JP2022008099A - Rotation axis center position measuring method of machine tool - Google Patents

Abstract

To provide a rotation axis center position measuring method of a machine tool capable of accurately measuring a center position of a rotation axis by simple calculation without using a touch probe.SOLUTION: A tool 3 is installed to a main shaft 18, and a detection unit 20 that can detect a position of the tool 3 without contacting is provided on a rotary table 13. About a C-axis that is a rotation axis of a measured object, the tool 3 and the rotary table 13 are indexed to a predetermined position. Detection action for detecting a position of the tool 3 with respect to the rotary table 13 is repeated by using the detection unit 20 at each angle position, and a center position of the C-axis is calculated from the position of the tool 3 at each angle position detected by the multiple detection actions.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for measuring the center position of a rotating shaft of a machine tool.

In a machine tool, a work placed on a table is machined by a tool mounted on a spindle. At the time of machining, an arbitrary three-dimensional shape can be machined on the work by three-dimensionally moving the tool and the work in each of the X-axis, Y-axis, and Z-axis directions.
Some machine tools are provided with a rotation axis that rotates the tool around the translation axis in addition to the translation axis in the XYZ direction in order to increase the degree of freedom in machining. Examples of the rotation axis to be added include an A axis that is a rotation around the X axis, a B axis that is a rotation around the Y axis, and a C axis that is a rotation around the Z axis. As such a multi-axis control machine tool, for example, a 5-axis control machine tool in which two axes, A-axis and C-axis, are added to three of X-axis, Y-axis, and Z-axis is used.

In the above-mentioned multi-axis control machine tool, in order to improve the machining accuracy, it is necessary to minimize the position error of the translation axis and to minimize the angle error of the rotation axis and the position accuracy of the center of rotation. be. Of these, in order to suppress a decrease in machining accuracy due to an error in the center position of the rotating shaft, the center position of the rotating shaft is measured and correction control is performed as a parameter during machining (see Patent Document 1). ..

In Patent Document 1, as a method of measuring the center position of the rotating shaft, a target sphere as a reference master is fixed on a table instead of a work, and a touch probe is attached to a spindle instead of a tool for measurement. The power axis of rotation is determined at multiple angles, the touch probe is brought into contact with the target sphere at each angle position, the center position of the target sphere is measured, and the center position of the rotation axis is calculated from the measured values at multiple angle positions. ing.
In particular, in Patent Document 1, a touch probe at a plurality of angular positions of a rotating shaft is used so that the center position of the rotating shaft can be measured with high accuracy even in a machine machine in which the operating range of the translation axis is structurally limited. The contact operation with the target sphere is performed only within the operable range of the translation axis, and the center position of the rotation axis is measured by calculation without performing the contact operation within the range where the movement is restricted.

On the other hand, even if the tool to be measured and the measuring device interfere with each other and the indexing range of the swivel axis (4th axis, 5th axis) is greatly limited, only one measuring device is used in all the X, Y, and Z directions. A cutting edge position detection method capable of measuring the amount of error in the above has been developed (Patent Document 2).
In Patent Document 2, two directions of the tool center point obtained by measuring two or more points of the lowest point of the tool on the rotation axis of the swivel table and two or more points of the outer circumference of the tool in the plane orthogonal to the rotation axis of the swivel table. The amount of cutting edge positioning error in the X, Y, and Z directions is obtained from the amount of error in.

JP-A-2019-152574 Japanese Unexamined Patent Publication No. 2020-28922

According to the measurement method of Patent Document 1 described above, the center position of the rotating shaft can be measured with high accuracy even in the case of a machine tool in which the operating range of the translational shaft is limited.
However, in the measurement method of Patent Document 1, in order to detect the position of the target sphere, a touch probe is attached to the spindle instead of the blade.
For this reason, the machine tool at the time of measurement is not in the state at the time of actual machining with the tool attached to the spindle, and the center position of the measured rotation shaft is different from the center position at the time of machining, and the measurement accuracy is limited. There was a problem.
Further, there is a problem that the measurement method of Patent Document 1 cannot be used in a machine tool in which a touch probe cannot be attached to a spindle.
On the other hand, in Patent Document 2, several methods are presented in order to obtain an error amount in two directions of the tool center point, but the tool type is limited to the ball end mill and the tool tip is treated as a "perfect circle". This is a premise, and it cannot be applied to tools with different tip shapes, making it difficult to measure the center position with high accuracy. Therefore, even for tools with various tip shapes, it has been required to be able to measure the center position of the rotating shaft with high accuracy by a simple calculation.

An object of the present invention is to provide a method for measuring the center position of a rotating shaft of a machine tool, which can measure the center position of the rotating shaft with high accuracy by a simple calculation without using a touch probe.
Another object of the present invention is to provide a method for measuring the center position of a rotating shaft of a machine tool, which can measure the center position of the rotating shaft with high accuracy by a simple calculation even for a tool having various tip shapes.

In the method for measuring the center position of a rotary shaft of a machine tool of the present invention, a tool is mounted on a spindle, a detection unit capable of detecting the position of the tool in a non-contact manner is installed on a table, and the rotary shaft to be measured is the tool. And the table are indexed to a predetermined angle position, the detection operation of detecting the position of the tool with respect to the table is repeated at each angle position using the detection unit, and each angle position detected by the detection operation a plurality of times. It is characterized in that the center position of the rotating shaft is calculated from the position of the tool in.

In the present invention as described above, the detection operation using the non-contact type detection unit is repeated a plurality of times, and the geometric calculation is performed from the position of the tool at each angle position to obtain the center position of the rotation axis with high accuracy. Can be measured.
In the measurement, a tool for machining can be attached to the spindle of the machine tool, and the spindle can be rotated to raise the temperature immediately before the measurement, and the measurement can be performed in the same state as during machining. It can also be widely applied to machine tools where the touch probe cannot be attached to the spindle.
Therefore, according to the present invention, it is possible to provide a method for measuring the center position of the rotation axis of a machine tool, which can measure the center position of the rotation axis with high accuracy by a simple calculation without using a touch probe.

In the present invention, if the position and orientation of the detection unit with respect to the table can be grasped with high accuracy, the rotation center of the rotation axis can be calculated with a smaller number of times, but the position and orientation of the detection unit with respect to the table can be calculated with high accuracy. Even if it cannot be grasped, by detecting the position of the tool at each angle position by a plurality of detection operations, it is possible to narrow down the tip position of the tool by geometric calculation and determine it with high accuracy.

In the method for measuring the center position of a rotary axis of a machine tool of the present invention, the detection unit can detect that the tip of the tool is at a specific position in the detection unit in a non-contact manner, and in the detection operation, the detection unit and the spindle The table is moved relative to each other to index the tool and the table into predetermined angular positions, and the relative positions of the spindle and the table so that the tool comes to the specific position of the detection unit at each angle position. In this state, it is preferable to detect the position of the tool with respect to the table at each angle position from the relative position between the spindle and the table.

In the present invention, when the detection unit is used as a detection operation to detect the position of the tool with respect to the table, the position of the tool may be detected by the detection unit, and the detection unit is used as a tool positioning jig to be used as a machine tool. The position data for control may be acquired from the control device of. That is, by operating the machine tool under the control of the control device, moving the spindle to place the tool at a specific position of the detection unit, and referring to the position data of the spindle in the control device of the machine tool in this state, the tool You can get the position of. As the specific position, the center position of the tool detection area in the detection unit can be used.

In the method for measuring the center position of the rotary axis of the machine tool of the present invention, the detection unit capable of detecting the radial position of the table of the tool is used, and the tool and the table are first sandwiched between the rotary shaft. The detection operation is performed at each of the two angular positions facing the directions and the two angular positions facing the second direction intersecting the first direction with the rotation axis in between. Detects the radial position of the table of the tool, passes through the midpoint of the line segment connecting the positions of the tools detected at the two angular positions facing the first direction, and intersects in the first direction. The first straight line to be used and the second straight line passing through the midpoint of the line segment connecting the positions of the tools detected at the two angular positions facing the second direction and intersecting the second direction are calculated. The intersection of the first straight line and the second straight line may be measured as the center position of the rotation axis.

In the present invention, as a detection unit capable of detecting the position of the tool in the radial direction of the table,
An image sensor that detects an image from the side surface of the tool and detects the position of the tool on the image can be installed so as to face the circumferential direction of the table.
As the four angle positions facing each other across the axis of rotation, for example, the 0 degree position and the 180 degree position of the table are set as two angle positions facing each other in the first direction, and the 90 degree position and the 270 degree position face each other in the second direction. It can be two angular positions.
According to the present invention, the estimated range of the center position, which cannot be determined by the detection operation at the angle positions of 0 and 180 degrees, is narrowed down by the position of the tool by the detection operation at the angle positions of 90 degrees and 270 degrees. The center of the rotation axis can be determined accurately, and the center position of the rotation axis can be measured with high accuracy by the detection operation at a total of four angle positions.

