JP2017037068A - Temperature correction method, temperature correction program, temperature correction device, and coordinate measuring machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature correction method capable of reducing a graduation error, a temperature correction program, a temperature correction device, and a coordinate measurement machine.SOLUTION: A temperature correction method includes: a step of obtaining a graduation error Eof a plurality of workpieces having different nominal sizes L; and a step of calculating an equivalent scale temperature coefficient error dkand a scale offset error dtfrom Expression (1): dk=(E-E)/a(L-L)(t-20) and Expression (2): dt=(EL-EL)/a(L-L), when arepresents a coefficient of thermal expansion of a scale, Lrepresents a measured length, and tis a temperature of the scale when the length Lhas been measured.SELECTED DRAWING: Figure 2

Description

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

ISO 1 defines a standard reference temperature for work geometry specification and verification, and the standard reference temperature is set to 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 temperature of the workpiece and the measuring instrument are equal. As a coordinate measuring machine that measures the length of such a workpiece, for example, in a three-dimensional measuring machine, temperature correction is performed in order to maintain measurement accuracy (for example, Patent Documents 1 to 3). In order to perform temperature correction, the CTE (Coefficient of Thermal Expansion) and the temperature of the scale arranged along each axis constituting the three-dimensional space in the CMM and the workpiece to be measured are known. 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 CTE uncertainty is about ± 1 × 10 ⁻⁶ / ° C. To do. For this reason, the measurement dimension uncertainty due to CTE uncertainty is 3 μm. This uncertainty cannot be corrected as long as it is measured at 23 ° C., and increases as the deviation from 20 ° C. increases.

  Patent Document 1 discloses a temperature correction method in which a temperature is monitored by a temperature sensor mounted on each axis scale and a temperature sensor that measures a workpiece, and a measurement result is converted into a value at 20 ° C. and output. ing. In Patent Documents 2 and 3, temperature correction is performed on the basis of the measured length of a workpiece having a low thermal expansion coefficient and a workpiece that thermally expands, and the reference length and the thermal expansion coefficient of the workpiece stored in advance in the control unit.

Also scale the error E by the conventional method, usually using the work, such as gauge blocks or steps gauge (made of steel), the value L _w and the work length of the measurement of the length of the workpiece as shown in the following formula (100) it represents a ratio of the difference between the calibration value L _c.
E = (L _w −L _c ) / L _c (100)

JP-A-11-190617 Japanese Patent Laid-Open No. 06-229705 Japanese Patent Laid-Open No. 06-229706

  However, the temperature correction method according to the above-mentioned patent document is not yet sufficient, and there is a problem that the scale error is large when the measured length is converted into the length at the standard reference temperature.

Further, the scale error E by the conventional method has not been evaluated for both the scale and the temperature correction of the workpiece, but only the scale offset error (scale magnification error) in which the scale error changes depending on the temperature to be evaluated. because they represent the ratio of the difference between the calibration value L _c of the length of the measurement L _w and the work of the workpiece, the scale offset error is overestimated, there is a problem that.

  Therefore, an object of the present invention is to provide a temperature correction method, a temperature correction program, a temperature correction device, and a coordinate measuring machine that can further reduce a scale error.

Temperature correction method of the coordinate measuring machine according to the present invention, the measurement steps of nominal size L to obtain the scale error E _c of different workpieces, the thermal expansion coefficient of the scale a _s, a length of the L _w the work value, when said scale temperature when measuring the t _s the length L _w, the following formulas (1) and (2), calculates an equivalent scale temperature coefficient error dk _s and scale offset error dt _s0 And a step.
_{dk s = (E c2 -E c1} ) / a s (L w2 -L w1) (t s -20) ··· (1)
_{dt s0 = (E c1 L w2} -E c2 L w1) / a s (L w2 -L w1) ··· (2)

Temperature correction program of the coordinate measuring machine according to the present invention, the computer, the steps of nominal size L to obtain the scale error E _c of different workpieces, the thermal expansion coefficient of the scale a _s, said L _w workpiece the value obtained by measuring the length of, when said scale temperature when measuring the t _s the length L _w, the above equation (1) and (2), the equivalent scale temperature coefficient error dk _s and scale offset error and a step of calculating dt _s0 .

Temperature correction device of the coordinate measuring machine according to the present invention, the nominal dimension L is based on the scale error E _c of different workpieces, the thermal expansion coefficient of the scale a _s, a L _w was measured a length of the workpiece value, when said scale temperature when measuring the t _s the length L _w, from the equation (1) and (2), to calculate the equivalent scale temperature coefficient error dk _s and scale offset error dt _s0 It is characterized by.

