JP2005265700A - Work piece temperature correction method in three-dimensional measuring machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure a work temperature while following a temperature change, and to temperature-correct precisely a measured length of a measuring portion in a work in response to the work temperature. <P>SOLUTION: The work is fixed in one portion onto a jig of a three-dimensional measuring instrument to allow linear expansion. Coordinate values of X-, Y-, Z-axes in at least two reference portions of the work are measured based on detection signals of a probe from the three-dimensional measuring instrument, and a work coordinate system is set based on the coordinate values. Coordinate values of X-, Y-, Z-axes are read based on a detection signal of the probe as to the measuring portion of the work, and a surface temperature of the work is measured by a radiation thermometer. The measuring length in the work coordinate system in the measuring portion is computed based on the coordinate values. The measuring length in the measuring portion is temperature-corrected into a measured length in the reference portion in the work at the reference temperature, based on a difference between the work temperature and the reference temperature. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a workpiece temperature correction method for correcting a measurement length of a workpiece measurement point measured by a three-dimensional measuring machine to a measurement length of a workpiece at a reference temperature.

Usually, the product drawing dimension is a dimension value at a temperature of 20 ° C. For this reason, precise three-dimensional measurement requires that the workpiece be brought into a temperature-controlled room controlled at 20 ° C and left for a predetermined time until the workpiece reaches 20 ° C, the same as the ambient temperature. It took a long time. With the recent improvement in production efficiency, the three-dimensional measuring machine is strongly demanded to perform measurement at a measurement place close to the processing manufacturing site, and the number of three-dimensional measuring machines is increasing around the site. For this reason, for example, as described in Patent Document 1, the holder for holding the probe can be moved relatively in the X, Y, and Z axis directions perpendicular to the workpiece, and the probe is in contact with the workpiece. In a three-dimensional measuring machine that reads the coordinate values of the X, Y, and Z axes when the relative position between the probe and the workpiece is read by an X, Y, and Z axis scale to measure the measurement length of the workpiece measurement point, It responds to temperature changes in the field by correcting the temperature of the coordinate values measured on the X, Y, and Z axis scales based on the temperature of each axis measured by the sensors that measure the temperatures of the Y, Z, and Z axes, respectively. Therefore, products that can measure the measurement length of workpieces with high accuracy against environmental temperature changes of 21 ± 5 ° C have been put on the market. However, regarding the response to the temperature change of the workpiece, as shown in Patent Document 1, linear correction is performed on the surface temperature of the workpiece measured with a contact-type thermometer, and measurement of the measurement location on the workpiece at the reference temperature of 20 ° C. It is only converted to length.
JP 11-190617 (3rd page, FIG. 2)

   However, since the contact-type thermometer measures the surface temperature of the workpiece by conducting heat from the workpiece to the sensor unit, the measured temperature changes depending on how the sensor unit contacts the workpiece, and the surface temperature of the workpiece is accurately measured. In some cases, the temperature correction accuracy of the workpiece decreases. In addition, the standard contact thermometer of the three-dimensional measuring machine has a response speed of 240 seconds and is poor in response. Therefore, when a workpiece is brought into the measurement room from a field environment of several degrees to 40 ° C. and immediately measured, It is impossible to follow the temperature change of the linear correction, and the accuracy of the linear correction is lowered. Therefore, as shown in FIG. 7, the measurement error between the measurement length and the true value of the center position of the measurement hole subjected to the workpiece temperature correction by such a conventional method is as follows. When the surface temperature is as high as about 40 ° C, it falls within one fifth of the tolerance position degree. However, as the workpiece surface temperature decreases, the correction accuracy deteriorates, and the measured length and true value of the center position of the measurement hole. There was a problem that the measurement error was 1/5 or more of the tolerance.

   The present invention has been made in order to eliminate the above-described conventional problems. The workpiece temperature is accurately measured by responsively responding to a temperature change, and the measurement length of the workpiece measurement point is increased according to the workpiece temperature. It is to provide a workpiece temperature correction method for a three-dimensional measuring machine capable of accurately correcting a temperature.

