JP2019211374A - Measuring device and measuring method - Google Patents

Abstract

To provide a measuring device and a measuring method with which it is possible to carry out efficient calibration that suits to a situation and carry out measurement of sufficient accuracy at low cost in a short time.SOLUTION: Provided are a measuring device 2 and a measuring method for performing a control process relating to calibration on the basis of a determined calibration class, the measuring device 2 comprising a measuring instrument 4 attached to a mobile member 20 of a machine tool and capable of changing a measurement position or direction by operation of the mobile member 20 and a control unit 6 for converting the local coordinates acquired by the measuring instrument 4 to world coordinates and calibrating the conversion from local coordinates to world coordinates, the control unit 6 determining a calibration class on the basis of the required accuracy of measurement or the type of constrained part 10 serving as an interface between the measuring instrument 4 and the mobile member 20.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a measuring apparatus for measuring an object to be measured, in particular, a measuring apparatus in which a measuring instrument is attached to a moving body of a machine tool, and a measuring method using the measuring apparatus.

  A three-dimensional measuring instrument for measuring an object to be measured placed on a machine tool on a machine tool has been proposed. In such a three-dimensional measuring instrument, calibration is often performed using a reference sphere, but in order to measure the surface of the reference sphere, it is necessary to use a measuring tool such as a dial gauge in addition to the reference sphere. .

  In order to cope with this, a measuring apparatus has been proposed in which a measuring device is attached to a moving body of a machine tool to measure an object to be measured (for example, see Patent Document 1).

Japanese Patent No. 5595798

  In the measuring apparatus described in Patent Document 1, a measuring tool such as a dial gauge is separately used by simply using a function of a moving body of a machine tool and simply installing a reference sphere at an arbitrary position on the machine tool. Instead, the three-dimensional offset of the measuring device can be obtained and the measuring device can be calibrated.

  However, in the measurement apparatus described in Patent Document 1, it takes a long time to acquire the three-dimensional offset of the measuring instrument. On the other hand, if measurement is performed without performing calibration due to time constraints, only insufficient measurement results may be obtained.

  The present invention has been made in view of the above problems, and can perform efficient calibration according to the situation, and can perform a sufficiently accurate measurement in a short time and at a low cost. The purpose is to provide.

In order to solve the above problems, a measuring apparatus according to one embodiment of the present invention includes:
A measuring instrument attached to a moving body of a machine tool and capable of changing a measuring position or a measuring direction by an operation of the moving body;
A controller that converts the local coordinates acquired by the measuring device into world coordinates and calibrates the conversion from the local coordinates to the world coordinates;
With
The control unit is
Based on the required measurement accuracy, or the type of constrained part that serves as an interface between the measuring device and the moving body, a calibration class is determined,
Based on the determined calibration class, control processing related to the calibration is performed.

A measurement method according to one embodiment of the present invention includes:
Using a measuring instrument attached to a moving body of a machine tool and capable of changing a measurement position and a measuring direction by operation of the moving body,
A measurement method for converting local coordinates acquired by the measuring device into world coordinates, and performing calibration of conversion from the local coordinates to the world coordinates,
Determining the required measurement accuracy, or the type of constrained portion that serves as an interface between the measuring instrument and the moving body;
Determining a calibration class based on the determined measurement accuracy or the type of the constrained portion;
When it is determined that the defined calibration class is a calibration execution class, the contents corresponding to the calibration class are calibrated, and the determined calibration class is a calibration non-execution class If it is determined that, the step of not performing calibration,
including.

  According to the measurement apparatus and the measurement method of the above embodiment, a measurement apparatus and a measurement method capable of performing efficient calibration according to the situation and capable of performing measurement with sufficient accuracy in a short time at low cost. Can be provided.

It is a perspective view showing typically a machine tool provided with a measuring device concerning one embodiment of the present invention. It is a block diagram which shows the control structure of the measuring apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the work flow of the general measuring method which measures a to-be-measured object using the measuring device attached to the machine tool. It is a flowchart which shows the control processing for the calibration in the measuring apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the table for performing determination of a calibration class. It is a figure which shows Example 1 which performs the control process regarding calibration based on the defined calibration class. It is a figure which shows an example of the image which the image probe acquired in the control processing shown to FIG. 6A.

