JP6586112B2 - Error identification method and error identification system for machine tools - Google Patents

Description

  The present invention relates to a method and a system for identifying a geometric error of a machine tool from a measurement result of a position of an object in the machine.

  FIG. 1 is a schematic diagram of a 5-axis control machining center having three translation axes and two rotation axes. The main shaft 2 is a translational axis and can move with two degrees of freedom of translation relative to the bed 1 by the X axis and the Z axis orthogonal to each other. The table 3 can move with one degree of freedom of rotation with respect to the cradle 4 by the C axis that is the rotation axis, and the cradle 4 can move with one degree of freedom of rotation with respect to the trunnion 5 with the A axis that is the rotation axis. Is possible. The A axis and the C axis are orthogonal to each other. Further, the trunnion 5 is a translational axis and is capable of translational movement with one degree of freedom with respect to the bed 1 by a Y axis orthogonal to the X and Z axes. Therefore, the main shaft 2 can move with respect to the table 3 with three translational degrees of freedom and two degrees of freedom of rotation. Each feed shaft is driven by a servo motor controlled by a numerical control device (not shown), and a workpiece is fixed to the table 3, a tool is mounted on the spindle 2, and the workpiece is rotated. Machining can be performed by controlling the relative position and the relative posture.

Major factors that affect the motion accuracy of such a 5-axis control machining center include errors in the center position of the rotating shaft (deviation from the assumed position) and tilt errors of the rotating shaft (perpendicularity and parallelism between axes). There is a geometric error between each axis. For example, the five-axis control machining center of FIG. 1 has three geometric errors related to the translation axis: a perpendicular angle between XY axes, a perpendicular angle between Y and Z axes, and a perpendicular angle between Z and X axes. There are two errors: tool-Y axis perpendicularity and tool-X axis perpendicularity. C-axis center position X-direction error, C-A axis offset error, and A-axis angle offset are geometric errors related to the rotation axis. There are 8 types: error, CA-axis perpendicularity, A-axis center position Y-direction error, A-axis center position Z-direction error, AZ-axis perpendicularity, and A-Y-axis perpendicularity, a total of 13 There is a geometric error.
If there is a geometric error, the movement accuracy of the machine deteriorates, and the machining accuracy of the workpiece deteriorates. For this reason, it is necessary to reduce the geometric error by adjustment, but it is difficult to make it zero, and high-precision machining can be performed by performing control for correcting the geometric error.

In order to perform such correction control, it is necessary to measure or identify a geometric error inherent in the machine. As a method for identifying the geometric error of the machine, the inventor has proposed a method as described in Patent Document 1. In the method of the present invention, the table is rotated and tilted at a plurality of angles by the rotation axis, and the center position of the sphere fixed on the table is measured by using the touch probe attached to the main axis. The machine geometric error is identified from the measured values.
The touch probe has a sensor that senses contact with the measurement object. At the moment the contact is sensed, the touch probe emits a signal using infrared rays or radio waves, and the signal is received by a receiver connected to the numerical controller. The current position (skip value) of each axis at the moment when the received or delayed time is taken into account is acquired, and this value is used as the measurement value.
However, in the measurement of the touch probe, it is necessary to correct the acquired position. This is because the position of the feed axis when the touch probe comes into contact with the object to be measured is a reference point for the position of the feed axis (the X and Y axes are the spindle center, the Z axis is the spindle end face) and the touch probe position. This is because the contact points are different. For example, the X and Y axis directions are offset by the radius of the stylus sphere of the touch probe, and offset due to the misalignment between the center of the spindle and the touch probe, the signal delay at the time of contact, the direction dependence of the sensor of the touch probe, etc. Exists. The Z-axis direction is offset by the length of the touch probe body and the stylus, and there is an offset due to a signal delay at the time of contact. Therefore, calibration for acquiring correction values for correcting these offsets is required.

As a calibration method of the radial direction correction value of the touch probe, there are known techniques as disclosed in Patent Documents 2 and 3.
In the method of Patent Document 2, a dial gauge is used to adjust the center position of the spindle so that the center of the reference ring gauge and the center of the spindle coincide with each other, and the skip value and the ring when contacting the inner diameter of the ring gauge. The diameter correction value of the touch probe is obtained from the inner diameter value of the gauge.
In the method of Patent Document 3, contact is made in one direction of the bore diameter as a reference, and the main shaft is rotated 180 ° when contacting in the opposite direction, and the bore center position is obtained from the average value of both skip values. The correction value in each direction is obtained.
On the other hand, a method using a reference tool (hereinafter referred to as “method 1”) is known as a calibration method for a long correction value. Here, the resistance when moving the block gauge by hand while manually operating the Z-axis so that the reference tool comes into contact with the reference surface such as the table top surface via the block gauge with the reference tool mounted on the spindle Then, a position where the gap between the block gauge and the reference tool is almost zero is found, and the position is recorded. Next, the reference plane is measured with the touch probe, that is, the Z-axis position when the touch probe contacts is acquired. From the Z-axis position acquired with the touch probe, the value obtained by subtracting the Z-axis position with the recorded reference tool and the thickness of the block gauge, the touch probe length, that is, the touch probe length correction value is obtained. Is.

Patent Document 4 describes a method for measuring the contact length of a touch probe using a CCD camera. Here, the position of the spindle when the touch probe is brought into contact with the upper surface of the press stand and a signal is output is obtained, and the tip position is measured by photographing the tip of the touch probe at the time of contact with a CCD camera. Next, the press stand is removed, and the length is returned to the length when the touch probe is not in contact, and the tip position is measured with the CCD camera. The amount of shrinkage at the time of contact is calculated from the difference between the two tip positions. The tip position of the reference tool is also measured with a CCD camera, and the position of the spindle at that time is also acquired. Based on the relationship between the amount of contraction at the time of contact, the tip position of the touch probe at the time of contact, the spindle position at the time of touch probe touch, the tip position of the reference tool, and the spindle position at the reference tool, The length correction value of the touch probe is obtained.
Furthermore, Patent Document 5 describes a method for correcting a workpiece position using a laser sensor and a reference block. The laser sensor emits a signal when the laser beam is blocked by the tip of the tool and the light receiving rate falls below a certain level, and the position of the feed shaft at the time when the machine tool control device receives the signal is used as the measurement value. is there. In this method, a reference block is prepared near the laser sensor, and the position of the laser beam and the position (height) of the upper surface of the reference block are matched. Further, the position at the time of mounting the reference tool is stored by the laser sensor. Next, the touch probe is brought into contact with the reference block to store the position. Then, the position is stored by bringing the touch probe into contact with the workpiece, and the workpiece position with respect to the reference tool is measured and corrected from the difference between both positions and the position of the reference tool. In this method, the workpiece position is measured without obtaining the length correction value of the touch probe.

