JP6960893B2 - Machine tool measurement error evaluation method and program - Google Patents

Description

The present invention broadly relates to a method for evaluating the measurement error and measurement ability of a machine tool, and more specifically, evaluates the measurement error and measurement ability of a numerical control machine (NC or CNC machine tool) capable of multi-axis control. , The method for calculating the correction value based on the evaluation.

Conventionally, when measuring the dimensions of mechanical parts or machining, for example, the tip of a probe (measurer) that can be moved and controlled in three dimensions is brought into contact with an object to be measured set on a measurement / machining table to a predetermined position. It has been practiced to evaluate the error and accuracy by making measurements. Then, in order to improve these errors and accuracy, various measures have been taken in the gauge and the correction processing method.

For example, considering that the gauge for calibrating a conventional 3D coordinate measuring machine is not always accurate, a gauge based on a national standard is provided and a 3D coordinate measuring machine using the gauge is provided. A calibration method has been proposed (Patent Document 1).

That is, in Patent Document 1, the sphere 2 is placed on the surface 3 of the block gauge 1 whose absolute value of the length between the first end surface 6 and the second end surface 7 is guaranteed as a national standard. By fixing, the 3D coordinate measuring machine calibration gauge 4 is configured, and when using it, three or more points are applied to the first end surface 6 with the stylus of the 3D coordinate measuring machine to specify the plane of the first end surface 6, and then. A three-point stylus is applied to the equatorial portion of the sphere 2, and a pole is also applied to specify the center coordinates of the sphere 2 and the diameter of the sphere from the plane of the first end surface 6, and then the stylus is applied to the second end surface 7. A method of correcting the above-mentioned specific values of the second end face and the sphere to obtain a three-dimensional coordinate measuring machine calibration gauge in which the coordinates of the three-dimensional space of the sphere are accurately specified is disclosed.

Further, a method capable of calibrating a three-dimensional coordinate measuring machine or the like having a wide operating space by using a small artifact has also been proposed (Patent Document 2).

That is, Patent Document 2 describes an installation step of installing the first artifact and the second artifact in the operation space of the motion mechanism having the parameters to be calibrated, and the standard coordinates of the first artifact by operating the motion mechanism. According to the first measurement step of measuring the above, the second measurement step of operating the motion mechanism to measure the standard coordinates of the second artifact, and the parameters of each coordinate value obtained in the first measurement step. The matrix whose component is the partial differential value is the P1 matrix, and the matrix whose component is the partial differential value according to each parameter for each coordinate value obtained in the second measurement step is the P2 matrix, which is obtained in the first measurement step. The R1 matrix is a matrix whose component is the partial differential value of each component of the coordinate conversion vector that converts the coordinate system of the motion mechanism into the coordinate system of the first artifact for each coordinate value to be measured, in the second measurement step. For each obtained coordinate value, the matrix when the matrix whose component is the partial differential value of each component of the coordinate conversion vector that converts the coordinate system of the motion mechanism into the coordinate system of the second artifact is the R2 matrix. A method of calibrating a motion mechanism is disclosed, which comprises a design matrix, a calculation step of estimating the parameters by the minimum square method, and a method of calibrating the motion mechanism.

Further, a three-dimensional coordinate measuring machine gauge that can be configured with higher accuracy and more easily is provided, and an accuracy evaluation method using the three-dimensional coordinate measuring machine gauge has also been proposed (Patent Document 3).

That is, Patent Document 3 describes a gauge for evaluating the accuracy of a three-dimensional coordinate measuring machine, which includes a substrate having a flat upper surface, a first row of spheres arranged on the upper surface of the substrate, and the substrate. A three-dimensional coordinate measuring machine gauge is disclosed, which comprises a second row of spheres that are arranged at an angle with respect to an upper surface.

