Fault identification method of a machine tool and fault identification system thereof

Abstract

An error identification method for measuring a position of a measured gauge (32) in a three-dimensional space and for identifying a geometric error in a machine tool in which the measured gauge (32) is mounted on a table (3), from a value of the position measured by a position measuring sensor (30) installed on a spindle (2) in the machine tool, wherein the machine tool includes three or more translation axes, one or more rotation axes, the rotatable spindle (2) to which a tool (9) is to be installed, the table (3), and a control device configured to control the respective translation axes, the rotation axis, and the spindle (2), the error identification method comprising: a tool sensor position acquiring step of installing a reference tool (8) as a length reference of the tool (9) on the spindle (2) and acquiring a sensing position of a distal end of the reference tool (8) with a tool sensor (40, 50); a reference block position acquiring step of acquiring positions of the translation axes when the reference tool (8) installed on the spindle (2) is brought into contact directly or indirectly with a reference block (42, 53) arranged on the side of the tool sensor (40, 50); a relative position calculation step of calculating a relative position of the reference block (42, 53) with respect to the perception position from the perception position obtained in the tool sensor position obtaining step and the positions of the translation axes obtained in the reference block position obtaining step; a reference tool position acquiring step of installing the reference tool (8) on the spindle (2) and acquiring a reference tool position with the tool sensor (40, 50), the reference tool position being a distal end position of the reference tool (8); a position measuring sensor measuring step of installing the position measuring sensor (30) on the spindle (2) and measuring a position of the reference block (42, 53) with the position measuring sensor (30); a length compensation value calculation step of calculating a compensation value of the position measuring sensor (30) in a longitudinal direction from the reference tool position obtained in the reference tool position obtaining step, the position of the reference block (42, 53) measured in the position measuring sensor measuring step, the relative position calculated in the relative position calculation step, and the length of the reference tool (8); a diameter compensation value obtaining step of obtaining a compensation value of the position measuring sensor (30) in a radial direction with the measured gauge (32); a position measuring step of indexing the rotation axis to a plurality of arbitrary given angles and measuring respective positions of the measured gauge (32) by the position measuring sensor (30); a position compensation step of compensating the position measurement value in the position measuring step using the compensation value in the longitudinal direction and the compensation value in the radial direction; and a geometric error identification step of identifying the geometric error from the compensation of a plurality of position measurement values ​​in the position compensation step.

Description

[0001] The invention relates to a method that identifies a geometric error in a machine tool from a measurement result of a position of an object in the machine, and to a system that identifies the geometric error.

[0002] Fig. Figure 1 is a schematic diagram of a five-axis control machining center including three translational and two rotational axes. A main spindle 2 is capable of two translational degrees of freedom movement along an X-axis and a Z-axis, which are translational axes and perpendicular to each other, relative to a bed 1. A table 3 is capable of one rotational degree of freedom movement about a C-axis, which is the rotational axis, relative to a carriage 4. A carriage 4 is capable of one rotational degree of freedom movement about an A-axis, which is the rotational axis, relative to a trunnion 5. The A-axis and the C-axis are perpendicular to each other. Furthermore, a trunnion 5 is capable of one translational degree of freedom movement about a Y-axis, which is the translational axis and perpendicular to the X-axis and the Z-axis, relative to the bed 1.Accordingly, movements with the three translational degrees of freedom and the two rotational degrees of freedom of the main spindle 2 relative to the table 3 are possible. Servomotors controlled by a numerical control unit (not shown) drive the respective feed axes. A workpiece is mounted on the table 3, and a tool is installed and rotated on the main spindle 2. Accordingly, the workpiece can be machined in a controlled relative position and relative posture.

[0003] There are geometric errors between the respective axes, such as a center position error of the rotation axis (an offset from an assumed position) and an inclination error of the rotation axes (perpendicularity and parallelism between the axes) as a major factor influencing the movement accuracy of the five-axis control machining center. For example, in the five-axis control machining center in Fig. 1 total of 13 geometric errors: three geometric errors of perpendicularity between the X and Y axes, of perpendicularity between the Y and Z axes, and of perpendicularity between the Z and X axes as geometric errors relating to the translation axes; two geometric errors of perpendicularity between the tool and the Y axis and of perpendicularity between the tool and the X axis as geometric errors relating to a main spindle; and eight geometric errors of the X-direction error of the C-axis center position, the offset error between the C and A axes, the angular offset error of the A-axis, the perpendicularity between the C and A axes, the Y-direction error of the A-axis center position, the Z-direction error of the A-axis center position, the perpendicularity between the A and Z axes, and the perpendicularity between the A and Y axes as geometric errors with respect to the rotation axes.

[0004] Geometric errors degrade the machine's movement accuracy, which in turn impairs the workpiece machining accuracy. Given this, geometric errors must be reduced through adjustment, but it is difficult to zero geometric errors. Performing control to compensate for geometric errors makes high-precision machining possible.

[0005] Such compensation control requires measuring or identifying the geometric error in the machine. The inventor has proposed a method disclosed in JP 2011-038902 A to identify the geometric error in the machine. In the method of the disclosure, a table is rotated and indexed around a rotation axis by a plurality of angles. Respective center positions of a ball mounted on the table are measured using a probe mounted on a main spindle, so that a geometric error in the machine is identified from the obtained measured values.