  In order to solve the above problems, the structural feature of the invention described in claim 1 is that a probe that can move relative to the workpiece attached to the jig in the X, Y, and Z axis directions detects the workpiece surface position. In the three-dimensional measuring apparatus that measures the measurement length of the measurement position of the workpiece by reading the coordinate values of the X, Y, and Z axes when the detection signal is transmitted, the workpiece is allowed to linearly expand in the jig. The workpiece coordinate system is set based on the coordinate values of the X, Y, and Z axes of at least two reference points of the workpiece measured based on the detection signal of the probe. The coordinate values of the X, Y, and Z axes are read for the location based on the detection signal of the probe, the surface temperature of the workpiece is measured by the radiation thermometer, and the measurement length in the workpiece coordinate system of the measurement location is measured based on the coordinate value. Calculate With the measured length in the workpiece coordinate system of the measuring point based on a difference between the workpiece surface temperature and the reference temperature is to work temperature compensation.

  The structural feature of the invention of claim 2 is that when a probe capable of relative movement in the X, Y, and Z-axis directions with respect to the workpiece attached to the jig detects the workpiece surface position and sends a detection signal. In a three-dimensional measuring apparatus that measures the measurement length of a workpiece measurement point by reading the coordinate values of the X, Y, and Z axes, the workpiece is fixed at one point while allowing the jig to undergo linear expansion. The initial workpiece coordinate system is set based on the coordinate values of the X, Y, and Z axes of at least two reference locations of the workpiece measured based on the detection signal of the probe, and the rough tolerance location where the tolerance is equal to or greater than a predetermined value The X, Y and Z axis coordinate values of the rough tolerance location are read based on the detection signal of the probe, the workpiece surface temperature is measured by a radiation thermometer, and the initial workpiece coordinates of the rough tolerance location are measured based on the coordinate values. Measuring length in the system The workpiece length is compensated for the measurement length in the initial workpiece coordinate system of the rough tolerance location based on the difference between the workpiece surface temperature and the reference temperature, and for the precision tolerance location where the tolerance is less than a predetermined value, the workpiece surface temperature Is within a predetermined range from the reference temperature, the coordinate values of the X, Y, and Z axes of the at least two reference points are measured again, and a work coordinate system for fine tolerance is set based on the coordinate values. Based on the detection signal of the probe, the coordinate values of the X, Y and Z axes of the precise tolerance points are read, the workpiece surface temperature is measured by the radiation thermometer, and the fine tolerance workpieces of the fine tolerance points are measured based on the coordinate values. In addition to calculating the measurement length in the coordinate system, the measurement length in the work coordinate system for fine tolerance at the precise tolerance point is corrected based on the difference between the workpiece surface temperature and the reference temperature.

  The structural feature of the invention described in claim 3 is that, in claim 1 or 2, a black body substance having a known emissivity is attached to a surface temperature measuring portion of a workpiece whose temperature is measured by the radiation thermometer. is there.

In the invention according to claim 1 configured as described above, the work is fixed to the jig of the three-dimensional measuring machine at one point so that linear expansion is possible. The coordinate values of the X, Y, and Z axes of at least two reference points of the workpiece are measured based on the detection signal of the probe of the three-dimensional measuring machine, and the workpiece coordinate system is set based on the coordinate values. The coordinate values of the X, Y, and Z axes are read based on the detection signal of the probe at the workpiece measurement location, and the surface temperature of the workpiece is measured with a radiation thermometer. Based on the coordinate value, the measurement length in the workpiece coordinate system of the measurement location is calculated. Based on the difference between the workpiece temperature and the reference temperature, the measurement length of the measurement location is corrected to the measurement length of the measurement location of the workpiece at the reference temperature.
As a result, the radiation thermometer does not change the measurement temperature depending on the contact condition with the workpiece like the contact thermometer, and the response speed is short, so the workpiece temperature is accurately measured by following the temperature change with good responsiveness. Thus, the measurement length of the measurement location of the workpiece can be temperature-corrected with high accuracy according to the workpiece temperature.