Japanese Unexamined Patent Publication No. 2000-180103 Japanese Unexamined Patent Publication No. 2004-333312 Japanese Unexamined Patent Publication No. 2012-58057

(About spatial coordinates and spatial correction)
A three-dimensional coordinate measuring machine or a machine tool that processes product parts always has a three-dimensional space on the machine for measuring and processing. As shown in FIG. 15, this space is generally composed of three orthogonal XYZ axial motion mechanisms and scales (high-precision electronic ruler, etc.) arranged in parallel with each axis. There is a mechanism to grasp the axial momentum of the machine by the reading value of each scale.

In addition, the reading value of each scale is called "coordinate value", and the three coordinate values of XYZ are collectively called "spatial coordinates". Based on these spatial coordinates, if it is a machine tool, "dimensions" in space. We are processing while grasping. In addition, since the spatial coordinates themselves are formed using a mechanical structure, they include structural errors compared to the ideal space, and the errors are originally reduced and removed unless mechanical adjustment is performed. It's difficult.

However, mechanical adjustment requires time and cost in addition to high technology, so it cannot be said to be an easy method, and it has been difficult to carry out it frequently in practice. As a useful method for this difficulty, there is a method of grasping the spatial error of the machine by some means and converting the detected coordinate value by electronic calculation so that the error can be reduced and removed. This technique is commonly referred to as "spatial correction".

Spatial correction applications are generally used to improve the accuracy of machine output values, and since they are mainly provided by the machine manufacturer in a method that is included in their own products, the machine user himself / herself is voluntary. It was difficult to implement it in a targeted manner.

On the other hand, in "machine measurement", which is a measurement on a machine tool that has become popular in recent years, the required accuracy is not a simple machining accuracy level, but the accuracy of a high-level measuring device. Since the measurement result is only electronic data, it is desired to effectively use the above-mentioned spatial correction as a means for improving the reliability of the measurement data after the measurement.

Therefore, the measurement error evaluation method according to the embodiment of the present invention is a method for evaluating the measurement error of a machine tool, and is a method of evaluating a long arm and the arm at substantially equal intervals in the long axial direction of the arm. It has a sphere row composed of a plurality of spheres fixed on the top, a rotation mechanism for rotating the arm around a vertical axis, and a rotation mechanism for rotating the arm around an axis orthogonal to the long axis of the arm. A gauge providing step for providing a gauge in which the distance between the spheres constituting the sphere row is a distance of a reference value guaranteed in advance, and a gauge arrangement for arranging the gauge in the measurement space of the machine tool. A step, a sphere row direction adjusting step in which the arm is rotated to a desired angle by the rotation mechanism to adjust the direction of the sphere row, and a distance between the spheres included in the sphere row are measured by the machine tool. The first calculation step, the second calculation step in which the calculated distance between the spheres is compared with the reference value of the distance between the spheres guaranteed in advance, and the error in the predetermined sphere row direction is calculated, and the second calculation step described above. It is characterized by including an evaluation step for evaluating the accuracy of the machine tool using the error calculated in the calculation step.

According to the measurement error evaluation method or the like according to the embodiment of the present invention, the space correction is effectively used to improve the reliability of the measurement error evaluation of the machine tool, or the machine tool is corrected with high accuracy. It has the effect of being able to be applied.