  A coordinate measuring machine according to the present invention includes the above temperature correction device.

According to the present invention, the thermometer that measures the temperature of the scale is corrected separately from the thermometer that measures the temperature of the workpiece, based on the scale errors E _c of a plurality of workpieces having different nominal dimensions L. Each thermometer can be corrected more accurately. The three-dimensional measuring machine can further reduce the scale error by performing temperature correction using the thermometer corrected as described above.

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 which shows the structure of the control apparatus which concerns on this embodiment. It is a graph with which it uses for description of a magnification error and an offset error. It is a graph which shows the scale error computed based on the result of having measured the length of a block gauge. It is a graph which shows the result of having calculated the scale error at the time of 20 degreeC, and the scale error after temperature correction based on the result of FIG. It is a graph which shows the result of having measured the temperature of the workpiece | work in the temperature sensor attached to the coordinate measuring machine, and the calibrated temperature sensor. It is a graph which shows the correlation of the result measured with the temperature sensor attached to the coordinate measuring machine and the calibrated temperature sensor based on the result of FIG. It is a graph which shows the result of having performed temperature correction of a scale and a work thermometer using a steel block gauge. It is a perspective view which shows typically the structure of the measuring machine main body used in the Example (Example 2). It is a graph which shows the scale error computed based on the result of having measured the length of a block gauge. Is a graph showing the scale error calculated as a temperature measured by a temperature sensor configured to scale temperature t _s. It is a graph which shows the result of having calculated the scale error at the time of 20 degreeC, and the scale error after temperature correction based on the result of FIG. It is a graph which shows the correlation of the result measured with the temperature sensor attached to the coordinate measuring machine and the calibrated temperature sensor based on the result of FIG. It is a graph which shows the result of having performed temperature correction of a scale and a work thermometer using a steel block gauge.

  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 machine as a coordinate measuring machine includes a measuring machine main body 10 shown in FIG. 1 and a control device to be described later. The measuring machine 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 moving body 16 has a pair of leg portions 15 and a beam portion 17 spanned between the upper ends of the leg portions 15, and the leg portion 15 travels along the Y-axis rail 14. The stage 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 moving body 19 is supported by the X-axis moving body 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 the tip.

  The measuring machine main body 10 includes a Y-axis scale 22 that measures the amount of movement of the probe 20 in the Y-axis direction, an X-axis scale 24 that measures the amount of movement of the probe 20 in the X-axis direction, and the 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. Actually, the measuring instrument main body 10 includes a detector (not shown) that reads the values of the X-axis scale 24, the Y-axis scale 22, and the Z-axis scale 26, respectively. The detector outputs a coordinate signal indicating the read result to the control device 30.

  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 28x is provided on the X-axis scale 24, the temperature sensor 28y is provided on the Y-axis scale 22, the temperature sensor 28z is provided on the Z-axis scale 26, and the temperature sensor 28w is provided on the workpiece W. Each temperature sensor 28 outputs the detected temperature signal to the control device 30.

  FIG. 2 is a block diagram showing the configuration of the control device 30. 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 32 reads various programs such as a basic program and a temperature correction processing program stored in advance, and controls the whole according to these various programs.

  Each temperature sensor 28 and the measuring machine main body 10 are electrically connected to the control device 30. The controller 30 receives the temperature signal output from each temperature sensor 28 and the coordinate signal output from the measuring machine main body 10. As shown in the figure, the coordinate measuring machine 1 includes a measuring machine main body 10, a control device 30, and each temperature sensor 28. The temperature correction device 38 includes each temperature sensor 28, a temperature calculation unit 32, a temperature correction unit 34, and a basic temperature correction unit 35.

Temperature calculating unit 32 converts the input temperature signal to the temperature data to calculate the temperature t _w of the temperature t _s and the workpiece W of the scale. The displacement calculation unit 36 calculates the displacement amount, that is, the length (hereinafter also referred to as “scale reading”) L _s of the probe 20 based on the input coordinate signal. For example, when measuring the length of the workpiece W in the X-axis direction, that is, the distance between two points, when the contact portion at the tip of the probe 20 comes into contact with the workpiece W, a coordinate signal related to the coordinates of the contact portion is measured. The main body 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 way.

Temperature t _s of the scale can be used the measured temperature by the temperature sensor 28 installed in the measuring unit. When using the temperature measured with the temperature sensor 28 installed in the main body of the measuring machine, the temperature sensor 28 preferably has an accuracy of about ± 0.05 ° C. The temperature t _s of scale, the temperature sensor 28 without, it is preferable to use the measured temperature calibrated temperature sensor.