According to the invention according to claim 2 configured as described above, the work is fixed to the jig of the three-dimensional measuring machine at one point so that linear expansion is possible. The coordinate values of the X, Y, and Z axes of at least two reference points of the workpiece are measured based on the detection signal of the probe of the three-dimensional measuring machine, and the initial workpiece coordinate system is set based on the coordinate values. For the coarse tolerance point where the tolerance is greater than or equal to a predetermined value, the coordinate values of the X, Y, and Z axes are read based on the probe detection signal, and the surface temperature of the workpiece is measured by a radiation thermometer. Based on the coordinate value, the measurement length in the initial workpiece coordinate system of the rough tolerance portion is calculated. Based on the difference between the workpiece temperature and the reference temperature, the measured length of the rough tolerance portion is temperature-corrected to the measured length of the rough tolerance portion of the workpiece at the reference temperature. For precise tolerance points where the tolerance is less than the specified value, measure the X, Y, and Z axis coordinate values of at least two reference points after the workpiece temperature falls within the specified range from the reference temperature. Set the work coordinate system for fine tolerance based on Based on the detection signal of the probe, the coordinate values of the X, Y, and Z axes are read, and the workpiece temperature is measured by a radiation thermometer. Based on the coordinate values, the measurement length in the work coordinate system for fine tolerances is calculated. Based on the difference between the workpiece temperature and the reference temperature, the measurement length of the fine tolerance point is corrected to the measurement length of the rough tolerance point in the reference temperature workpiece.
As a result, the measurement length of the rough tolerance point can be measured with the required measurement accuracy with respect to the rough tolerance even if the measurement is performed without performing the temperature leveling on the rough tolerance point, thereby shortening the measurement time. be able to. For precision tolerance points, after the workpiece temperature falls within the specified range from the reference temperature, reset the workpiece coordinate system for precision tolerance, and set the measurement length of the precision tolerance point calculated in the workpiece tolerance coordinate system to the temperature. Since the correction is made, it is possible to measure the measurement length of the precise tolerance portion with the high measurement accuracy required for the fine tolerance. Specifically, the coarse tolerance location can be a location where the positional tolerance satisfies 0.1 to 0.5. The position tolerance of the fine tolerance point can satisfy 0.06 to 0.1.

   According to the invention according to claim 3 configured as described above, since the black body material having a known emissivity is attached to the surface temperature measurement portion of the workpiece, the black body material immediately becomes the workpiece surface temperature, and the emissivity is Since it is a known high value and does not reflect heat rays from other heat sources toward the radiation thermometer, the workpiece temperature can be accurately measured.

   Hereinafter, a method for correcting a workpiece temperature of a coordinate measuring machine according to the present invention and an embodiment of a coordinate measuring machine for carrying out the method will be described. The three-dimensional measuring machine 11 is arranged in a measurement chamber 13 in which the room temperature is controlled to a set temperature of 20 ° C. by the air conditioner 12 in order to guarantee a measurement accuracy with respect to a temperature change, for example, 21 ± 5 ° C. In the coordinate measuring machine 1, a column 15 is mounted on a base 14 so as to be movable in the Y-axis direction perpendicular to the paper surface in FIG. 1, and a head 16 is mounted on the column 15 so as to be movable in the left and right X-axis directions. A ram 17 is mounted on the head 16 so as to be movable in the vertical Z-axis direction. A probe 18 is attached to the tip of the ram 17, and when the probe 18 comes into contact with the surface of the workpiece W fixed on the base 14 via a jig 19, a detection signal is sent and input to the control device 20. ing. The Y-, X-, and Z-axis scales are attached to the base 14, the column 15, and the head 16, respectively, and the reading heads fixed to the column 15, the head 16, and the ram 17 are respectively connected to the Y-, X-, and Z-axis scales. , Read each coordinate value of the Z axis. When the probe 18 capable of relative movement in the X, Y, and Z axis directions with respect to the workpiece W attached to the jig 19 detects the surface position of the measurement location of the workpiece W and sends a detection signal, each read head moves to X , Y, and Z-axis coordinate values are read and input to the control device 20.

