensor different from the temperature sensor 28 attached to the three-dimensional measuring machine 1 and a temperature sensor 28 w that measures the temperature of the workpiece W. Thus, the control device 30 compares the temperature data of the calibrated temperature sensor with the temperature data of the temperature sensor 28 w of the workpiece W, and calculates a work offset error dt _w0 , that is, a temperature after correction t _w -corr. Thus, the control unit 30, based on the work offset error _{dt w0,} it is possible to correct the temperature sensor 28w.

Coordinate measuring machine 1, used as the corrected temperature sensors 28x, 28y, 28z, the 28w, a _{t s} a corrected temperature _{t s-corr,} and _{t w} is the corrected temperature _{t w-corr} The temperature correction can be performed on the reading L _{s of} each scale by using the above equation (10), and the measurement value L _w with less error can be calculated.

Since the temperature correction device 38 according to the present embodiment immediately calculates the scale offset error dt _s0 from the scale error E _{c1 at} the reference temperature (20 ± 0.5 ° C.), the scale error E _c can be more easily reduced. it can.

Equivalent Scale Temperature Coefficient error dK _s and scale offset error dt _s0 is caused by deviation from the standard reference temperature, it includes various errors. Accordingly, the temperature correction device 38, by calculating the equivalent scale temperature coefficient error dK _s and scale offset error dt _s0, the error contained in the reading of the scale L _s by the temperature correction, can be removed.

The case of measuring two or more lengths with different nominal dimensions L of the step gauge with low thermal expansion coefficient as the work W under the reference temperature (20 ± 0.5 ° C.) and the temperature environment different from the reference temperature has been described The present invention is not limited to this. Temperature correction may be performed by measuring the length of one nominal dimension L using a zero point proportional equation. That is, the length L of the nominal dimension L of the step gauge having a low thermal expansion coefficient as the work W is measured under a temperature environment different from the measured value L _W1 measured at the reference temperature (20 ± 0.5 ° C.) and the reference temperature. Based on the value L _W2 , the scale offset error dt _s0 and the equivalent scale temperature coefficient error dK _s may be calculated by the above equations (15) and (19).

Although the case where a step gauge with a low thermal expansion coefficient is used as the work W has been described, the present invention is not limited thereto, and a step gauge with a thermal expansion coefficient may be used. In this case, the scale error E _c represented by the equation (11) can be expressed by the following equation (21), where L _w is a measured value of the work W.

_{E c ≒ a s dt s0 L} w + a s dK s (t s -20) L w -a w dt w0 L w -a w dK w (t w -20) L w ··· (21)

Here, when measuring the step gauge with a thermal expansion coefficient, it can be considered that dK _w = 0, so a _w dK _w (t _w −20) L _w = 0. Further, by correcting dt _w0 by comparing the calibrated thermometer and the work thermometer attached to the three-dimensional measuring device, a _w dt _w0 L _w = 0 is obtained. Therefore, the above equation (21) can be expressed as the above equation (14).

(3) Modification (Modification 1)
In the above embodiment, the reference temperature (20 ± 0.5 ℃) measurements were determined in _{L w1L1, L w1L2,} and _L W2L1 measured at standard temperature different _{environment, L W2L2} a low thermal expansion as the work W Although it was set as the value measured using the step gauge of the coefficient, the present invention is not limited to this. For example, as the measurement values _Lw1L1 , _Lw1L2 , _Lw2L1 and _Lw2L2 , as shown in FIG. 3, values measured by the laser interference length measuring device 40 may be used. The laser interference length measuring device 40 includes a laser light source 42, an interference mirror 44, and a reflection mirror 46. In the case of this figure, the laser light source 42 is arranged to emit laser light in the Y-axis direction. The interference mirror 44 is disposed on the optical path of the laser light, reflects the first polarization component of the incident light in the lateral X direction, and reflects and re-incidents the second polarization component. The reflection mirror 46 is fixed to the tip of the Z axis moving body instead of the probe, and reflects the first polarization component reflected in the X direction by the interference mirror 44. The laser light source 42 includes a light receiving unit (not shown), and is electrically connected to the arithmetic processing unit 48 (for example, a personal computer). The arithmetic processing unit 48 measures a change in light and dark due to interference fringes from the output signal of the light receiver and performs length measurement.