Embodiments for carrying out the present invention will be described below with reference to the drawings. The embodiment described below is for embodying the technical idea of the present invention, and the present invention is not limited to the following unless otherwise specified.
In each drawing, members having the same function may be denoted by the same reference numerals. In view of ease of explanation of the main points or ease of understanding, the embodiments may be shown separately for convenience, but partial replacement or combination of configurations shown in different embodiments is possible. In the embodiment described later, description of matters common to the above-described embodiment is omitted, and only different points will be described. In particular, the same operational effects by the same configuration will not be sequentially described for each embodiment. The size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation.

(Measurement device according to one embodiment)
First, an outline of a measuring apparatus according to one embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view schematically showing a machine tool provided with a measuring device according to one embodiment of the present invention. FIG. 2 is a block diagram showing a control configuration of the measuring apparatus according to one embodiment of the present invention.

  In FIG. 1, six degrees of freedom in which an object moves: an X-axis direction, a Y-axis direction, and a Z-axis direction, and an A direction, a B direction, and a C direction that are rotation directions around each axis are indicated by arrows. In the machine tool 100 according to the present embodiment, the spindle 20 of the spindle head 30 to which the tool is attached can move in the X-axis, Y-axis, and Z-axis directions, and can swing (rotate) in the B-direction around the Y-axis. It has become. Further, the rotary table 40 on which the object to be measured S is placed is rotatable in the C direction around the Z axis.

As shown in FIG. 2, the measuring apparatus 2 according to this embodiment includes a measuring device 4 and a control unit 6 that is electrically connected to the measuring device 4.
The measuring device 4 is attached to the spindle 20 of the spindle head 30 via the shank 10. The shank is also called a tool holder. Usually, a tool is comprised from a blade edge | tip and a shank, and a tool is attached to the main axis | shaft 20 by inserting and fixing a shank in the hole provided in the main axis | shaft 20. FIG. In the present embodiment, the measuring instrument 4 is joined to the shank 10, and the measuring instrument 4 is attached to the tip of the spindle 20 by inserting and fixing the shank 10 into the hole of the spindle 20, as in the case of the tool. It is done. Thereby, the measuring instrument 4 can change the measurement position or the measurement direction by the operation of the spindle 20, and can perform the three-dimensional measurement of the object S to be measured.

  The main shaft 20 to which the measuring device 4 is attached can be referred to as a moving body, and a shank that serves as an interface between the measuring device 4 and the main shaft (moving body) 20 can be referred to as a constrained portion.

The measuring device 4 and the control unit 6 can be connected by wire or wirelessly. The control unit 6 may be provided separately from the control device of the machine tool 100, or may be incorporated in the control device of the machine tool 100.
The control unit 6 converts the local coordinates acquired by the measuring device 4 into world coordinates. Further, when measuring the object to be measured S, calibration of conversion from local coordinates to world coordinates can be performed.

  Here, the local coordinates are relative coordinates based on the measuring device 4. The world coordinates are absolute coordinates of the space where the machine tool to which the measuring device 4 is attached is present. Each time the measuring device 4 is attached to the main shaft 20, the relative position and posture of the measuring device 4 with respect to the main shaft 20 are not constant. That is, when the measuring instrument 4 is attached to the main shaft 20, an offset from the reference position of attachment occurs. Therefore, when the measured value of the local coordinate measured by the measuring instrument 4 is converted into the world coordinate, it is necessary to correct the offset, which is called calibration.

  In the present embodiment, the spindle 20 of the spindle head 30 is illustrated as a moving body to which the measuring device 4 is attached. However, the present invention is not limited to this, and any mechanism that attaches and moves a tool or an object to be measured, For example, a shaft head, a rotary table, a pedestal, etc. can be employed. Even if the moving body has a degree of freedom of movement, it can be moved in any degree of freedom among the six degrees of freedom in the X-axis direction, Y-axis direction, Z-axis direction, A-direction, B-direction, and C-direction.

(Measurement method of measured object)
Next, with reference to FIG. 3, a general measurement method in the case where a measuring instrument is attached to a machine tool and a measurement object is measured will be described. FIG. 3 is a flowchart showing a work flow of a general measurement method for measuring an object to be measured using a measuring instrument attached to a machine tool.

  As shown in FIG. 3, first, a measuring instrument is attached to the machine tool and energized to achieve temperature equilibrium (step S10). Then, the measurement apparatus is calibrated (step S12). The accuracy with which the measuring device is attached to the moving body is naturally limited, and in particular depends on the type of shank. Therefore, in order to maintain the reproducibility of the measurement, it is necessary to perform a calibration for acquiring the three-dimensional offset from the reference position of the attached measuring instrument and correcting the measurement value obtained by the measuring instrument. By this calibration, an accurate measurement of the object to be measured can be realized.