   As shown in FIGS. 1 and 2, a door 23 is attached to the front of the measurement chamber 13 so that it can be opened and closed. The jig 19 is pulled out by opening the door 23, and the workpiece W is detached and pushed back into the measurement chamber 13. Then, the door 23 is closed and measurement is performed. The base 24 of the jig 19 placed on the base 14 is provided with a large number of small holes opened on the lower surface, and the jig 19 floats from the upper surface of the base 14 when compressed air is ejected from the small holes by opening the on-off valve 25. The measurement position at which both sides of the base 24 are guided by the pair of guides 26 and the base 24 abuts the stopper 27 in the measurement chamber 13 and the attachment / detachment position pulled out to attach / detach the workpiece W to the front are provided. It becomes possible to slide in the Y-axis direction. When the supply of compressed air is shut off by closing the on-off valve 25, the jig 19 is seated and fixed on the base 14 by its own weight. A conical hole 28 is formed in the side surface of the base 24, and an engagement pin 29 having a taper formed at the tip is mounted on one guide 26 so as to be slidable in the X-axis direction. The force is biased toward the side surface of the base 24. When the jig 19 is pushed back to the vicinity of the measurement position, the engagement pin 29 engages with the conical hole 28, and the taper of the engagement pin 29 contacts the inclined surface of the conical hole 28 to press the base 24 against the stopper 27. The jig 19 is positioned at the measurement position.

   As shown in FIG. 3, a plurality of workpiece receivers 31 to 33 are erected on the base 24 of the jig 19, and a concave groove parallel to the YZ plane is formed on the upper end portion of the workpiece receiver 31. W is inserted into the groove and allowed to expand linearly and fixed at one point. A work presser is rotatably provided at the tip of a fixing screw 34 that is threaded into one side wall of the concave groove and a handle 35 is fixed to the other end. The fixing screw 34 is moved in the X-axis direction by the rotation of the handle 35 and the work W is pressed against the other side wall of the concave groove through the work presser, whereby the work W is fixed to the jig 19 at one point. . The workpiece W is supported on the upper end surfaces parallel to the XY plane of the workpiece receivers 32 and 33 while allowing linear expansion.

   A black body tape 21 whose emissivity is guaranteed to 0.95 is attached to the work W as a black body material having a known emissivity to the surface temperature measurement portion of the work W. On the base 14, the radiation thermometer 22 is attached. Is fixed to face the black body tape 21, and the surface temperature of the workpiece W is measured in a non-contact manner. The contact-type thermometer has a response time of 240 seconds for temperature change and a measurement accuracy of about ± 0.1 ° C. In this embodiment, the response time is as fast as 0.7 seconds and the measurement accuracy is about ± 1 ° C. A radiation thermometer 22 is used. A black spray, a marker, or the like whose emissivity is maintained at a known value of 0.9 or more may be attached to the surface temperature measurement portion of the workpiece as a black body material with an emissivity known.