The basic temperature correction unit 35 performs a basic temperature correction process on the scale reading L _s based on the temperature data of each part 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 (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 at each location obtained by the temperature calculation unit 32. First, the temperature correction unit 34 is a temperature sensor provided in each scale based on scale errors E _c at a plurality of lengths of a block gauge having a small thermal expansion coefficient (hereinafter referred to as “block gauge having a low thermal expansion coefficient”) as the workpiece W. 28x, 28y, and 28z are corrected, and then the temperature sensor 28w of the workpiece W is corrected using a separately prepared temperature sensor.

First, a case where the temperature sensors 28x, 28y, and 28z are corrected will be described. When the calibration value of the length of the workpiece W and L _c, the scale error E can be expressed by the following equation (11).

_{E = 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.} Further error in the measured temperature t _s of the scale, the magnification error, and a offset error.

The error of the workpiece W, an error in the thermal expansion coefficient a _w of the workpiece W, an error of the temperature t _w, which is measured by the temperature sensor 28w provided on the workpiece W, is believed to include error calibration values L _c. Further, errors in the measured temperature t _w of the workpiece W includes a magnification error, and a offset error.

  Here, the magnification error and the offset error will be described with reference to FIG. FIG. 3 is a graph showing errors included in the temperature data measured by the temperature sensor. The horizontal axis shows the deviation from 20 ° C. when measured by the temperature sensor provided in the coordinate measuring machine 1, and the vertical axis Deviation from 20 ° C. when measured with a temperature sensor calibrated in the same environment with the axis. In the case of an ideal temperature sensor having no error, the result measured by the temperature sensor provided in the coordinate measuring machine 1 coincides with the result measured by the calibrated temperature sensor. It becomes a straight line with an inclination of 1. On the other hand, when there is an error in the temperature sensor provided in the coordinate measuring machine 1, the measurement result is a straight line with a different inclination or a straight line that does not pass through the origin. Among these, an error appearing in the slope of the straight line is called a magnification error. 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 is indistinguishable because it occurs. Offset error of the magnification error and the temperature t _s of the scale of each scale reading L _s indistinguishable as well. Of error for the workpiece W, the offset error of the temperature t _w of the error and the workpiece W magnification errors, and calibration values L _c of the temperature t _w of the error and the workpiece W in the thermal expansion coefficient a _w of the workpiece W also indistinguishable. In addition, when the calibration value _Lc and the value of the thermal expansion coefficient _aw of the workpiece W can be regarded as known with high accuracy, it can be assumed that there is no error. Therefore, there are four possible temperature sensor errors. That is, the magnification error and the scale of the temperature t _s of the scale consists of error in the thermal expansion coefficient a _s error dK s _{(hereinafter,} referred to as "equivalent scale Temperature factor error"), the temperature t _s of the scale consists of offset error and the magnification error of each scale error dt s0 _{(hereinafter,} referred to as "scale offset error"), is constructed with an error of the thermal expansion coefficients a _w magnification error and the workpiece W in the temperature t _w of the workpiece W that error dk w _{(hereinafter,} referred to as "equivalent work temperature factor error"), and the error correction value L _c of the offset error and the workpiece W in the temperature t _w of the workpiece W error dt w0 _{(hereinafter,} "work offset Called "error").

When the temperature _{t w} of the temperature _{t s} and the workpiece W of each scale to the correct temperature of each scale and the workpiece W, the measured temperature _t ^w of the measured temperature _t ^{s *} and the workpiece W of each scale ^* is represented by the following formula (12), (13).

t _s ^* = (1 + dk _s ) t _s + dt _s0 (12)
t _w ^* = (1 + dk _w ) t _w + dt _w0 (13)

Thereby, the scale error E can be expressed by the following equation (14), where L _w is the measurement value of the workpiece W.

_{E = L w -L c = L} s (1 + a s (t s * -20) -a w (t w * -20)) - L c
_{= A s dt s0 + a s} dk s (t s -20) L w -a w dt w0 -a w dk w (t w -20) L w ··· (14)

When using the block gauge of the low thermal expansion coefficient as the work W, since the thermal expansion coefficient a _w of the workpiece W is 0, the scale error E _c can be represented by the following formula (15).

_{E c = L w -L c =} L s (1 + a s (t s * -20)) - L c
_{= A s dt s0 + a s} dk s (t s -20) L w ··· (15)

Here, at block gauge low thermal expansion coefficient, a plurality of nominal dimensions L are different, in this embodiment, the _L of the two measurements as _{w L w1} and _{L w2,} the scale error _{E c1} and _{E c2} as _{E c,} It can be calculated by the following formulas (16) and (17).

