Evaluation system, evaluation method, and correction method for coordinate measuring machine

Abstract

To evaluate an error related to thermal expansion correction in a coordinate measuring machine.SOLUTION: The evaluation system 100 includes the laser length measuring device 110, the scale high-accuracy thermometer 126, and the evaluation controller 130, and the evaluation controller 130 obtains the scale offset errors dtS0 based on the temperature of the scale 24 measured by the scale thermometer 26 and the temperature of the scale 24 measured by the scale high-accuracy thermometer 126. Based on the obtained scale offset errors dtS0, the moving amount LS of the moving body measured by the scale 24, the moving amount LM of the moving body measured by the laser length measuring machine 110, and the temperature tS of the scale 24 measured by the scale thermometer 26, equivalent scale temperature coefficient errors dkS are obtained.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an evaluation system, an evaluation method, and a correction method for a coordinate measuring machine. [Background technology]

[0002] Coordinate measuring machines are widely used in the machinery industry as measuring machines for measuring the shape, dimensions, position, etc. of machine parts. To ensure the quality of the objects being measured, there is a demand for higher accuracy in coordinate measuring machines.

[0003] Patent Document 1 discloses a coordinate measuring machine equipped with a temperature detection means, in which measured coordinate values ​​are corrected based on the temperature measured by the temperature detection means, the thermal expansion coefficient of the scale, and the thermal expansion coefficient of the workpiece. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-190617 Summary of the Invention [Problem to be solved by the invention]

[0005] In the coordinate measuring machine disclosed in Patent Document 1, the measured values ​​are corrected in accordance with temperature changes, assuming that there is no error in the thermal expansion coefficient of the scale and the temperatures of the scale and workpiece measured by the temperature detection means. However, in reality, the thermal expansion coefficient of the scale and the temperatures of the scale and workpiece measured by the temperature detection means contain errors. If these errors are large, it is not possible to appropriately correct the thermal expansion caused by temperature changes, and the measurement accuracy of the coordinate measuring machine decreases. For these reasons, there is a need to evaluate errors related to thermal expansion correction, such as errors in the thermal expansion coefficient of the scale and errors in the thermometer.

[0006] Therefore, an object of the present invention is to evaluate errors related to thermal expansion compensation in a coordinate measuring machine. [Means for solving the problem]

[0007] The present invention is a system for evaluating a coordinate measuring machine equipped with a scale that measures the amount of movement of a moving body, a scale thermometer that measures the temperature of the scale, and a work thermometer that measures the temperature of a workpiece, and includes a laser length measuring device that measures the amount of movement of the moving body, a scale high-precision thermometer that measures the temperature of the scale with higher measurement accuracy than the scale thermometer, and an evaluation control unit that evaluates the scale thermometer, wherein the evaluation control unit determines a scale offset error, which is an offset error of the temperature of the scale measured by the scale thermometer, based on the temperature of the scale measured by the scale thermometer and the temperature of the scale measured by the scale high-precision thermometer, and determines an equivalent scale temperature coefficient error, which is an error in the thermal expansion coefficient of the scale, based on the determined scale offset error, the amount of movement of the moving body measured by the scale, the amount of movement of the moving body measured by the laser length measuring device, and the temperature of the scale measured by the scale thermometer.

[0008] The present invention also provides a method for evaluating a coordinate measuring machine equipped with a scale that measures the amount of movement of a moving body, a scale thermometer that measures the temperature of the scale, and a work thermometer that measures the temperature of a workpiece, the method comprising: determining a scale offset error, which is an offset error of the temperature of the scale measured by the scale thermometer, based on the temperature of the scale measured by the scale thermometer and the temperature of the scale measured by a high-precision scale thermometer that has higher measurement accuracy than the scale thermometer; and determining an equivalent scale temperature coefficient error, which is an error in the thermal expansion coefficient of the scale, based on the determined scale offset error, the amount of movement of the moving body measured by the scale, the amount of movement of the moving body measured by a laser length measuring device, and the temperature of the scale measured by the scale thermometer. [Effects of the Invention]

[0009] According to the present invention, the error of the scale thermometer of the coordinate measuring machine and the error of the thermal expansion coefficient of the scale of the coordinate measuring machine are calculated together, so that the error of the scale thermometer of the coordinate measuring machine and the error of the thermal expansion coefficient of the scale of the coordinate measuring machine can be evaluated together, and errors related to thermal expansion compensation in the coordinate measuring machine can be evaluated. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view schematically showing a coordinate measuring machine 10 to be evaluated using an evaluation system according to the present invention. [Figure 2] FIG. 2 is a block diagram showing the configuration of the coordinate measuring machine shown in FIG. [Figure 3] 1 is a perspective view schematically illustrating an evaluation system 100 according to the present invention. [Figure 4] FIG. 4 is a block diagram showing the configuration of the evaluation system shown in FIG. 3. [Figure 5] 10 is a graph illustrating a magnification error and an offset error of the temperature of a scale measured by a scale thermometer. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an evaluation system and an evaluation method according to an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, X, Y, and Z axes are appropriately shown as three-dimensional orthogonal axes. The Z axis is an axis along the vertical direction, the X axis is an axis perpendicular to the Z axis, and the Y axis is an axis perpendicular to the X and Z axes.