[0006] The probe contains a sensor that detects contact with a measurement target. When contact is detected, the sensor transmits a signal, for example, via infrared light or radio waves. A receiver coupled to a numerical control unit obtains the current positions of the respective axes (step values) at the time the signal is received, or at a time taking into account the delay, and these values ​​are determined as the measured values.

[0007] However, measurement by the probe requires compensation of the acquired positions. This is because when the probe touches the measurement target, the contact points of control points, which serve as references for the positions of the feed axes (the X and Y axes are the main spindle center, and the Z axis is the main spindle end face), with the probe differ from the positions of the feed axes. For example, the X and Y axes are shifted by the radius of the probe tip ball. This shift occurs due to, for example, an offset between the main spindle center and the probe center, a signal delay upon contact, and a directional dependence of the sensor in the probe. The X and Y axes are shifted in the Z direction by the lengths of the probe body and the probe ball, and this shift occurs due to, for example, a signal delay upon contact.Accordingly, calibration is required to obtain compensation values ​​to compensate for these shifts.

[0008] As disclosed in JP H04 - 63 664 A and JP S58 - 82 649 A, calibration methods of a compensation value of the probe in the radial direction are known.

[0009] In the method disclosed in JP H04-63664 A, the position of a main spindle center is adjusted using a dial indicator so that the center of a ring gauge, as a reference, coincides with the main spindle center. A diameter compensation value of the probe is obtained from a jump value when the probe is brought into contact with the inner diameter of the ring gauge and an inner diameter value of the measuring ring.

[0010] In the method disclosed in JP S58-82649 A, the probe is brought into contact with a hole inner diameter as a reference in one direction. When the probe contacts the hole inner diameter in the opposite direction, a main spindle is rotated 180°, and a hole center position is obtained from an average of both jump values, and then the compensation values ​​in the respective directions are obtained.

[0011] On the other hand, a method using a reference tool (hereinafter referred to as "Method 1") is known as a calibration method of a length compensation value. In Method 1, a reference tool is installed on a main spindle, and a position at which a distance between a block gauge and the reference tool becomes approximately zero is found and recorded. The position is determined from a resistance when the block gauge is manually moved while a Z-axis is manually operated so that the reference tool contacts a reference surface, such as a table top surface, via the block gauge. Next, a probe measures the reference surface, that is, acquires a Z-axis position when the probe is in contact.A length of the probe-in-contact, namely the length compensation value of the probe, is obtained from a value found by subtracting the recorded Z-axis position of the reference tool and a thickness of the block gauge found from the Z-axis position obtained by the probe.

[0012] Publication JP 2012-061570 A discloses a measuring method for a probe-in-contact length using a CCD camera. In this method, the probe is brought into contact with an upper surface of a support block, a position of the main spindle is obtained when a signal is output, and a distal end of the probe-in-contact is photographed by the CCD camera to measure a distal end position. Next, the support block is removed to restore the length when the probe is not in contact, and the distal end position is measured by the CCD camera. An amount of reduction in contact is calculated from a difference between both distal end positions. A distal end position of a reference tool is measured by the CCD camera, so that a position of the main spindle at that time is also obtained.A probe-in-contact length, namely a probe length compensation value, is obtained from a relationship among the obtained amount of reduction in contact, a remote end position of the probe-in-contact, a main spindle position while the probe is in contact, a remote end position of the reference tool, and a main spindle position, and the reference tool.

[0013] Furthermore, publication JP 2001-105279 A discloses a workpiece position compensation method using a laser sensor and a reference block. When laser light is blocked by a distal tool end, and therefore a light reception rate becomes a certain rate or less, the laser sensor generates a signal. Positions of feed axes at a time when a control device of a machine tool receives the signal are determined as measured values. In this method, the reference block is prepared near the laser sensor, and a position of the laser light is matched with a position (height) of a top surface of the reference block. The laser sensor memorizes a position with the installed reference tool.Next, the probe is brought into contact with the reference block and the position is stored. The probe is also brought into contact with the workpiece and the position is stored. The workpiece position relative to the reference tool is measured and compensated using the difference between the two positions and the position of the reference tool. In this method, the workpiece position is measured without obtaining the probe's length compensation value.

[0014] The probe must be calibrated before measurement to identify any geometric errors. Furthermore, the probe's condition may change due to thermal displacement, such as heat generation in the main spindle, and long-term changes, thus changing the required compensation value. Given this, calibration is preferably performed immediately before measurement.

[0015] However, the methods in JP H04 - 63 664 A and JP S58 - 82 649 A have the problem that additional preparation of another measuring device, such as a dial indicator, or a reference of, for example, a workpiece with a ring gauge or a bore, is required.

[0016] Furthermore, this complicates the work, as JP H04 - 63 664 A, JP S58 - 82 649 A, and Method 1 require physical labor. Consequently, once performed, calibration is often not performed afterward. In this case, if the condition of the probe changes due to, for example, thermal deformation, the measurement accuracy of the probe deteriorates, causing the problem of failing to accurately identify the geometric error in the machine.

[0017] The method of JP 2012-061570 A has the problem of acquiring the measuring device, namely the expensive CCD camera. In addition, this causes the problem of a reduction in the work cycle due to the physical labor required to move the holding block. To move the holding block automatically, a mechanism for moving the holding block and an actuator are required, which causes the problem of increased costs.