In the method for measuring the center position of the rotation axis of a machine tool of the present invention, the detection unit capable of detecting the position of the tool along the surface of the table is used, and the tool and the table face each other with the rotation axis interposed therebetween. A line segment connecting the positions of the tool in the two detection operations to detect the position of the tool along the surface of the table of the tool by performing the detection operation at each angle position. The midpoint may be calculated and measured with the midpoint as the center position of the rotation axis.

In the present invention, as a detection unit capable of detecting the position of the tool along the surface of the table, a detection unit capable of detecting the radial position and the circumferential position of the table of the tool can be used, and more specifically, the detection unit can be used. , An image sensor system with an autofocus function is installed on the table facing the circumferential direction of the table, the position of the tool on the image from the side of the tool is the radial position, and the depth of the image detected by the autofocus function. The position of the tool in the direction can be detected as the position in the circumferential direction.
The two angular positions facing each other across the rotation axis can be, for example, a 0 degree position and a 180 degree position of the table.
According to the present invention as described above, the center position of the rotating shaft can be measured with high accuracy by a simple operation of detection operation at two angular positions.

In the method for measuring the center position of the rotation axis of a machine tool of the present invention, the detection unit capable of detecting the radial position of the table of the tool is used, and the tool and the table are designated with the rotation axis as the center. The position of the tool obtained by performing the detection operation at each angle position is detected at a plurality of angular positions within the angle range, the radial position of the table of the tool is detected, and the position of the tool obtained by the detection operation is performed a plurality of times. You may plot and calculate the center position of the rotation axis by approximate calculation.

In the present invention as described above, even if the detection operation cannot be performed in a part of the angle range around the rotation axis due to the structural restrictions of the machine tool, the detection operation is performed a plurality of times in a limited angle range excluding the same angle range. By repeating, the candidate position of the center position of the rotation axis can be plotted in an arc shape, for example, and the center position can be determined by an approximate calculation such as the least squares method.

In the method for measuring the center position of a rotating shaft of a machine tool of the present invention, it is preferable that the detection unit has a fixing means to the table.
In the present invention, it is necessary that the detection unit installed on the table does not change its installation position with respect to the table during the detection operation at each angle position. When the table is facing upward, it is sufficient that the table is simply placed, that is, the movement is restricted by frictional force with respect to the table surface. If the table is not facing up, it is preferable to use other fixing means to the table to prevent the detection unit from falling off the table.
As the fixing means, those that are easily attached and detached are preferable, and for example, adsorption by a magnet, adhesion by an adhesive sheet or an adhesive, or mechanical fixing such as a clamp may be used. Since the detection unit is non-contact type, there is basically no movement due to contact with the tool, and it is not necessary to firmly fix the detection unit to the table.

In the method for measuring the center position of the rotation axis of a machine tool of the present invention, the detection unit includes an illumination unit that irradiates a parallel light flux and an image pickup unit that detects the parallel light flux, and the image detected by the image pickup unit. It is preferable to detect the tip position of the tool arranged in the parallel luminous flux.

In the present invention, as the irradiation unit, a light beam is formed by using a point light source and a telecentric lens, a parallel light flux is formed by a linearly arranged light source, and a light beam is shaken in parallel to be pseudo-parallel. Those that form a light source can be used as appropriate.
In the present invention, it is preferable to use an image detector capable of outputting data and processing the captured image, such as a CCD (Charge Coupled Device) type camera, as the image pickup unit.
In the present invention, when the tip position of the tool arranged in the parallel light beam is detected from the image detected by the image pickup unit, the existing image processing is performed on the image detected by the image pickup unit to perform parallel processing. It is possible to use software that calculates the tip position of the tool by detecting the shadow of the tool placed in the light beam and calculating the center position from the contour of the tip of the tool by edge detection.
In the present invention as described above, the position of the tip of the tool can be detected with high accuracy without contact by performing optical detection.
Further, in the position detection, it is only necessary to arrange the tip of the tool in the parallel light flux between the illumination unit and the image pickup unit, and the detection operation is easy.

In the method for measuring the center position of the rotation axis of a machine tool of the present invention, the image is detected by the image pickup unit in a state where the tool is rotated with respect to the image pickup unit, the contour of the tool is detected from the image, and the tool is detected. It is preferable to detect the central axis of the tool from the symmetry of the contour and detect the intersection of the central axis and the contour as the tip position of the tool.
In the present invention as described above, the central axis of the tool can be detected by utilizing the fact that the contour of the rotating tool becomes axisymmetric, and the intersection of the detected central axis and the contour of the tool is taken to obtain the tool of the tool. The tip position can be determined. At this time, there are no restrictions on the tip shape of the tool, and the tip position can be determined for tools having various tip shapes. Further, the tip position can be determined only by the geometric calculation process on the image of the tool, and the tip position of the tool or the center position of the rotation axis can be measured with high accuracy by a simple calculation.

In the method for measuring the center position of the rotation axis of the machine tool of the present invention, when the intersection of the center axis and the contour is detected as the tip position of the tool, a pair of parallel lines are separated from each other on both sides of the center axis. Is set, an auxiliary contour line that passes through the intersection of the pair of parallel lines and the contour and is orthogonal to the central axis is set, and the intersection of the central axis and the auxiliary contour is detected as the tip position of the tool. It is preferable to do so.
In the present invention as described above, the auxiliary contour line is also provided for a tool having a plurality of protrusions at the tip, a tool having a biased tip, and the like, in which the shape of the contour of the tip becomes unclear in a rotated state. By setting, the tip position of the tool can be determined from the center. As a result, even for tools with various tip shapes, the tip position of the tool or the center position of the rotation axis can be measured with high accuracy by simple calculation.

In the method for measuring the center position of the rotation axis of the machine tool of the present invention, a plurality of transversals crossing the contour are set in the extending direction of the tool, and for each of the transversals, two intersections with the contour and two said heads. The midpoint of the intersection can be detected, and the straight line passing through the midpoint of each transversal line can be set as the central axis of the tool.
In the present invention as described above, the exact central axis (rotational symmetry axis) of the tool can be detected by using the extension direction of the tool (direction of the tool, approximate axis direction). At this time, the tip position of the tool or the center position of the rotation axis can be easily measured with high accuracy by the geometric calculation process using a plurality of crossing lines.

In the method for measuring the center position of the rotation axis of a machine tool of the present invention, the shape of one side of the contour is detected as a reference pattern with respect to the stretching direction of the tool, and a symmetrical pattern matching the inverted shape of the reference pattern is detected as the contour. A straight line that is detected from the above and passes between the reference pattern and the symmetrical pattern can be used as the central axis of the tool.
In the present invention as described above, the exact central axis (rotational symmetry axis) of the tool can be detected by using the extension direction of the tool (direction of the tool, approximate axis direction). At this time, by recognizing the pattern on the image, the tip position of the tool or the center position of the rotation axis can be easily measured with high accuracy.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for measuring the center position of a rotating shaft of a machine tool, which can measure the center position of the rotating shaft with high accuracy by a simple calculation without using a touch probe. Further, even for tools having various tip shapes, it is possible to provide a method for measuring the center position of the rotation axis of a machine tool, which can measure the center position of the rotation axis with high accuracy by a simple calculation.

The perspective view which shows the machine tool of 1st Embodiment of this invention. The perspective view which shows the detection unit of the 1st Embodiment. The schematic diagram which shows the detection unit of the 1st Embodiment. The perspective view which shows the detection operation of the 1st Embodiment. The schematic diagram which shows the tool tip in the detection operation of the 1st Embodiment. The schematic diagram which shows the detection operation of the 1st Embodiment. The schematic diagram which shows the C-axis position measurement operation of the 1st Embodiment. The schematic diagram which shows the C-axis position measurement operation of the 1st Embodiment. The schematic diagram which shows the C-axis position measurement operation of the 1st Embodiment. The schematic diagram which shows the C-axis position measurement operation of the 2nd Embodiment of this invention. The schematic diagram which shows the C-axis position measurement operation of the 3rd Embodiment of this invention. The schematic diagram which shows the C-axis position measurement operation of the 3rd Embodiment. The schematic diagram which shows the modification of the 1st to 3rd Embodiment. The schematic diagram which shows the A-axis position measurement operation of 4th Embodiment of this invention. The schematic diagram which shows the A-axis position measurement operation of the 4th Embodiment. The schematic diagram which shows the A-axis position measurement operation of the 4th Embodiment. The schematic diagram which shows the A-axis position measurement operation of 5th Embodiment of this invention. The schematic diagram which shows the A-axis position measurement operation of the 5th Embodiment. The schematic diagram which shows the A-axis position measurement operation of the 5th Embodiment. The schematic diagram which shows the A-axis position measurement operation of the 5th Embodiment. The schematic diagram which shows the A-axis position measurement operation of the 6th Embodiment of this invention. The schematic diagram which shows the modification of the A-axis position measurement operation of the 6th Embodiment. The schematic diagram which shows the modification of the A-axis position measurement operation of the 6th Embodiment. The schematic diagram which shows the tool tip position detection process of the 7th Embodiment. The schematic diagram which shows the tool tip position detection process of a different direction of the 7th Embodiment. The schematic diagram which shows the tool tip position detection process of the 8th Embodiment. The schematic diagram which shows the tool tip shape of the 9th Embodiment and the image thereof. The schematic diagram which shows the tool tip position detection process of the 9th Embodiment.