[0012] The evaluation system and evaluation method are used to evaluate measurement errors in a coordinate measuring machine 10. First, the configuration of the coordinate measuring machine 10 will be described with reference to Figures 1 and 2. The coordinate measuring machine 10 measures the coordinates of a workpiece W and determines the length of the workpiece W.

[0013] Because objects tend to expand due to heat, ISO 1 specifies 20°C as the reference temperature for specifying and verifying the geometric characteristics of objects. When the length of an object is measured in a temperature environment different from the reference temperature, the measured length of the object must be corrected to the length under the reference temperature environment. The coordinate measuring machine 10 is configured to be able to correct the measured length of the workpiece W to the length under the reference temperature environment.

[0014] Fig. 1 is a perspective view showing a coordinate measuring machine 10. As shown in Fig. 1, the coordinate measuring machine 10 includes a base 12, a Y-axis rail 14, a Y-axis direction movable body 16y, an X-axis direction movable body 16x, and a Z-axis direction movable body 16z. A workpiece W is placed on the base 12.

[0015] The Y-axis rail 14 is provided on the base 12 along the Y-axis. The Y-axis mover 16y has a pair of legs 15 spaced apart from each other in the X-axis direction, and a beam 17 spanning between the upper ends of the pair of legs 15. When the legs 15 move along the Y-axis rail 14, the beam 17 moves on the base 12 in the Y-axis direction.

[0016] The X-axis direction movable body 16x is supported by the beam portion 17 of the Y-axis direction movable body 16y so as to be movable in the X-axis direction. The Z-axis direction movable body 16z is supported by the X-axis direction movable body 16x so as to be movable in the Z-axis direction. The Z-axis direction movable body 16z holds a probe 22 at its tip. In the following, the X-axis direction movable body 16x, the Y-axis direction movable body 16y, and the Z-axis direction movable body 16z may be collectively referred to as movable body 16.

[0017] The coordinate measuring machine 10 includes an X-axis scale 24x that measures the X-axis movement amount of the X-axis mover 16x, a Y-axis scale 24y that measures the Y-axis movement amount of the Y-axis mover 16y, and a Z-axis scale 24z that measures the Z-axis movement amount of the Z-axis mover 16z. The X-axis scale 24x is provided on the beam portion 17, the Y-axis scale 24y is provided on the Y-axis rail 14, and the Z-axis scale 24z is provided on the Z-axis mover 16z. Hereinafter, the X-axis scale 24x, the Y-axis scale 24y, and the Z-axis scale 24z may be collectively referred to as scales 24.

[0018] The amount of movement in the X-axis direction of the X-axis mover 16x corresponds to the amount of movement in the X-axis direction of the probe 22, the amount of movement in the Y-axis direction of the Y-axis mover 16y corresponds to the amount of movement in the Y-axis direction of the probe 22, and the amount of movement in the Z-axis direction of the Z-axis mover 16z corresponds to the amount of movement in the Z-axis direction of the probe 22. In other words, the amount of movement of the mover 16 corresponds to the amount of movement of the probe 22. Therefore, the coordinates of the workpiece W can be measured by using the amount of movement of the probe 22 when the probe 22 comes into contact with the workpiece W.

[0019] The coordinate measuring machine 10 is equipped with an X-axis scale thermometer 26x, a Y-axis scale thermometer 26y, and a Z-axis scale thermometer 26z that measure the temperatures of the X-axis scale 24x, the Y-axis scale 24y, and the Z-axis scale 24z, respectively, and a work thermometer 26w that measures the temperature of the workpiece W. The X-axis scale thermometer 26x, the Y-axis scale thermometer 26y, and the Z-axis scale thermometer 26z are provided on the X-axis scale 24x, the Y-axis scale 24y, and the Z-axis scale 24z, respectively. The work thermometer 26w is provided on the workpiece W.

[0020] In the following, the X-axis scale thermometer 26x, the Y-axis scale thermometer 26y, and the Z-axis scale thermometer 26z may be collectively referred to as the scale thermometer 26.

[0021] The scale thermometer 26 and the work thermometer 26w are, for example, thermistors, but may also be thermocouples.

[0022] 1, the X-axis scale thermometer 26x is disposed near the middle of the X-axis scale 24x in the X-axis direction, but it may also be disposed near one end of the X-axis scale 24x. The same applies to the Y-axis scale thermometer 26y and the Z-axis scale thermometer 26z. The number of X-axis scale thermometers 26x is not limited to one, and may be two or more. The same applies to the Y-axis scale thermometer 26y and the Z-axis scale thermometer 26z.

[0023] In the example shown in FIG. 1, two workpiece thermometers 26w are provided on the workpiece W, but the number of workpiece thermometers 26w may be one or three or more.