[0018] Furthermore, JP 2001-105279 A discloses a method for measuring the position of the workpiece without using the length compensation value of the probe. However, this method requires that the laser light position of the laser sensor coincide with the reference block position or that a positional relationship between the two be known in advance. This required information in the method of JP 2001-105279 A means that a relationship between the length of the reference tool measured by the laser sensor and the length of the probe with which the reference block is brought into contact, i.e., the length compensation value of this probe, must be known in advance. However, JP 2001-105279 A does not disclose a method for knowing the positional relationship between the two in advance.

[0019] Therefore, it is an object of the invention to provide an error identification method and an error identification system that can perform calibrations of diameter / length compensation values ​​of a position measuring sensor simultaneously when a measured gauge, such as a target ball, is measured with the position measuring sensor, such as a probe, in order to identify a geometric error in a machine tool including three translation axes and at least one rotation axis from a position of the measured gauge.

[0020] The problem is solved by a fault identification method having the features of patent claim 1 and by a fault identification system having the features of patent claim 7. Furthermore, the problem is further solved by a fault identification method having the features of patent claim 8 and by a fault identification system having the features of patent claim 14.

[0021] To achieve the above-described object, an error identification method according to a first aspect of the invention is provided. The error identification method may be for measuring a position of a measured gauge in a three-dimensional space by a position measuring sensor installed on a main spindle in a machine tool, the measured gauge being mounted on a table. The machine tool may include three or more translation axes, one or more rotation axes, the rotatable main spindle on which a tool is to be installed, the table, and a control device configured to control the respective translation axes, the rotation axis, and the main spindle. The error identification method may identify a geometric error in the machine tool from a value of the measured position (position measurement value).The error identification method may perform a tool sensor position acquisition step, a reference block position acquisition step, a relative position calculation step, a reference tool position acquisition step, a position measurement sensor measurement step, a length compensation value calculation step, a diameter compensation value acquisition step, a position measurement step, a position compensation step, and a geometric error identification step. The tool sensor position acquisition step may install a reference tool as a length reference of the tool on the main spindle and acquire a sensing position of a distal end of the reference tool using a tool sensor.The reference block position acquisition step may acquire positions of the translation axes when the reference tool installed on the main spindle is brought into direct or indirect contact with a reference block arranged on the tool sensor side. The relative position calculation step may calculate a relative position of the reference block with respect to the sensing position from the sensing position acquired in the tool sensor position acquisition step and the positions of the translation axes acquired in the reference block position acquisition step. The reference tool position acquisition step may install the reference tool on the main spindle and acquire a reference tool position using the tool sensor. The reference tool position may be a remote end position of the reference tool.The position sensor measuring step may install the position sensor on the main spindle and measure a position of the reference block with the position sensor. The length compensation value calculation step may calculate a compensation value of the position sensor in a longitudinal direction from the reference tool position obtained in the reference tool position acquisition step, the position of the reference block measured in the position sensor measuring step, the relative position calculated in the relative position calculation step, and the length of the reference tool. The diameter compensation value acquisition step may obtain a compensation value of the position sensor in a radial direction using the measured gauge. The position measurement step may index the rotation axis to a plurality of given angles and measure relative positions of the measured gauge by the position sensor.The position compensation step may compensate the position measurement value in the position measurement step using the compensation value in the longitudinal direction and the compensation value in the radial direction. The geometric error identification step may identify the geometric error from the plurality of position measurement values ​​compensated in the position compensation step.

[0022] Here, "the tool sensor side" can obviously include the case of directly arranging the reference block on the tool sensor, as well as the case of separately arranging the reference block near the tool sensor. The same applies to the following invention.

[0023] With the error identification method according to a second aspect of the invention included in the first aspect of the invention, the steps from the tool sensor position acquisition step to the relative position calculation step may be configured to be executed once. The steps from the reference tool position acquisition step to the geometric error identification step may be configured to be executed multiple times.

[0024] With the fault identification method according to a third aspect of the invention included in the first or second aspect of the invention, the positions measured by the position measuring sensor may be positions of the translation axes when the position measuring sensor detects contact with a measurement object.

[0025] With the failure identification method according to a fourth aspect of the invention included in any one of the first to third aspects of the invention, the positions measured by the tool sensor may be positions of the translation axes when the tool installed on the main spindle moves in the translation axes and the tool sensor detects contact with the tool or passing of the tool.

[0026] With the defect identification method according to a fifth aspect of the invention included in any one of the first to fourth aspects of the invention, the measured gauge may have a spherical shape.

[0027] With the error identification method according to a sixth aspect of the invention included in the fifth aspect of the invention, the diameter compensation value acquisition step can measure an initial position of the measured gauge by the position measuring sensor. The diameter compensation value acquisition step can acquire a compensation value of the position measuring sensor in a radial direction.