  Next, using the result of calibration performed in step 12, a teaching that defines the measurement point and measurement path of the measurement object S is created (step S14). Then, along the measurement path defined by teaching, the moving body to which the measuring device is attached is moved to acquire measurement data at a predetermined measurement point (step 16). Based on the local coordinates obtained from the measurement data, the calibrated world coordinates are calculated, and the measurement result is output (step S18).

  When a measuring instrument is attached to a machine tool to measure an object to be measured, calibration can be performed without using a separate measuring tool by effectively using the function of the moving body of the machine tool. However, increasing the calibration accuracy increases the number of calibration points and increases the calculation accuracy, so that calibration takes a long time. Further, the work flow of FIG. 3 is an example in which teaching creation and measurement are sequentially performed. However, when teaching and measurement sandwich the attachment / detachment of the measuring instrument, calibration is performed twice, and more time is required. It will take.

(Calibration according to this embodiment)
Therefore, the measurement apparatus 2 according to the present embodiment performs a control process for calibration as described below.
Specifically, the control unit 6 determines the calibration class based on the required measurement accuracy or the type of the shank (constrained part) 10 that serves as an interface between the measuring instrument 4 and the spindle (moving body) 20. Perform the control process to be determined. Then, based on the determined calibration class, control processing related to calibration is performed.

  Here, “required measurement accuracy” includes not only the required measurement accuracy in the inspection of the final product, that is, the tolerance on the design drawing, but also the required measurement accuracy in the midway process, for example, the process drawing and the process instruction. Required tolerances entered by the operator, demand tolerances input by the operator, and the like are also included. For example, when the required accuracy of the final product is not strict, it is possible to select a calibration class that corrects fewer items than when the required accuracy of the final product is strict.

  In addition, if the required tolerance (measurement accuracy) according to each process, for example, measurement path creation process, rough machining process, is specified in the process drawing, process instruction, and operator input, the specified required tolerance It is possible to select a calibration class for correcting items according to (measurement accuracy). For example, when creating a measurement path, an error of about 1 mm can be tolerated. Therefore, a very rough calibration is sufficient, and a calibration class suitable for the calibration is selected. Further, in the measurement after the rough machining, it is only necessary to obtain a measurement value with relatively low accuracy, so a calibration class corresponding to the measurement value is selected.

  Typical types of the shank (constrained portion) 10 include BT (JIS standard), HSK (DIN standard), CAPTO (registered trademark), and the like. The mounting accuracy varies depending on the type of the shank (restrained portion) 10. For example, the error after attaching the measuring instrument 4 to the spindle (moving body) 20 is suppressed in CAPTO (registered trademark) compared to BT (JIS standard), and the calibration class corrects only limited items. Is selected.

  Furthermore, a calibration class can be determined based on a combination of measurement accuracy and the type of shank (constrained portion) 10. For example, when a measurement after a rough machining process with a required accuracy is not strict using a shank (constrained portion) 10 with a small error, a calibration class that performs only a very limited calibration is selected. In some cases, as will be described later, a calibration class for which calibration is not performed may be selected.

  As described above, in the present embodiment, the calibration class is determined based on the measurement accuracy or the type of the constrained part, and the control process related to the calibration is performed based on the determined calibration class. Efficient calibration can be performed with items omitted, and sufficiently accurate measurement can be performed in a short time and at low cost.

  In more detail about “perform calibration control processing based on a defined calibration class”, not only when calibration corresponding to the calibration class is performed, but also when calibration is not performed. Cases are also included.

  Furthermore, in the “calibration of contents corresponding to the calibration class”, there are six degrees of freedom in which the measuring device 4 attached to the main shaft (moving body) 20 may move relative to the main shaft (moving body) 20 ( Among the X axis, Y axis, Z axis, A, B, and C directions), it is conceivable to perform calibration with respect to the degree of freedom corresponding to the calibration class.

By performing calibration regarding the degree of freedom corresponding to the calibration class, it is possible to reliably perform measurement with sufficient accuracy in a short time and at low cost.
Depending on the measurement accuracy and the type of shank (constrained part) 10, calibration is performed with respect to at least three degrees of freedom (for example, X, Y and Z axis directions, X, Y axis and B directions) among the above six degrees of freedom. In many cases, it is considered that sufficient accuracy can be achieved efficiently.
For example, the major axis of the constrained portion is the Z axis, and the measurement plane is an XY plane orthogonal to the measurement plane. When the shank (constrained portion) 10 has play in the C direction (rotation direction) around the X axis, the Y axis direction, and the Z axis (long axis), among the six degrees of freedom, the X, Y axis, and C Calibration is preferably performed with respect to three degrees of freedom in the direction.