[0024] FIG. 2 is a block diagram showing the configuration of the coordinate measuring machine 10. As shown in FIG. 2, the coordinate measuring machine 10 includes a thermal expansion correction control unit 30 that performs calculation processing for thermal expansion correction. The thermal expansion correction control unit 30 is a microcomputer that includes, for example, a CPU (Central Processing Unit) that executes a control program, a ROM (Read-Only Memory) that stores the control program executed by the CPU, and a RAM (Random Access Memory) that stores the calculation results of the CPU. The thermal expansion correction control unit 30 may be configured with one microcomputer or multiple microcomputers. The thermal expansion correction control unit 30 reads a pre-stored program and operates in accordance with the program.

[0025] The thermal expansion correction control unit 30 is electrically connected to the scale 24, the scale thermometer 26, and the workpiece thermometer 26w. S , the temperature t of the scale 24 measured by the scale thermometer 26 S and the temperature t of the work W measured by the work thermometer 26w W The above information is input to the thermal expansion correction control unit 30.

[0026] The thermal expansion correction control unit 30 functionally comprises a work length calculation unit 32 and a work length thermal expansion correction unit 34. The work length calculation unit 32 and the work length thermal expansion correction unit 34 are virtual units that implement the functions of the thermal expansion correction control unit 30.

[0027] The work length calculation unit 32 calculates the movement amount L of the moving body 16 measured by the scale 24. S Based on the work length L W Ask for.

[0028] The work length L calculated by the work length calculation unit 32 W is a value measured in the environment where the coordinate measuring machine 10 is installed. W is a value measured when the scale 24 and the workpiece W are thermally expanded (thermally contracted) relative to the reference temperature. Therefore, the length of the workpiece W under the reference temperature environment, L WC In order to calculate this, the work length L calculated by the work length calculation unit 32 is W needs to be corrected.

[0029] The work length thermal expansion correction unit 34 corrects the work length L W Correct the work length L under the reference temperature WC Specifically, the work length thermal expansion correction unit 34 calculates the work length L calculated by the work length calculation unit 32. W , the thermal expansion coefficient a of scale 24 S , the temperature t of the scale 24 measured by the scale thermometer 26 S , the thermal expansion coefficient a of the workpiece W W , the temperature t of the work W measured by the work thermometer 26w W , and reference temperature t R Using the above, the work length L under the reference temperature WC is calculated using the following formula: L WC =L W {1+a S (t S -t R )―a W (t W -t R )} ···(1)

[0030] In equation (1), the thermal expansion coefficient a of the scale 24 S and the thermal expansion coefficient a of the workpiece W W is stored in advance in a storage unit (not shown), and the thermal expansion correction control unit 30 acquires the thermal expansion coefficient a of the scale 24 from the storage unit. S and the thermal expansion coefficient a of the workpiece W W The thermal expansion coefficient a of scale 24 is read and obtained. S and the thermal expansion coefficient a of the workpiece W W may be input by the operator.

[0031] The work length L under the reference temperature obtained by the work length thermal expansion correction unit 34 WC is displayed on a monitor (not shown), for example.

[0032] In such a coordinate measuring machine 10, the thermal expansion coefficient a of the scale 24 S , the temperature t of the scale 24 measured by the scale thermometer 26 S , and the temperature t of the work W measured by the work thermometer 26w W Each of these includes an error. If these errors are large, it is not possible to appropriately correct the thermal expansion caused by temperature changes, and the measurement accuracy of the coordinate measuring machine 10 decreases. Therefore, it is necessary to evaluate these errors and correct the thermal expansion coefficient of the scale 24, the scale thermometer 26, and the workpiece thermometer 26w as necessary.

[0033] The evaluation system 100 and the evaluation method according to this embodiment are S The error of the temperature t of the scale 24 measured by the scale thermometer 26 S and the temperature t of the work W measured by the work thermometer 26w w The evaluation system 100 and the evaluation method are described in detail below.

[0034] Fig. 3 is a perspective view that schematically shows the evaluation system 100. As shown in Fig. 3, the evaluation system 100 includes a laser length measuring device 110 that measures the amount of movement of the moving body 16, scale high-precision thermometers 126x, 126y, and 126z that have higher measurement accuracy than the scale thermometer 26, and a work high-precision thermometer 126w that has higher measurement accuracy than the work thermometer 26w.

[0035] The laser length measuring device 110 splits a laser beam into a first polarized component and a second polarized component, and measures the length by utilizing interference caused by the optical path difference between the first polarized component and the second polarized component. The first polarized component is also called measurement light, and the second polarized component is also called reference light.

[0036] Here, a case where an interference mirror 112 and a reflecting mirror 114 are used will be described. The interference mirror 112 splits the laser light into a first polarized component and a second polarized component. The reflecting mirror 114 is fixed to the tip of a Z-axis direction movable body 16z instead of the probe 22 (see FIG. 1). In other words, measuring the amount of movement of the reflecting mirror 114 is synonymous with measuring the amount of movement of the movable body 16.