[0028] To achieve the above-described object, an error identification system according to a seventh aspect of the invention is provided. The error identification system may be for measuring a position of a measured gauge in a three-dimensional space by a position measuring sensor installed on a main spindle in a machine tool, the measured gauge being fixed to a table. The machine tool may include three or more translation axes and one or more rotation axes, the rotatable main spindle on which a tool is to be installed, the table, and a controller configured to control the respective translation axes, the rotation axis, and the main spindle. The error identification system may identify a geometric error in the machine tool from a value of the measured position (the position measurement value).The error identification system may include a reference tool, a tool sensor, a reference block, a tool sensor position acquisition means, a reference block position acquisition means, a relative position calculation means, a reference tool position acquisition means, a measurement position acquisition means, a length compensation value calculation means, a diameter compensation value acquisition means, a position compensation means, and a geometric error identification means. The reference tool may be a length reference of the tool. The tool sensor may be configured to detect a remote end position of the reference tool installed on the main spindle. The reference block may be installed on the tool sensor side.The tool sensor position acquisition means may be configured to move the reference tool installed on the main spindle along the translational axes to acquire and store a sensing point of a distal end of the reference tool with the tool sensor. The reference block position acquisition means may be configured to move the reference tool installed on the main spindle along the translational axes to bring the reference tool into direct or indirect contact with the reference block. The reference block position acquisition means may be configured to acquire and store positions of the translational axes at the time of contact.The relative position calculation means may be configured to calculate and store a relative position of the reference block with respect to the sensing position from the sensing position acquired in the tool sensor position acquisition means and the positions of the translation axes acquired in the reference block position acquisition means. The reference tool position acquisition means may be configured to move the reference tool installed on the main spindle in the translation axes. The reference tool position acquisition means may be configured to acquire and store a reference tool position using the tool sensor. The reference tool position may be the remote end position of the reference tool. The measurement position acquisition means may be configured to measure and store a position of the reference block using the position measurement sensor installed on the main spindle.The length compensation value calculation means may be configured to calculate and store a compensation value of the position measuring sensor in the longitudinal direction from the reference tool position obtained by the reference tool position acquisition means, the position of the reference block obtained by the measurement position acquisition means, the relative position obtained by the relative position calculation means, and the length of the reference tool. The diameter compensation value acquisition means may be configured to acquire and store a compensation value of the position measuring sensor in the radial direction using the measured gauge.The position compensation means may be configured to index the rotation axis to a plurality of arbitrary given angles to compensate and store the respective position measurement values ​​of the measured gauge measured by the position measuring sensor using the compensation value in the longitudinal direction and the compensation value in the radial direction. The geometric error identification means may be configured to identify the geometric error from the plurality of position measurement values ​​compensated in the position compensation means.

[0029] To achieve the above-described object, an error identification method according to an eighth aspect of the invention is provided. The error identification method may be for measuring a position of a measured gauge in a three-dimensional space by a position measuring sensor installed on a main spindle in a machine tool, the measured gauge being mounted on a table. The machine tool may include three or more translation axes, one or more rotation axes, the rotatable main spindle on which a tool is to be installed, the table, and a controller configured to control the respective translation axes, the rotation axis, and the main spindle. The error identification method may identify a geometric error in the machine tool from a value of the measured position (position measurement value).The error identification method may use a tool sensor and a reference block arranged on the tool sensor side. The error identification method may perform a tool sensor position acquisition step, a reference tool measurement position acquisition step, a position measurement sensor measurement position acquisition step, a position measurement sensor length calculation step, a first reference block position acquisition step, a relative position calculation step, a reference tool position acquisition step, a second reference block position acquisition step, a length compensation value calculation step, a diameter compensation value acquisition step, a position measurement step, a position compensation step, and a geometric error identification step.The tool sensor position acquisition step may install a reference tool as a tool length reference on the main spindle and use the tool sensor to acquire a sensing position of a distal end of the reference tool. The reference tool measurement position acquisition step may acquire any given tool measurement position using the reference tool installed on the main spindle. The position measurement sensor measurement position acquisition step may acquire any given sensor measurement position using the position measurement sensor installed on the main spindle. The position measurement sensor length calculation step may acquire a difference between the tool measurement position and the sensor measurement position and obtain a position measurement sensor length based on the difference and the length of the reference tool. The reference block position acquisition step may measure a position of the reference block using the position measurement sensor installed on the main spindle.The relative position calculation step may calculate a relative position of the reference block with respect to the sensing position from the sensing position obtained in the tool sensor position acquisition step, the position of the reference block obtained in the first reference block position acquisition step, the length of the position measuring sensor calculated in the position measuring sensor length calculation step, and the length of the reference tool. The reference tool position acquisition step may install the reference tool on the main spindle and acquire a reference tool position using the tool sensor. The reference tool position may be a distal end position of the reference tool. The second reference block position acquisition step may install the position measuring sensor on the main spindle and measure a position of the reference block using the position measuring sensor.The length compensation value calculation step can calculate a compensation value of the position measuring sensor in the longitudinal direction from the reference tool position obtained 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 length of the reference tool. The diameter compensation value acquisition step can obtain a compensation value of the position measuring sensor in the radial direction using the measured gauge. The position measuring step can index the rotation axis to a plurality of arbitrary given angles and measure respective positions of the measured gauge using the position measuring sensor.The position compensation step may compensate the position measurement value in the position measurement step using the compensation value in the longitudinal direction and the compensation value in the radial direction. The geometric error identification step may identify the geometric error from the plurality of position measurement values ​​compensated in the position compensation step.

[0030] In the defect identification method according to a ninth aspect of the invention included in the eighth aspect of the invention, the steps from the tool sensor position acquisition step to the relative position calculation step may be configured to be executed once. The steps from the reference tool position acquisition step to the geometric defect identification step may be configured to be executed multiple times.

[0031] In the fault identification method according to a tenth aspect of the invention included in the eighth or ninth aspect of the invention, positions measured by the position measuring sensor may be positions of the translation axes when the position measuring sensor detects contact with a measurement object.