_{E c1 = a s dt s0 +} a s dk s (t s -20) L w1 ··· (16)
_{E c2 = a s dt s0 +} a s dk s (t s -20) L w2 ··· (17)

From this equivalence scale temperature coefficient error dk _s and scale offset error _{dt s0} is the following formula (18) can be calculated by (19).

_{dk s = (E c2 -E c1} ) / a s (L w2 -L w1) (t s -20) ··· (18)
_{dt s0 = (E c1 L w2} -E c2 L w1) / a s (L w2 -L w1) ··· (19)

In this way, the temperature correction unit 34 from the scale error E _c1 and E _c2 differ in a plurality of nominal dimension L of the block gauge of the low thermal expansion coefficient, to obtain an equivalent scale temperature coefficient error dk _s and scale offset error dt _s0. The resulting equivalent scale temperature coefficient errors dk _s, calculates the temperature _{t s} from the scale offset error _{dt s0,} and the equation (12). The temperature calculated in this way is referred to as a corrected temperature _ts-corr . By calculating the corrected temperature ts _-corr for each scale, the temperature sensors 28x, 28y, 28z of each scale can be corrected. Specifically, the temperature sensor 28x, 28y, 28z can be corrected by changing the setting to the corrected temperature ts _-corr .

Next, a plurality of steel block gauges as workpiece W, two lengths L _w1 and L _w2 in the case of this embodiment, are measured and measured by temperature sensors 28x, 28y, 28z corrected as described above. using temperature _{t s,} the scale error _{E M,} can be represented by the following formula (20).

_{E M = L w -L c =} L s (1 + a s (t s -20) -a w (t w * -20)) - L c
_{= -A w dt w0 + a w} dk w (t w -20) L w ··· (20)

From the above equation, the equivalent workpiece temperature coefficient error dk _w and the workpiece offset error dt _w0 can be calculated by the following equations (21) and (22).

_{dk w = - (E M2 -E} M1) / a w (L w2 -L w1) (t w -20) ··· (21)
_{dt w0 = (E M1 L w2} -E M2 L w1) / a w (L w2 -L w1) ··· (22)

  Thus, the temperature correction unit 34 can correct the temperature sensor 28w of the workpiece W using the corrected temperature sensor 28x.

Incidentally, the error of thermal expansion coefficients a _w of the workpiece W contained in the equivalent work temperature coefficient errors dk _w Since vary workpiece W of interest to be able separated magnification error of the workpiece W, the equivalent of the temperature sensor 28w work Correction by the temperature coefficient error dk _w is not possible. Therefore, in this embodiment, the equivalent work temperature coefficient error dk _w is ignored.

Error calibration values _{L c} of the work W contained in the work offset error _{dt w0} is the case of 500mm block gauge (K grade), 0.14 .mu.m: Since a (JIS B 7506 2004), the work offset error _{dt w0} It is considered that the effect is small. Thus in the present embodiment, the error of the calibration values L _c of the work W is to be ignored. As described above, the temperature correction unit 34 calculates the workpiece offset error dt _w0 , that is, the corrected temperature tw _−corr by comparing the temperature sensor 28 _w that measures the temperature tw of the workpiece W with the calibrated temperature sensor. The temperature sensor 28w is corrected.

Controller 30, the correction temperature sensor 28 the temperature t _s of the scale as measured _by, based on the temperature t _w of the workpiece W, the measured value of the workpiece W subjected to temperature correction for scale reading L _{s Lw} is calculated.

(2) Operation and Effect Using the coordinate measuring machine 1 configured as described above, the temperature sensors 28x, 28y, and 28z are corrected, the temperature sensor 28w is corrected using the calibrated temperature sensor, and these corrections are made. A procedure for correcting the temperature of the scale reading L _s at the temperature measured using each temperature sensor 28 will be described.

First, as the workpiece W, two or more lengths having different nominal dimensions L of a block gauge having a low thermal expansion coefficient are measured. Specifically, the block 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 block gauge are detected. The detection result is output from the measuring machine body 10 to the control device 30 as a coordinate signal. The control device 30 calculates the length L _s of the block gauge in the X-axis direction based on the obtained two-point coordinate signals. Repeating the block gauge of this procedure is the nominal dimension L different, obtaining two or more different length L _s.

Next, for each obtained length L _s , the control device 30 sets the calibration value of the block gauge as L _c , the measured value calculated from the above equation (10) as L _w , and the scale error E _c as E _c = L calculated respectively _w -L _c. Since the used workpiece W is a block gauge having a low thermal expansion coefficient, the scale error E _c can be said to be an error caused by the X-axis scale 24 when it is considered that the workpiece W does not thermally expand regardless of the temperature.