  When the laser light emitted from the laser light source 42 enters the interference mirror 44, the first polarization component is reflected in the X direction at the splitter surface (not shown), and emitted toward the reflection mirror 46 as measurement light. The measurement light is perpendicularly incident on the reflection surface of the reflection mirror 46, is reflected, and reversely travels. The measurement light is reflected by the interference mirror 44 and enters the light receiver. The second polarized light component is reflected by the interference mirror 44 and enters the light receiver as a reference light. The interference mirror 44 reflects the light axis of the incident light as a light which is translated in parallel. For this reason, the optical axis of the laser beam emitted from the laser light source 42 and the optical axis of the reference beam incident on the light receiver are parallel lines separated from each other.

  The combination of the reference light and the measurement light branched by the interference mirror 44 causes interference in accordance with the optical path difference between them. The light receiver detects a change in brightness depending on the interference. The change in brightness is counted by the arithmetic processing unit 48, converted into a change in distance from a preset measurement origin, and output as an output value from the laser interference length measuring device 40.

For example, in the measuring machine main body 10, the reflection mirror 46 provided at the tip of the Z-axis moving body 16 is moved in the X-axis direction by a predetermined distance. Then feed position output from the controller 30, i.e. the X-direction displacement and the measured value L _w. At the same time, the output value obtained by the laser interferometer length measuring apparatus 40 and the calibration value L _c. The measured value L _w and the calibration value L _c can be applied as they are to the temperature correction method in the above embodiment. An error (L _w −L _c ) obtained from the measurement value L _w which is the feed position and the output value L _c obtained by the laser interference length measuring device 40 is called a positioning error E _c . Therefore, the temperature correction method according to the present modification can achieve the same effect as that of the above embodiment.

The measured values L _w1L1 and L _w1L2 measured at the reference temperature (20 ± 0.5 ° C.) in the above embodiment are not necessarily limited to the values actually measured at the reference temperature (20 ± 0.5 ° C.), and other than the reference temperature The value obtained by simulation from the measured value measured at the temperature of

(Modification 2)
Although the case of calculating the scale offset error dt _s0 using the equation (15) or the equation (17) has been described in the above embodiment, the present invention is not limited to this. As described above, among the offset error and the magnification error of each scale of temperature t _s of the scale constituting the scale offset error dt _s0, that the magnification error of each scale is very small value, from the experimental results so far know. That is, the scale offset error dt _s0 is largely affected by the offset error of the temperature t _s of each scale. Therefore, the difference between the temperature t _{s of} each scale and the temperature measured by the calibrated temperature sensor may be used as the scale offset error dt _s0 . As a _result , there is no need to measure a plurality of measurement values L _w1L1 and L _w1L2 having different nominal dimensions L whose thermal expansion coefficients are known at the reference temperature (20 ° C. ± 0.5 ° C.), and correction can be performed more simply. Can.

2. Example (Example 1)
Indeed, by using a laser interference length measuring machine to calculate the equivalent scale temperature coefficient error dK _s and scale offset error dt _s0. The positioning error was calculated by measuring 0 to 700 mm at a 50 mm pitch under three conditions of different measurement temperatures by changing the measurement date. The scale temperature t _s was a temperature measured by the temperature sensor 28 x. The results are shown in FIG. In FIG. 4, the horizontal axis is the measurement position (mm) and the vertical axis is the positioning error (μm). Positioning error _{E c} is the calibration value measurements by laser interference length measuring machine _{L c,} when the measured value of the workpiece W and _{L w,} can be expressed by E _{c =} L w -L _c.