[0032] In the failure identification method according to an eleventh aspect of the invention included in any one of the eighth to tenth aspects of the invention, the positions measured by the tool sensor may be positions of the translation axes when the tool installed on the main spindle moves in the translation axes and the tool sensor detects contact with the tool or passing of the tool.

[0033] In the defect identification method according to a twelfth aspect of the invention included in any one of the eighth to eleventh aspects of the invention, the measured gauge may have a spherical shape.

[0034] In the defect identification method according to a thirteenth aspect of the invention included in the twelfth aspect of the invention, the diameter compensation value acquisition step may measure an initial position of the measured gauge by the position measuring sensor. The diameter compensation value acquisition step may acquire a compensation value of the position measuring sensor in a radial direction.

[0035] To achieve the above-described object, a defect identification system according to a fourteenth aspect of the invention is provided. The defect identification system may be for measuring a position of a measured gauge in a three-dimensional space, wherein the measured gauge is mounted on a table. The machine tool may include three or more translation axes, one or more rotation axes, the rotatable main spindle on which a tool is to be installed, the table, and a controller configured to control the respective translation axes, the rotation axis, and the main spindle. The defect identification system may identify a geometric error in the machine tool from a value of the measured position (position measurement value).The error identification system may include a reference tool, a tool sensor, a reference block, a tool sensor position acquisition means, a reference tool measurement position acquisition means, a position measurement sensor measurement position acquisition means, a position measurement sensor length calculation means, a first reference block position acquisition means, a relative position calculation means, a reference tool position acquisition means, a second reference block position acquisition means, a length compensation value calculation means, a diameter compensation value acquisition means, a position compensation means, and a geometric error identification means. The reference tool may be a length reference of the tool. The tool sensor may be configured to detect a remote end position of the reference tool installed on the main spindle. The reference block may be installed on the tool sensor side.The tool sensor position acquisition means may be configured to move the reference tool installed on the main spindle along the translation axes and to acquire and store a sensing position of the distal end of the reference tool using the tool sensor. The reference tool measurement position acquisition means may be configured to acquire and store any tool measurement position using the reference tool installed on the main spindle. The position measurement sensor measurement position acquisition means may be configured to acquire and store any given sensor measurement position using the position measurement sensor installed on the main spindle. The position measurement sensor length calculation means may be configured to acquire a difference between the tool measurement position and the sensor measurement position.The position measuring sensor length calculation means may be configured to calculate and store a length of the position measuring sensor based on the difference and the length of the reference tool. The first reference block position acquisition means may be configured to measure and store a position of the reference block using the position measuring sensor installed on the main spindle. The relative position calculation means may be configured to calculate and store a relative position of the reference block with respect to the sensing position from the sensing position acquired in the tool sensor position acquisition means, the position of the reference block acquired in the first reference block position acquisition means, the length of the position measuring sensor calculated in the position measuring sensor length calculation means, and the length of the reference tool.The reference tool position acquisition means may be configured to move the reference tool installed on the main spindle along the translation axes. The reference tool position acquisition means may be configured to acquire and store a reference tool position using the tool sensor. The reference tool position may be the remote end position of the reference tool. The second reference block position acquisition means may be configured to measure and store a position of the reference block using the position measuring sensor installed on the main spindle.The length compensation value calculation means may be configured to calculate and store a compensation value of the position measuring sensor in the longitudinal direction from the reference tool position obtained by the reference tool position acquisition means, the position of the reference block obtained by the second reference block position acquisition means, the relative position calculated by the relative position calculation means, and the length of the reference tool. The diameter compensation value acquisition means may be configured to acquire and store a compensation value of the position measuring sensor in the radial direction using the measured gauge.The position compensation means may be configured to index the rotation axis to a plurality of arbitrary given angles and to compensate and store the respective position measurement values ​​of the measured gauge measured by the position measurement sensor using the compensation value in the longitudinal direction and the compensation value in the radial direction. The geometric error identification means may be configured to identify the geometric error from a plurality of position measurement values ​​compensated in the position compensation means.

[0036] With the invention, the calibration of the length and diameter compensation values ​​of the position measuring sensor is possible during a sequence of measurements for identifying the geometric error. The need for physical labor, except for preparatory work, is eliminated. Accordingly, the preparation of an additional gauge or similar preparation is not required, which ensures a reduction in the burden on the machine operator and reliable calibration of the position measuring sensor during geometric error identification. This does not degrade the measurement accuracy of the position measuring sensor even in a state where the position measuring sensor changes due to, for example, thermal displacement, ensuring highly accurate identification of the geometric error in the machine tool.