[0037] 3, the laser length measuring device 110 is disposed so as to emit laser light in the Y-axis direction. The interference mirror 112 reflects a first polarized component of the laser light emitted from the laser length measuring device 110 in the X-axis direction toward the reflecting mirror 114, and also reflects a second polarized component of the laser light toward the laser length measuring device 110. The reflecting mirror 114 reflects the first polarized component reflected by the interference mirror 112 toward the interference mirror 112. The first polarized component reflected by the reflecting mirror 114 toward the interference mirror 112 is reflected by the interference mirror 112 toward the laser length measuring device 110. In other words, the branched first polarized component and second polarized component are combined by the interference mirror 112 and travel toward the laser length measuring device 110. At this time, interference occurs according to the optical path difference between the first polarized component and the second polarized component, causing a change in brightness.

[0038] The laser length measuring device 110 is equipped with a photodetector that detects changes in brightness due to interference, and by counting the changes in brightness, it is possible to measure the optical path difference between the first polarization component and the second polarization component, i.e., the length between the interference mirror 112 and the reflecting mirror 114. By moving the reflecting mirror 114 in the X-axis direction while keeping the position of the interference mirror 112 fixed, it is possible to measure the amount of movement in the X-axis direction of the X-axis movable body 16x.

[0039] The error in length measurement using the laser length measuring device 110 is about 0.3 μm / m, and the influence of thermal expansion is smaller than in length measurement using the scale 24. Therefore, by using the laser length measuring device 110, it is possible to measure the amount of movement of the moving body 16 more accurately.

[0040] The high-precision scale thermometer 126x is provided on the X-axis scale 24x and measures the temperature of the X-axis scale 24x. The high-precision scale thermometer 126y is provided on the Y-axis scale 24y and measures the temperature of the Y-axis scale 24y. The high-precision scale thermometer 126z is provided on the Z-axis scale 24z and measures the temperature of the Z-axis scale 24z. The high-precision scale thermometers 126x, 126y, and 126z are preferably disposed near the X-axis scale thermometer 26x, the Y-axis scale thermometer 26y, and the Z-axis scale thermometer 26z, respectively. Hereinafter, the high-precision scale thermometers 126x, 126y, and 126z may be collectively referred to as the high-precision scale thermometer 126.

[0041] It is preferable that the temperature accuracy of the scale high-precision thermometer 126 is about 10 times that of the scale thermometer 26. For example, if the temperature accuracy of the scale thermometer 26 is about ±0.3°C, it is preferable that the temperature accuracy of the scale high-precision thermometer 126 is about ±0.03°C.

[0042] The high-precision work thermometer 126w is provided on the work W and measures the temperature of the work W. The high-precision work thermometer 126w is preferably disposed near the work thermometer 26w. The high-precision work thermometer 126w preferably has a temperature accuracy approximately 10 times that of the work thermometer 26w. For example, if the temperature accuracy of the work thermometer 26w is approximately ±0.3°C, the temperature accuracy of the high-precision work thermometer 126w is preferably approximately ±0.03°C.

[0043] FIG. 4 is a block diagram showing the configuration of the evaluation system 100. As shown in FIG. 4, the evaluation system 100 includes an evaluation control unit 130. The evaluation control unit 130 is a microcomputer including, for example, a CPU (Central Processing Unit) that executes a control program, a ROM (Read-Only Memory) that stores the control program executed by the CPU, and a RAM (Random Access Memory) that stores the results of CPU calculations, etc. The evaluation control unit 130 may be configured with one microcomputer or multiple microcomputers. The evaluation control unit 130 reads out a pre-stored program and operates in accordance with the program.

[0044] The evaluation control unit 130 is electrically connected to the coordinate measuring machine 10, the laser length measuring device 110, the scale high-precision thermometer 126, and the workpiece high-precision thermometer 126w. Information output from the coordinate measuring machine 10, information on the amount of movement of the moving body 16 measured by the laser length measuring device 110, information on the temperature of the scale 24 measured by the scale high-precision thermometer 126, and information on the temperature of the workpiece W measured by the workpiece high-precision thermometer 126w are input to the evaluation control unit 130. The information output from the coordinate measuring machine 10 includes the amount of movement L of the moving body 16 measured by the scale 24, S Information on the temperature t of the scale 24 measured by the scale thermometer 26 S The information on the temperature t of the workpiece W measured by the workpiece thermometer 26w W and the work length L under the reference temperature calculated by the work length thermal expansion correction unit 34.WC Contains information on:

[0045] The evaluation control unit 130 evaluates the error related to thermal expansion compensation based on the information output from the coordinate measuring machine 10, the amount of movement of the movable body 16 measured by the laser length measuring device 110, the temperature of the scale 24 measured by the high-precision scale thermometer 126, and the temperature of the workpiece W measured by the high-precision workpiece thermometer 126w. The evaluation control unit 130 also corrects the thermal expansion coefficient of the scale 24, the scale thermometer 26, and the workpiece thermometer 26w based on the evaluation of the error related to thermal expansion compensation. A method for evaluating the error related to thermal expansion compensation and a method for correcting the thermal expansion coefficient of the scale 24, the scale thermometer 26, and the workpiece thermometer 26w will be described in detail below.