JP 2011-38902 A Japanese Patent Laid-Open No. 4-63664 JP 58-82649 A JP 2012-61570 A JP 2001-105279 A

The calibration of the touch probe needs to be performed before measurement for identifying the geometric error. In addition, the state of the touch probe changes due to thermal displacement due to heat generation of the spindle or the change with time, and the necessary correction value changes. For this reason, it is desirable to perform immediately before measurement.
However, the methods of Patent Documents 2 and 3 have a problem in that it is necessary to separately prepare another measuring instrument such as a dial gauge and a reference such as a work having a ring gauge and a bore.
Further, in Patent Documents 2 and 3 and Method 1, since manual work is required, the work becomes troublesome, and once calibration is performed, it is often not performed after that. In this case, when there is a change in the state of the touch probe due to thermal deformation or the like, the measurement accuracy of the touch probe deteriorates, and there is a problem that the geometric error of the machine cannot be identified with high accuracy.
The method of Patent Document 4 has a problem that an expensive CCD camera measurement device is required. In addition, since it is necessary to move the presser base, there is a problem that the frequency of work is reduced when it is performed manually, and a mechanism and an actuator for driving the presser base are necessary for automatic removal, which is costly. There is a problem of becoming higher.
The method of Patent Document 5 performs workpiece position measurement without using the touch probe length correction value. However, it is necessary to make the laser beam position of the laser sensor coincide with the reference block position, or to make the positional relationship known, and the length of the reference tool measured by the laser sensor and the touch probe when contacting the reference block This is synonymous with the need to make the relationship with the length, that is, the length correction value of the touch probe known. However, there is no description about a method for making both positional relationships known.

  Therefore, the present invention measures a geometric error of a machine tool having at least one translational axis and at least one rotational axis by measuring a measurement target such as a target sphere using a position measurement sensor such as a touch probe. An object of the present invention is to provide an error identification method and an error identification system capable of simultaneously calibrating the diameter / length correction values of the position measurement sensor in identifying from the position of the jig.