[0037] Furthermore, the measuring system with the CCD camera or a similar system is not required, which allows for a comparatively low price. Fig. Figure 1 is a schematic diagram of a machining center. Fig. Figure 2 is a schematic diagram showing an example of a laser sensor. Fig. 3 is a schematic diagram showing a modification example of the laser sensor. Fig. 4 is a schematic diagram of the laser sensor of the invention mounted on the machining center. Fig. 5 is a schematic diagram showing an example of a touch sensor. Fig. 6 is a schematic diagram showing a modified example of the touch sensor. Fig. Figure 7 is a flowchart for a measurement preparation work. Fig. Figure 8 is an explanatory view for step SR1 in the measurement preparation work. Fig. 9 is an explanatory view for step SR2 in the measurement preparation work. Fig. 10 is an explanatory view for step S1-2 for a fault identification method of the invention. Fig. 11 is a flowchart for the fault identification method of the invention. Fig. Figure 12 is a schematic diagram of a probe and a target ball. Fig. 13 is a flowchart for S1 in the fault identification method of the invention. Fig. 14 is a flowchart for S2 in the fault identification method of the invention. Fig. 15 is a schematic diagram of a relationship between a measured value in an initial position measurement of the target ball of the invention and a ball center point. Fig. 16 is a schematic diagram of a relationship between the measured values ​​and the probe diameter compensation values ​​in the initial position measurement of the target ball of the invention. Fig. 17 is a flowchart for a measurement preparation work of a modified example. Fig. 18 is an explanatory view for step SQ2 in the measurement preparation work of the modified example. Fig. 19 is an explanatory view for step SQ3 in the measurement preparation work of the modified example.

[0038] The following describes embodiments of the invention based on the drawings.

[0039] Fig. 1 is a schematic diagram of a machining center, which is an embodiment of a machine tool, and which includes three translational axes that are perpendicular to each other and two rotational axes that are perpendicular to each other. A two-degree-of-freedom movement for translation of a main spindle 2 along an X-axis and a Z-axis, which are the translational axes and are perpendicular to each other, is possible with respect to a bed 1. A one-degree-of-freedom movement for rotation of the table 3 about a C-axis, which is the rotational axis, is possible with respect to a carriage 4. A one-degree-of-freedom movement for rotation of the carriage 4 about an A-axis, which is the rotational axis perpendicular to the C-axis, is possible with respect to a pivot 5.A one-degree-of-freedom movement of the trunnion 5 along a Y-axis, which is the translational axis and perpendicular to the X-axis and the Z-axis, is possible with respect to the bed 1. Accordingly, three-degree-of-freedom movements of the main spindle 2 and two-degree-of-freedom movements of the main spindle 2 are possible with respect to the table 3. Servomotors controlled by a numerical control unit (not shown) drive respective feed axes. A workpiece is fixed to the table 3, a tool is installed on the main spindle 2 and rotates, and a relative position and posture between the workpiece and the tool are controlled to ensure machining of the workpiece.

[0040] A machine related to the invention is not limited to the machining center, but may be a machine tool such as a lathe, a multi-purpose machine, or a grinding machine. The number of axes is not limited to five axes, but may be four axes or six axes. Furthermore, the mechanism is not limited to one in which the table 3 has two or more degrees of freedom for rotation in the rotation axes; rather, a mechanism in which the main spindle 2 has two or more degrees of freedom for rotation, and a mechanism in which both the main spindle 2 and the table 3 have one or more degrees of freedom for rotation can be employed.

[0041] Fig. Figure 2 is a schematic diagram of a laser sensor 40 as an example of a tool sensor of the invention. While the laser sensor 40 includes a light emitting section 11, a light receiving section 12, and a base section 13, the laser sensor 40 here includes a reference block 42 between the light emitting section 11 and the light receiving section 12. Each of the light emitting section 11, the light receiving section 12, and the reference block 42 is attached to the base section 13. It should be noted that, as in Fig. 3, the reference block 42 can be arranged separately near the laser sensor 40.

[0042] As in Fig. 4, the laser sensor 40 is mounted on the pivot pin 5 of the machining center via a sensor mounting block 41 in Fig. 4 mounted.

[0043] In the laser sensor 40, the light emitting section 11 outputs laser light 14, and the light receiving section 12 receives the laser light 14. When the laser light 14 is blocked by a material and therefore a light receiving proportion becomes a predetermined proportion or less, the laser sensor 40 generates a signal. A controller (not shown) receives this signal and determines positions of feed axes at a time of receiving the signal or at a time taking the delay into account as measured values. For example, the tool mounted on the main spindle 2 is caused to approach a laser light in the Z-axis to acquire a Z-axis position Zt at a time when the tool intercepts the laser light. A Z-axis position Zb of a reference tool is similarly acquired. A length of the tool with respect to the reference tool can be obtained from a difference between Zt and Zb.Subtracting a length Td of the reference tool can also achieve an absolute length of the tool.

[0044] Fig. Figure 5 is a schematic diagram of a touch sensor 50 as an example of the tool sensor of the invention. The touch sensor 50 includes a base portion 51, a touch sensor portion 52, and a reference block 53. The touch sensor portion 52 and the reference block 53 are mounted on the base portion 51. The touch sensor 50 is mounted on the pivot 5 of the machining center in the same manner as the laser sensor 40. Fig. 1. As shown in Fig. 6, the reference block 53 may be arranged separately near the touch sensor 50.

[0045] The following describes a fault identification method and system in the case of using the laser sensor 40 as the tool sensor (corresponding to claims 1 to 7). It should be noted that the case of using the touch sensor 50 differs only in a sensing method and is essentially identical.

[0046] First, the following describes, based on a flowchart in Fig. 7. A procedure for measurement preparation work. Measurement preparation work must be performed in advance before performing measurement of a target ball (measured gauge) and geometric error identification using a probe as a position measurement sensor, which will be described later. Measurement preparation work is only required with infrequency in cases such as laser sensor malfunction and replacement due to laser sensor failure.