[0046] First, a method for evaluating errors related to thermal expansion correction of the scale 24 and a method for correcting the scale thermometer 26 will be described.

[0047] The amount of movement L of the moving object 16 measured by the scale 24 S is a value measured when the scale 24 is thermally expanded (thermally contracted) relative to the reference temperature. Therefore, the calibrated value L of the length of the workpiece W is C In order to calculate this, the movement amount L of the moving body 16 measured by the scale 24 is S Specifically, the calibration value L of the length of the workpiece W must be corrected. C The movement amount L of the moving body 16 measured by the scale 24 S , the thermal expansion coefficient a of scale 24 S , the temperature t of the scale 24 measured by the scale thermometer 26 S Using this, it is calculated using the following formula. L C =L S {1+a S (t S -t R )} ···(2)

[0048] Calibration value L of the length of the workpiece W C is the thermal expansion coefficient a of scale 24 Sand the temperature t of the scale 24 measured by the scale thermometer 26. S Since the error in the measurement using the laser length measuring device 110 is smaller than that in the measurement using the scale 24, the movement amount L of the moving body 16 measured by the laser length measuring device 110 is M can be regarded as the true value of the movement amount of the moving body 16. Therefore, the calibrated value L of the length of the workpiece W C The positioning error E, which is the difference between the actual value of the movement amount of the moving body 16 and the actual value of the movement amount L of the moving body 16 measured by the laser length measuring device 110, is expressed as a ratio. M Using the above, it can be calculated using the following formula: E=(L C -L M ) / L M ···(3)

[0049] Substituting equation (2) into equation (3) gives the following equation: E={L S {1+a S (t S -t R )}―L M} / L M ···(4)

[0050] The positioning error E is the calibrated value L of the length of the workpiece W. C The error of the calibration value L of the length of the workpiece W is evaluated. C The following errors can be considered as errors that

[0051] (1) Thermal expansion coefficient a of scale 24 s Error (2) the temperature t of the scale 24 measured by the scale thermometer 26 S Magnification error and offset error (3) The amount of movement L of the moving object 16 measured by the scale 24 S Magnification error

[0052] Here, the magnification error and offset error will be explained. S5 is a graph for explaining the magnification error and offset error of the scale 24. In FIG. S is the deviation from the reference temperature (temperature t S -Reference temperature t R The vertical axis shows the true temperature value of the scale 24 as the deviation from the reference temperature (true value - reference temperature t R )

[0053] If the scale thermometer 26 is an ideal thermometer and can measure temperature without error, the temperature t of the scale 24 measured by the scale thermometer 26 S corresponds to the true value of the temperature on the scale 24. That is, the temperature t measured by the ideal thermometer, as shown by the solid line in the graph of FIG. S There is a proportional relationship between the true value of temperature and the value of the temperature, which is expressed by a straight line equation with a slope of 1 and an intercept of 0 (zero).

[0054] The temperature t measured by the scale thermometer 26 S As shown by the dashed line in the graph of Figure 5, there may be a proportional relationship between the temperature t of the scale 24 measured by the scale thermometer 26 and the true value of the temperature, which is expressed by a straight line equation whose slope is not "1" but whose intercept is "0 (zero)." In the graph of Figure 5, the difference between the slope of the solid line and the slope of the dashed line is the temperature t of the scale 24 measured by the scale thermometer 26. S is the magnification error.

[0055] Also, the temperature t measured by the scale thermometer 26 S A proportional relationship may be established between the true value of the temperature and the temperature, which is expressed by a linear equation with a slope of 1 and an intercept that is not 0 (zero), as shown by the dashed line in the graph of Figure 5. In the graph of Figure 5, the difference between the intercept of the solid line and the intercept of the dashed line is the temperature t of the scale 24 measured by the scale thermometer 26. S is the offset error.

[0056] Note that the actual error is a combination of magnification error and offset error. However, since the magnification error of a thermometer is generally smaller than the offset error, its impact on the positioning error is also relatively small. Therefore, from now on, we will consider the thermometer's magnification error to be nonexistent.

[0057] The amount of movement L of the moving object 16 measured by the scale 24 S The magnification error of is almost the same as the temperature magnification error explained in Figure 5, so a detailed explanation will be omitted here. Also, as with the temperature magnification error, the effect on positioning error is relatively small, so hereafter it will be considered that there is no scale magnification error.

[0058] Hereafter, the thermal expansion coefficient a of scale 24 S The error of the equivalent scale temperature coefficient error dk S、 The temperature t of the scale 24 measured by the scale thermometer 26 S The offset error of the scale offset error dt S0 Equivalent scale temperature coefficient error dk S and scale offset error dt S0 By evaluating the coefficient of thermal expansion of the scale 24 and the error due to the scale thermometer 26, the coefficient of thermal expansion of the scale 24 and the error due to the scale thermometer 26 can be evaluated.