In order to achieve the above object, the invention described in claim 1 includes three or more translation shafts, one or more rotation shafts, a spindle that can be rotated by mounting a tool, a table, and the translation shaft. And a position measuring sensor mounted on the spindle to measure a position in a three-dimensional space of the jig to be measured fixed on the table by a machine tool having a control device for controlling the rotating shaft and the spindle. A method for identifying a geometric error of the machine tool from the position measurement value,
A tool sensor position acquisition step of mounting a reference tool serving as a reference for the length of the tool on the spindle and acquiring a detection position of the tip of the reference tool using a tool sensor;
A reference block position obtaining step for obtaining the position of the translation shaft when the reference tool mounted on the spindle is brought into direct or indirect contact with a reference block provided on the tool sensor side;
A relative position calculation step of calculating a relative position of the reference block with respect to the detection position from the detection position acquired in the tool sensor position acquisition step and the position of the translation axis acquired in the reference block position acquisition step;
A reference tool position acquisition step of mounting the reference tool on the spindle and acquiring a reference tool position that is a tip position of the reference tool using the tool sensor;
A position measurement sensor measurement step of mounting the position measurement sensor on the spindle and measuring the position of the reference block using the position measurement sensor;
The reference tool position acquired in the reference tool position acquisition step, the position of the reference block measured in the position measurement sensor measurement step, the relative position calculated in the relative position calculation step, and the length of the reference tool From the long correction value calculation step of calculating the long direction correction value of the position measurement sensor,
A diameter correction value acquisition step of acquiring a radial direction correction value of the position measurement sensor using the measurement target jig,
A position measurement stage in which the rotation axis is indexed to an arbitrary plurality of angles and the position of the measurement jig is measured by the position measurement sensor,
Using the long direction correction value and the radial direction correction value, a position correction step for correcting the position measurement value in the position measurement step;
Performing a geometric error identifying step of identifying the geometric error from a plurality of the position measurement values corrected in the position correcting step.
Here, the “tool sensor side” includes not only a case where a reference block is directly provided on the tool sensor but also a case where a separate reference block is provided in the vicinity of the tool sensor. The following invention is also the same.
According to a second aspect of the present invention, in the configuration of the first aspect, the tool sensor position acquisition stage to the relative position calculation stage are executed once, and a plurality of processes from the reference tool position acquisition stage to the geometric error identification stage are performed. It is characterized by being executed once.
According to a third aspect of the present invention, in the configuration of the first or second aspect, the position measured by the position measurement sensor is the position of the translational axis when the position measurement sensor detects that the measurement object has been contacted. It is a position.
According to a fourth aspect of the present invention, in the configuration according to any one of the first to third aspects, the position measured by the tool sensor is such that a tool mounted on the main shaft moves by the translation shaft and contacts the tool sensor. Or it is the position of the said translation axis at the time of detecting having passed.
According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, the jig to be measured has a spherical shape.
According to a sixth aspect of the present invention, in the configuration of the fifth aspect, in the diameter correction value acquisition stage, an initial position of the jig to be measured is measured by the position measurement sensor, and a radial direction of the position measurement sensor is measured. A correction value is acquired.
To achieve the above object, the invention described in claim 7 includes three or more translation axes, one or more rotation axes, a spindle that can be rotated by mounting a tool, a table, and the translation axes. And a position measuring sensor mounted on the spindle to measure a position in a three-dimensional space of the jig to be measured fixed on the table by a machine tool having a control device for controlling the rotating shaft and the spindle. And a system for identifying a geometric error of the machine tool from the position measurement value,
A reference tool serving as a reference for the length of the tool;
A tool sensor for detecting a tip position of the reference tool mounted on the spindle;
A reference block installed on the tool sensor side;
Tool sensor position acquisition means for moving the reference tool mounted on the spindle by the translation shaft and acquiring and storing the detection position of the tip of the reference tool using the tool sensor;
Reference block position acquisition for acquiring and storing the position of the translation axis at the time of contact with the reference block by moving the reference tool mounted on the spindle by the translation axis to directly or indirectly contact the reference block Means,
A relative position for calculating and storing a relative position of the reference block with respect to the detection position from the detection position acquired by the tool sensor position acquisition means and the position of the translation axis acquired by the reference block position acquisition means. A calculation means;
A reference tool position acquisition means for moving the reference tool mounted on the spindle by the translation shaft and acquiring and storing a reference tool position which is a tip position of the reference tool using the tool sensor;
Measurement position acquisition means for measuring and storing the position of the reference block with the position measurement sensor mounted on the spindle;
The reference tool position acquired by the reference tool position acquisition means, the position of the reference block acquired by the measurement position acquisition means, the relative position acquired by the relative position calculation means, and the reference tool A length correction value calculating means for calculating and storing a length direction correction value of the position measurement sensor from the length;
Diameter correction value acquisition means for acquiring and storing a radial direction correction value of the position measurement sensor using the jig to be measured;
The rotational axis is determined at an arbitrary plurality of angles, and each position measurement value of the measurement target jig measured by the position measurement sensor is corrected using the long direction correction value and the radial direction correction value. Position correction means for storing;
Geometric error identification means for identifying the geometric error from the plurality of position measurement values corrected by the position correction means.
In order to achieve the above object, the invention described in claim 8 is directed to three or more translation axes, one or more rotation axes, a spindle that can be rotated by mounting a tool, a table, and the translation axes. And a position measuring sensor mounted on the spindle to measure a position in a three-dimensional space of the jig to be measured fixed on the table by a machine tool having a control device for controlling the rotating shaft and the spindle. A method for identifying a geometric error of the machine tool from the position measurement value,
Using a tool sensor and a reference block provided on the tool sensor side,
A tool sensor position acquisition step of mounting a reference tool serving as a reference for the length of the tool on the spindle, and acquiring a detection position of a tip of the reference tool using the tool sensor;
A reference tool measurement position acquisition step of acquiring an arbitrary tool measurement position using the reference tool mounted on the spindle;
A position measurement sensor measurement position acquisition stage for acquiring an arbitrary sensor measurement position using the position measurement sensor mounted on the spindle;
A position measurement sensor length calculation step for obtaining a difference between the tool measurement position and the sensor measurement position and obtaining a length of the position measurement sensor based on the difference and the length of the reference tool;
A first reference block position acquisition step of measuring the position of the reference block using the position measurement sensor mounted on the spindle;
The detection position acquired in the tool sensor position acquisition stage, the position of the reference block acquired in the first reference block position acquisition stage, and the length of the position measurement sensor calculated in the position measurement sensor length calculation stage And a relative position calculating step for calculating a relative position of the reference block with respect to the detected position from the length of the reference tool;
A reference tool position acquisition step of mounting the reference tool on the spindle and acquiring a reference tool position that is a tip position of the reference tool using the tool sensor;
A second reference block position acquisition step of mounting the position measurement sensor on the spindle and measuring the position of the reference block using the position measurement sensor;
The reference tool position acquired in the reference tool position acquisition step, the position of the reference block measured in the second reference block position acquisition step, the relative position calculated in the relative position calculation step, and the reference tool A length correction value calculating step of calculating a length direction correction value of the position measurement sensor from the length of
A diameter correction value acquisition step of acquiring a radial direction correction value of the position measurement sensor using the measurement target jig,
A position measurement stage in which the rotation axis is indexed to an arbitrary plurality of angles and the position of the measurement jig is measured by the position measurement sensor,
Using the long direction correction value and the radial direction correction value, a position correction step for correcting the position measurement value in the position measurement step;
Performing a geometric error identifying step of identifying the geometric error from a plurality of the position measurement values corrected in the position correcting step.
According to a ninth aspect of the present invention, in the configuration of the eighth aspect, the tool sensor position acquisition stage to the relative position calculation stage are executed once, and a plurality of processes from the reference tool position acquisition stage to the geometric error identification stage are performed. It is characterized by being executed once.
A tenth aspect of the present invention is the configuration according to the eighth or ninth aspect, wherein the position measured by the position measurement sensor is the same as that of the translational axis when the position measurement sensor detects that the position measurement sensor has contacted the measurement object. It is a position.
According to an eleventh aspect of the present invention, in the configuration according to any one of the eighth to tenth aspects, the position measured by the tool sensor is such that a tool mounted on the main shaft moves by the translation shaft and contacts the tool sensor. Or it is the position of the said translation axis at the time of detecting having passed.
According to a twelfth aspect of the present invention, in the configuration according to any one of the eighth to eleventh aspects, the jig to be measured has a spherical shape.
According to a thirteenth aspect of the present invention, in the configuration of the twelfth aspect, in the diameter correction value acquisition stage, an initial position of the jig to be measured is measured by the position measurement sensor, and a radial direction of the position measurement sensor is measured. A correction value is acquired.
In order to achieve the above object, the invention described in claim 14 includes three or more translation axes, one or more rotation axes, a spindle that can be rotated by mounting a tool, a table, and the translation axes. And a position measuring sensor mounted on the spindle to measure a position in a three-dimensional space of the jig to be measured fixed on the table by a machine tool having a control device for controlling the rotating shaft and the spindle. And a system for identifying a geometric error of the machine tool from the position measurement value,
A reference tool serving as a reference for the length of the tool;
A tool sensor for detecting a tip position of the reference tool mounted on the spindle;
A reference block installed on the tool sensor side;
Tool sensor position acquisition means for moving the reference tool mounted on the spindle by the translation shaft and acquiring and storing the detection position of the tip of the reference tool using the tool sensor;
Reference tool measurement position acquisition means for acquiring and storing an arbitrary tool measurement position using the reference tool mounted on the spindle;
Position measurement sensor measurement position acquisition means for acquiring and storing an arbitrary sensor measurement position using the position measurement sensor mounted on the spindle;
A position measurement sensor length calculation means for obtaining a difference between the tool measurement position and the sensor measurement position, calculating and storing the length of the position measurement sensor based on the difference and the length of the reference tool;
First reference block position acquisition means for measuring and storing the position of the reference block using the position measurement sensor mounted on the spindle;
The detection position acquired by the tool sensor position acquisition means, the position of the reference block acquired by the first reference block position acquisition means, and the length of the position measurement sensor calculated by the position measurement sensor length calculation means And relative position calculation means for calculating and storing the relative position of the reference block with respect to the detection position from the length of the reference tool,
A reference tool position acquisition means for moving the reference tool mounted on the spindle by the translation shaft and acquiring and storing a reference tool position which is a tip position of the reference tool using the tool sensor;
Second reference block position acquisition means for measuring and storing the position of the reference block with the position measurement sensor mounted on the spindle;
The reference tool position acquired by the reference tool position acquisition means, the position of the reference block measured by the second reference block position acquisition means, the relative position calculated by the relative position calculation means, A length correction value calculating means for calculating and storing a length direction correction value of the position measurement sensor from the length of the reference tool;
Diameter correction value acquisition means for acquiring and storing a radial direction correction value of the position measurement sensor using the jig to be measured;
The rotational axis is determined at an arbitrary plurality of angles, and each position measurement value of the measurement target jig measured by the position measurement sensor is corrected using the long direction correction value and the radial direction correction value. Position correction means for storing;
Geometric error identification means for identifying the geometric error from the plurality of position measurement values corrected by the position correction means.

According to the present invention, it is possible to calibrate the length / diameter correction value of the position measurement sensor during each series of measurements for geometric error identification. In addition, no manual work other than pre-preparation work is required, and there is no need to prepare jigs separately, reducing the burden on the machine operator and ensuring calibration of the position measurement sensor during geometric error identification. Will be performed. Thereby, even if the state of the position measurement sensor changes due to thermal displacement or the like, the measurement accuracy by the position measurement sensor does not deteriorate, and the geometric error of the machine tool can be identified with high accuracy.
In addition, a measurement system using a CCD camera or the like is not necessary and can be realized at a relatively low cost.