  As a further example, if the major axis of the shank (constrained part) 10 is the Z axis in the measuring instrument 4 for a three-dimensional measurement, for example, a plane orthogonal to the major axis (for example, a detection plane of the measuring instrument 4). There are six degrees of freedom in the A, B, and C directions around the X, Y, and X, Y, and Z axes. When the interval between the shank (constrained part) 10 and the detection point is long, the shake (movement (rotation) in the A and B directions) of the shank (constrained part) 10 causes the detection point in the X and Y axis directions. There is a possibility that the gap will increase. For example, when the distance from the mounting surface to the measurement point is 200 mm, the mounting runout may be about 20 μm. In this case, it is necessary to perform calibration with respect to two degrees of freedom in the X and Y axis directions among the six degrees of freedom.

  Furthermore, in the measuring device 4 having a measurement range of two or more dimensions, an error in the rotation direction is also a measurement error. Depending on the shape of the shank attached to the spindle, the rotation error may be several tens of μm in terms of measurement error. For example, when the shank (constrained portion) 10 is HSK-A (DIN standard), the error in the XY plane is small, and calibration in the X-axis and Y-axis directions is unnecessary. On the other hand, the shake in the C direction around the Z axis is large, and calibration in the C direction is necessary. Therefore, it is necessary to perform calibration for one of the six degrees of freedom.

  As described above, taking into account the required measurement accuracy for each degree of freedom, extract the degrees of freedom that require calibration, and do not perform calibration for the degrees of freedom that do not affect the required measurement accuracy. It is preferable to define a calibration class. In some cases, calibration may be performed with respect to a limited degree of freedom depending on the shape and orientation of the measurement surface of the object to be measured.

  Furthermore, regarding “calibration of contents corresponding to the calibration class”, the number of points for acquiring local coordinates, the measurement position, and the measurement direction can be determined according to the calibration class. For example, if the calibration before the measurement path is created or the calibration before the measurement after the rough machining, the accuracy as high as the calibration before the measurement after the final machining is not required, so the local coordinates are acquired for calibration. It is possible to reduce the number of points to be measured, the measurement position, and the measurement direction.

As described above, the number of points for acquiring local coordinates, the measurement position, and the measurement direction are determined in accordance with the measurement accuracy and the type of the shank (constrained portion) 10. Therefore, measurement with sufficient accuracy can be efficiently performed in each situation. realizable.
As the measuring device 4 according to the present embodiment, a light cutting type light cutting probe, a phase shift type phase shift probe, or an image type image probe can be employed.

  In the light cutting method, slit-like light is projected from the light source onto the object to be measured, the reflected light is detected by the light receiving element, and the three-dimensional data of the slit-like light can be acquired by performing the triangulation. By scanning the slit-shaped light, a three-dimensional measurement shape of the object to be measured can be obtained.

  The phase shift method is also called a time fringe diffraction method, and is a method of measuring a distance by analyzing an image captured by shifting the phase of a sine wave fringe pattern. By acquiring images of at least three sinusoidal fringe patterns having different phases, a three-dimensional measurement shape of the object to be measured can be obtained.

  The image method is a method for obtaining a two-dimensional measurement shape from an image of an object to be measured obtained by image acquisition means such as a camera.

Regardless of which type of measuring device 4 is used, it is possible to perform efficient calibration without unnecessary correction items, and to perform sufficiently accurate measurement in a short time and at low cost. .
(Control processing for calibration)
Next, a control process for calibration performed by the control unit 6 of the measurement apparatus 2 according to one embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 is a flowchart showing a control process for calibration in the measurement apparatus according to one embodiment of the present invention. FIG. 5 is a diagram illustrating an example of a table for determining a calibration class.

As shown in FIG. 4, first, data A related to the measuring instrument 4 stored in the storage unit is read (step S20). In this case, the data A stored in the storage unit of the control unit 6 in advance may be read out, or the data A input by the operator and temporarily stored in the storage unit may be read out.
The data A includes the measurement method of the measuring instrument 4, information on the moving body to which the measuring instrument 4 is attached, and the like. The data A can define the degree of freedom in which calibration is possible.