Furthermore, the control device 30, from the calculated scale error _{E c,} the equation (18), using (19), calculates an equivalent scale temperature coefficient error dk _s and scale offset error _{dt s0.} The temperature sensor 28x is corrected by calculating the corrected temperature t _s-corr from the obtained equivalent scale temperature coefficient error dk _s , scale offset error dt _s0 , and the above equation (15). Similarly, the temperature sensors 28y and 28z are corrected for the Y-axis scale 22 and the Z-axis scale 26.

Next, the control device 30 receives temperature signals from a calibrated temperature sensor different from the temperature sensor 28 attached to the coordinate measuring machine 1 and a temperature sensor 28 w that measures the temperature of the workpiece W. In this way, the control device 30 compares the temperature data of the calibrated temperature sensor with the temperature data of the temperature sensor 28w of the workpiece W, and calculates the workpiece offset error dt _w0 , that is, the corrected temperature tw _-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, the above manner corrected temperature sensors 28x, 28y, 28z, using 28w, a _{t s} a corrected temperature _{t s-corr,} and the corrected temperature _{t w-corr} the _{t w} Thus, the temperature correction is performed on the reading L _{s of} each scale using the above equation (10), and the measured value L _w is calculated.

  The temperature correction device 38 according to the present embodiment corrects each temperature sensor 28 more accurately by individually correcting the temperature sensors 28x, 28y, and 28z of each scale and the temperature sensor 28w of the workpiece W. be able to. The coordinate measuring machine 1 can further reduce the scale error by performing temperature correction at the temperature measured using each temperature sensor 28 corrected as described above.

The formula (18), is calculated using (19), the equivalent scale temperature coefficient error dk _s and scale offset error dt _s0 is caused by deviation from the standard reference temperature, and the magnification error shown in various error (FIG. 3 Offset error). Accordingly, the temperature correction device 38, the equation (18), using (19), by calculating the equivalent scale temperature coefficient error dk _s and scale offset error _{dt s0,} various error included in scale reading _{L s} Can be removed by temperature correction.

In the above embodiment, the method of correcting the temperature by correcting the temperature sensors 28x, 28y, and 28z of each scale described above based on the equivalent scale temperature coefficient error dk _s and the scale offset error dt _s0 has been described. Is not limited to this, and the temperature may be corrected by correcting the thermal expansion coefficient of each scale. In order to correct the thermal expansion coefficient of each scale, first, the inherent thermal expansion coefficient a _s ^* of the scale is calculated by the following formula (23), and the correct scale reading L _s ^* is calculated by the following formula (24).

a _s ^* = (dk _s × a _s ) + a _s (23)
L _s ^* = L _s + (dt _s0 × a _s ) (24)

Based on a _s ^* and L _s ^* obtained as described above, the measured value L _w of the workpiece W can be obtained by the following formula (25).

_{^{L w = L s * (1}} + a s * (t s -20) -a w (t w -20)) ··· (25)

Measurements _{L w} of the workpiece W obtained by the above formula (25), the temperature sensor 28x according to the above embodiment, 28y, is substantially the same as the measured value _{L w} obtained by correcting 28z.

2. Example (Example 1)
Indeed, using the block gauge of the low thermal expansion coefficient as the work W, to calculate the equivalent scale temperature coefficient error dk _s and scale offset error dt _s0. Three types of block gauges having nominal sizes of 200 mm, 400 mm, and 600 mm were prepared. In addition, the length in the X-axis direction was measured under four conditions with different measurement temperatures by changing the measurement date, and a scale error was calculated. Scale temperature t _s was the temperature measured by temperature sensor 28x. The result is shown in FIG. In FIG. 4, the horizontal axis is the nominal size (mm) of the block gauge, and the vertical axis is the scale error (μm). Scale error can be expressed calibration value of the block gauge _{L c,} the measured value of the workpiece W in _{L w,} the scale error Then _{E c, E c = L w} -L c.

Then, the equation (18), using (19), to calculate the equivalent scale temperature coefficient error dk _s and scale offset error _{dt s0.} When the thermal expansion coefficient _{a s} the X-axis scale 24 and 10.44 × ^{10 -6} / ℃, the equivalent scale temperature coefficient errors dk _s is 0.042, the scale offset error _{dt s0} was -0.139.