[0059] Equivalent scale temperature coefficient error dk S and scale offset error dt S0 The formula for calculating this will be explained below.

[0060] Scale offset error dt S0 is the temperature t of the scale 24 measured by the scale thermometer 26 S is the difference between the true value of the temperature on scale 24 and

[0061] Here, since the scale high-precision thermometer 126 has a higher measurement accuracy than the scale thermometer 26, the temperature t of the scale 24 measured by the scale high-precision thermometer 126 is SHcan be considered as the true value of the temperature of the scale 24. Therefore, the scale offset error dt S0 is the temperature t of the scale 24 measured by the scale thermometer 26 S and the temperature t of scale 24 measured by the scale high-precision thermometer 126 SH and can be calculated from the following equation: dt S0 =t S -t SH ···(5)

[0062] Also, the equivalent scale temperature coefficient error dk S is the nominal value of the thermal expansion coefficient of scale 24. S , its true value is a SH This is expressed as follows: dk S =a S -a SH ···(6) At this time, the true value L of the movement amount of the moving object 16 M is expressed as follows: L M =L S {1+a SH (t SH -t R )} (7)

[0063] From equations (5), (6), and (7), the positioning error E in equation (4) is the equivalent scale temperature coefficient error dk S and scale offset error dt S0 is expressed as follows using the following equation: E={a S ·dt S0 +dk S (t S -dt S0 -t R )} / {1+(a S -dk S )(t S -dt S0 -t R )} (8)

[0064] Equivalent scale temperature coefficient error dk Sis expressed as follows by modifying equation (8): dk S ={E(1+a S (t S -dt S0 -t R ))-a S ·dt S0} / {(1+E)(t S -dt S0 -t R )} (9)

[0065] In equation (9), the positioning error E is calculated by the calibration value L of the length of the workpiece W as shown in equation (3). C and the movement amount L of the moving body 16 measured by the laser length measuring device 110. M The scale offset error dt can be calculated using S0 can be calculated from equation (5). The thermal expansion coefficient a of the scale 24 S is the calibration value L of the length of the workpiece W C The value used to calculate the temperature t of scale 24 can be used. S is the value measured by the scale thermometer 26.

[0066] Thus, the equivalent scale temperature coefficient error dk S and the scale offset error dt S0 Both of these can be calculated from equations (9) and (5) using values ​​measured under one temperature environment. Therefore, the equivalent scale temperature coefficient error dk S and scale offset error dt S0 The scale thermometer 26 can be easily evaluated.

[0067] The correction of the scale thermometer 26 is the scale offset error dt S0 Specifically, the scale thermometer 26 is based on the scale offset error dt S0The thermal expansion coefficient of the scale 24 is corrected based on the equivalent scale temperature coefficient error dks so that the absolute value of the equivalent scale temperature coefficient error dks is reduced. Therefore, by correcting the temperature of the scale thermometer 26 and the thermal expansion coefficient of the scale 24, the thermal expansion of the scale caused by temperature changes can be appropriately corrected, and the workpiece length under reference temperature L obtained by the coordinate measuring machine 10 can be reduced. WC The accuracy of the calculation can be improved.

[0068] Next, a method for correcting the workpiece thermometer 26w will be described.

[0069] When the length of the workpiece W is corrected to the length under the standard temperature environment, the corrected length of the workpiece W is considered to include the following errors. W However, this error is small compared to other errors and has little effect on the measurement, so it is not included here.

[0070] (1) Thermal expansion coefficient a of workpiece W W The error of the equivalent work temperature coefficient error dk W (2) The temperature t of the workpiece W measured by the workpiece thermometer 26w W The work offset error dt W0

[0071] Equivalent work temperature coefficient error dk W The thermal expansion coefficient a of the workpiece W is W The error varies depending on the workpiece W, so the equivalent workpiece temperature coefficient error dk W Therefore, the work offset error dt W0 By evaluating the work thermometer 26w only consider evaluating.

[0072] Work offset error dt W0 The formula for calculating this will be explained below.

[0073] Work offset error dt W0 is the temperature t of the workpiece W measured by the workpiece thermometer 26w. W Since this is an offset error, the temperature t of the workpiece W measured by the workpiece thermometer 26w W and the true value of the temperature of the workpiece W.

[0074] Here, since the workpiece high-precision thermometer 126w has higher measurement accuracy than the workpiece thermometer 26w, the temperature t of the workpiece W measured by the workpiece high-precision thermometer 126w WH can be considered as the true value of the temperature of the workpiece W. Therefore, the workpiece offset error dt W0 is the work temperature t measured by the work thermometer 26w W and the temperature t of the work W measured by the work high-precision thermometer 126w. WH and can be calculated from the following equation: dt W0 =t W -t WH ···(10)

[0075] The workpiece thermometer 26w can be easily evaluated using equation (10).