FIG. 5 is a graph in which only the positioning error E _{c1 at the} reference temperature (19.65 ° C.) is extracted from the graph of FIG. 4. Based on this figure, the scale offset error dt _s0 can be determined by the above equation (15) or equation (17). In this embodiment, the case of _obtaining the scale offset error dt _s0 using a straight line obtained by the least squares method will be described. The straight line in the figure was determined by the least squares method. _Assuming that the positioning error E _c1 is the inclination of the straight line (0.001), and the thermal expansion coefficient a _s of the scale is 8.00 × 10 ⁻⁶ / ° C., the scale offset is obtained by the above equation (15) or equation (17) The error dt _s0 is calculated to be 0.125 ° C. By correcting the scale offset error dt _s0 , the positioning error E _c1 can be made 0.5 μm or less (○ in FIG. 5).

FIG. 6 is a graph showing a positioning error E _r obtained by correcting the scale offset error dt _s0 with respect to the positioning error E _{c2 at} temperatures other than the reference temperature. In this figure, the horizontal axis is the measurement position (mm), and the vertical axis is the positioning error (μm). Correction of scale offset error _{dt s0} is the equation (18) in _{(E c2 -a s dt s0 L} w2), or _{(E c2L2} -E _c2L1) in the formula _{(20) -a s dt s0 (} L w2L1 - It corresponds to _Lw2L2 ).

Then, replacing the above positioning error _{E r} a positioning error _{E r20} when the 20 ° C.. The positioning error _Er 20 was calculated by dividing each slope of FIG. 6 by the deviation from 20 ° C. The results are shown in FIG. Calculation for obtaining the positioning error _{E r20,} the above equation in _{(18) (E c2 -a s} dt s0 L w2) / (t s -20) L w2, or the formula (20) in _{{(E c2L2 -E c2L1} ) corresponding to the _{-a s dt s0 (L w2L1 -L} w2L2)} / (L w2L1 -L w2L2) (t s -20). Therefore, the equivalent scale temperature coefficient error dK _s can be obtained by dividing by the thermal expansion coefficient a _s of the above scale.

In this embodiment, the case where the equivalent scale temperature coefficient error dK _s is obtained by the least squares method will be described. The graph shown in FIG. 7 shows one straight line obtained by the least square method from two graphs corresponding to the two conditions of the measurement temperature. The equivalent scale temperature coefficient error dK _s is calculated to be 0.019 by dividing the slope (0.00015) of the straight line by the thermal expansion coefficient a _s of the scale. Calculated to obtain an equivalent scale temperature coefficient errors dK _s is in the formula _{(18) (E c2 -a s} dt s0 L w2) / a s (t s -20) L w2, or the formula (20) {(E _{c2L2 -E c2L1) -a s dt s0} (L w2L1 -L w2L2)} / a s (L w2L1 -L w2L2) corresponding to (t s -20). A positioning error _obtained by correcting the equivalent scale temperature coefficient error dK _s with respect to the positioning error Er 20 is shown in FIG. As described above, by correcting the scale offset error dt _s0 and the equivalent scale temperature coefficient error dK _s , the positioning error can be made 0.5 μm or less.

Then, a temperature sensor 28 _w for measuring the temperature t _w of the step gauge with a low thermal expansion coefficient installed on the base 12 and a calibrated temperature sensor were installed next to each other to acquire temperature data. A correlation diagram of temperature data measured by the temperature sensor 28 w and the calibrated temperature sensor is shown in FIG. FIG. 9 shows the deviation of the temperature sensor 28w from 20 ° C. on the horizontal axis and the deviation from 20 ° C. of the temperature sensor on the vertical axis. From this figure, it can be confirmed that the work offset error dt _w0 is 0.0576 ° C.