It is explanatory drawing explaining the structural concept of the system module and the like which carry out the measurement error evaluation method and the like which concerns on one Embodiment of this invention. Among the modules shown in FIG. 1, it is explanatory drawing explaining the structural concept of the submodule and the like in the measurement program generation module. It is explanatory drawing explaining the appearance structure of the gauge adopted in the measurement error evaluation method and the like which concerns on one Embodiment of this invention. It is a flow figure explaining the processing flow in the measurement error evaluation method and the like which concerns on one Embodiment of this invention. It is explanatory drawing explaining the accuracy inspection procedure of the machine using the length inspection adopted in the measurement error evaluation method and the like which concerns on one Embodiment of this invention. It is explanatory drawing explaining the inspection procedure of 6 directions adopted in the measurement error evaluation method and the like which concerns on one Embodiment of this invention. It is explanatory drawing explaining the detail of the calculation process in the measurement error evaluation method and the like which concerns on one Embodiment of this invention. It is explanatory drawing explaining the detail of the calculation process in the measurement error evaluation method and the like which concerns on one Embodiment of this invention. It is explanatory drawing explaining the detail of the calculation process in the measurement error evaluation method and the like which concerns on one Embodiment of this invention. It is explanatory drawing explaining the detail of the correction process in the measurement error evaluation method and the like which concerns on one Embodiment of this invention. It is explanatory drawing explaining the variation of the system configuration which carries out the measurement error evaluation method and the like which concerns on one Embodiment of this invention. It is explanatory drawing explaining the variation of the system configuration which carries out the measurement error evaluation method and the like which concerns on one Embodiment of this invention. It is explanatory drawing explaining the variation of the system configuration which carries out the measurement error evaluation method and the like which concerns on one Embodiment of this invention. It is explanatory drawing explaining the variation of the system configuration which carries out the measurement error evaluation method and the like which concerns on one Embodiment of this invention. It is explanatory drawing explaining the coordinate system of the three-dimensional space provided on the machine (on the machine) in the conventional machine tool and the like.

The measurement error evaluation method and program according to the embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a configuration concept of a system module or the like that implements the measurement error evaluation method according to the embodiment of the present invention. These system modules and the like are premised on the following hardware (not shown in FIG. 1) in one embodiment.
[Hardware configuration example]
(1) Machine tools such as NC (3 to 6-axis machining center or multi-tasking machine)
(2) External terminal (PC, etc.)
For the machine tool, a measurement program generation module (in one embodiment, product name: NC gauge can be adopted) and statistical analysis software (in one embodiment, product name: O-QIS, SolaraMP can be adopted). Can be) is implemented. Alternatively, these software may be implemented in an external terminal such as a PC (in this case, the measurement data is sequentially transmitted from the machine tool to the external terminal).

Here, the measurement program generation module communicates via the API (Application Programming Interface) on the machine tool side. In addition, the statistical analysis software performs various processes for analyzing the results measured by the measurement program generation module.

In FIG. 1, the system module 100 includes a machine tool control module 110 mounted on the machine tool side such as NC and a terminal side module 120 mounted on the terminal side such as a PC. In one embodiment of the present invention, the machine tool control module 110 receives measurement signals from two types of probes connected to a machine tool (not shown) such as NC.

One of the two types of probes is the probe 191 for measuring the shape of the work. The other one is a probe 192 for measuring the temperature of the work.
In the present invention, the two types of probes are not indispensable, and at least a probe 191 for measuring the shape of the work may be provided.

Further, in calibrating the probe and the like, as one embodiment, a master gauge 199 (a gauge characteristic in the present invention will be described later with reference to FIG. 3) is used. The present invention is not limited to this, but specifically, the probe used for the measurement is registered in the measurement program generation module, and the probe is calibrated. The calibration result is used to correct the measurement result of the measurement program generation module. In the case of a 5-axis control machining center, it is also necessary to calibrate the rotation axis (the C-axis which is the fifth axis and the A-axis or B-axis which is the fourth axis).

The machine tool control module 110 includes a measurement program generation module 111 for receiving and processing measurement data from the work shape measurement probe 191 and a dedicated macro for receiving and processing measurement data from the work temperature measurement probe 192. It includes a program 112 and a macro variable generation module 113 that writes temperature information and the like in macro variables.

In one embodiment of the present invention, the macro variables related to the temperature generated by the module 113 for generating macro variables, etc. are transmitted to the temperature correction module 122 in the terminal side module 120, and are subjected to temperature correction processing (detailed description is omitted). By feeding back to the measurement program generation module 111, the reliability of the measurement error evaluation can be improved.

In one embodiment of the present invention, the data processed by the measurement program generation module 111 can be transmitted to the gauge capacity evaluation module 121 in the terminal side module 120 to evaluate the gauge capacity.