Next, the data B related to the required measurement accuracy stored in the storage unit is read (step S22). Also in this case, the data B stored in the storage unit of the control unit 6 in advance may be read out, or the data B input by the operator and temporarily stored in the storage unit may be read out.
As described above, the data B includes the required measurement accuracy in the inspection of the final product, the required measurement accuracy in the midway process, etc., and the required tolerances according to each process (measurement path creation process, rough machining process, etc.) (Measurement accuracy) is also included.

  Next, data C relating to the shank (constrained part) stored in the storage unit is read (step S24). Also in this case, the data C stored in the storage unit of the control unit 6 in advance may be read out, or the data C input by the operator and temporarily stored in the storage unit may be read out.

  Data C includes information on the type of shank (constrained part), for example, BT (JIS standard), BBT (enterprise standard), HSK-A (DIN standard), HSK-T (DIN standard), and CAPTO (registered trademark). ) And the like, and information on the mounting accuracy at each degree of freedom for each shank (constrained portion).

  Next, a control process for determining a calibration class is performed based on the read data A to data C (step S26). In the present embodiment, the calibration class is determined using a table as shown in FIG. Each table is provided according to the measurement method of the measuring device 4 corresponding to the data A. The required measurement accuracy corresponding to data B is shown in the column of the table, and the type of attachable shank (constrained part) corresponding to data C is shown in the row. A calibration class is set in each column of such a matrix. That is, in step S26, the calibration class is determined based on the combination of the measurement accuracy and the type of the shank (constrained portion).

In FIG. 5, a table applied to a machine tool to which a BT standard shank (constrained part) shown as the machine tool 1 can be attached, and a machine to which an NSK standard shank (constrained part) shown as the machine tool 2 can be attached. Although the table applied to the machine and the table applied to the machine tool to which the CAPTO type shank (constrained portion) shown as the machine tool 3 can be attached are collectively shown, in the actual control processing, the machine tool 1 to 1 Any one of the three tables is used.
Further, in the table of FIG. 5, a specific allowable upper limit is defined for the required measurement accuracy, but it is not limited to this. For example, the contents of each process, for example, the measurement path creation process, rough machining, etc. It can also be defined by a process or the like.

  Next, based on the calibration class determined in step S26, it is determined whether or not to perform calibration (step S28). If it is determined in this determination that the calibration is not performed (NO), the control process relating to the calibration is terminated as it is. If it is determined in step S28 that calibration is to be performed (YES), then the number of points, the measurement position, and the measurement direction for acquiring local coordinates corresponding to the calibration class are determined (step S30). . Then, the degree of freedom for performing the calibration corresponding to the calibration class is determined (step S32), and based on the conditions set in step S30 and step S32, the moving body to which the measuring instrument 4 is attached (for example, the spindle head 30). The main spindle 20) is driven to execute actual calibration (step S34), and the control process for a series of calibrations is terminated.

As described above, in the measurement method according to the present embodiment, the measuring instrument is attached to the moving body of the machine tool 100 (for example, the main spindle 20 of the spindle head 30) and can change the measurement position and the measurement direction by the operation of the moving body. 4 is used to convert the local coordinates acquired by the measuring instrument 4 into world coordinates and calibrate the conversion from local coordinates to world coordinates.
In particular, in the measurement method according to this embodiment,
Determining the required measurement accuracy, or the type of shank (constrained part) 10 that serves as an interface between the measuring instrument 4 and the moving body;
Determining a calibration class based on the defined measurement accuracy or type of shank (constrained part) 10;
When it is determined that the defined calibration class is a calibration execution class, the content corresponding to the calibration class is calibrated, and the determined calibration class is determined to be a calibration non-execution class. Step that does not perform calibration, and
including.

  As a result, efficient calibration can be performed without unnecessary correction items, and sufficient accuracy can be measured in a short time at low cost.

  In particular, the calibration class can be determined and calibrated by using the local coordinates acquired by the measuring device 4 from the measured object S in a state where the measured object S is attached to the machine tool 100. Therefore, the calibration class can be determined and calibrated using the workpiece S during or immediately after processing without using a special member for calibration. It can be implemented.

Next, a specific example in which the control process for the calibration is performed will be described.
(Example 1)
First, Example 1 will be described with reference to FIGS. 6A and 6B. FIG. 6A is a diagram illustrating the first embodiment in which control processing related to calibration is performed based on a defined calibration class. FIG. 6B is a diagram illustrating an example of an image acquired by the image probe in the control process illustrated in FIG. 6A.