   Next, the operation of the above embodiment will be described with reference to a flowchart showing a procedure for measuring the measurement length of the measurement location of the workpiece W shown in FIG. With the door 23 of the measurement chamber 13 opened, the open / close valve 25 opened, and the base 24 of the jig 19 lifted from the base 14 by the air pressure, the jig 19 is pulled out to the attaching / detaching position, and the open / close valve 25 is closed. The jig 19 is seated on the base. The workpiece W brought in from the processing / manufacturing site is affixed with the black body tape 21 at the surface temperature measurement position and placed on the workpiece receivers 31 to 33 of the jig 19. The fixing screw 34 is rotated by the handle 35 to pivot, and the workpiece W is pressed against the side wall of the concave groove of the workpiece receiver 31 through the workpiece holder, and the workpiece W is allowed to linearly expand and fixed to the jig 19 at one point. (Procedure 1). In order to simplify the explanation, it is assumed that the workpiece W is fixed to the jig 19 so that the surface on which the measurement location of the workpiece W exists is parallel to the YZ plane. When the workpiece W is fixed to the jig 19, the open / close valve 25 is opened and the base 24 is lifted from the base 14 by the air pressure, the jig 19 is returned to the vicinity of the measurement position, and the engagement pin 29 is conical. It is positioned at the measurement position by engaging with the hole 28 and pressing the base 24 against the stopper 27. The on-off valve 25 is closed to block air ejection from a small hole on the lower surface of the base 24, and the jig 19 is seated and fixed on the base 14. Thereafter, the door 23 of the measurement chamber 13 is closed.

  When the probe 18 is moved in the X, Y, and Z axis directions and abuts against both inner peripheral wall surfaces of the Y axis and Z axis direction diameter portions of the two reference holes 37 and 38, and sends a detection signal, The X, Y, and Z axis coordinate values indicating the position of the probe 18 are read, input to the control device, and stored in the memory. The control device 20 includes coordinate values of the X, Y, and Z axes that indicate the position of the probe 18 when the probe 18 abuts against both inner circumferential wall surfaces of the reference holes 37 and 38 in the Y-axis and Z-axis directions. From each of the two Y-axis coordinate values indicating the positions of both inner wall surfaces in the Y-axis direction of the reference holes 37 and 38, and two Z-axis coordinate values indicating the positions of both wall surfaces in the Z-axis direction. Are respectively arithmetically averaged to measure the coordinate values of the center positions of the reference holes 37 and 38. Then, on the YZ plane that coincides with the surface where the measurement location of the workpiece W exists, the coordinate value of the center position of the reference hole 37 is the origin of the initial workpiece coordinate system, and the coordinate values of the center positions of the reference holes 37 and 38 are The initial workpiece coordinate system is set with the Y ′ axis tied and the axis perpendicular to the Y ′ axis passing through the origin as the Z ′ axis (Procedure 2).

  Of the large number of measurement holes 39 (measurement locations), the coarse tolerance holes 39r (rough tolerance locations) having a positional degree (tolerance) of a predetermined value or more are based on the detection signal of the probe 18 as in the case of the reference holes 37 and 38. Then, four sets of X, Y, and Z axis coordinate values are read, and the surface temperature of the workpiece W is measured by the radiation thermometer 22 and input to the control device 20 and stored in the memory (procedure 3). The control device 20 calculates the Y and Z axis coordinate values of the center position of each rough tolerance hole 39r based on the four sets of X, Y, and Z axis coordinate values, converts the coordinates, and converts each coarse tolerance hole 39r. The measurement length from the Y ′ axis and the Z ′ axis in the initial workpiece coordinate system of the center position Or is calculated. The control device 20 obtains the average value of the surface temperatures measured four times for each rough tolerance hole 39r based on the detection signal of the probe as the surface temperature of the workpiece when the center position of each rough tolerance hole 39r is measured, and the reference temperature A temperature difference ΔT from 20 ° C. is calculated. The control device 20 corrects the workpiece temperature based on the temperature difference ΔT on the measured lengths LY ′ and LZ ′ from the Y ′ axis and the Z ′ axis in the initial workpiece coordinate system of the center position Or of the rough tolerance hole 39r to obtain the center position. The measurement length (LY ′ / (1 + α × ΔT)) and (LZ ′ / (1 + α × ΔT)) from the Y ′ axis and the Z ′ axis of Or is calculated (procedure 4).