FIG. 2 shows the configuration concept of the submodules and the like in the measurement program generation module among the modules shown in FIG. In FIG. 2, the sub-module 200 is a software module in which the machine tool side controller 201 has a macro 202, a measurement program generation module 203, and a three-dimensional measurement module (a software module capable of generating a measurement program offline from CAD data, and in one embodiment. , Product name: PC-DMIS NC etc. can be adopted) It is configured to control 204, and the data measured by these modules is converted into a predetermined data format by the conversion unit 205 and reported. It is transmitted to the module (trade name: O-QIS can be adopted in one embodiment) 206, the measurement result data is processed, and the report data is generated. Then, it is transmitted to the graphic analysis module 207 as needed, and the report information is visually displayed. At this time, it may be processed in real time according to the change of the report information.

FIG. 3 shows the appearance configuration of the gauge adopted in the measurement error evaluation method or the like according to the embodiment of the present invention.

The gauge 300 includes a base 301, pedestals 302a and 302b fixed on the base 301, rotation support members 305a and 305b attached to the pedestal 302b, an arm 303 fixed to the rotation support member 305a, and an arm 303. It has spheres 304a to 304d installed and fixed at substantially equal intervals. In one embodiment of the present invention, the base 301 is a square flat plate of about 200 mm square. The pedestal 302b has a substantially cylindrical shape, and is configured to be rotatable around the axis of the cylinder with respect to the base 301 and the pedestal 302a. By rotating the pedestal 302b, the arm 303 can be rotated at an arbitrary angle in the horizontal direction. The rotation support member 305a is attached to the pedestal 302b via the rotation support member 305b, and is configured to rotate around the axis of the rotation member support 305b orthogonal to the axial direction of the pedestal 302b. By rotating the rotation support member 305a, in one embodiment, the arm 303 can be rotated at an arbitrary angle up to a maximum of 45 ° in the vertical direction.

In this way, the positions of the spheres 304a to 304d can be variously adjusted (referred to as "sphere row direction adjustment") by the rotation mechanism that rotates the arm 303 at an arbitrary angle (desired angle) in the horizontal direction and / or the vertical direction. Therefore, it is possible to create an arbitrary setting condition and measure the error. In one embodiment, the arm 303 is a long body having a length of 620 mm. The spheres 304a to 304d are fixed on the arm 303 at substantially equal intervals of about 200 mm. In other embodiments, the arm 303 may have a length of 600 mm to 1000 mm, whereby the distance between the spheres 304a to 304d can be made wider.

An arm of about 100 mm has been adopted in the conventional gauge, but by adopting an arm having a length of about 10 times that of the conventional one as in the present embodiment, it is possible to detect an error with high accuracy. In other words, it greatly enhances the reliability of the detected error and the overall error tendency read from it. In one embodiment of the present invention, four spheres are fixed on the arm at equal intervals, but the number of spheres in the present invention is not limited to four, and may be five or more.

FIG. 4 shows a processing flow in the measurement error evaluation method or the like according to the embodiment of the present invention. This processing flow describes the procedure for grasping the spatial error of a machine tool or the like and correcting the error at the time of actual measurement, and can be roughly divided into the following four procedures.
Step 1: Check the accuracy of the machine using a standard.
Step 2: Six spatial correction parameters are calculated from the inspection result.
Step 3: Perform on-board measurement to be corrected and acquire measurement data.
Step 4: Correct the measurement data using the spatial correction parameters.

Prior to step 1, a standard device whose length value is guaranteed (calibrated) with an accuracy higher than the target accuracy is prepared (step 401). As a standard device, for example, as described with reference to FIG. 3, a ball-shaped coordinate gauge that fixes a plurality of balls having a high degree of sphericity and provides an invariant distance between the centers of the balls can be used. Using a high-precision 3D measuring machine for the ball-shaped coordinate gauge, the center coordinates of the sphere are calculated from the contact points on the surface of the sphere, and the spatial distances of multiple spheres are calculated with high accuracy based on the values. Then, as shown in FIG. 5A, the inter-sphere distances La, Lb, and Lc are obtained as calibration values (step 402). Lc is a sphere set and fixed to the right of the sphere B (not shown in FIG. 5).