It is a schematic diagram of a machining center. It is a schematic diagram which shows an example of a laser sensor. It is a schematic diagram which shows the example of a change of a laser sensor. It is a schematic diagram of the laser sensor of this invention attached to the machining center. It is a schematic diagram which shows an example of a touch sensor. It is a schematic diagram which shows the example of a change of a touch sensor. It is a flowchart of a measurement preparation work. It is explanatory drawing of step SR1 of measurement preparation work. It is explanatory drawing of step SR2 of measurement preparation work. It is explanatory drawing of step S1-2 of the error identification method of this invention. It is a flowchart of the error identification method of this invention. It is a schematic diagram of a touch probe and a target sphere. It is a flowchart of S1 of the error identification method of this invention. It is a flowchart of S2 of the error identification method of this invention. It is a schematic diagram of the relationship between the measured value in the initial position measurement of the target sphere of this invention, and a sphere center. It is a schematic diagram of the relationship between the measured value in the initial position measurement of the target sphere of this invention, and a touch probe diameter correction value. It is a flowchart of the measurement preparation work of the example of a change. It is explanatory drawing of step SQ2 of the measurement preparation work of the example of a change. It is explanatory drawing of step SQ3 of the measurement preparation work of the example of a change.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view of a machining center which is an embodiment of a machine tool and has three mutually orthogonal translation axes and two mutually orthogonal rotation axes.
The main shaft 2 is a translational axis and can move with two degrees of freedom of translation relative to the bed 1 by the X axis and the Z axis orthogonal to each other. The table 3 can move with one degree of freedom of rotation with respect to the cradle 4 by a C-axis which is a rotation axis. The cradle 4 is a rotation axis and can move with one degree of freedom of rotation with respect to the trunnion 5 by an A axis orthogonal to the C axis. The trunnion 5 is a translational axis and can move with one degree of freedom of translation relative to the bed 1 by a Y-axis orthogonal to the X-axis and the Z-axis. Therefore, the main shaft 2 can move with respect to the table 3 with three translational degrees of freedom and two degrees of freedom of rotation. Each feed shaft is driven by a servo motor controlled by a numerical control device (not shown), and a workpiece is fixed to the table 3, a tool is mounted on the spindle 2 and rotated, and a relative position between the workpiece and the tool is determined. The workpiece can be processed by controlling the relative posture.

  The machine according to the present invention is not limited to a machining center, and may be a machine tool such as a lathe, a multi-task machine, or a grinding machine. Further, the number of axes is not limited to five, but may be four or six. Furthermore, the mechanism is not limited to a mechanism in which the table 3 has two or more degrees of freedom of rotation by the rotating shaft, but a mechanism in which the main shaft 2 has two or more degrees of freedom of rotation, or a mechanism in which the main shaft 2 and the table 3 each have one or more degrees of freedom of rotation. Good.

FIG. 2 is a schematic diagram of a laser sensor 40 which is an example of the tool sensor of the present invention. The laser sensor 40 includes a light emitting unit 11, a light receiving unit 12, and a base unit 13. Here, a reference block 42 is provided between the light emitting unit 11 and the light receiving unit 12. The light emitting unit 11, the light receiving unit 12, and the reference block 42 are each fixed to the base unit 13. However, as shown in FIG. 3, the reference block 42 may be separately provided in the vicinity of the laser sensor 40.
As shown in FIG. 4, the laser sensor 40 is attached to the trunnion 5 of the machining center shown in FIG.
In the laser sensor 40, the laser beam 14 is output from the light emitting unit 11, received by the light receiving unit 12, and a signal is emitted when the laser beam 14 is blocked by an object and the light receiving rate becomes below a certain level. The control device (not shown) receives this signal, and the position of the feed shaft at the time when the signal is received or when the delay is taken into consideration is taken as the measured value. For example, the tool is mounted on the spindle 2, the tool is brought close to the laser beam by the Z axis, and the Z axis position Zt at the time when the tool cuts off the laser beam is acquired. Similarly, the Z-axis position Zb is acquired for the reference tool. From the difference between Zt and Zb, the length of the tool relative to the reference tool can be determined. The absolute length of the tool can also be obtained by subtracting the length Td of the reference tool.

  FIG. 5 is a schematic diagram of a touch sensor 50 which is an example of the tool sensor of the present invention. The touch sensor 50 includes a base part 51, a touch sensor part 52, and a reference block 53, and the touch sensor part 52 and the reference block 53 are fixed on the base part 51. The touch sensor 50 is attached to the trunnion 5 of the machining center in FIG. As shown in FIG. 6, the reference block 53 may be separately provided in the vicinity of the touch sensor 50.

Hereinafter, an error identification method and an error identification system when the laser sensor 40 is used as a tool sensor will be described (corresponding to claims 1 to 7). However, the touch sensor 50 is essentially the same except for the detection method.
First, the procedure of the measurement preparation work will be described based on the flowchart of FIG. The measurement preparation work is work performed in advance before measurement of a target sphere (measurement jig) by a touch probe as a position measurement sensor described later and identification of a geometric error. However, it may be performed at a low frequency, for example, when the laser sensor has deteriorated or has been replaced due to failure.
In step SR1, as shown in FIG. 8, the reference tool 8 is mounted on the spindle 2, and measurement is performed by the laser sensor 40. Here, the Z-axis is moved so that the reference tool 8 approaches the laser beam 14, and the point when the tip of the reference tool 8 blocks the laser beam 14 and the light receiving rate falls below the threshold or when the signal delay is taken into consideration. Get the Z-axis position. The acquired Z-axis position Zl is stored in a storage unit in a control device (not shown) (tool sensor position acquisition stage and tool sensor position acquisition means, where the control apparatus functions as each means for executing each stage of the present invention. ). The length Td of the reference tool 8 is also stored in advance in the storage unit. Here, the reference tool tip position Zl ′ (= Zl−Td) may be calculated from Zl and Td and stored.

Next, in step SR2, the position of the reference block 42 with the reference tool 8 is acquired. Here, as shown in FIG. 9, with the reference tool 8 mounted on the spindle 2, the reference block 42 is contacted via the block gauge 43, the Z-axis position Zb at that time is obtained, and the thickness Hb of the block gauge 43 is obtained. The value Zb ′ (= Zb−Hb) obtained by subtracting is stored in a storage unit (not shown) in the control device (reference block position acquisition step and reference block position acquisition means). Here, the reference block upper surface position Zb ″ (= Zb−Hb−Td) may be calculated and stored using Td. The block gauge 43 may be a block having a known thickness dimension.
Next, in step SR3, the relative position dZb (= Zl−Zb ′) of the reference block 42 with respect to the detection position of the laser sensor 40 from the Z-axis position Zl stored in step SR1 and the Z-axis position Zb ′ stored in step SR2. And is stored in a storage unit in the control device (relative position calculation step and relative position calculation means). Here, the block gauge thickness Hb may also be stored in the storage unit, and dZb may be calculated from Zl, Zb, and Hb (dZb = Zl−Zb−Hb). However, when Zl ′ and Zb ″ are stored, it can be calculated by dZb = Zl′−Zb ″.