Next, the effectiveness of the temperature sensor 28x corrected as described above was confirmed using a steel block gauge as the work W. The block gauge had a nominal dimension of 500 mm, and the length in the X-axis direction was measured under five conditions of different measurement temperatures by changing the measurement date, and the scale error was calculated. The results are shown in FIG. In FIG. 10, the horizontal axis indicates the deviation (° C.) from 20 ° C., and the vertical axis indicates the scale error (μm). Scale error _{E MX} is the calibration value _{L c,} the measured value as _{L w,} determined at E MX ₌ L w -L _c. The scale error E _MX-s-corr is a result of temperature correction using the temperature sensor 28 x of the corrected X-axis scale 24 and obtained using the temperature after correction at t _s of the above equation (10) The measured value was calculated as L _w . Furthermore, the scale error E _MX-corr is a result of temperature correction using the temperature sensor 28 w of the corrected workpiece W, and is obtained using the temperature after correction to t _s and t _w in the above equation (10). It was calculated from the measured value L _w.

In the figure, ● indicates a scale error E _MX , ▲ indicates a scale error E _MX-s-corr , and ○ indicates a scale error E _MX-corr . It can be seen from this figure that the scale error changes in accordance with the deviation from 20 ° C. Moreover, before correcting the temperature sensors 28x and 28w of the X axis scale 24 and the work W, the maximum graduation error was −2.7 (μm) and the standard deviation was 0.59 (μm), but after correction It was confirmed that the maximum graduation error was reduced to -0.8 (.mu.m) and the standard deviation was reduced to 0.27 (.mu.m).

(Example 2)
Based on the measurement results shown in FIG. 4 of the first embodiment, the temperature correction in the case where the difference between the scale temperature t _s and the temperature measured by the calibrated temperature sensor is regarded as the scale offset error dt _s0 was verified. The calibrated temperature sensor was attached to the X axis scale 24 to acquire temperature data. A correlation diagram of temperature data measured by the temperature sensor 28x and the calibrated temperature sensor is shown in FIG. FIG. 11 shows the deviation of the temperature sensor 28x from 20 ° C. on the horizontal axis and the deviation from 20 ° C. of the temperature sensor on the vertical axis. From this figure, the scale offset error dt _s0 is -0.1315 ° C.

FIG. 12 is a graph showing a positioning error E _r obtained by correcting the scale offset error dt _s0 with respect to the positioning error E _{c2 at} temperatures other than the reference temperature. In this figure, the horizontal axis is the measurement position (mm), and the vertical axis is the positioning error (μm). Correction of scale offset error _{dt s0} is the equation (18) in _{(E c2 -a s dt s0 L} w2), or _{(E c2L2} -E _c2L1) in the formula _{(20) -a s dt s0 (} L w2L1 - It corresponds to _Lw2L2 ).

Then, replacing the above positioning error _{E r} a positioning error _{E r20} when the 20 ° C.. The positioning error _Er 20 was calculated by dividing each slope in FIG. 12 by the deviation from 20 ° C. The results are shown in FIG. Calculation for obtaining the positioning error _{E r20,} the above equation in _{(18) (E c2 -a s} dt s0 L w2) / (t s -20), or the formula in _{(20) {(E c2L2 -E} c2L1) - _{a s dt s0 (L w2L1 -L} w2L2)} corresponding to _/ (t s -20). Therefore, the equivalent scale temperature coefficient error dK _s can be obtained by dividing by the thermal expansion coefficient a _s of the above scale.

In this embodiment, the case where the equivalent scale temperature coefficient error dK _s is obtained by the least squares method will be described. The graph shown in FIG. 13 shows one straight line obtained by the least square method from two graphs corresponding to the two conditions of the measurement temperature. Subsequently, the equivalent scale temperature coefficient error dK _s is calculated as 0.020 by dividing the slope (0.00016) of the straight line by the thermal expansion coefficient a _s of the scale. The calculation for obtaining the equivalent scale temperature coefficient error dK _s is (E _r1 −E _r2 ) / (L _{w2 L1} −L _{w2 L2} ) a _s (t _s −20) in the equation (18), or {( _{E c2L2 -E c2L1) -a s dt} s0 (L w2L1 -L w2L2)} / a s (L w2L1 -L w2L2) corresponding to (t s -20). A positioning error _obtained by correcting the equivalent scale temperature coefficient error dK _s with respect to the positioning error Er 20 is shown in FIG. As described above, by correcting the scale offset error dt _s0 and the equivalent scale temperature coefficient error dK _s , it is possible to make the positioning error equal to or smaller than 0.5 μm as in the first embodiment.