In step 1-1, this ball-shaped coordinate gauge is placed on the machine for on-board measurement, and the sphere center coordinates and the distance between each sphere are detected using the contact points on the surface of the sphere as in the case of calibration. Then, the inter-sphere distances La', Lb', and Lc'are obtained (step 411).

In step 1-2, the inter-ball distances La, Lb, and Lc, which are calibration values corresponding to the standard device, are registered in advance (step 412), and the detected inter-ball distances La', Lb', and Lc'are used. , The distances between balls La, Lb, and Lc, which are calibration values, are subtracted, and the error at each length on the machine is calculated as shown in the following equation (step 413).
La'-La = error a
Lb'-Lb = error b
Lc'-Lc = error c
This procedure 1-1 and procedure 1-2 are repeatedly performed on the evaluation machine in the X direction, the Y direction, and the four diagonal spatial directions (V4, V5, V6, V7) shown in FIG. 6 in each direction. Calculate the error in.

In step 2, first, as shown in FIG. 7, a plurality of length errors in a predetermined direction calculated in step 1 are plotted, and a statistical calculation such as the least squares method is used to show the overall expansion / contraction tendency of the length in the direction. The expansion / contraction coefficient S is obtained. This is carried out in the X direction, the Y direction, and the four diagonal directions (V4, V5, V6, V7) to obtain the expansion / contraction coefficients Sx, Sy, Sv4, Sv5, Sv6, and Sv7, respectively (step 414).
Then, the overall expansion / contraction tendency Sva, which is a statistical synthesis of Sv4 to Sv7, is calculated. More specifically, Sva is calculated as the average of the slopes of the lengths (V4, V5, V6, V7) in the four space directions.

Next, a calculation table is prepared for the influence components of Sx and Sy contained in Sva, with the arrangement angle at the time of inspection in the diagonal direction as a variable, and the actual coefficients are obtained by substituting the actual Sx and Sy. As shown in FIG. 8, this coefficient is used to exclude the influence of Sx and Sy from Sva, and the expansion / contraction coefficient Sz in the Z direction, which is not actually inspected, is obtained as a virtual value (step 415).
As described above, Sz can be said to be an assumed value of the slope of the length of the Z-axis obtained by removing the influence of the slope of the lengths of the X-axis and the Y-axis, which has already been known, from the above-mentioned Sva.

Further, it is estimated by calculation how much the crossing angle of the XYZ3 axes deviates from the right angle (referred to as "axis deviation coefficient") from the variation tendency of the four spatial diagonal direction expansion / contraction tendencies Sv4, Sv5, Sv6, and Sv7. Specifically, as shown in FIGS. 9 (A) and 9 (B), the four spatial diagonal stretch tendencies Sv4 to Sv7 are set to be two diagonal lines on the orthogonal coordinate planes of XY, XZ, and YZ. The projection process is performed to obtain XYθ, XZθ, and YZθ from the diagonal ratios (step 416).
By the above calculation, six spatial correction parameters Sx, Sy, Sz, XYθ, XZθ, and YZθ are obtained.

In step 3, the machine that has acquired the spatial correction parameters performs on-board measurement of the product parts that are measurement elements, and saves the measurement data (step 417). Here, the stored measurement data is data representing the coordinate values in one coordinate system on the machine, and this coordinate system is the coordinate system having the same direction as the coordinate system at the time of accuracy evaluation in step 1. And. Further, the measurement data is a coordinate point data group in which each point point of the measurement element is represented by a coordinate value.

In step 4, the following calculation is performed for all the coordinate values of the measurement data to be corrected (step 418).
(1) The X coordinate value is converted by dividing the X coordinate value by the parameter Sx (expansion / contraction coefficient of the X axis).
(2) The Y coordinate value is converted by dividing the Y coordinate value by the parameter Sy (expansion coefficient of the Y axis).
(3) The Z coordinate value is converted by dividing the Z coordinate value by the parameter Sz (expansion / contraction coefficient of the virtual Z axis).