Next, the flow of geometric error identification in the present invention will be described based on the flowchart of FIG.
First, in step S1, calibration of the length correction value of the touch probe 30 is performed. Details will be described later.
Next, in step S2, as shown in FIG. 12, the initial position of the target sphere 32 fixed on the table 3 is measured, and the diameter correction value calibration of the touch probe 30 is performed using the target sphere 32 (diameter correction). Value acquisition stage and diameter correction value acquisition means). Details will be described later.
Next, in step S3, using the target sphere initial position measured in step S2 and the length (length correction value) of the touch probe 30, measurement conditions (index angle of each rotation axis) set in advance are set. Etc.) to calculate the target sphere center position and the tip position of the touch probe after the movement expected by rotating and tilting the rotation axis (position measurement stage and position correction means). Further, a command value list is created in which the three-dimensional position coordinate values calculated at each index angle are used as command values for the X, Y, and Z axes, and the respective index angles are used as command values for the rotation axis.

Next, in step S4, based on each feed axis command value in the command value list created in step S3, the touch probe 30 is brought into contact with four or more points on the surface of the target sphere 32, and the length correction value acquired in step S1. And the diameter correction value acquired in step S2 to obtain the center position and diameter of the target sphere 32 (position correction stage and position correction means). Here, by using the diameter calibration value of the target sphere 32 measured in advance with a three-dimensional measuring machine or the like, the center position of the target sphere 32 can also be obtained by measurement by three-point contact.
In step S5, machine geometric error identification calculation is performed based on the acquired coordinate value of the center position of the target sphere 32 and the command value at each position (geometric error identification stage and geometric error identification means). Details will be described later.

Here, the length correction value calibration in step S1 will be described based on the flowchart of FIG.
First, in step S1-1, as in step SR1 described with reference to FIG. 8, the reference tool 8 is mounted on the spindle 2 and measurement is performed by the laser sensor 40, and the Z-axis position Zd is stored in a control device (not shown). (Reference tool position acquisition step and reference tool position acquisition means). Note that Td may be used to store Zd ′ = Zd−Td.
Next, in step S1-2, as shown in FIG. 10, the touch probe 30 is attached to the spindle 2, and the reference block 42 is measured by the touch probe 30. Here, the Z axis is moved so that the touch probe 30 approaches the reference block 42, and the Z axis position Zp at the time when the stylus at the tip of the touch probe 30 comes into contact and the trigger signal is transmitted or when the signal delay is taken into consideration. get. The acquired Z-axis position Zp is stored in a storage unit (not shown) in the control device (position measurement sensor measurement stage and measurement position acquisition means).

  Next, in step S <b> 1-3, the length of the touch probe 30 at the time of contact, which is a correction value in the long direction of the touch probe 30, is calculated. That is, Zd stored in step S1-1, Zp stored in step S1-2, the relative position dZb of the reference block 42 stored in the storage unit in the control device, and the reference tool length Td Then, a long direction correction value (contact length) Tp (= Zp−Zd + dZb + Td) is obtained and stored in the storage unit (long correction value calculation step and length correction value calculation means). Here, Tp (= Zp−Zd′−dZb) may be obtained from Zd ′, Zp, and dZb.

Next, details of step S2 will be described based on the flowchart of FIG.
First, before carrying out step S2, as shown in FIG. 12, a touch probe 30 having a stylus ball at the tip is attached to the main shaft 2 of the 5-axis control machining center, and a target ball 32 is set on the table 3. Keep it fixed.
In step S2-1, the touch probe 30 is moved in the Z-direction to make contact with the vicinity of the vertex of the target sphere in the Z + direction, and the Z-axis coordinate value zm1 at the time of contact is stored.
Next, in step S2-2, using the diameter d0 of the target sphere 32 measured in advance with a coordinate measuring machine or the like and the touch probe axial direction correction value t1 acquired in advance, the temporary Z center position zt is obtained from the following equation (1).

[Equation 1]
zt = zm1-d0 / 2-t1

Next, in step S <b> 2-3, the spindle 2 is indexed at 0 °, the touch probe 30 is moved to the vicinity of the X + apex of the target sphere 32, and then the touch probe 30 is moved in the X− direction. The X-axis coordinate value xm1 at the time of contact is stored in contact with the vicinity of the X + side vertex.
Next, in step S2-4, the spindle 2 is indexed at 180 ° so that the touch probe 30 contacts the target sphere 32 at the same point as the point of the stylus sphere contacted in step S2-3. After the touch probe 30 is moved in the vicinity of the − side vertex, the touch probe 30 is moved in the X + direction to make contact with the vicinity of the X− side vertex of the target sphere 32, and the X-axis coordinate value xp1 at the time of contact is stored.
Next, in step S2-5, using the stored xm1 and xp1, the X center position xo is obtained from the following equation (2).
Here, in step S2-3 and step S2-4, as shown in FIG. 15, the touch probe 30 is in contact with the target sphere 32 at the same point of the stylus sphere of the touch probe 30, so Xo can be accurately obtained without being affected by the difference in characteristics due to the difference in the contact direction and the influence of the shake of the touch probe 30 and the spindle 2.

[Equation 2]
xo = (xp1 + xm1) / 2

Next, in step S2-6, as described above, the spindle 2 is indexed to 270 °, the touch probe 30 is moved to the vicinity of the Y + apex of the target sphere 32, and then the touch probe 30 is moved in the Y− direction. Then, the target sphere 32 is brought into contact with the vicinity of the Y + side vertex, and the Y-axis coordinate value ym1 at the time of contact is stored.
Next, in Step S2-7, as described above, the spindle 2 is indexed at 90 °, the touch probe 30 is moved to the vicinity of the Y-side vertex of the target sphere 32, and then the touch probe 30 is moved in the Y + direction. Then, the target sphere 32 is brought into contact with the vicinity of the Y-side vertex, and the Y-axis coordinate value yp1 at the time of contact is stored.
In step S2-8, using the stored ym1 and yp1, the Y center position yo is obtained from the following equation (3).

[Equation 3]
yo = (yp1 + ym1) / 2

Next, in step S2-9, as in step S2-3, the main axis 2 is determined as 0 °, the X + apex of the target sphere 32 is measured, and the X-axis coordinate value xm1 is updated.
Next, in step S2-10, as in step S2-4, the main axis 2 is determined at 180 °, the X-side vertex of the target sphere 32 is measured, and the X-axis coordinate value xp1 is updated.
Next, in step S2-11, the X center position xo is recalculated from Equation 2 using the updated xm1 and xp1.
Next, in Step S2-12, the spindle 2 is indexed at 0 ° (an angle that is indexed during normal measurement).
Next, in step S2-13, the touch probe 30 is positioned immediately above the vertex of the target sphere 32 in the X-coordinate xo, Y-coordinate yo, and Z-axis directions, and the touch probe 30 is moved in the Z-direction to move the target sphere 32. The Z + coordinate direction zm2 at the time of contact is stored.
In step S2-14, the Z center position zo is obtained from the following equation 4.