And based on the corrected temperature t _s-corr temperature correcting the measurement results using the above equation (10), shown in Figure 5 the result of calculating the scale error E _c. In FIG. 5, the horizontal axis is the nominal size (mm) of the block gauge, and the vertical axis is the scale error (μm) when it is 20 ° C. Incidentally straight line in the figure, the measurement results based on the temperature sensor before correction, a memory error E ₂₀ calculated in terms of 20 ° C.. Scale error E ₂₀ was calculated by dividing the deviation from 20 ° C. coefficients x of a straight line shown in FIG. As apparent from the figure, by correcting the temperature sensor of the X-axis scale 24, scale error E _c it was confirmed that reduced to 0.5μm or less.

Then, a temperature sensor 28w for measuring the temperature t _w of the block gauge low thermal expansion coefficient is placed on the base 12, established a calibrated temperature sensor next to the results obtained temperature data, shown in FIG. 6 . In FIG. 6, the horizontal axis is time, the vertical axis is temperature (° C.), tw is the temperature measured by the temperature sensor 28 _w , and _twX is the temperature measured by the calibrated temperature sensor. From this figure, it was confirmed that the magnification error of the temperature sensor 28w was about 0.01 ° C. with respect to a temperature change of 10 ° C. and was extremely small.

FIG. 7 shows a correlation diagram between the temperature sensor 28w and temperature data measured by the calibrated temperature sensor. FIG. 7 shows the deviation from 20 ° C. of the temperature sensor 28 w on the horizontal axis, and the deviation from 20 ° C. of the calibrated temperature sensor on the vertical axis. From this figure, it was confirmed that the offset error dt _w0 was 0.170 ° C.

Next, the effectiveness of the temperature sensor 28x corrected as described above was confirmed using a steel block gauge as the workpiece W. A block gauge having a nominal size of 600 mm was used, the length in the X-axis direction was measured under six conditions with different measurement temperatures by changing the measurement date, and the scale error was calculated. The result is shown in FIG. In FIG. 8, the horizontal axis indicates a deviation (° C.) from 20 ° C., and the vertical axis indicates a 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. Scale error _{E MX-s-corr} is a result of the temperature correction using the temperature sensor 28x of the corrected X-axis scale 24 was obtained using the corrected temperature _{t s} of the above formula (10) the measured values were calculated as L _w. Further scale error _{E MX-corr} is a result of the temperature correction using the temperature sensor 28w of the corrected workpiece W, using a _{t s,} and _{t w} the corrected temperature of the above formula (10) obtained and it was calculated using the measured values 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 . From this figure, it can be seen that the scale error changes according to the deviation from 20 ° C. The maximum scale error was 3.0 (μm) and the standard deviation was 2.04 (μm) before correcting the temperature sensors 28x and 28w of the X-axis scale 24 and the workpiece W. It was confirmed that the graduation error was reduced to -1.3 (μm) and the standard deviation was reduced to 1.03 (μm).

(Example 2)
Next, as shown in FIG. 9, using steps gauge low coefficient of thermal expansion as the work W, to calculate the equivalent scale temperature coefficient error dk _s and scale offset error dt _s0. In addition, the length in the X-axis direction was measured under two conditions with different measurement temperatures by changing the measurement date, and a scale error was calculated. Scale temperature t _s indicates the result of the temperature measured by the temperature sensor 28x in FIG. In FIG. 10, the horizontal axis represents the nominal size (mm) of the step gauge, and the vertical axis represents the scale error (μm). The scale error can be expressed as E _c = L _w −L _c, where the calibration value of the step gauge is L _c , the measured value of the workpiece W is L _w , and the scale error is E _c . In this figure, the scale temperature _{t s} is 15.88 ° C. and 26.50 ° C., the absolute value of the slope of the line is significantly different. This is believed to be due to the scale temperature t _s as measured by the temperature sensor 28x contains a large error.

So by using the temperature measured by a calibrated temperature sensor as a scale temperature t _s, it was calculated scale error. When the temperature measured by the temperature sensor 28x was 15.88 ° C., the difference from the temperature measured by the calibrated temperature sensor was 0.14 ° C. When the temperature measured by the temperature sensor 28x was 26.50 ° C., the difference from the temperature measured by the calibrated temperature sensor was 0.12 ° C. The result is shown in FIG. From this figure, by using the temperature measured by a calibrated temperature sensor as a scale temperature t _s, an absolute value of the slope of the line is almost the same value.

Then, the equation (18), using (19), to calculate the equivalent scale temperature coefficient error dk _s and scale offset error _{dt s0.} When the thermal expansion coefficient _{a s} the X-axis scale 24 and 8.0 × ^{10 -6} / ℃, the equivalent scale temperature coefficient errors dk _s 0.025, the scale offset error _{dt s0} was 0.130.