[First Embodiment]
In FIG. 1, the machine tool 1 has a moving table 12 and a rotary table 13 on the upper surface of the bed 11.
The moving table 12 is movably supported along the upper surface of the bed 11, is moved by an X-axis moving mechanism (not shown) formed on the bed 11, and can be positioned at a predetermined position in the X-axis direction.
The rotary table 13 is rotatably installed on the upper surface of the moving table 12, is rotated by a C-axis rotation mechanism (not shown) formed on the moving table 12, and can be positioned at a predetermined angle position around the C-axis.
The work 2 to be machined is fixed to the upper surface of the rotary table 13.

The machine tool 1 has a gate-shaped column 14 on the upper surface of the bed 11.
The column 14 is formed in a gate shape so as to straddle the movement path in the X-axis direction of the movement table 12. A spindle head 17 is supported on the column 14 via a saddle 15 and a slider 16.
The saddle 15 is movably supported along the horizontal bar of the column 14, is moved by a Y-axis moving mechanism (not shown) installed on the column 14, and can be positioned at a predetermined position in the Y-axis direction.
The slider 16 is supported up and down along the vertical surface of the saddle 15 and is moved by a Z-axis moving mechanism (not shown) installed on the saddle 15 so that it can be positioned at a predetermined position in the Z-axis direction.

The spindle head 17 is rotatably supported on the lower surface of the slider 16, is rotated by an A-axis rotation mechanism (not shown) formed on the slider 16, and can be positioned at a predetermined angle position around the A-axis.
The spindle 18 is rotatably supported by the spindle head 17, and the tool 3 is mounted on the tip of the spindle 18.
The spindle 18 is rotated by a motor installed on the spindle head 17, and the tool 3 can be rotated at a predetermined rotation speed and torque required for cutting the work 2.

The machine tool 1 has the above-mentioned X-axis movement of the moving table 12, Y-axis movement of the saddle 15, Z-axis movement of the slider 16, C-axis rotation of the rotary table 13, and A-axis rotation of the spindle head 17. Various cutting operations can be performed on the work 2 by the 5-axis control with the addition of one. In order to control these operations, a CNC (Computer Numerical Control) type control device 9 is connected to the machine tool 1.
In such a machine tool 1, the center position of the rotation axis of the C axis of the rotary table 13 is measured by the following procedure.

In FIG. 2, in the present embodiment, the detection unit 20 is installed on the rotary table 13 in order to measure the C-axis center position of the machine tool 1.
In FIG. 3, the detection unit 20 has a case 21 and can be attached to and detached from the surface of the rotary table 13 by the legs 22 at both ends of the case 21. The leg portion 22 has adhesive or fixing means such as a magnet or a suction cup, and is fixed to the surface of the rotary table 13 so as not to be displaced.

The case 21 has an opening 23 that opens toward the upper surface of the intermediate portion. Inside the case 21, an illumination unit 24 is installed on one side of the opening 23, and a telecentric lens 25, a CCD camera 26 as an image pickup unit, and a calculation unit 27 are installed on the opposite side.
The illumination unit 24 can irradiate the parallel light beam 28 toward the telecentric lens 25 through the opening 23.
The parallel luminous flux 28 is focused by the telecentric lens 25 and photographed by the CCD camera 26.

The CCD camera 26, which is an imaging unit, detects a cross-sectional image of the parallel luminous flux 28 from the incident focused light. Here, when the detection object 29 is arranged in the opening 23, a part of the parallel luminous flux 28 is blocked and a shadow 281 is formed.
The calculation unit 27 can detect the width and height of the detection object 29 in a non-contact manner by processing the detection image of the CCD camera 26 and measuring the width and height of the shadow 281 appearing in the detection image.

In FIG. 4, by introducing the tip of the tool 3 into the opening 23 of the detection unit 20 described above, the tip of the tool 3 is arranged in the parallel luminous flux 28 as a detection object 29, and the position of the tip of the tool 3 is detected. be able to.
In the detection unit 20, the parallel light beam 28 is in the circumferential direction of the rotary table 13 (the direction orthogonal to the radial direction of the rotary table 13), that is, the illumination unit 24 and the CCD camera 26 are along the circumferential direction of the rotary table 13. Keep facing each other.
The position of the detection unit 20 may be a position away from the center of the rotary table 13, and it is not necessary to measure an accurate position. Further, the orientation of the detection unit 20 does not have to be such that the parallel luminous flux 28 is exactly along the circumferential direction of the rotary table 13. This is because even if there is an inaccurate component, the inaccurate component is canceled at the time of calculation at the facing positions (angle position A0 and angle position A180, angle position A90 and angle position A270) described later.
When the tool 3 is introduced into the detection unit 20, the position is adjusted so that the tip position of the tool 3 is in the center of the detection image (detection image 261 of FIG. 5) of the CCD camera 26.

In FIG. 5, the shadow 281 at the tip of the tool 3 appears in the detection image 261 of the CCD camera 26.
In the detection image 261, the coordinates (Tv, Th) of the tip position 283 of the tool 3 can be accurately determined from the contour 282 of the shadow 281.
Of the coordinates (Tv, Th) detected by the detected image 261, the vertical coordinate Tv corresponds to the Z-axis coordinate of the machine tool 1. On the other hand, the horizontal coordinate Th is the radial position Rc (distance in the radial direction) of the tool 3 with respect to the center of the rotary table 13, and is the X-axis coordinate and the Y-axis of the machine tool 1 according to the angular position of the rotary table 13. Projected to the coordinates. For example, when the rotary table 13 is at the angle position A0 in FIG. 7A, the detection image 261 intersects the X axis of the machine tool 1 and the coordinate Th becomes the coordinate Ty of the Y axis of the machine tool 1. When the rotary table 13 is at the angle position A90 in FIG. 8A, the detection image 261 intersects the Y axis of the machine tool 1 and the coordinate Th becomes the coordinate Tx of the X axis of the machine tool 1.

In determining the coordinates (Tv, Th) of the tip position 283 of the tool 3, the calculation unit 27 may detect the tip position of the tool 3 by image processing of the detection image 261, and the detection unit 20 may be positioned for the tool 3. It may be used as a tool, and the position data of the machine tool 1 may be acquired and used as the tip position of the tool 3. At this time, the detection process of the tip position of the tool 3 can be performed by the arithmetic unit 27 installed in the detection unit 20, and the detection unit 20 also performs image detection by the CCD camera 26 to process or process the detected image 261. The detection of the tip position of the tool 3 may be performed by the control device 9 of the machine tool 1.

In FIG. 6, the control device 9 of the machine tool 1 has an operation control unit 91 for controlling each axis movement and the like described above, and the detection image 261 acquired from the detection unit 20 is image-processed to process the tip of the tool 3. It has a tool position detecting unit 92 for detecting a position.
In the detection operation, the machine tool 1 is operated under the control of the operation control unit 91, the spindle 18 is moved to introduce the tool 3 into the opening 23 of the detection unit 20, and the tip of the tool 3 is the detection unit. The relative position between the spindle 18 and the rotary table 13 is adjusted so as to come to the specific position of 20. In this state, the tool position detection unit 92 acquires the position data of the spindle 18 (Z-axis coordinates, X-axis coordinates and Y-axis coordinates of the machine tool 1) from the motion control unit 91, and obtains the coordinates Tv and Th in the detection image 261. It can be calculated and used as the tip position of the tool 3.

As the specific position, the center position of the opening 23, which is the tool detection area in the detection unit 20, can be used. In order to arrange the tip of the tool 3 at a specific position, a marker or the like indicating the specific position can be displayed on the detection image 261 of the CCD camera 26. On the other hand, the central position of the detected image 261 of the CCD camera 26 may be set as a specific position, and the specific position may be determined only by visual confirmation. This is because even if the specific position is not accurate, the inaccurate components are canceled at the time of calculation at the facing positions (angle position A0 and angle position A180, angle position A90 and angle position A270) described later.

In the present embodiment, the C-axis center position of the machine tool 1 is measured by the following procedure using the detection unit 20 described above.
In FIG. 7A, first, the rotary table 13 is set to the angular position A0, and the detection unit 20 is placed at a position away from the center of the rotary table 13.
The angle position A0 of the rotary table 13 is such that the optical axis of the CCD camera 26 is along the X axis of the machine tool 1. However, the angle position A0 may be any angle.