  Next, the effectiveness of the temperature sensor 28x corrected as described above was confirmed using the measurement data of the steel block gauge used in Example 1. The results are shown in FIG. FIG. 15 shows the deviation (° C.) from 20 ° C. on the horizontal axis, and the scale error (μm) on the vertical axis.

In the figure, ● indicates a scale error E _MX , ▲ indicates a scale error E _MX-s-corr , and ○ indicates a scale error E _MX-corr . It can be seen from this figure that the scale error changes in accordance with the deviation from 20 ° C. Moreover, before correcting the temperature sensors 28x and 28w of the X axis scale 24 and the work W, the maximum graduation error was −2.7 (μm) and the standard deviation was 0.59 (μm), but after correction It was confirmed that the maximum calibration error was reduced to -1.0 (.mu.m) and the standard deviation was reduced to 0.33 (.mu.m), and results equivalent to those of Example 1 were obtained.

1 Three-Dimensional Measuring Machine 30 Control Device 32 Temperature Calculation Unit 34 Temperature Correction Unit 36 Displacement Calculation Unit 38 Temperature Correction Device

Claims (9)

Assuming that the thermal expansion coefficient of the scale is a _s , the temperature of the scale is t _s , and the graduation error is E _c ,
Measured value L _w1 of nominal dimension L with known thermal expansion coefficient at reference temperature (20 ° C. ± 0.5 ° C.) and scale error E _c1 of measured value L _w1 using the following formula (1) for scale offset Calculating the difference between the temperature of the scale measured by the thermometer which has calculated or calibrated the error dt _s0 and the temperature measured by the thermometer of the scale as the scale offset error dt _s0 ;
Under the temperature environment different from the reference temperature, the equivalent scale temperature coefficient error using the following equation (2) based on the measured value L _w2 of the nominal dimension L whose thermal expansion coefficient is known and the scale error E _c2 of the measured value L _w2 calculating the temperature dK _s .
dt _s0 = E _c1 / a _s L _w1 (1)
dK _s = (E _c2 −a _s dt _s0 L _w2 ) / a _s (t _s −20) L _w2 (2) When the measurement value L _W1 is a plurality of measurement values L _W1L1 and L _W1L2 having different nominal dimensions L whose thermal expansion coefficients are known, and the graduation error E _C1 are E _{C1 L1} and E _{C1 L2} , the above equation (1) Is represented by the following formula (3),
The measured value _{L W2,} thermal expansion coefficient is a known nominal dimension L is different measurements _{L W2L1, L W2L2,} and, when the scale error _{E C2} and _{E C2L1, E C2L2,} the formula (2) The temperature correction method of the coordinate measuring machine according to claim 1, wherein is expressed by the following equation (4).
dt _s0 = ( _{Ec1L1 -Ec1L2} ) / ( _{Lw1L1 -Lw1L2} ) a _s (3)
_{dK s = {(E c2L2 -E} c2L1) -a s dt s0 (L w2L1 -L w2L2)} / a s (L w2L1 -L w2L2) (t s -20) ··· (4) The method according to claim 1 or 2, further comprising the step of changing the temperature t _{s of} each scale to the corrected temperature t _s ^* calculated using the following equation (5).
^{_{t s * = (1 + dK}} s) t s + dt s0 ··· (5) For the computer,
Assuming that the thermal expansion coefficient of the scale is a _s , the temperature of the scale is t _{s, and the} graduation error is E _c ,
Measured value L _w1 of nominal dimension L with known thermal expansion coefficient at reference temperature (20 ° C. ± 0.5 ° C.) and scale error E _c1 of measured value L _w1 using the following formula (1) for scale offset Calculating the difference between the temperature of the scale measured by the thermometer which has calculated or calibrated the error dt _s0 and the temperature measured by the thermometer of the scale as the scale offset error dt _s0 ;