Further, FIG. 12 shows the result of calculating the scale error E _c by correcting the temperature of the measurement result using the above equation (10) based on the corrected temperature t _s-corr . In FIG. 12, the horizontal axis is the nominal size (mm) of the step gauge, and the vertical axis is the scale error (μm) when it is 20 ° C. Incidentally straight line in the figure, the measurement results based on the temperature sensor before correction, a memory error E ₂₀ calculated in terms of 20 ° C.. Scale error E ₂₀ was calculated by dividing the deviation from 20 ° C. coefficients of linear x shown in FIG. 11. As apparent from the figure, by correcting the temperature sensor of the X-axis scale 24, scale error E _c it was confirmed that reduced to 0.5μm or less.

FIG. 13 shows a correlation diagram between the temperature sensor 28w and the temperature data measured by the calibrated temperature sensor. FIG. 13 shows the deviation from 20 ° C. of the temperature sensor 28 w on the horizontal axis, and the deviation from 20 ° C. of the calibrated temperature sensor on the vertical axis. From this figure, it was confirmed that the offset error dt _w0 was 0.0576 ° C.

Next, the effectiveness of the temperature sensor 28x corrected as described above was confirmed using a steel block gauge as the workpiece W. A block gauge having a nominal size of 500 mm was used, the length in the X-axis direction was measured under five conditions with different measurement temperatures by changing the measurement date, and the scale error was calculated. The result is shown in FIG. In FIG. 14, the horizontal axis indicates deviation from 20 ° C. (° C.), and the vertical axis indicates 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. Scale error _{E MX-s-corr} is a result of the temperature correction using the temperature sensor 28x of the corrected X-axis scale 24 was obtained using the corrected temperature _{t s} of the above formula (10) the measured values were calculated as L _w. Further scale error _{E MX-corr} is a result of the temperature correction using the temperature sensor 28w of the corrected workpiece W, using a _{t s,} and _{t w} the corrected temperature of the above formula (10) obtained and it was calculated using the measured values L _w.

In the figure, ● represents a scale error E _MX , ▲ represents a scale error E _MX-s-corr , and ○ represents a scale error E _MX-corr . From this figure, it can be seen that the scale error changes according to the deviation from 20 ° C. The maximum scale error was -2.7 (μm) and the standard deviation was 0.59 (μm) before correcting the temperature sensors 28x and 28w of the X-axis scale 24 and the workpiece W. It was confirmed that the maximum graduation error was reduced to -1.2 (μm) and the standard deviation was decreased to 0.49 (μm).

3. The present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the gist of the present invention.

In the above embodiment, by measuring a plurality of lengths using the block gauge of the low thermal expansion coefficient as the work W, it is assumed that calculates an equivalent scale temperature coefficient error dk _s and scale offset error dt _s0, the present invention Is not limited to this. For example, the value of the thermal expansion coefficient using a known block gauge with high accuracy, by measuring a plurality of lengths, may be calculated equivalent scale temperature coefficient error dk _s and scale offset error dt _s0.

In this case, the error of the thermal expansion coefficient aw of the workpiece W included in the equivalent workpiece temperature coefficient error dk _w can be ignored. Since the magnification error of the temperature t _w of the workpiece W can be regarded as substantially zero than 7, the equation (14) can be omitted the section dk _w, the following equation (26).

_{E = a s dt s0 + a} s dk s (t s -20) L w -a w dt w0 ··· (26)

In the above equation, the work offset error dt _w0 can be obtained with a calibrated temperature sensor. Thus since the thermal expansion coefficient a _w of the block gauge is known, it is possible to calculate the equivalent scale temperature coefficient error dk _s and scale offset error dt _s0 from the above equation (26).

In the above embodiment, the temperature sensor 28w for measuring the temperature t _w of the workpiece W, but it was decided to calculate the work offset error dt _w0 by comparing with calibrated temperature sensors, the present invention is not limited thereto .