After installing the detection unit 20, the spindle 18 (see FIG. 1) is lowered from above the rotary table 13, and the tool 3 is introduced into the opening 23 of the detection unit 20. Then, the position P0 (Tx0, Ty0) of the tool 3 at the angle position A0 is recorded by the detection unit 20.

Next, after raising the tool 3 and pulling it out from the detection unit 20, the rotary table 13 is rotated 180 degrees from the angle position A0 with the detection unit 20 mounted, and the first step is to sandwich the C axis with respect to the angle position A0. The angle position A180 facing the direction D1.
In FIG. 7B, the tool 3 is introduced into the detection unit 20 again with the rotary table 13 at the angle position A180. Then, the tip position P180 (Tx180, Ty180) of the tool 3 at the angle position A180 is recorded by the detection unit 20.

In FIG. 7C, when the positions P0 and P180 of the tool 3 at the angle position A0 and the angle position A180 are obtained, the first unit 27 passes through the center position of the C axis and intersects the first direction D1. Calculate the straight line L1. Specifically, the position P0 of the tool 3 at the angle position A0 and the tip position P180 of the tool 3 at the angle position A180 are connected by a line segment L01, and a straight line passing through the midpoint and intersecting the first direction D1 is drawn. Let it be the first straight line L1.

When the first straight line L1 is obtained by the detection operations of FIGS. 7A to 7C, the second straight line L2 is calculated by the same procedure.
In FIG. 8A, the detection unit 20 and the rotary table 13 are set at an angle position A90 (an angle position rotated 90 degrees from the angle position A0), and the tool 3 is introduced into the opening 23 of the detection unit 20. Then, the tip position P90 (Tx90, Ty90) of the tool 3 at the angle position A90 is recorded by the detection unit 20.
In FIG. 8B, by the same operation, the detection unit 20 and the rotary table 13 are placed at an angle position facing the second direction D2 (intersecting the first direction D1) with the C axis interposed therebetween with respect to the angle position A90. It is set to A270, and the tip position P270 (Tx270, Ty270) of the tool 3 at the angle position A270 is recorded by the detection unit 20.

In FIG. 8C, when the tip positions P90 and P270 of the tool 3 at the angle position A90 and the angle position A270 are obtained, the calculation unit 27 passes through the C-axis center position and intersects the second direction D2. Calculate the straight line L2. Specifically, a straight line connecting the tip position P90 of the tool 3 at the angle position A90 and the tip position P270 of the tool 3 at the angle position A270 by a line segment L02, passing through the midpoint thereof and intersecting the second direction D2. Is the second straight line L2.
In FIG. 9, when the first straight line L1 and the second straight line L2 are obtained, the calculation unit 27 calculates the intersection Pc between the first straight line L1 and the second straight line L2. As a result, the possible range of the C-axis center position is limited to one point of the intersection Pc, and the accurate C-axis center position of the machine tool 1 can be measured.

According to the present embodiment as described above, there are the following effects.
In the present embodiment, the tool 3 is mounted on the spindle 18, the detection unit 20 capable of detecting the position of the tool 3 in a non-contact manner is installed on the rotary table 13, and the tool 3 and the rotary table 13 are provided for the C axis to be measured. Is calculated at a predetermined angle position (A0, A90, A180, A270), and the detection operation of detecting the position (P0, P90, P180, P270) of the tool 3 with respect to the rotary table 13 by the detection unit 20 at each angle position is repeated. The center position (Pc) of the C axis was calculated from the position of the tool 3 at each angle position detected by the four detection operations.

In such an embodiment, the detection operation using the non-contact type detection unit 20 is repeated four times, and the geometric calculation is performed from the position of the tool 3 at each angle position to perform the geometric calculation to the center position of the C axis. (Pc) can be measured with high accuracy.
In the measurement, the machining tool 3 can be attached to the spindle 18 of the machine tool 1, and the spindle 18 can be rotated to raise the temperature immediately before the measurement, and the measurement can be performed in the same state as during machining. Further, it can be widely applied to the machine tool 1 in which the touch probe cannot be attached to the spindle 18.
Therefore, according to the present embodiment, the center position of the C axis can be measured with high accuracy by a simple calculation without using a touch probe.

In this embodiment, in particular, a detection unit 20 capable of detecting the radial position of the rotary table 13 of the tool 3 is used, and the tool 3 and the rotary table 13 face each other in the first direction D1 with the C axis interposed therebetween. The angle positions A0 and A180, and the two angle positions A90 and A270 facing the second direction D2 intersecting the first direction D1 with the C axis sandwiched between them are indexed to four angle positions, and the detection operation is performed at each angle position. The radial positions (P0, P90, P180, P270) of the rotary table 13 of the tool 3 are detected, and the positions P0 and P180 of the tool 3 detected at the two angular positions A0 and A180 facing the first direction D1 are obtained. It connects the first straight line L1 that passes through the midpoint of the line segment L01 and intersects the first direction D1 and the positions P90 and P270 of the tool 3 detected at the two angular positions A90 and A270 facing the second direction D2. The second straight line L2 passing through the midpoint of the line segment L02 and intersecting the second direction D2 was calculated, and the intersection Pc of the first straight line L1 and the second straight line L2 was measured as the center position of the C axis.

Therefore, the detection unit 20 of the present embodiment only needs to be able to detect the position of the tool 3 in the radial direction of the rotary table 13, and detects the detection image 261 (see FIG. 5) from the side surface of the tool 3. An image sensor (illumination unit 24 to CCD camera 26, see FIG. 3) for detecting the position of the tool 3 on the image can be used, which is installed so as to face the circumferential direction of the rotary table 13.
According to this embodiment, the estimated range (straight line L1) of the C-axis center position, which cannot be determined by the detection operation at the angle positions A0 and A180 of 0 degree and 180 degrees, is set to the angle position A90 of 90 degrees and 270 degrees. , The position of the tool 3 (straight line L2) by the detection operation at A270 can be narrowed down to determine the exact center of the C axis, and the detection operation at a total of four angular positions (A0, A90, A180, A270) , The center position of the C axis can be measured with high accuracy.

In the present embodiment, the detection unit 20 is arranged in the parallel light beam 28 from the detection image 261 and the illumination unit 24 that irradiates the parallel light flux 28, the image pickup unit (telecentric lens 25 and the CCD camera 26) that detects the parallel light beam 28. It is assumed that the calculation unit 27 for detecting the tip position of the tool 3 is provided, and the shadow 281 of the tool 3 arranged in the parallel luminous flux 28 is detected by performing the existing image processing on the detected image 261. Then, the tip position 283 of the tool 3 can be calculated by calculating the center position from the contour 282 of the tip of the tool 3 by edge detection.
As a result, the detection unit 20 can detect the tip position of the tool 3 with high accuracy without contact by performing optical detection.
Further, in the position detection, it is only necessary to arrange the tip of the tool 3 in the parallel luminous flux 28 between the illumination unit 24 and the image pickup unit (telecentric lens 25 and the CCD camera 26), and the detection operation is easy.
In the present embodiment, since the detection unit 20 has a fixing means to the rotary table 13, the installation position of the detection unit 20 with respect to the rotary table 13 can be prevented from changing during the detection operation at each angle position.

[Second Embodiment]
FIG. 10 shows a second embodiment of the present invention.
In the first embodiment described above, in order to measure the C-axis center position of the machine tool 1 (see FIG. 1), the detection unit 20 is installed on the rotary table 13 (see FIGS. 2 and 3), and the angle position A0. , The first straight line L1 is detected by the radial position detection operation of the tool 3 at A180, the second straight line L2 is detected by the same detection operation at the angle positions A90 and A270, and the intersection Pc is the exact point Pc of the machine tool 1. It was measured as the center position of the C axis.
On the other hand, in the present embodiment, in the detection operation at the angle positions A0 and A180, the machine tool 1 is detected by detecting the circumferential position together with the radial position of the tool 3, that is, the planar position along the surface of the rotary table 13. Measure the exact C-axis center position of.

In FIG. 10A, the detection unit 20A is placed on the rotary table 13 at the angle position A0.
The detection unit 20A has the same basic configuration as the detection unit 20 of the first embodiment, and can further detect coordinates in the depth direction of the image using the autofocus function. As the coordinate detection using the autofocus function, for example, in the detection image 261 of FIG. 5, the edge is detected for the contour 282 of the shadow 281 of the tool 3, and the focal position at which the contrast is maximized is detected to detect the focal position of the image. The coordinates in the depth direction can be detected accurately.
Therefore, by introducing the tool 3 into the detection unit 20A placed on the rotary table 13, the radial position Rc and the circumferential position Cc of the tool 3 with respect to the rotary table 13 can be detected. By such a detection operation at the angle position A0, the plane position PA0 with respect to the rotary table 13 of the tool 3 is measured.