[0076] The correction of the workpiece thermometer 26w is the workpiece offset error dt W0 Specifically, the workpiece temperature sensor 26w is based on the evaluation of the workpiece offset error dt W0 Therefore, the workpiece thermometer 26w can be appropriately corrected, and the workpiece length under the reference temperature L obtained by the coordinate measuring machine 10 is WC The accuracy can be further improved.

[0077] The evaluation control unit 130 calculates the equivalent scale temperature coefficient error dk S , scale offset error dt S0 and work offset error dt W0Specifically, the evaluation control unit 130 includes a scale measurement value correction unit 132, a positioning error calculation unit 134, a scale offset error calculation unit 136, an equivalent scale temperature coefficient error calculation unit 138, a work offset error calculation unit 140, and a scale thermal expansion coefficient correction unit 200. The scale measurement value correction unit 132, the positioning error calculation unit 134, the scale offset error calculation unit 136, the equivalent scale temperature coefficient error calculation unit 138, the work offset error calculation unit 140, and the scale thermal expansion coefficient correction unit 200 are virtual units that implement the functions of the evaluation control unit 130.

[0078] The scale measurement value correction unit 132 calculates the calibration value L of the length of the workpiece W using equation (2). C The positioning error calculation unit 134 calculates the positioning error E using equation (3). The scale offset error calculation unit 136 calculates the scale offset error dt S0 The equivalent scale temperature coefficient error calculation unit 138 calculates the equivalent scale temperature coefficient error dk S The work offset error calculation unit 140 calculates the work offset error dt W0 Calculate.

[0079] Therefore, the equivalent scale temperature coefficient error dk S , scale offset error dt S0 , and the work offset error dt W0 Therefore, the thermal expansion coefficient of the scale 24, the scale thermometer 26, and the work thermometer 26w can be easily evaluated.

[0080] The evaluation control unit 130 includes a scale thermometer correction unit 142 that corrects the scale thermometer 26, a scale thermal expansion coefficient correction unit 200 that corrects the thermal expansion coefficient of the scale 24, and a work thermometer correction unit 144 that corrects the work thermometer 26w. The scale thermometer correction unit 142, the scale thermal expansion coefficient correction unit 200, and the work thermometer correction unit 144 are virtual units that implement the functions of the evaluation control unit 130.

[0081] The scale thermometer correction unit 142 calculates the calculated scale offset error dt S0 Specifically, the scale thermometer correction unit 142 corrects the scale thermometer 26 based on the evaluation of the scale offset error dt S0 Therefore, the scale thermometer 26 can be appropriately corrected, and the workpiece length under the reference temperature L obtained by the coordinate measuring machine 10 can be calculated. WC The accuracy of the calculation can be improved.

[0082] The scale thermal expansion coefficient correction unit 200 corrects the thermal expansion coefficient of the scale 24 based on the obtained equivalent scale temperature coefficient error dks. WC The accuracy of the calculation can be improved.

[0083] The workpiece temperature correction unit 144 calculates the calculated workpiece offset error dt W0 Specifically, the workpiece thermometer correction unit 144 corrects the workpiece thermometer 26w based on the evaluation of the workpiece offset error dt W0 Therefore, the workpiece thermometer 26w can be appropriately corrected, and the workpiece length under the reference temperature L obtained by the coordinate measuring machine 10 is WC The accuracy can be further improved.

[0084] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments and examples, and can be modified as appropriate within the scope of the spirit of the present invention. [Explanation of symbols]

[0085] 10: Coordinate measuring machine 16: Mobile 24: Scale 26: Scale thermometer 26w: Work thermometer 100: Rating System 110: Laser length measuring instrument 126: Scale high precision thermometer 126w: High-precision workpiece thermometer 130: Evaluation control unit W: Work

Claims

1. A system for evaluating a coordinate measuring machine including a scale for measuring a movement amount of a moving body, a scale thermometer for measuring a temperature of the scale, and a workpiece thermometer for measuring a temperature of a workpiece, a laser length measuring device for measuring the amount of movement of the moving body; a scale high-precision thermometer that measures the temperature of the scale with higher measurement accuracy than the scale thermometer; an evaluation control unit that evaluates the scale thermometer, The evaluation control unit calculating a scale offset error, which is an offset error of the temperature of the scale measured by the scale thermometer, based on the temperature of the scale measured by the scale thermometer and the temperature of the scale measured by the scale high-precision thermometer; determining an equivalent scale temperature coefficient error, which is an error in the thermal expansion coefficient of the scale, based on the determined scale offset error, the amount of movement of the moving body measured by the scale, the amount of movement of the moving body measured by the laser length measuring device, and the temperature of the scale measured by the scale thermometer; Rating system.