  The measurement errors between the measurement lengths LY ′ and LZ ′ from the Y ′ axis and the Z ′ axis in the initial workpiece coordinate system of the center position Or of the rough tolerance hole 39r obtained by correcting the workpiece temperature in this way and the true value are as follows: As shown in FIG. 5, the position that is the tolerance of the rough tolerance hole 39r regardless of whether the surface temperature of the workpiece when the center position Or of the coarse tolerance hole 39r is measured is between 40 ° C. and 20 ° C. It is within one fifth of the degree.

  Before measuring the precision tolerance hole 39f (precision tolerance location) where the degree of position is less than a predetermined value, the control device 22 determines that the current workpiece surface temperature measured by the radiation thermometer 22 is a set temperature 1, for example, 10 ° C. or more. To determine whether the temperature is below a set temperature, for example, 30 ° C., in other words, whether it is within a predetermined range from the reference temperature 20 ° C., and wait until the current workpiece surface temperature is within the predetermined range from the reference temperature. (Procedure 5).

  When the current workpiece surface temperature falls within a predetermined range from the reference temperature, the probe 18 is moved in the X, Y, and Z axis directions as in the setting of the initial workpiece coordinate system, and the centers of the two reference holes 37 and 38 are moved. The coordinate value of the position is measured again, and the coordinate value of the center position of the reference hole 37 is set as the origin of the work coordinate system for precision tolerance on the YZ plane that coincides with the surface where the measurement location of the workpiece W exists. , 38 to connect the coordinate values of the center positions to be the Y ′ axis, and the axis that is perpendicular to the Y ′ axis through the origin is set as the Z ′ axis (step 6).

  Among a large number of measurement holes 39, for the fine tolerance holes 39f (fine tolerance points) whose degree of position is equal to or less than a predetermined value, four sets of X and Y are set based on the detection signal of the probe 18 as in the case of the coarse tolerance holes 39r. , The Z-axis coordinate value is read, and the surface temperature of the workpiece W is measured by the radiation thermometer 22 and input to the control device 20 and stored in the memory. The control device 20 calculates the coordinate values of the Y and Z axes at the center position of each precision tolerance hole 39f based on the four sets of coordinate values of the X, Y, and Z axes, and performs coordinate conversion to calculate each coordinate value. The measurement length from the Y ′ axis and the Z ′ axis in the work coordinate system for the fine tolerance of the center position Of of the fine tolerance hole 39f is calculated. Then, the control device 20 calculates the temperature difference ΔT between the surface temperature of the workpiece and the reference temperature when the center position Of of each precision tolerance hole 39f is measured, and the precision tolerance workpiece of the center position Of of the precision tolerance hole 39f. The measured lengths LY ′ and LZ ′ from the Y ′ axis and the Z ′ axis in the coordinate system are corrected for the workpiece temperature based on the temperature difference ΔT (procedure 7).

  Thus, after the current workpiece surface temperature falls within a predetermined range from the reference temperature, the coordinate values of the center positions of the reference holes 37 and 38 are measured again to set the work coordinate system for fine tolerance, and the fine tolerance hole 39f. Since the measurement length of the center position Of in the precision tolerance work coordinate system is corrected for the work temperature, the Y ′ axis and Z in the precision tolerance work coordinate system of the center position Of of the precision tolerance hole 39f whose work temperature has been corrected are corrected. 'As shown in FIG. 6, the measurement error between the measurement length from the axis and the true value is any of the surface temperature of the workpiece between 30 ° C and 20 ° C when the center position Of of the precision tolerance hole 39f is measured. Even the temperature is within one fifth of the tolerance of the fine tolerance hole 39f.