In the first embodiment, a case where an image probe (two-dimensional probe) having a visual field of 40 mm × 40 mm is used as the measuring device 4 will be described. At this time, when HSK-A is used as the shank (constrained portion) 10, the reproducibility of the offset in the XY plane is almost the same as the tool runout, and about 5 μm can be expected.
On the other hand, HSK-A has a large shake in the rotational direction and may be displaced by nearly 100 μm with respect to the 20 mm field of view. Therefore, it is necessary to perform calibration in the C direction around the Z axis (long axis).

  In this case, since only calibration in the C direction is required, the calibration target T is placed on the turntable 40, the center of the turntable 40 is set as the origin, and the measuring instrument (image probe) 4 is placed. Then, the measuring instrument (image probe) 4 is moved from the position −15 mm to the position +15 mm (position indicated by P in FIG. 6A to position Q) in the X-axis direction, and two calibration targets T at that time are moved. Get the image. As shown in FIG. 6B, the obtained two images are superimposed and correlated to obtain an offset in the C direction for calibration.

  If the required measurement accuracy is 0.01 mm or less and the offset is 5 μm, the offset in the XY plane cannot be ignored. In this case, it is possible to perform calibration by acquiring offsets in the X-axis and Y-axis directions by acquiring the images of the three points P, Q, and R in FIG. it can.

(Example 2)
Next, Example 2 will be described. Example 2 shows a case where a phase shift probe (three-dimensional probe) having a visual field of 40 mm × 40 mm × 20 mm is used as the measuring device 4. At this time, when CAPTO (registered trademark) is used as the shank (constrained portion) 10, the offset in the X-axis, Y-axis, Z-axis direction, and the C-direction around the Z-axis (long axis) are shifted by about 5 μm. There is.

  Assuming that the required measurement accuracy is a measurement for teaching creation in which the operation mode defines a measurement path or the like, the error is in a negligible range, so a calibration class that does not execute calibration is determined.

  Although the embodiments and embodiments of the present invention have been described, the disclosed contents may vary in the details of the configuration, and combinations of elements and changes in the order of the embodiments, embodiments, etc. are claimed in the present invention. It can be realized without departing from the scope and spirit of the present invention.

2 Measuring device 4 Measuring device 6 Control part 10 Shank (restraint part)
20 Spindle (moving body)
30 Spindle head 40 Rotary table 100 Machine tool S Object T Calibration target

Claims (7)

A measuring instrument attached to a moving body of a machine tool and capable of changing a measuring position or a measuring direction by an operation of the moving body;
A controller that converts the local coordinates acquired by the measuring device into world coordinates and calibrates the conversion from the local coordinates to the world coordinates;
With
The control unit is
Based on the required measurement accuracy, or the type of constrained part that serves as an interface between the measuring device and the moving body, a calibration class is determined,
A measuring apparatus that performs control processing related to the calibration based on the determined calibration class.   The calibration is performed with respect to a degree of freedom corresponding to the calibration class among six degrees of freedom in which the measuring device attached to the moving body may move relative to the moving body. The measuring apparatus according to 1.   The measurement apparatus according to claim 2, wherein calibration is performed with respect to at least three degrees of freedom among the six degrees of freedom.   4. The measuring apparatus according to claim 1, wherein the number of points, the measurement position, and the measurement direction for acquiring the local coordinates are determined according to the calibration class.   5. The measuring apparatus according to claim 1, wherein the measuring device is based on a light cutting method, a phase shift method, or an image method. Using a measuring instrument attached to a moving body of a machine tool and capable of changing a measurement position and a measuring direction by operation of the moving body,
A measurement method for converting local coordinates acquired by the measuring device into world coordinates, and performing calibration of conversion from the local coordinates to the world coordinates,
Determining the required measurement accuracy, or the type of constrained portion that serves as an interface between the measuring instrument and the moving body;
Determining a calibration class based on the determined measurement accuracy or the type of the constrained portion;
When it is determined that the defined calibration class is a calibration execution class, the contents corresponding to the calibration class are calibrated, and the determined calibration class is a calibration non-execution class If it is determined that, the step of not performing calibration,
A measurement method comprising:   The calibration class is determined and the calibration is performed using the local coordinates acquired from the measurement object by the measuring instrument in a state where the measurement object is attached to the machine tool. 6. The measuring method according to 6.

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