In FIG. 10B, after the detection operation at the angle position A0 is completed, the rotary table 13 is moved to the angle position A180, and the same detection operation is performed at the angle position A180. Position PA180 is measured.
In FIG. 10C, when the plane position PA0 and the plane position PA180 are obtained, the calculation unit 27 calculates the midpoint PAc of the line segment LA connecting the plane position PA0 and the plane position PA180. With this midpoint PAc, the accurate C-axis center position of the machine tool 1 can be measured.

According to the present embodiment as described above, the same effect as that of the first embodiment described above can be obtained, and the detection operation of the tip of the tool 3 can be performed at two points of the angle positions A0 and A180, thereby improving the work efficiency. Can be done.
Further, in the present embodiment, since the detection operation at other angle positions such as the angle positions A90 and A270 in the first embodiment is not required, for example, the angle positions A90 and A270 are structurally restricted by the translation axis (XYZ axis). Therefore, even if the machine tool 1 is out of the range of the detection operation, the accurate C-axis center position can be measured by the detection operation at the angle positions A0 and A180.

[Third Embodiment]
11 to 12 show a third embodiment of the present invention.
In the first embodiment described above, the detection operation is performed at the angle positions A0 and A180 and the angle positions A90 and A270, and in the second embodiment, the detection operation is performed at the angle positions A0 and A180. It was necessary to perform a detection operation at the angle positions A0 and A180 facing each other.
On the other hand, in the present embodiment, the detection operation of the tip position of the tool 3 is performed at each of the plurality of angle positions An less than 180 degrees from the angle position A0 as in the first embodiment, and the machine tool is calculated by calculating the detection result. Measure the exact C-axis center position of 1.
In the present embodiment, the machine tool 1, the rotary table 13, and the detection unit 20 are the same as those in the first embodiment described above, and duplicate description regarding these configurations will be omitted.

In FIG. 11A, first, the rotary table 13 in which the detection unit 20 is installed is arranged at the angle position A0, the tip of the tool 3 is introduced into the opening 23 of the detection unit 20, and the position is determined by the detection unit 20. It is detected and set to the position P0 of the tool 3.
In FIG. 11B, the rotary table 13 is then rotated by 30 degrees to be rotated to the next angle position A30, and the position P30 of the tool 3 is detected by the same operation as the angle position A0.
In FIG. 11C, the rotary table 13 is further rotated by 30 degrees to be rotated to the next angle position A60, and the position P60 of the tool 3 is detected by the same operation as the angle position A0.
In FIG. 12A, the rotary table 13 is rotated to the next angle position A120, and the position P120 of the tool 3 is detected by the same operation as the angle position A0.
In FIG. 12B, the rotary table 13 is rotated to the next angle position A150, and the position P150 of the tool 3 is detected by the same operation as the angle position A0.

In FIG. 12C, the positions P0 to P150 of the tool 3 detected at the above-mentioned angle positions A0 to A150 are arranged in an arc shape when plotted on the screen. The position of the arcuate center point PBc can be calculated with high accuracy for the point sequence of the arcuate positions P0 to P150 by, for example, the minimum square method, and the center point PBc obtained here can be calculated. It can be measured as an accurate C-axis center position of the machine tool 1.

Even with this embodiment, the same effect as that of the first embodiment described above can be obtained, and the possible range of the detection operation is less than 180 degrees due to the structural restriction of the translational axis (XYZ axis) in the machine tool 1. Even if there is, the accurate C-axis center position can be measured by the detection operation at a plurality of positions.

[Modifications of the first to third embodiments]
In the first to third embodiments described above, an image of the tip of the tool 3 is taken by the detection unit 20 during the detection operation at the angle position An, but the position on the detection image of the tool 3 is the angle position An. It may be shifted for each.
In FIG. 13, in the detection image 261 of the detection unit 20, the position of the contour 282 of the shadow 281 of the tool 3 on the detection image 261 may not always be the same at the angle position A0 and the other angle position An. However, if the amount of deviation dc0 from the position of the angle position A0 (two-dot chain line) can be calculated by the image processing of the detected image 261, the coordinates of the tool 3 can be determined by the correction thereof, and the detected image of the tool 3 can be determined. The position on 261 may be deviated for each angle position An.

[Fourth Embodiment]
14 to 16 show a fourth embodiment of the present invention.
In this embodiment, the distance (offset amount) of the deviation from the center position of the A-axis to the tip of the tool 3 in the machine tool 1 is measured.
Since the machine tool 1 and the detection unit 20 used for measurement in the present embodiment are the same as those in the first embodiment described above, overlapping description will be omitted.

In this embodiment, the detection unit 20 is installed on the rotary table 13.
The detection unit 20 is arranged so that the opening 23 is at the center of the rotary table 13 (position at the center of rotation of the C axis). Then, the direction of the detection unit 20 is adjusted so that the direction of the parallel luminous flux 28 is the X-axis direction of the machine tool 1. The orientation of the detection unit 20 may be adjusted by rotating the C-axis of the rotary table 13.
After the detection unit 20 can be installed, the spindle head 17 is brought closer to the detection unit 20 by the operation of each axis of the machine tool 1, and the tip of the tool 3 mounted on the spindle 18 is introduced into the opening 23 to perform the detection operation.

In FIG. 15A, first, the A-axis rotation of the machine tool 1 causes the tool 3 to face the Y-axis “+” direction (angle position A0 around the A-axis), and each of the machine tools 1 is in this state. The tip of the tool 3 is introduced into the opening 23 by moving the axis. Further, by moving the Y-axis and Z-axis of the machine tool 1, in the detection image 262 obtained by the detection unit 20, the tip position 283 of the shadow 281 of the tool 3 is adjusted so as to be in the center of the detection image 262. The Y-axis position and Z-axis position (Y1, Z1 in FIG. 16) of the machine tool 1 are recorded.

In FIG. 15B, next, the A-axis rotation of the machine tool 1 causes the tool 3 to face the Y-axis “−” direction (angle position A180 facing the angle position A0 across the A-axis). In this state, the tip of the tool 3 is introduced into the opening 23 by moving each axis of the machine tool 1. Further, by moving the Y-axis and Z-axis of the machine tool 1, in the detection image 262 obtained by the detection unit 20, the tip position 283 of the shadow 281 of the tool 3 is adjusted so as to be in the center of the detection image 262. The Y-axis position and Z-axis position (Y2, Z2 in FIG. 16) of the machine tool 1 are recorded.

In FIG. 16, the difference between the Y-axis position Y1 and the Z-axis position Z1 of the machine tool 1 at the angle position A0 and the Y-axis position Y2 and the Z-axis position Z2 of the machine tool 1 at the angle position A180 is the tool 3 respectively. As a result of arranging the tips of the above in the same position, it is based on the runout of the center of rotation on the A axis (rotation axis 171 of the spindle head 17).
Therefore, the distance (offset amount) of the deviation from the A-axis center position of the machine tool 1 to the tip of the tool 3 from 1/2 of the difference between the respective axis positions at the angle position A0 and the angle position A180 (Y = (Y1-Y1-). Y2) / 2, Z = (Z1-Z2) / 2) can be measured.
Even with this embodiment as described above, the same effect as that of the first embodiment described above can be obtained in measuring the distance (offset amount) of the deviation from the center position of the A-axis to the tip of the tool 3.

[Fifth Embodiment]
17 to 20 show a fifth embodiment of the present invention.
In this embodiment, the coordinates at which the center position of the A-axis and the tip of the tool 3 in the so-called cradle-type machine tool 1A coincide with each other are measured.
In FIG. 17, the rotary table 13 is supported by the moving table 12 (see FIG. 1) via the cradle 131 and is rotatable about the C axis with respect to the cradle 131. The cradle 131 is rotatable about the A axis with respect to the moving table 12 by a pair of trunnions 132.
In the machine tool 1A, the spindle head 17 is fixed to the slider 16 (see FIG. 1), does not rotate on the A axis, and is always held downward on the Z axis.

In this embodiment, the detection unit 20 is installed on the rotary table 13. Since the detection unit 20 is the same as that of the first embodiment described above, a duplicate description will be omitted.
The detection unit 20 is arranged so that the opening 23 is at the center of the rotary table 13 (position at the center of rotation of the C axis). Then, the direction of the detection unit 20 is adjusted so that the direction of the parallel luminous flux 28 is the X-axis direction of the machine tool 1A. The orientation of the detection unit 20 may be adjusted by rotating the C-axis of the rotary table 13.
After the detection unit 20 can be installed, the spindle head 17 is brought closer to the detection unit 20 by the operation of each axis of the machine tool 1A, and the tip of the tool 3 mounted on the spindle 18 is introduced into the opening 23 to perform the detection operation.

In FIG. 18A, first, the rotary table 13 is oriented in the Y-axis “+” direction (angle position A0 around the A-axis) by rotating the cradle 131 on the A-axis, and each of the machine tools 1A is in this state. The tip of the tool 3 is introduced into the opening 23 by moving the axis.
In FIG. 19A, the tip position 283 of the shadow 281 of the tool 3 in the detection image 263 obtained by the detection unit 20 by moving the Y-axis and the Z-axis of the machine tool 1A with the cradle 131 at the angle position A0. Is adjusted so as to be in the center of the detected image 263, and the Y-axis position and the Z-axis position (Y1, Z1 in FIG. 20) of the machine tool 1A at this time are recorded.