DESCRIPTION OF SYMBOLS 1 CMM 30 Control apparatus 32 Temperature calculation part 34 Temperature correction part 36 Displacement calculation part 38 Temperature correction apparatus W Workpiece

Claims (16)

Obtaining scale errors E _c for a plurality of workpieces having different nominal dimensions L;
thermal expansion coefficient of the scale a _s, L _w a value obtained by measuring the length of the workpiece, when said scale temperature when measuring the t _s the length L _w, the following formula (1) and (2 ) from the temperature correction method of the coordinate measuring machine, characterized in that it comprises the step of calculating the equivalent scale temperature coefficient error dk _s and scale offset error dt _{s0.
dk s = (E c2 -E c1} ) / a s (L w2 -L w1) (t s -20) ··· (1)
_{dt s0 = (E c1 L w2} -E c2 L w1) / a s (L w2 -L w1) ··· (2) Temperature t _s of the scale, the temperature correction method of the coordinate measuring machine according to claim 1, characterized in that the measured temperature calibrated thermometer. Furthermore, from the following formula (3), calculating the inherent thermal expansion coefficient a _s ^* of the scale,
3. The temperature correction of a coordinate measuring machine according to claim 1, further comprising a step of calculating a correct scale reading L _s ^* from the following equation (4), where L _s is the scale reading: Method.
a _s ^* = (dk _s × a _s ) + a _s (3)
L _s ^* = L _s + (dt _s0 × a _s ) (4) The temperature correction method for a coordinate measuring machine according to claim 1, further comprising a step of calculating a corrected temperature t _s-corr from the following equation (5).
_{E c = a s dt s0 +} a s dk s (t s-corr -20) L w ··· (5) Further the temperature t _w of the workpiece, calibrated temperature correction method of the coordinate measuring machine according to any one of claims 1-4, characterized in that it comprises a step of correcting the measured temperature thermometer. Against the computer,
Obtaining scale errors E _c for a plurality of workpieces having different nominal dimensions L;
thermal expansion coefficient of the scale a _s, L _w a value obtained by measuring the length of the workpiece, when said scale temperature when measuring the t _s the length L _w, the following formula (1) and (2 ) from the equivalent scale temperature coefficient error dk _s and temperature correction program coordinate measuring machine, characterized in that and a step of calculating the scale offset error dt _{s0.
dk s = (E c2 -E c1} ) / a s (L w2 -L w1) (t s -20) ··· (1)
_{P b = (E c1 L w2} -E c2 L w1) / a s (L w2 -L w1) ··· (2) Temperature t _s of the scale, temperature correction program coordinate measuring machine according to claim 6, characterized in that the temperature measured by the calibrated thermometer. Furthermore, from the following formula (3), calculating the inherent thermal expansion coefficient a _s ^* of the scale,
8. The temperature of the coordinate measuring machine according to claim 6, wherein when L _s is the scale reading, a step of calculating a correct scale reading L _s ^* from the following equation (4) is executed: Correction program.
a _s ^* = (dk _s × a _s ) + a _s (3)
L _s ^* = L _s + (dt _s0 × a _s ) (4) The temperature correction program for a coordinate measuring machine according to claim 6 or 7, wherein a step of calculating a corrected temperature _ts-corr is executed from the following equation (5).
_{E c = a s dt s0 +} a s dk s (t s-corr -20) L w ··· (5) Further the temperature t _w of the workpiece, calibrated temperature correction program coordinate measuring machine according to any one of claims 6-9, characterized in that to perform the step of correcting the measured temperature thermometer. Based on the scale error E _c of a plurality of workpieces having different nominal dimensions L,
thermal expansion coefficient of the scale a _s, L _w a value obtained by measuring the length of the workpiece, when said scale temperature when measuring the t _s the length L _w, the following formula (1) and (2 ) from the temperature correcting apparatus of the coordinate measuring machine and calculating the equivalent scale temperature coefficient error dk _s and scale offset error dt _{s0.
dk s = (E c2 -E c1} ) / a s (L w2 -L w1) (t s -20) ··· (1)
_{dt s0 = (E c1 L w2} -E c2 L w1) / a s (L w2 -L w1) ··· (2) The temperature t _s of scale, the temperature correcting apparatus of the coordinate measuring machine according to claim 11, characterized in that the temperature measured by the calibrated thermometer. Furthermore, from the following formula (3), the intrinsic thermal expansion coefficient a _s ^* of the scale is calculated,
13. The temperature correction apparatus for a coordinate measuring machine according to claim 11 or 12, wherein when L _s is the scale reading, a correct scale reading L _s ^* is calculated from the following equation (4).
a _s ^* = (dk _s × a _s ) + a _s (3)
L _s ^* = L _s + (dt _s0 × a _s ) (4) The temperature correction device for a coordinate measuring machine according to claim 11 or 12, further comprising calculating a corrected temperature _ts-corr from the following equation (5).
_{E c = a s dt s0 +} a s dk s (t s-corr -20) L w ··· (5) Further the temperature t _w of the workpiece, the temperature correcting apparatus of the coordinate measuring machine according to any one of claims 11 to 14, characterized in that to correct the temperature measured by calibrated thermometer. A coordinate measuring machine comprising the temperature correction device according to claim 11.

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