[Equation 4]
zo = zm2-d0 / 2-t1

Next, in step S2-15, after the touch probe 30 is moved to the vicinity of the X + side vertex of the target sphere 32, the touch probe 30 is moved in the X-direction to contact the vicinity of the X + side vertex of the target sphere 32, The X-axis coordinate value xm2 at the time of contact is stored.
Next, in step S2-16, after moving the touch probe 30 to the vicinity of the X-side vertex of the target sphere 32, the touch probe 30 is moved in the X + direction so as to contact the vicinity of the X-side vertex of the target sphere 32. The X-axis coordinate value xp2 at the time of contact is stored.
Next, in step S2-17, after moving the touch probe 30 to the vicinity of the Y + apex of the target sphere 32, the touch probe 30 is moved in the Y− direction to contact the vicinity of the Y + apex of the target sphere 32, The Y-axis coordinate value ym2 at the time of contact is stored.
Next, in step S2-18, after moving the touch probe 30 to the vicinity of the Y-side apex of the target sphere 32, the touch probe 30 is moved in the Y + direction to make contact with the vicinity of the Y-side apex of the target sphere 32. The Y-axis coordinate value yp2 at the time of contact is stored.
Next, in step S2-19, touch probe diameter correction values tc1, tc2, tc3, and tc4 for X +, X−, Y +, and Y− direction contact are obtained using the following formula 5. Here, since the main axis center and the target sphere center at the time of positioning at the position (xo, yo) coincide with each other, the respective correction values are obtained from the moving distance from the target sphere diameter and the target sphere diameter as shown in FIG. Can do.

[Equation 5]
tc1 = xo-xp2-d0 / 2
tc2 = xo-xm2 + d0 / 2
tc3 = yo-yp2-d0 / 2
tc4 = yo-ym2 + d0 / 2

As described above, in step S2, the center position (xo, yo, zo) of the target sphere 32 is measured together with the acquisition of the touch probe diameter correction values tc1, tc2, tc3, tc4.
If the measured value of each axis when contacting any point on the surface of the sphere toward the center of the target sphere 32 is (xs, ys, zs), any point can be obtained by using the following equation (6). It is also possible to obtain touch probe correction values (tax, tay, taz).

[Equation 6]
tax = xo-xs-d0 / 2
tay = yo−ys + d0 / 2
taz = zo-zs + d0 / 2

Next, details of step S5 will be described.
Under one measurement condition, one of the rotation axes is fixed, and the other is calculated at a plurality of angles to measure the target sphere center position. The difference vector of the measured value of the sphere center position with respect to the command value under this measurement condition can be distributed to the radial direction, axial direction, and tangential direction components of the index axis. Each of these components can be approximated by the least square method or the like as a zero-order component (radius error), a first-order component (center deviation), or a quadratic component (elliptical shape) Fourier series, that is, an arc having an error.
Radial component DRR _i, axial component dRa _i, radial component DRT _i measurements in the k-th index angle theta _ijk of the j-th rotary shaft in the measurement condition i can be expressed as the following Equation 7 .

[Equation 7]
_{dRr i = ra0 i + ra1 i} * cos (θ ijk) + rb1 i * cos (θ ijk) + ra2 i cos (2θ ijk)
+ Rb2 _i sin (2θ _ijk )
dRa _i = aa 0 _i + aa 1 _i * cos (θ _ijk ) + ab 1 _i * cos (θ _ijk ) + aa 2 _i cos (2θ _ijk )
+ Ab2 _i sin (2θ _ijk )
_{dRt i = ta0 i + ta1 i} * cos (θ ijk) + tb1 i * cos (θ ijk) + ta2 i cos (2θ ijk)
+ Tb2 _i sin (2θ _ijk )

As geometric errors existing in the 5-axis control machining center of FIG. 1, the perpendicularity between XY axes is dCyx, the perpendicularity between YZ axes is dAxz, the perpendicularity between ZZ axes is dBxz, and the C axis center position X direction The error is dXca, the C-A axis offset error is dYca, the A-axis angle offset error is dAca, the CA-axis perpendicularity is dBca, the A-axis center position Y-direction error is dYay, and the A-axis center position Z-direction error is dZay, the AZ axis perpendicularity is dBay, and the A-Y axis perpendicularity is dCay.
In addition, measurement condition 1 is A axis 0 °, C axis is 0 ° to 360 °, measurement condition 2 is C axis −90 °, A axis is −90 ° to + 90 °, and measurement condition 3 is A axis −90 °. Assuming that the C-axis is 0 ° to 180 °, the relationship between each coefficient in Equation 7 and each geometric error is expressed by Equation 8 below. Here, R ₁ , R ₂ , and R ₃ are distances from the rotation center to the sphere center position on the plane on which the commanded sphere center position on the measurement conditions 1, ₂ , and ₃ is placed, that is, the radius of the arc locus. It is. By transforming Equation 8, each geometric error can be obtained.

[Equation 8]
ra1 ₁ = −dXca− (dBca + dBay + dBxz) * H
rb1 ₁ = dYca + dYay- (dAca + dAxz) * H
_{rb2 1 = dCyx * R 1/} 2
aa1 ₁ = dBca + dBay
ab1 ₁ = dAca
ra1 ₂ = -dYay
rb1 ₂ = dZay
_{rb2 2 = -dAxz * R 2/} 2
aa1 ₂ = dCay
ab1 ₂ = − (dBay + dBxz)
_{rb2 3 = dBxz * R 3/} 2

As described above, according to the error identification method and the error identification system of the above embodiment, it is possible to calibrate the length / diameter correction value of the touch probe 30 during each series of measurements for geometric error identification. In addition, since manual work is not necessary other than pre-preparation work and there is no need to separately prepare jigs, the load on the machine operator can be reduced, and the touch probe 30 can be reliably calibrated at the time of geometric error identification. Will be performed. Thereby, even if the state of the touch probe 30 changes due to thermal displacement or the like, the measurement accuracy by the touch probe 30 does not decrease, and the geometric error can be identified with high accuracy.
In addition, a measurement system using a CCD camera or the like is not necessary and can be realized at a relatively low cost.

In the above embodiment, when the reference block position is acquired, the reference tool is indirectly brought into contact with the reference block using a block gauge. However, the reference tool may be directly brought into contact with the reference block without the block gauge. .
In the above embodiment, the tool sensor position acquisition stage to the geometric error identification stage are executed once, but the tool sensor position acquisition stage to the relative position calculation stage are executed once, and the geometric error from the reference tool position acquisition stage is performed. The process up to the identification stage may be executed a plurality of times.

Next, an error identification method and an error identification system corresponding to claims 8 to 14 will be described. However, since it is the same as the previous embodiment except for the measurement preparation work, the measurement preparation work will be described based on the flowchart of FIG.
First, step SQ1 is the same as step SR1 of FIG. That is, as shown in FIG. 8, the reference tool 8 is attached to the spindle 2 and measurement is performed by the laser sensor 40. Here, the Z-axis is moved so that the reference tool 8 approaches the laser beam 14, and the point when the tip of the reference tool 8 blocks the laser beam 14 and the light receiving rate falls below the threshold or when the signal delay is taken into consideration. Get the Z-axis position. The acquired Z-axis position Zl is stored in a storage unit (not shown) in the control device (tool sensor position acquisition stage and tool sensor position acquisition means). The length Td of the reference tool 8 is also stored in advance in the storage unit.
Next, in step SQ2, the position of an arbitrary reference surface such as a table or jig upper surface of the reference tool 8 is acquired (reference tool measurement position acquisition stage and reference tool measurement position acquisition means). For example, as shown in FIG. 18, with the reference tool 8 mounted on the spindle 2, it is brought into contact with the upper surface of the table 3 via the block gauge 43, the Z-axis position Za at that time is obtained, and the thickness of the block gauge 43 A value Za ′ (= Za−Hb) obtained by subtracting Hb is stored in a storage unit in the control device (not shown). A block having a known thickness may be used instead of the block gauge.