In FIG. 18B, subsequently, by rotating the cradle 131 on the A axis, the rotary table 13 is oriented in the Y-axis “−” direction (angle position A180 facing the angle position A0 across the A axis). In this state, the tip of the tool 3 is introduced into the opening 23 by moving each axis of the machine tool 1A.
In FIG. 19B, with the cradle 131 at the angle position A180, the tip position 283 of the shadow 281 of the tool 3 in the detection image 263 obtained by the detection unit 20 by moving the Y-axis and the Z-axis of the machine tool 1A. Is adjusted so as to be in the center of the detected image 263, and the Y-axis position and the Z-axis position (Y2, Z2 in FIG. 20) of the machine tool 1A at this time are recorded.

In FIG. 20, the difference between the Y-axis position Y1 and the Z-axis position Z1 of the machine tool 1A at the angle position A0 and the Y-axis position Y2 and the Z-axis position Z2 of the machine tool 1A at the angle position A180 is the tool 3, respectively. As a result of arranging the tips of the cradle 131 at the same position, it is based on the runout of the A-axis rotation center of the cradle 131.
Therefore, from each axis position at the angle position A0 and the angle position A180, the A-axis center position of the machine tool 1A and the tip of the tool 3 are set by the equation (Y = (Y1 + Y2) / 2, Z = (Z1 + Z2) / 2). Matching coordinates can be measured.
Even with this embodiment as described above, the same effect as that of the first embodiment described above can be obtained in measuring the coordinates at which the center position of the A axis and the tip of the tool 3 coincide with each other.

[Sixth Embodiment]
21 to 23 show a sixth embodiment of the present invention.
In this embodiment, the distance (offset amount) of the deviation from the center position of the A-axis in the machine tool 1 to the tip of the tool 3 is measured by using the same configuration as that of the fourth embodiment described above.
However, in the fourth embodiment, the Y-axis positions Y1 and Y2 of the machine tool 1 are at two positions, the angle position A0 and the angle position A180 facing the angle position A0 across the A-axis (that is, at an interval of 180 degrees). And Z-axis positions Z1 and Z2 are detected, whereas in the present embodiment, the Y-axis position and the Z-axis position are detected at a plurality of angle positions An within a range of 180 degrees from the angle position A0.

In FIG. 21A, first, the tool 3 is oriented in the Y-axis “+” direction (angle position A0 around the A-axis) due to the A-axis rotation of the machine tool 1 (rotation of the rotation shaft 171 of the spindle head 17). ), And in this state, the tip of the tool 3 is introduced into the opening 23 by moving each axis of the machine tool 1.
In FIG. 21B, after the tool 3 is arranged at the angle position A0, the tip position of the shadow 281 of the tool 3 in the detection image 264 obtained by the detection unit 20 by moving the Y-axis and the Z-axis of the machine tool 1 The 283 is adjusted so as to be in the center of the detection image 264, and the Y-axis position and the Z-axis position of the machine tool 1 at this time are recorded. The recorded Y-axis position and Z-axis position are the A-axis center position Q0 at each angle position An.

Subsequently, the tool 3 is set to the angle position A30 (a state rotated by 30 degrees from the angle position A0) by the A-axis rotation of the machine tool 1, and in this state, the tool is moved by each axis movement of the machine tool 1 in the same manner as the angle position A0. The tip of 3 is introduced into the opening 23, and the tip position 283 of the shadow 281 of the tool 3 is adjusted so as to be in the center of the detection image 264 in the detection image 264 obtained by the detection unit 20, and the Y of the machine tool 1 at that time is adjusted. Record the axis position and the Z-axis position (A-axis center position Q30).
Further, by rotating the A-axis of the machine tool 1, the tool 3 is set to the angle position A60 (a state rotated by 60 degrees from the angle position A0), and the Y-axis position and the Z-axis of the machine tool 1 are set in the same procedure as the angle positions A0 and A30. Record the position (A-axis center position Q60).
Similarly, the Y-axis position and the Z-axis position (A-axis center positions Q90, Q120, Q150, Q180) of the machine tool 1 at the angle positions A90, A120, A150, and A180 are recorded.

In FIG. 21C, when the A-axis center positions Qn (Q0 to Q180) at the angular positions An (A0 to A180) obtained by repeating the above detection operation are plotted on the screen, they are arranged in an arc shape. It becomes a point sequence QC. For these point sequences QC, the position of the center point QCc of the arcuate point sequence QC (the tip position of the tool 3 common to each angle position An) can be calculated with high accuracy by, for example, the least squares method. can. With the center point QCc obtained here, the distance (offset amount) of the deviation from the A-axis center position Qn of the machine tool 1 to the tip of the tool 3 can be accurately measured.

Even with this embodiment as described above, the same effects as those of the first embodiment and the fourth embodiment described above can be obtained, and the possible range of the detection operation due to the structural restriction of the translational axis (XYZ axis) in the machine tool 1. Even if is less than 180 degrees, the deviation distance (offset amount) from the A-axis center position Qn to the tip of the tool 3 can be accurately measured by the detection operation at a plurality of angular positions An.

[Variation example of the sixth embodiment]
In FIG. 22, the distance (offset amount) of the deviation from the A-axis center position Qn measured in the sixth embodiment described above to the tip of the tool 3 is registered in the NC device of the machine tool 1, and the operation of the machine tool 1 is performed. It is referred to as the correction value of the time.
When registering in the NC device of the machine tool 1, the distance D (offset amount) from the center point QCc, which is the tip position of the tool 3, to the actual A-axis center position Qn is required. By the minimum square method calculation of the arcuate point sequence QC by the A-axis center position Qn, the approximate arc radius indicating the distance D (approximate value) from the center point QCc to the A-axis center position Qn can be obtained together with the position of the center point QCc. Therefore, this radius can be set as the actual distance D between the center point QCc and the A-axis center position Qn.

When registering in the NC device of the machine tool 1, the distance D must be separated into a component Dz in the Z-axis direction parallel to the tool 3 and a component Dy in the Y-axis direction orthogonal to the tool 3. For this purpose, the angle θ of the line segment connecting the A-axis center position Qn and the tip of the tool 3 (center point QCc) is required. However, the least squares method used to calculate the center point QCc does not give the angle θ of the line segment that gives the approximate arc radius (distance D).
In FIG. 23A, in addition to not being able to obtain the above-mentioned angle θ, the A-axis center position Qn (sampling) detected as an arcuate point sequence QC at the above-mentioned plurality of angle positions An (A0 to A180). The points) have variations (displacements in the radial direction) with respect to the approximate arc of the point sequence QC. Further, when the reference line Ln extending from the center point QCc is drawn at an angle (0 degree to 180 degrees) set as the angle position An for detecting the A-axis center position Qn, the A-axis center position Qn at each angle is these references. There is also variation (displacement in the circumferential direction) with respect to the line Ln.
Under such an error distribution, the following operation can be adopted to determine the optimum value of the above angle θ.

In FIG. 23B, as the first operation, the tool 3 adopts the A-axis center position Q90 in the direction along the Z-axis (angle position A90). Specifically, a line segment extending from the center point QCc to the A-axis center position Q90 is obtained, and the angle formed by this line segment and the Z-axis is defined as θ.
Such an operation does not result in overall optimization, but is the most suitable standard.

In FIG. 23C, as a second operation, the center point QCc to A in the direction (angle position A130 from the angle position A0 to 130 degrees) at which the tool 3 is at a predetermined angle (for example, 40 degrees) with respect to the Z axis. A line segment extended to the axis center position Q130 may be obtained, and the angle formed by this line segment and the reference line L130 forming 40 degrees from the Z axis may be set as θ.

Further, at the A-axis center position Qn at the plurality of angle positions An, the angle θn with the reference line Ln may be obtained, and the average value thereof may be obtained.
According to such an operation, although the operation is complicated, it is possible to obtain an angle θ that is optimal overall.
At the A-axis center position Qn at the plurality of angle positions An described above, the entire range may be evenly divided to obtain the angle θ, but the sampling density of some of the angle ranges may be increased or decreased. May be good.
After the angle θ is obtained by the above operation, the above-mentioned component Dz in the Z-axis direction and the component Dy in the Y-axis direction orthogonal to the tool 3 (see FIG. 22) are calculated as Dz = Dcosθ and Dy = Dsinθ, respectively. be able to.