2. The evaluation control unit The temperature of the scale measured by the scale thermometer is t Ｓ The temperature of the scale measured by the scale high-precision thermometer is t ＳＨ In this case, the scale offset error dt Ｓ０ Seeking The amount of movement of the moving body measured by the scale is L Ｓ , the nominal value of the thermal expansion coefficient of the scale is a Ｓ , the temperature of the scale measured by the scale thermometer is t Ｓ , the reference temperature is t Ｒ In this case, the calibration value L given by the following formula (2) Ｃ Seeking The movement amount of the moving body measured by the laser length measuring device is L Ｍ In this case, the positioning error E is calculated using the following equation (3): Using the following equation (4), the equivalent scale temperature coefficient error dk Ｓ Asking for, The evaluation system of claim 1 . dt Ｓ０ =t Ｓ -t ＳＨ ・・・(1) L Ｃ =L Ｓ {1+a Ｓ (t Ｓ -t Ｒ )} ・・・(2) E=(L Ｃ ―L Ｍ ) / L Ｍ ・・・(3) dk Ｓ ={E(1+a Ｓ (t Ｓ -dt Ｓ０ -t Ｒ ))-a Ｓ ・dt Ｓ０ } / {(1+E)(t Ｓ -dt Ｓ０ -t Ｒ )} ・・・(4)

3. Further provided is a high-precision workpiece thermometer that measures the temperature of the workpiece with higher measurement accuracy than the workpiece thermometer, The evaluation control unit further determining a work offset error, which is an offset error of the work temperature measured by the work thermometer, based on the work temperature measured by the work thermometer and the work temperature measured by the high-precision work thermometer; The evaluation system of claim 1 .

4. The evaluation control unit The temperature of the workpiece measured by the workpiece thermometer is expressed as t Ｗ The temperature of the workpiece measured by the workpiece high-precision thermometer is t ＷＨ In this case, the work offset error dt Ｗ０ Asking for, The evaluation system according to claim 3 . dt Ｗ０ =t Ｗ -t ＷＨ ・・・(5)

5. the evaluation control unit corrects the thermal expansion coefficient of the scale and the scale thermometer based on the obtained equivalent scale temperature coefficient error and the scale offset error. The evaluation system of claim 1 .

6. the evaluation control unit corrects the workpiece thermometer based on the determined workpiece offset error. The evaluation system according to claim 3 .

7. A method for evaluating a coordinate measuring machine including a scale for measuring a movement amount of a moving body, a scale thermometer for measuring a temperature of the scale, and a workpiece thermometer for measuring a temperature of a workpiece, the method comprising: a scale offset error, which is an offset error of the temperature of the scale measured by the scale thermometer, is calculated based on the temperature of the scale measured by the scale thermometer and the temperature of the scale measured by a high-precision scale thermometer having a measurement accuracy higher than that of the scale thermometer; calculating an equivalent scale temperature coefficient error, which is an error in the thermal expansion coefficient of the scale, based on the calculated scale offset error, the amount of movement of the moving body measured by the scale, the amount of movement of the moving body measured by a laser length measuring device, and the temperature of the scale measured by the scale thermometer; Evaluation method.

8. The temperature of the scale measured by the scale thermometer is t Ｓ The temperature of the scale measured by the scale high-precision thermometer is t ＳＨ In this case, the scale offset error dt Ｓ０ Seeking The amount of movement of the moving body measured by the scale is L Ｓ , the nominal value of the thermal expansion coefficient of the scale is a Ｓ , the temperature of the scale measured by the scale thermometer is t Ｓ , the reference temperature is t Ｒ In this case, the calibration value L given by the following formula (7) Ｃ Seeking The movement amount of the moving body measured by the laser length measuring device is L Ｍ In this case, the positioning error E is calculated by the following equation (8): Using the following equation (9), the equivalent scale temperature coefficient error dk Ｓ Asking for, The evaluation method according to claim 7. dt Ｓ０ =t Ｓ -t ＳＨ ・・・(6) L Ｃ =L Ｓ {1+a Ｓ (t Ｓ -t Ｒ )} ・・・(7) E=(L Ｃ ―L Ｍ ) / L Ｍ ・・・(8) dk Ｓ ={E(1+a Ｓ (t Ｓ -dt Ｓ０ -t Ｒ ))-a Ｓ ・dt Ｓ０ } / {(1+E)(t Ｓ -dt Ｓ０ -t Ｒ )} ・・・(9)

9. further determining a work offset error, which is an offset error of the temperature of the work measured by the work thermometer, based on the temperature of the work measured by the work thermometer and the temperature of the work measured by a high-precision work thermometer having higher measurement accuracy than the work thermometer; The evaluation method according to claim 7.

10. The temperature of the workpiece measured by the workpiece thermometer is expressed as t Ｗ The temperature of the workpiece measured by the workpiece high-precision thermometer is t ＷＨ In this case, the work offset error dt Ｗ０ Asking for, The evaluation method according to claim 9. dt Ｗ０ =t Ｗ -t ＷＨ ・・・(10)

11. and correcting the thermal expansion coefficient of the scale and the scale thermometer based on the equivalent scale temperature coefficient error and the scale offset error obtained using the evaluation method according to claim 7. Correction method.

12. correcting the workpiece thermometer based on the workpiece offset error determined using the evaluation method according to claim 9; Correction method.

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