Next, in step SQ3, the touch probe 30 is attached to the spindle 2, and the position of the same reference plane as in step SQ2 is measured by the touch probe 30 (position measurement sensor measurement position acquisition stage and position measurement sensor measurement position acquisition). means). For example, as shown in FIG. 19, the Z-axis is moved so that the touch probe 30 approaches the upper surface of the table 3, and the trigger signal is transmitted when the stylus of the touch probe 30 comes into contact or when the signal delay is taken into consideration. The Z-axis position Zq is acquired. The acquired Z-axis position Zq is stored in a storage unit in the control device (not shown).
Next, in step SQ4, the length of the touch probe at the time of contact is calculated. The touch probe contact length Tp (= Zq−Za + Td) is obtained from Za stored in step SQ2, Zq stored in step SQ3, and the reference tool length Td, and stored in the storage unit (position measurement). Sensor length calculation stage and position measurement sensor length calculation means).

Next, in step SQ5, the reference block 42 is measured by the touch probe 30 (first reference block position acquisition step and first reference block position acquisition means). That is, as shown in FIG. 10, the Z-axis is moved so that the touch probe 30 approaches the reference block 42, and the trigger signal is transmitted when the stylus of the touch probe 30 comes into contact or when the signal delay is considered. The Z-axis position Zp is acquired. The acquired Z-axis position Zp is stored in a storage unit in the control device (not shown).
Next, in step SQ6, the Z-axis position Zl stored in step SQ1, the contact probe length Tp calculated in step SQ4, the Z-axis position Zp stored in step SQ5, and the reference tool length Td From this, the relative position dZb (= Zl−Td−Zp + Tp) of the reference block 42 with respect to the laser sensor 40 is calculated and stored in the storage unit in the control device. (Relative position calculating step and relative position calculating means).

The subsequent geometric error identification flow is the same as that of the previous embodiment described with reference to FIGS. 11 to 16, but step S1-2 in FIG. 13 is the second reference corresponding to claims 8 and 14. It becomes a block position acquisition step and second reference block position acquisition means.
Also in this modified example, the tool sensor position acquisition step in step SQ1 to the relative position calculation step in step SQ6 are executed once, and the subsequent reference tool position acquisition step to geometric error identification step are executed a plurality of times. It may be.

  1 .... bed, 2 .... main shaft, 3 .... table, 4 .... cradle, 5 .... trunnion, 8 .... reference tool, 9 .... tool, 11 .... light emitting part, 12 .... light receiving part, 13 ....・ Base part, 14 ・ ・ Laser beam, 30 ・ ・ Touch probe, 32 ・ ・ Target sphere, 40 ・ ・ Laser sensor, 41 ・ ・ Sensor mounting base, 42 ・ ・ Reference block, 43 ・ ・ Block gauge, 50 ・ ・Touch sensor 51 ·· Base portion 52 · · Touch sensor portion 53 · · Reference block.

Claims (14)