[Modifications of the first to sixth embodiments]
In each of the first to sixth embodiments described above, the tip position of the tool 3 was detected by the detection units 20 and 20A, respectively.
For example, in the first embodiment, as shown in FIG. 5, the tip position of the tool 3 is captured in the center of the detection image 261 of the CCD camera 26, and from the contour 282 of the shadow 281 of the tip of the tool 3 appearing in the detection image 261. The coordinates (Tv, Th) of the tip position 283 of the tool 3 were calculated.
At this time, the coordinates may not be accurately detected depending on the shape of the tip of the tool 3, such as the uneven shape of the tip of the tool 3 being complicated.
On the other hand, in order to easily and accurately detect the tip position (Tv, Th) of the tool 3, the procedure shown below can be used.

[7th Embodiment]
As shown in FIG. 24A, a shadow 281 at the tip of the tool 3 appears in the detection image 261 of the CCD camera 26 (see FIG. 3) (similar to FIG. 5). The tip position 283 of the tool 3 appears in a part of the contour 282 of the shadow 281, and the measurement of its coordinates (Tv, Th) is required.
In the present embodiment, the detection image 265 is detected by the CCD camera 26 in a state where the tool 3 is rotated with respect to the CCD camera 26 (similar to the detection images 261 to 264 in the first to sixth embodiments), and the detection image is detected. The contour 282 of the tool 3 is detected from 265.
In the present embodiment, since the tool 3 is rotated, the contour 282 appearing in the detection image 265 becomes symmetric with respect to the center of rotation, and the central axis 284 of the tool 3 is accurately detected from the symmetry of the contour 282. The intersection of the central axis 284 and the contour 282 can be detected as the tip position 283 of the tool 3.

In the present embodiment, when the central axis 284 of the tool 3 is detected from the contour 282, the following arithmetic processing is performed.
As shown in FIG. 24B, in the detection image 265, the tool 3 is arranged at a predetermined angle position (for example, the angle position A90 shown in FIG. 21B), and the extension direction D90 of the tool 3 at that time is used. .. Next, a plurality of crossing lines 30 that cross the contour 282 while being orthogonal to the stretching direction D90 are set in parallel along the stretching direction D90 at predetermined intervals.
As shown in FIG. 24C, two intersections 31 and 32 with the contour 282 are detected for each of the set plurality of crossing lines 30, and a midpoint 33 of the two intersections 31 and 32 is detected. .. Then, by detecting a straight line passing through the midpoint 33 of each crossing line 30, this straight line can be set as the central axis 284 of the tool 3.

In such an embodiment, the extension direction Dn of the tool 3 (each angle position An, the direction of the tool 3, the approximate axis direction) is used to detect the axis of rotational symmetry, thereby accurately detecting the tool 3. The central axis 284 can be detected, and the coordinates (Th, Tv) of the tip position 283 of the tool 3 can be detected with high accuracy from the accurate intersection of the central axis 284 and the contour 282.
At this time, the detection of the central axis 284 is performed by detecting the midpoint of a plurality of crossing lines 30, and the detection of the tip position 283 is performed by detecting the intersection with the contour 282. This makes it possible to easily measure the tip position 283 of the tool 3 or the center position of the rotation axis (A-axis or C-axis) with high accuracy.

In the present embodiment, the orientation of the tool 3 (stretching direction Dn) can be any angle (angle position An).
In FIG. 25A, the tool 3 is set at the angle position A150, and a plurality of crossing lines 30 orthogonal to the stretching direction D150 are set.
As shown in FIG. 25B, two intersections 31 and 32 and a midpoint 33 are detected at each crossing line 30, and the tool 3 is located at the intersection of the central axis 284 and the contour 282 passing through the plurality of midpoints 33. The coordinates (Th, Tv) of the tip position 283 can be accurately detected.

[Eighth Embodiment]
In the seventh embodiment described above, when the central axis 284 of the tool 3 is detected from the contour 282, the midpoint of a plurality of crossing lines 30 is detected.
On the other hand, in the present embodiment, the central axis 284 of the tool 3 is detected by pattern recognition on each side of the contour 282 which is a rotationally symmetric figure.
As shown in FIG. 26 (A), in the detection image 265, the tool 3 is arranged at a predetermined angle position (for example, the angle position A90 shown in FIG. 21 (B)), and the extension direction D90 of the tool 3 at that time is used. .. Next, the shape 41 on one side of the contour 282 with respect to the stretching direction D90 (a part of the contour 282 divided into two by a straight line along the stretching direction D90) is detected as the reference pattern 40.
As shown in FIG. 26B, when the reference pattern 40 can be detected, the symmetry pattern 42 matching the inverted shape of the reference pattern 40 is calculated, and the shape 43 matching the symmetry pattern 42 is detected from the contour 282. .. When the symmetry pattern 42 can be detected, the straight line passing between the reference pattern 40 and the symmetry pattern 42 (the axis of line symmetry between the reference pattern 40 and the symmetry pattern 42) is set as the central axis 284 of the tool 3.

In such an embodiment, the extension direction Dn of the tool 3 (each angle position An, the direction of the tool 3, the approximate axial direction) is used, and the pattern recognition of each side of the contour 282 is performed to accurately recognize the tool 3. The central axis 284 can be detected, and the coordinates (Th, Tv) of the tip position 283 of the tool 3 can be detected with high accuracy from the accurate intersection of the central axis 284 and the contour 282.
At this time, as pattern recognition for each side of the contour 282, the detection of the reference pattern 40 and the symmetric pattern 42 can be executed by geometrical arithmetic processing, respectively, whereby the tip position 283 or the rotation axis (A axis or the rotation axis) of the tool 3 can be executed. The center position of the C axis) can be measured with high accuracy and easily.

[9th Embodiment]
In the seventh embodiment described above, after detecting the central axis 284 of the tool 3 from the contour 282, the intersection of the central axis 284 and the contour 282 is detected and the tip position of the tool 3 is set to 283.
On the other hand, in the present embodiment, by setting an auxiliary contour line on the contour 282 of the tip of the tool 3, the tool 3 having a plurality of protrusions at the tip, the tool 3 having a tip deviated from the center, and the like can be rotated. Even for the tool 3 in which the shape of the contour 282 of the tip portion becomes unclear in this state, the tip position of the tool 3 can be determined.

As shown in FIGS. 27 (A) and 27 (B), it is assumed that a pair of cutting edge 3Ts facing each other with the center of rotation interposed therebetween are formed at the tip of the tool 3. In FIG. 27B, the cutting edge 3T shown by the solid line moves to the position shown by the two-dot chain line by the rotation of the tool 3.
In each of the above-described embodiments, the tip of the tool 3 is photographed by the CCD camera 26 from the side of the tool 3 (the direction intersecting the rotation axis of the tool 3).
For example, assuming that the CCD camera 26 photographs the tool 3 from the lower side in the figure of FIG. 27 (B), a pair of cutting edges 3T face each other in the direction orthogonal to the optical axis of the CCD camera 26 (solid line in FIG. 27 (B)). In the state of), both of the pair of cutting edges 3T can be contained in the focusing range Rf0 of the CCD camera 26. However, as the tool 3 rotates and the pair of cutting edges 3T approaches the state along the optical axis of the CCD camera 26 (the state of the two-point chain line in FIG. 27B), from the CCD camera 26 to each cutting edge 3T. The difference in distance is widened, one is in the depth of focus range Rf1 far from the CCD camera 26, and the other is in the depth of focus range Rf2 close to the CCD camera 26, and the CCD camera 26 focuses on both of the pair of cutting edges 3T. You can't.

By rotating the tool 3 in this way, the distance of the pair of cutting edges 3T from the CCD camera 26 changes periodically, and the image captured by the CCD camera 26 is partially blurred.
As shown in FIG. 27 (C), the contour 282 of the shadow 281 of the tool 3 is clear except for the tip, but the tip is blurred because the pair of cutting edges 3T are displaced in the optical axis direction of the CCD camera 26. It becomes the state where it occurred. As a result, unlike the seventh to eighth embodiments described above, the coordinates of the tip position 283 of the tool 3 cannot be determined by the intersection of the central axis 284 and the contour 282.
On the other hand, in the present embodiment, the central axis 284 is detected in the same manner as in the seventh or eighth embodiment described above, and an auxiliary contour line is set in the contour 282 of the tip portion of the tool 3, and this contour auxiliary line is set. The intersection of the center axis 284 and the center axis 284 is detected as the tip position 283 of the tool 3. Specifically, the following procedure is used.

In FIG. 28A, when the central axis 284 is detected with respect to the shadow 281 of the tool 3, a pair of parallel lines M and Mb parallel to the central axis 284 are set on both sides of the central axis 284 with predetermined distances Ofs. Set. Here, the predetermined distance Ofs is set so that the intersection points Ca and Cb of the pair of parallel lines Ma and Mb and the contour 282 pass through the portion where the contour 282 is not blurred. The predetermined distance Ofs may be adjusted by looking at the state of the contour 282, or may be set based on the design dimensions of the cutting edge 3T of the tool 3.
In FIG. 28B, when the intersections Ca and Cb of the pair of parallel lines Ma and Mb and the contour 282 are obtained, the auxiliary contour 285 passing through the pair of intersections Ca and Cb and orthogonal to the central axis 284 is set. The intersection of the central axis 284 and the auxiliary contour 285 is detected as the tip position 283 of the tool 3.