[0047] In step SR1, as in Fig. 8, a reference tool 8 is installed on the main spindle 2 and is measured by the laser sensor 40. Here, the Z-axis is moved so that the reference tool 8 approaches the laser light 14, and the Z-axis position is acquired at a time when a distal end of the reference tool 8 intersects the laser light 14 and a light reception ratio is a threshold or less, or at a time taking a signal delay into account. A storage unit (not shown) in the controller stores the acquired Z-axis position Z1 (a tool sensor position acquisition step and a tool sensor position acquisition means. Here, the controller functions as a means that performs respective steps of the invention). The storage unit also stores the length Td of the reference tool 8 in advance. Here, a position Z1' of the distal end of the reference tool can be calculated and stored from Z1 and Td (=Z1-Td).

[0048] Next, in step SR2, the position of the reference block 42 is obtained using the reference tool 8. Here, as in Fig. As shown in Fig. 9, with the reference tool 8 installed on the main spindle 2, the reference tool 8 is brought into contact with the reference block 42 via a block gauge 43 to obtain the Z-axis position Zb at that time. The storage unit (not shown) in the controller stores a value Zb' found by subtracting a thickness Hb of the block gauge 43 (=Zb-Hb) (a reference block position obtaining step and a reference block position obtaining means). Here, a reference block upper surface position Zb'' may also be calculated and stored using Td (=Zb-Hb-Td). The block gauge 43 may be a block with an already known thickness dimension or a similar block.

[0049] In step SR3, a relative position dZb (=Z1-Zb') of the reference block 42 with respect to a sensing position of the laser sensor 40 is calculated from the Z-axis position Z1 stored in step SR1 and the Z-axis position Zb' stored in step SR2, and stored in the storage unit in the controller (a relative position calculation step and relative position calculation means). Here, the storage unit also stores the thickness Hb of the block gauge, and dZb can be calculated from Z1, Zb, and Hb (dZb = Z1 - Zb - Hb). Note that storing Z1' and Zb'' enables the calculation by dZb = Z1' - Zb''.

[0050] The following describes a procedure of identifying the geometric error of the invention based on a flow chart in Fig. 11.

[0051] First, in step S1, calibration of a length compensation value of a probe 30 is performed. The details will be described later.

[0052] Next, in step S2, an initial position of a target ball 32 attached to the table 3 as shown in Fig. 12. A diameter compensation value calibration of the probe 30 is performed using the target sphere 32 (a diameter compensation value acquisition step and a diameter compensation value acquisition means). The details will be described later.

[0053] In step S3, after moving by rotating and tilting the rotation axes under preset measurement conditions (such as a step angle of the respective rotation axes), respective expected center positions of the target sphere and distant end positions of the probe are calculated using the target sphere initial position measured in step S2 and the length of the probe 30 (length compensation value) (a position measuring step and position measuring means).

[0054] Furthermore, three-dimensional position coordinate values ​​calculated at the respective indexing angles are set as instruction values ​​of the respective X, Y, and Z axes. An instruction value list that sets the respective indexing angles as the instruction values ​​of the rotation axes is generated. In step S4, the probe 30 is brought into contact with a surface of the target sphere 32 at four or more points based on respective feed axis instruction values ​​in the instruction value list generated in step S3. Compensation is performed using the length compensation value obtained in step S1 and the diameter compensation value obtained in step S2 to obtain the center position and the diameter of the target sphere 32 (a position compensation step and a position compensation means).Here, the use of a diameter calibration value of the target ball 32 measured in advance by a coordinate measuring machine or similar machine enables the center position of the target ball 32 to be obtained by the three-point contact measurement.

[0055] In step S5, the geometric error identification calculation is performed in the machine based on the acquired center position coordinate values ​​of the target ball 32 and the instruction values ​​at the respective positions (a geometric error identification step and a geometric error identification means). The details will be described later.

[0056] Here, the following describes a calibration of a length compensation value in step S1 based on a flowchart in Fig. 13.

[0057] First, in the same way as in the Fig. In step SR1 described in Figure 8, the reference tool 8 is installed on the main spindle 2 in step S1-1, and the laser sensor 40 performs the measurement. The storage unit in the controller (not shown) stores a Z-axis position Zd (a reference tool position acquisition step and a reference tool position acquisition means). Using Td, Zd' = Zd-Td can be stored.

[0058] Next, as in Fig. As shown in Figure 10, the probe 30 is installed on the main spindle 2 to measure the reference block 42 through the probe 30. Here, the Z-axis is moved so that the probe 30 approaches the reference block 42, and a Z-axis position Zb at the time when a probe at a distal end of the probe 30 touches the reference block 42 and the probe 30 transmits a trigger signal, or at a time taking the signal delay into account, is acquired. The storage unit in the controller (not shown) stores the acquired Z-axis position Zp (a position measurement sensor measuring step and measurement position acquisition means).

[0059] In step S1-3, the probe-in-contact length, which is the compensation value of the probe 30 in the longitudinal direction, is calculated. That is, the compensation value in the longitudinal direction (length-in-contact) Tp (=Zp - Zd + dZb + Td) is obtained from Zd stored in step S1-1, Zp stored in step S1-2, the relative position dZb of the reference block 42, and the reference tool length Td, which are stored in the storage unit in the controller. The storage unit stores the compensation value in the longitudinal direction Tp (a length compensation value calculation step and a length compensation value calculation means). Here, Tp (=Zp - Zd' - dZb) can be obtained from Zd', Zp, and dZb.