In one embodiment of the present invention, the following calculation is performed on the converted X coordinate value, Y coordinate value, and Z coordinate value, and further on the converted coordinate value.
(4) The X coordinate value and the Y coordinate value are converted by trigonometric function calculation using the XY axis right angle error (XYθ-90 °).
(5) The X coordinate value and the Z coordinate value are converted by trigonometric function calculation using the XZ axis right angle error (XZθ-90 °).
(6) The Y coordinate value and the Z coordinate value are converted by trigonometric function calculation using the YZ axis right angle error (YZθ-90 °).

Subsequently, the measurement element is evaluated based on the coordinate point data group of the measurement element corrected by the above procedure, and the result is output as an evaluation report (step 419).

11 to 14 show variations of the system configuration for implementing the measurement error evaluation method and the like according to the embodiment of the present invention. As shown in these figures, the measurement error evaluation method according to the present invention can have various software module configurations. Hereinafter, for convenience of explanation, one form of the system configuration will be described with reference to FIG. 14, and the system configurations shown in FIGS. 11 to 13 will be sequentially described.

The system configuration shown in FIG. 14 is a form in which almost all the functions described so far are implemented on an NC gauge (the measurement program generation module described above) (the system configuration shown in FIG. 4 corresponds to this). do).

As shown in FIG. 14, the following functions (F1) to (F6) are realized on the NC gauge.
(F1) Accuracy inspection of on-board measuring equipment (F2) Accuracy evaluation function (f2-1) Standard instrument calibration value registration (f2-2) Equipment accuracy evaluation (F3) Correction parameter calculation function (f3-1) Expansion and contraction coefficient in each direction Calculation (f3-2) Virtual Z expansion / contraction coefficient calculation (f3-3) 3 Right angle calculation (F4) On-board measurement function of measurement evaluation object (F5) Correction calculation function (f5-1) Coordinate value correction calculation (F6) Measurement Element evaluation function

FIG. 11 shows other variations of the system configuration. In the figure, the functions implemented in the NC gauge are (F1), (F4), and (F6), and the others are implemented as evaluation correction comprehensive software (software independent of the NC gauge). .. Therefore, inspection data and point cloud data are transmitted and received between the NC gauge and the evaluation correction comprehensive software as data exchanged between the illustrated functions.

FIG. 12 shows yet another variation of the system configuration. In the figure, the functions implemented in the NC gauge are (F1), (F4), and (F6), and among the other functions, except for (F5), they are implemented as evaluation correction comprehensive software (F5). Software independent of NC gauge). Further, (F5) is independently configured as correction calculation software. Therefore, inspection data, correction parameters, and point cloud data are transmitted and received between the NC gauge, the evaluation correction comprehensive software, and the correction calculation software as data exchanged between the illustrated functions.

FIG. 13 shows yet another variation of the system configuration. In the figure, the functions implemented in the NC gauge are (F1), (F4), (F5), and (F6), and the others are implemented as accuracy evaluation / parameter calculation software (from the NC gauge). Independent software). Therefore, inspection data and correction parameters are transmitted and received between the NC gauge and the accuracy evaluation / parameter calculation software as data exchanged between the illustrated functions.

Although the embodiment of the measurement error evaluation method of the machine tool according to the embodiment of the present invention has been described above based on the specific example, the embodiment of the present invention includes a method or a program for carrying out the evaluation. In addition, it is also possible to take an embodiment as a storage medium (for example, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a magnetic tape, a hard disk, a memory card) on which a program is recorded. be.

Further, the implementation form of the program is not limited to the application program such as the object code compiled by the compiler and the program code executed by the interpreter, and may be in the form of a program module or the like incorporated in the operating system. good.

Further, the program does not necessarily have to perform all processing only on the CPU on the control board, and if necessary, an expansion board added to the board or another processing unit (DSP, etc.) mounted on the expansion unit. ), Or as an independent program on another PC, a part or all of it may be implemented.