In the present embodiment, by setting the auxiliary contour 285, for example, a tool 3 having a plurality of protrusions at the tip such as a pair of cutting edges 3T, a tool 3 having a biased tip, or the like, the contour 282 of the tip portion in a rotated state. Even for the tool 3 whose shape is unclear, the tip position 283 of the tool 3 can be determined by the intersection of the central axis 284 and the auxiliary contour 285. As a result, even for a tool 3 having various tip shapes, the tip position 283 of the tool 3 or the center position of the rotation axis (A-axis or C-axis) can be measured with high accuracy by a simple calculation.

[Other embodiments]
The present invention is not limited to the above-described embodiment, and modifications to the extent that the object of the present invention can be achieved are included in the present invention.
In each of the above embodiments, the rotation center positions of the C-axis or the A-axis of the 5-axis controlled machine tools 1 and 1A are measured, but the machine tool and the axis to which the present invention is applied can be arbitrarily selected.
For example, the machine tool may be a 5-axis control having an A-axis and a B-axis as rotation axes, or the rotation center position of the B-axis may be measured. Further, the machine tool may be 4-axis control or 6-axis control, and may have at least a rotation axis at which the center position of the rotation axis becomes a problem.

In the above embodiment, the detection units 20 and 20A are used to detect the tip position of the tool 3, but the detection units 20 and 20A are not limited to those forming the parallel luminous flux 28, and the laser beam is shaken in parallel. An object that scans the object (which becomes a pseudo parallel luminous flux) may be used. Further, it may be non-contact with the tool 3 and may be another detection method.

INDUSTRIAL APPLICABILITY The present invention can be used as a method for measuring the center position of a rotating shaft of a machine tool.

1,1A ... Machine, 2 ... Work, 3 ... Tool, 3T ... Cutting edge, 9 ... Control device, 91 ... Motion control unit, 92 ... Tool position detection unit, 11 ... Bed, 12 ... Moving table, 13 ... Rotating table , 131 ... Cradle, 132 ... Tranion, 14 ... Column, 15 ... Saddle, 16 ... Slider, 17 ... Main shaft head, 171 ... Rotating shaft, 18 ... Main shaft, 20, 20A ... Detection unit, 21 ... Case, 22 ... Fixing means 23 ... opening, 24 ... lighting unit, 25 ... telecentric lens, 26 ... CCD camera which is an imaging unit, 261 to 265 ... detected image, 27 ... arithmetic unit, 28 ... parallel light beam, 281 ... shadow, 282 ... contour, 283 ... tip position, 284 ... central axis, 285 ... auxiliary contour line, 29 ... detection target, 31, 32 ... intersection, 33 ... middle point, A0 to A270, An ... angular position, Ca, Cb ... Intersection point, Cc ... Circumferential position, D ... Distance, D1 ... First direction, D2 ... Second direction, dc0 ... Deviation amount, Dy ... Y-axis direction component, Dz ... Z-axis direction component, L01, L02 ... Line Minutes, L1 ... 1st straight line, L130 ... reference line, L2 ... 2nd straight line, LA ... line segment, Ln ... reference line, Ma, Mb ... parallel lines, Ofs ... predetermined intervals, P0 to P270 ... tool tip position, PA0 , PA180 ... plane position, PAc ... middle point, PBc ... center point, Pc ... intersection point, Q0 to Q180, Qn ... A-axis center position, QC ... point sequence, QCc ... center point, Rc ... radial position, Th, Tv ... Coordinates of tip position, Tx0 to Tx270 ... X-axis coordinates, Ty0 to Ty270 ... Y-axis coordinates, Y1, Y2 ... Y-axis position, Z1, Z2 ... Z-axis position, θ, θn ... Angle.

Claims (11)

A tool is attached to the spindle, and a detection unit that can detect the position of the tool in a non-contact manner is installed on the table.
With respect to the rotation axis to be measured, the tool and the table are determined at predetermined angle positions, and the detection operation of detecting the position of the tool with respect to the table using the detection unit at each angle position is repeated.
A method for measuring the center position of a rotation axis of a machine tool, which calculates the center position of the rotation axis from the position of the tool at each angle position detected by the detection operation a plurality of times. In the method for measuring the center position of the rotation axis of a machine tool according to claim 1,
The detection unit can non-contactly detect that the tip of the tool is at a specific position in the detection unit.
In the detection operation, the spindle and the table are relatively moved to determine the tool and the table at predetermined angle positions, and the tool is brought to the specific position of the detection unit at each angle position. Rotation of a machine tool, characterized in that the relative position of the spindle and the table is adjusted, and in this state, the position of the tool with respect to the table at each angle position is detected from the relative position of the spindle and the table. Axis center position measurement method. In the method for measuring the center position of a rotating shaft of a machine tool according to claim 1 or 2.
Using the detection unit capable of detecting the radial position of the table of the tool,
The tool and the table are at two angular positions facing the first direction across the rotation axis and two angular positions facing the first direction across the rotation axis. It is indexed to four angle positions, and the detection operation is performed at each angle position to detect the radial position of the table of the tool.
A first straight line that passes through the midpoint of the line segment connecting the positions of the tools detected at the two angular positions facing the first direction and intersects the first direction, and two facing the second direction. A second straight line that passes through the midpoint of the line segment connecting the positions of the tools detected at the angular position and intersects in the second direction is calculated, and the intersection of the first straight line and the second straight line is rotated. A method for measuring the center position of a rotating shaft of a machine tool, which is characterized by measuring as the center position of the shaft. In the method for measuring the center position of a rotating shaft of a machine tool according to claim 1 or 2.
Using the detection unit capable of detecting the position of the tool along the surface of the table,
The tool and the table are indexed at two angle positions facing each other across the rotation axis, and the detection operation is performed at each angle position to detect the position of the tool along the surface of the table.
A method for measuring the center position of a machine tool, which comprises calculating the midpoint of a line segment connecting the positions of the tools in the two detection operations and measuring the midpoint as the center position of the rotation axis. .. In the method for measuring the center position of a rotating shaft of a machine tool according to claim 1 or 2.
Using the detection unit capable of detecting the radial position of the table of the tool,
The tool and the table are indexed to a plurality of angular positions within a predetermined angle range about the rotation axis, and the detection operation is performed at each angle position to detect the radial position of the table of the tool. ,
A method for measuring the center position of a rotation axis of a machine tool, which comprises plotting the positions of the tools obtained by the detection operations a plurality of times and calculating the center position of the rotation axis by approximate calculation. In the method for measuring the center position of a rotating shaft of a machine tool according to any one of claims 1 to 5.
A method for measuring the center position of a rotation axis of a machine tool, wherein the detection unit has a fixing means to the table. In the method for measuring the center position of a rotating shaft of a machine tool according to any one of claims 1 to 6.
The detection unit has an illumination unit that irradiates a parallel light flux and an image pickup unit that detects the parallel light flux.
A method for measuring the center position of a rotation axis of a machine tool, which comprises detecting the tip position of the tool arranged in the parallel luminous flux from an image detected by the image pickup unit. In the method for measuring the center position of the rotation axis of a machine tool according to claim 7.
With the tool rotated with respect to the image pickup unit, the image pickup unit detects the image.
The contour of the tool is detected from the image, and the central axis of the tool is detected from the symmetry of the contour.
A method for measuring the center position of a rotation axis of a machine tool, which comprises detecting the intersection of the center axis and the contour as the tip position of the tool. In the method for measuring the center position of the rotation axis of a machine tool according to claim 8.
When detecting the intersection of the central axis and the contour as the tip position of the tool,
A pair of parallel lines are set on both sides of the central axis at a predetermined distance, and an auxiliary contour line that passes through the intersection of the pair of parallel lines and the contour and is orthogonal to the central axis is set.
A method for measuring the center position of a rotating shaft of a machine tool, characterized in that the intersection of the center axis and the auxiliary contour line is detected as the tip position of the tool. In the method for measuring the center position of a rotating shaft of a machine tool according to claim 8 or 9.
A plurality of transversals crossing the contour are set in the extending direction of the tool, two intersections with the contour and the midpoint of the two intersections are detected for each of the crossing lines, and each of the crossing lines A method for measuring the center position of a rotating shaft of a machine tool, wherein a straight line passing through the midpoint is set as the center axis of the tool. In the method for measuring the center position of a rotating shaft of a machine tool according to claim 8 or 9.
The shape of one side of the contour with respect to the stretching direction of the tool is detected as a reference pattern, a symmetric pattern matching the shape obtained by inverting the reference pattern is detected from the contour, and an intermediate between the reference pattern and the symmetric pattern is detected. A method for measuring the center position of a rotation axis of a machine tool, wherein a straight line passing through the tool is used as the center axis of the tool.

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