The figure which shows the three-dimensional measuring machine for implementing the workpiece | work temperature correction method of the three-dimensional measuring machine which concerns on embodiment of this invention. The figure which shows the aspect which moves a jig between a measurement position and an attachment / detachment position. The figure which shows the state which fixed the workpiece | work to the jig. The flowchart which shows the procedure of the length measurement of the measurement location of the workpiece | work W. FIG. The figure which shows the measurement error of the measurement length of the center position of the rough tolerance hole measured at the time of each workpiece | work temperature by the method of this embodiment. The figure which shows the measurement error of the measurement length of the center position of the rough tolerance hole measured at the time of each workpiece | work temperature by the method of this embodiment. The figure which shows the measurement error of the measurement length of the measurement location measured at the time of each workpiece | work temperature by the conventional method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Three-dimensional measuring machine, 12 ... Air conditioner, 13 ... Measurement room, 14 ... Base, 15 ... Column, 16 ... Head, 17 ... Ram, 18 ... Probe, 19 ... Jig, 20 ... Control device, 21 ... Black body tape 22 ... Radiation thermometer, 23 ... Door, 24 ... Base, 25 ... Open / close valve, 26 ... Guide, 27 ... Stopper, 28 ... Conical hole, 29 ... Engagement pin, 30 ... Compression spring, 31-33 ... Workpiece 34, fixing screw, 35, handle, 37, 38, reference hole, 39, measurement hole, 39r, rough tolerance hole, 39f, fine tolerance hole.

Claims (3)

Read X, Y, and Z coordinate values when a probe that can move relative to the workpiece attached to the jig detects the workpiece surface position and sends a detection signal. In the three-dimensional measuring apparatus for measuring the measurement length of the measurement location of the workpiece by the above, the workpiece is fixed at one point while allowing the jig to linearly expand, and the workpiece measured based on the detection signal of the probe is used. A workpiece coordinate system is set based on the coordinate values of the X, Y, and Z axes of at least two reference points, and the coordinate values of the X, Y, and Z axes are read based on the detection signal of the probe for the measurement points; Measure the surface temperature of the workpiece with the radiation thermometer, calculate the measurement length in the workpiece coordinate system of the measurement location based on the coordinate value, and measure the measurement location based on the difference between the workpiece surface temperature and the reference temperature Work temperature correction method for three-dimensional measuring device, characterized in that the workpiece temperature correcting measurement length in the workpiece coordinate system. Read X, Y, and Z coordinate values when a probe that can move relative to the workpiece attached to the jig detects the workpiece surface position and sends a detection signal. In the three-dimensional measuring apparatus for measuring the measurement length of the measurement location of the workpiece by the above, the workpiece is fixed at one point while allowing the jig to linearly expand, and the workpiece measured based on the detection signal of the probe is used. An initial workpiece coordinate system is set based on the coordinate values of the X, Y, and Z axes of at least two reference points, and a rough tolerance point having a tolerance greater than or equal to a predetermined value is determined based on the detection signal of the probe. The coordinate values of the X, Y, and Z axes are read, the workpiece surface temperature is measured by a radiation thermometer, the measurement length in the initial workpiece coordinate system of the rough tolerance location is calculated based on the coordinate values, and the workpiece surface temperature When Based on the difference from the quasi-temperature, the measurement length in the initial workpiece coordinate system of the rough tolerance location is corrected for the workpiece temperature, and for the precision tolerance location where the tolerance is less than the specified value, the workpiece surface temperature is within the specified range from the reference temperature. After that, the coordinate values of the X, Y, and Z axes of the at least two reference points are measured again, a work coordinate system for fine tolerance is set based on the coordinate values, and the precise coordinate based on the detection signal of the probe is set. The coordinate values of the X, Y, and Z axes of the tolerance location are read, the workpiece surface temperature is measured by the radiation thermometer, and the measurement length in the workpiece coordinate system for the tolerance tolerance is calculated based on the coordinate value. A workpiece temperature correction method for a three-dimensional measuring machine, wherein the workpiece temperature is corrected for the measurement length in the workpiece coordinate system for the tolerances of the tolerances based on the difference between the workpiece surface temperature and the reference temperature. 3. The work temperature correction method for a three-dimensional measuring machine according to claim 1, wherein a black body material having a known emissivity is attached to a surface temperature measurement portion of the work whose temperature is measured by the radiation thermometer.

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