These features are mutually exclusive for all of the components described herein (including claims, abstracts, and drawings) and / or for all steps of all disclosed methods or processes. Any combination can be combined except for the combination of.

Also, each of the features described herein, including claims, abstracts, and drawings, serves the same, equivalent, or similar purpose, unless expressly denied. Can be replaced with alternative features. Therefore, unless explicitly denied, each of the disclosed features is merely an example of a comprehensive set of identical or equal features.

Furthermore, the present invention is not limited to any of the specific configurations of the embodiments described above. The present invention describes all novel features or combinations thereof described herein (including claims, abstracts, and drawings), or all novel methods or processing steps described, or them. Can be extended to a combination of.

100 Measurement error evaluation system module 110 NC machine tool control module (in NC)
111 Measurement program generation module 112 Dedicated macro program 113 Macro variable generation module 120 Terminal (PC, etc.) side module 121 Gauge capacity evaluation module 122 Temperature compensation module 191 Probe for workpiece shape measurement 192 Probe for workpiece temperature measurement 199 Master gauge 200 Sub-module 201 Machine-side controller 202 Macro 203 Measurement program generation module 204 Three-dimensional measurement module 205 Conversion unit 206 Report module 207 Graphic analysis module 300 Gauge 301 Base 302a, 302b Pedestal 303 Arm 304a, 304b, 304c, 304d Sphere 305a, 305b Rotational support member

Claims (8)

It is a method to evaluate the measurement error of machine tools.
A long arm, a row of spheres composed of a plurality of spheres fixed on the arm at substantially equal intervals in the long axis direction of the arm, a rotation mechanism for rotating the arm around a vertical axis, and the vertical shaft. Provided is a gauge having a rotation mechanism that rotates around an axis orthogonal to the long axis of the arm, and a distance between each sphere constituting the sphere row is a distance of a reference value guaranteed in advance. Gauge provision steps and
A gauge placement step for arranging the gauge in the measurement space of the machine tool,
A sphere row direction adjustment step of rotating the arm to a desired angle by the rotation mechanism and adjusting the direction of the sphere row.
The first calculation step of measuring the distance between the spheres included in the sphere row by the machine tool, and
A second calculation step of comparing the calculated distance between spheres with a pre-guaranteed reference value of the distance between spheres and calculating an error in a predetermined sphere row direction,
A method for evaluating a measurement error of a machine tool, which comprises an evaluation step of evaluating the accuracy of the machine tool using the error calculated in the second calculation step. The first calculation step and the second calculation step are repeated to calculate the error corresponding to each of the plurality of sphere row directions.
The measurement error evaluation method for a machine tool according to claim 1, wherein the evaluation step evaluates the accuracy of the machine tool using errors corresponding to each of the plurality of spherical row directions. In the evaluation step, an expansion / contraction coefficient representing the degree of error in a predetermined sphere row direction is calculated using the error calculated in the second calculation step, and the accuracy of the machine tool is evaluated using the expansion / contraction coefficient. The method for evaluating a measurement error of a machine tool according to claim 1. The evaluation step uses the expansion / contraction coefficient to indicate how much the intersection angle of each axis of the measurement coordinate system including the vertical axis in the measurement space of the machine tool and the three axes substantially orthogonal to each other deviates from the right angle. The measurement error evaluation method for a machine tool according to claim 3, wherein the deviation coefficient is calculated and the machine tool is evaluated using the expansion / contraction coefficient and the axis deviation coefficient. It is characterized by including a correction step for correcting the measurement result of the object to be measured by the machine tool based on the evaluation obtained by the measurement error evaluation method of the machine tool according to any one of claims 1 to 4. How to correct the measurement result of the machine tool. A method in which at least a part of each step according to any one of claims 1 to 5 is performed on a device independent of the machine tool. A program that runs on a machine tool
A program characterized in that the step according to any one of claims 1 to 5 is executed on the machine tool. A program that is executed on a machine tool and a device independent of the machine tool.
A program characterized in that the step according to any one of claims 1 to 5 is executed on the machine tool and a device independent of the machine tool.

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