Under the temperature environment different from the reference temperature, the equivalent scale temperature coefficient error using the following equation (2) based on the measured value L _w2 of the nominal dimension L whose thermal expansion coefficient is known and the scale error E _c2 of the measured value L _w2 and a step of calculating dK _s .
dt _s0 = E _c1 / a _s L _w1 (1)
dK _s = (E _c2 −a _s dt _s0 L _w2 ) / a _s (t _s −20) L _w2 (2) When the measurement value L _W1 is a plurality of measurement values L _W1L1 and L _W1L2 having different nominal dimensions L whose thermal expansion coefficients are known, and the graduation error E _C1 are E _{C1 L1} and E _{C1 L2} , the above equation (1) Is represented by the following formula (3),
The measured value _{L W2,} thermal expansion coefficient is a known nominal dimension L is different measurements _{L W2L1, L W2L2,} and, when the scale error _{E C2} and _{E C2L1, E C2L2,} the formula (2) The temperature correction program of the coordinate measuring machine according to claim 4, wherein is expressed by the following equation (4).
dt _s0 = ( _{Ec1L1 -Ec1L2} ) / ( _{Lw1L1 -Lw1L2} ) a _s (3)
_{dK s = {(E c2L2 -E} c2L1) -a s dt s0 (L w2L1 -L w2L2)} / a s (L w2L1 -L w2L2) (t s -20) ··· (4) The temperature correction program for a coordinate measuring machine according to claim 4 or 5, further comprising the step of changing the temperature t _{s of} each scale to the corrected temperature t _s ^* calculated using the following equation (5). .
^{_{t s * = (1 + dK}} s) t s + dt s0 ··· (5) Assuming that the thermal expansion coefficient of the scale is a _s , the temperature of the scale is t _{s, and the} graduation error is E _c ,
Measured value L _w1 of nominal dimension L with known thermal expansion coefficient at reference temperature (20 ° C. ± 0.5 ° C.) and scale error E _c1 of measured value L _w1 using the following formula (1) for scale offset The difference between the temperature of the scale measured by the thermometer which has calculated or calibrated the error dt _s0 and the temperature measured by the thermometer of the scale is taken as the scale offset error dt _s0
Under the temperature environment different from the reference temperature, the equivalent scale temperature coefficient error using the following equation (2) based on the measured value L _w2 of the nominal dimension L whose thermal expansion coefficient is known and the scale error E _c2 of the measured value L _w2 A coordinate measuring machine with a temperature correction function characterized by comprising a controller for calculating dK _s .
dt _s0 = E _c1 / a _s L _w1 (1)
dK _s = (E _c2 −a _s dt _s0 L _w2 ) / a _s (t _s −20) L _w2 (2) When the measurement value L _W1 is a plurality of measurement values L _W1L1 and L _W1L2 having different nominal dimensions L whose thermal expansion coefficients are known, and the graduation error E _C1 are E _{C1 L1} and E _{C1 L2} , the above equation (1) Is represented by the following formula (3),
The measured value _{L W2,} thermal expansion coefficient is a known nominal dimension L is different measurements _{L W2L1, L W2L2,} and, when the scale error _{E C2} and _{E C2L1, E C2L2,} the formula (2) The coordinate measuring machine with a temperature correction function according to claim 7, characterized in that is expressed by the following equation (4).
dt _s0 = ( _{Ec1L1 -Ec1L2} ) / ( _{Lw1L1 -Lw1L2} ) a _s (3)
_{dK s = {(E c2L2 -E} c2L1) -a s dt s0 (L w2L1 -L w2L2)} / a s (L w2L1 -L w2L2) (t s -20) ··· (4) 9. The coordinate measuring machine with a temperature correction function according to claim 7, further comprising changing the temperature t _{s of} each scale to a corrected temperature t _s ^* calculated using the following equation (5).
^{_{t s * = (1 + dK}} s) t s + dt s0 ··· (5)

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