A machine having three or more translation axes, one or more rotation axes, a spindle that can be rotated by mounting a tool, a table, and a controller that controls the translation axis, the rotation axis, and the spindle, respectively. In a machine, a method of measuring a position in a three-dimensional space of a jig to be measured fixed on the table by a position measurement sensor mounted on the spindle, and identifying a geometric error of the machine tool from the position measurement value Because
A tool sensor position acquisition step of mounting a reference tool serving as a reference for the length of the tool on the spindle and acquiring a detection position of the tip of the reference tool using a tool sensor;
A reference block position obtaining step for obtaining the position of the translation shaft when the reference tool mounted on the spindle is brought into direct or indirect contact with a reference block provided on the tool sensor side;
A relative position calculation step of calculating a relative position of the reference block with respect to the detection position from the detection position acquired in the tool sensor position acquisition step and the position of the translation axis acquired in the reference block position acquisition step;
A reference tool position acquisition step of mounting the reference tool on the spindle and acquiring a reference tool position that is a tip position of the reference tool using the tool sensor;
A position measurement sensor measurement step of mounting the position measurement sensor on the spindle and measuring the position of the reference block using the position measurement sensor;
The reference tool position acquired in the reference tool position acquisition step, the position of the reference block measured in the position measurement sensor measurement step, the relative position calculated in the relative position calculation step, and the length of the reference tool From the long correction value calculation step of calculating the long direction correction value of the position measurement sensor,
A diameter correction value acquisition step of acquiring a radial direction correction value of the position measurement sensor using the measurement target jig,
A position measurement stage in which the rotation axis is indexed to an arbitrary plurality of angles and the position of the measurement jig is measured by the position measurement sensor,
Using the long direction correction value and the radial direction correction value, a position correction step for correcting the position measurement value in the position measurement step;
A geometric error identification step for identifying the geometric error from a plurality of the position measurement values corrected in the position correction step;
An error identification method for a machine tool, characterized in that From the tool sensor position acquisition stage to the relative position calculation stage is executed once,
The machine tool error identification method according to claim 1, wherein the process from the reference tool position acquisition stage to the geometric error identification stage is executed a plurality of times.   3. The machine tool according to claim 1, wherein the position measured by the position measurement sensor is a position of the translational axis when the position measurement sensor detects that the object is in contact with a measurement object. Error identification method.   The position measured by the tool sensor is a position of the translation axis when it is detected that a tool attached to the spindle moves by the translation axis and contacts or passes through the tool sensor. An error identification method for a machine tool according to any one of claims 1 to 3.   5. The machine tool error identification method according to claim 1, wherein the measurement jig has a spherical shape.   6. The radial correction value acquisition step according to claim 5, wherein in the diameter correction value acquisition step, an initial position of the measurement target jig is measured by the position measurement sensor, and a correction value in a radial direction of the position measurement sensor is acquired. Error identification method for machine tools. A machine having three or more translation axes, one or more rotation axes, a spindle that can be rotated by mounting a tool, a table, and a controller that controls the translation axis, the rotation axis, and the spindle, respectively. In a machine, a position measurement sensor mounted on the spindle measures a position in a three-dimensional space of a jig to be measured fixed on the table, and identifies a geometric error of the machine tool from the position measurement value Because
A reference tool serving as a reference for the length of the tool;
A tool sensor for detecting a tip position of the reference tool mounted on the spindle;
A reference block installed on the tool sensor side;
Tool sensor position acquisition means for moving the reference tool mounted on the spindle by the translation shaft and acquiring and storing the detection position of the tip of the reference tool using the tool sensor;
Reference block position acquisition for acquiring and storing the position of the translation axis at the time of contact with the reference block by moving the reference tool mounted on the spindle by the translation axis to directly or indirectly contact the reference block Means,
A relative position for calculating and storing a relative position of the reference block with respect to the detection position from the detection position acquired by the tool sensor position acquisition means and the position of the translation axis acquired by the reference block position acquisition means. A calculation means;
A reference tool position acquisition means for moving the reference tool mounted on the spindle by the translation shaft and acquiring and storing a reference tool position which is a tip position of the reference tool using the tool sensor;
Measurement position acquisition means for measuring and storing the position of the reference block with the position measurement sensor mounted on the spindle;
The reference tool position acquired by the reference tool position acquisition means, the position of the reference block acquired by the measurement position acquisition means, the relative position acquired by the relative position calculation means, and the reference tool A length correction value calculating means for calculating and storing a length direction correction value of the position measurement sensor from the length;
Diameter correction value acquisition means for acquiring and storing a radial direction correction value of the position measurement sensor using the jig to be measured;
The rotational axis is determined at an arbitrary plurality of angles, and each position measurement value of the measurement target jig measured by the position measurement sensor is corrected using the long direction correction value and the radial direction correction value. Position correction means for storing;
Geometric error identification means for identifying the geometric error from a plurality of the position measurement values corrected by the position correction means;
An error identification system for a machine tool characterized by comprising: A machine having three or more translation axes, one or more rotation axes, a spindle that can be rotated by mounting a tool, a table, and a controller that controls the translation axis, the rotation axis, and the spindle, respectively. In a machine, a method of measuring a position in a three-dimensional space of a jig to be measured fixed on the table by a position measurement sensor mounted on the spindle, and identifying a geometric error of the machine tool from the position measurement value Because
Using a tool sensor and a reference block provided on the tool sensor side,
A tool sensor position acquisition step of mounting a reference tool serving as a reference for the length of the tool on the spindle, and acquiring a detection position of a tip of the reference tool using the tool sensor;
A reference tool measurement position acquisition step of acquiring an arbitrary tool measurement position using the reference tool mounted on the spindle;
A position measurement sensor measurement position acquisition stage for acquiring an arbitrary sensor measurement position using the position measurement sensor mounted on the spindle;
A position measurement sensor length calculation step for obtaining a difference between the tool measurement position and the sensor measurement position and obtaining a length of the position measurement sensor based on the difference and the length of the reference tool;
A first reference block position acquisition step of measuring the position of the reference block using the position measurement sensor mounted on the spindle;
The detection position acquired in the tool sensor position acquisition stage, the position of the reference block acquired in the first reference block position acquisition stage, and the length of the position measurement sensor calculated in the position measurement sensor length calculation stage And a relative position calculating step for calculating a relative position of the reference block with respect to the detected position from the length of the reference tool;
A reference tool position acquisition step of mounting the reference tool on the spindle and acquiring a reference tool position that is a tip position of the reference tool using the tool sensor;
A second reference block position acquisition step of mounting the position measurement sensor on the spindle and measuring the position of the reference block using the position measurement sensor;
The reference tool position acquired in the reference tool position acquisition step, the position of the reference block measured in the second reference block position acquisition step, the relative position calculated in the relative position calculation step, and the reference tool A length correction value calculating step of calculating a length direction correction value of the position measurement sensor from the length of
A diameter correction value acquisition step of acquiring a radial direction correction value of the position measurement sensor using the measurement target jig,
A position measurement stage in which the rotation axis is indexed to an arbitrary plurality of angles and the position of the measurement jig is measured by the position measurement sensor,
Using the long direction correction value and the radial direction correction value, a position correction step for correcting the position measurement value in the position measurement step;
A geometric error identification step for identifying the geometric error from a plurality of the position measurement values corrected in the position correction step;
An error identification method for a machine tool, characterized in that From the tool sensor position acquisition stage to the relative position calculation stage is executed once,
9. The error identification method for a machine tool according to claim 8, wherein the steps from the reference tool position acquisition step to the geometric error identification step are executed a plurality of times.   10. The machine tool according to claim 8, wherein the position measured by the position measurement sensor is a position of the translational axis when the position measurement sensor detects that the object is in contact with a measurement object. Error identification method.   The position measured by the tool sensor is a position of the translation axis when it is detected that a tool attached to the spindle moves by the translation axis and contacts or passes through the tool sensor. The machine tool error identification method according to claim 8.   The machine tool error identification method according to claim 8, wherein the jig to be measured has a spherical shape.   The radial correction value acquisition step according to claim 12, wherein in the diameter correction value acquisition step, an initial position of the measurement target jig is measured by the position measurement sensor, and a correction value in a radial direction of the position measurement sensor is acquired. Error identification method for machine tools. A machine having three or more translation axes, one or more rotation axes, a spindle that can be rotated by mounting a tool, a table, and a controller that controls the translation axis, the rotation axis, and the spindle, respectively. In a machine, a position measurement sensor mounted on the spindle measures a position in a three-dimensional space of a jig to be measured fixed on the table, and identifies a geometric error of the machine tool from the position measurement value Because
A reference tool serving as a reference for the length of the tool;
A tool sensor for detecting a tip position of the reference tool mounted on the spindle;
A reference block installed on the tool sensor side;
Tool sensor position acquisition means for moving the reference tool mounted on the spindle by the translation shaft and acquiring and storing the detection position of the tip of the reference tool using the tool sensor;
Reference tool measurement position acquisition means for acquiring and storing an arbitrary tool measurement position using the reference tool mounted on the spindle;
Position measurement sensor measurement position acquisition means for acquiring and storing an arbitrary sensor measurement position using the position measurement sensor mounted on the spindle;
A position measurement sensor length calculation means for obtaining a difference between the tool measurement position and the sensor measurement position, calculating and storing the length of the position measurement sensor based on the difference and the length of the reference tool;
First reference block position acquisition means for measuring and storing the position of the reference block using the position measurement sensor mounted on the spindle;
The detection position acquired by the tool sensor position acquisition means, the position of the reference block acquired by the first reference block position acquisition means, and the length of the position measurement sensor calculated by the position measurement sensor length calculation means And relative position calculation means for calculating and storing the relative position of the reference block with respect to the detection position from the length of the reference tool,
A reference tool position acquisition means for moving the reference tool mounted on the spindle by the translation shaft and acquiring and storing a reference tool position which is a tip position of the reference tool using the tool sensor;
Second reference block position acquisition means for measuring and storing the position of the reference block with the position measurement sensor mounted on the spindle;
The reference tool position acquired by the reference tool position acquisition means, the position of the reference block measured by the second reference block position acquisition means, the relative position calculated by the relative position calculation means, A length correction value calculating means for calculating and storing a length direction correction value of the position measurement sensor from the length of the reference tool;
Diameter correction value acquisition means for acquiring and storing a radial direction correction value of the position measurement sensor using the jig to be measured;
The rotational axis is determined at an arbitrary plurality of angles, and each position measurement value of the measurement target jig measured by the position measurement sensor is corrected using the long direction correction value and the radial direction correction value. Position correction means for storing;
Geometric error identification means for identifying the geometric error from a plurality of the position measurement values corrected by the position correction means;
An error identification system for a machine tool characterized by comprising:

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