[0060] The following describes details of step 2 based on a flowchart in Fig. 14.

[0061] First, before step S2 is executed, as shown in Fig. 12, the probe head 30 having a probe ball at a distal end is mounted to the main spindle 2 of the five-axis control machining center, and the target ball 32 is installed and fixed on the table 3.

[0062] In step S2-1, the probe head 30 is moved in the -Z direction to bring the probe head 30 into contact with a side near a tip in the +Z direction of the target ball 32, and a Z-axis coordinate value Zm1-in-contact is stored.

[0063] Next, in step S2-2, a temporary Z-center position zt is obtained from the following formula 1 using a diameter d0 of the target ball 32 measured in advance by the coordinate measuring machine or a similar machine and a probe diameter compensation value t1 obtained in advance. zt=zm1−d0 / 2−t1

[0064] In step S2-3, the main spindle 2 is indexed to 0°, and the probe head 30 is moved to a side near the tip on the +X side of the target ball 32. After that, the probe head 30 is moved in the -X direction to bring the probe head 30 into contact with a side near the tip on the +X side of the target ball 32, and an X-axis coordinate value in contact xm1 is stored.

[0065] In step S2-4, the main spindle 2 is indexed 180° so that the probe head 30 contacts the target ball 32 at the point identical to the contact point on the probe ball in step S2-3. After the probe head 30 is moved to the side near the tip on the -X side of the target ball 32, the probe head 30 is moved in the +X direction to bring the probe head 30 into contact with the side near the tip on the -X side of the target ball 32, and an X-axis coordinate value in contact xp1 is stored.

[0066] In step S2-5, an X-center position x0 is obtained from the following formula 2 using the stored xm1 and xp1.

[0067] Here the probe touches 30, as in Fig. 15, the target ball 32 in step S2-3 and step S2-4 at the identical point of the probe ball of the probe head 30. This ensures accurate acquisition of x0 without being affected by a difference in the property due to a difference in the contact direction of the probe head 30 and a swing of the probe head 30 and the main spindle 2. x0=(xp1+xm1) / 2

[0068] In step S2-6, in the same manner as in the above-described operations, the main spindle 2 is indexed to 270°, and the probe head 30 is moved to the side near the tip on the +Y side of the target ball 32. Thereafter, the probe head 30 is moved in the -Y direction to bring the probe head 30 into contact with the side near the tip on the +Y side of the target ball 32, and a Y-axis coordinate value in contact ym1 is stored.

[0069] In step S2-7, in the same manner as in the above-described operations, the main spindle 2 is indexed to 90°, and the probe head 30 is moved to the side near the tip on the -Y side of the target ball 32. Thereafter, the probe head 30 is moved in the +Y direction to bring the probe head 30 into contact with the side near the tip on the -Y side of the target ball 32, and a Y-axis coordinate value in contact yp1 is stored.

[0070] In step S2-8, using the stored ym1 and yp1, a Y-center position y0 is obtained from the following equation 3. y0=(yp1+ym1) / 2

[0071] In step S2-9, the main spindle 2 is indexed to 0° in the same manner as in step S2-3. The peak on the +X side of the target ball 32 is measured to update the X-axis coordinate value xm1.

[0072] In step S2-10, the main spindle 2 is indexed to 180° in the same manner as in step S2-4. The tip on the -X side of the target ball 32 is measured to update the X-axis coordinate value xp1.

[0073] In step S2-11, the X-center position x0 is recalculated using the updated xm1 and xp1 from Formula 2.

[0074] In step S2-12, the main spindle 2 is indexed to 0° (an angle indexed in conventional measurement). In step S2-13, the probe head 30 is positioned at the X coordinate x0, the Y coordinate y0, and in the Z-axis direction just above the tip of the target sphere 32. The probe head 30 is moved in the -Z direction to bring the probe head 30 into contact with a side near the tip in the positive +Z direction of the target sphere 32, and a Z-axis coordinate in-contact value zm2 is stored.

[0075] In step S2-14, a Z center position z0 is obtained from the following formula 4. z0=zm2−d0 / 2−t1

[0076] In step S2-15, the probe head 30 is moved to the side near the tip on the +X side of the target ball 32. After that, the probe head 30 is moved in the -X direction to bring the probe head 30 into contact with the side near the tip on the +X side of the target ball 32, and an X-axis coordinate value xm2 in contact is stored.

[0077] In step S2-16, the probe head 30 is moved to the side near the tip on the -X side of the target ball 32. After that, the probe head 30 is moved in the +X direction to bring the probe head 30 into contact with the side near the tip on the -X side of the target ball 32, and an X-axis coordinate value in contact xp2 is stored.

[0078] In step S2-17, the probe head 30 is moved to the side near the tip on the +Y side of the target ball 32. Thereafter, the probe head 30 is moved in the -Y direction to bring the probe head 30 into contact with the side near the tip on the +Y side of the target ball 32, and a Y-axis coordinate value in contact y2 is stored.

[0079] In step S2-18, the probe head 30 is moved to the side near the tip on the -Y side of the target ball 32. After that, the probe head 30 is moved in the +Y direction to bring the probe head 30 into contact with the side near the tip on the -Y side of the target ball 32, and a Y-axis coordinate value in contact y2 is stored.

[0080] In step S2-19, using the following formula 5, probe contact diameter compensation values ​​tc1, tc2, tc3, and tc4 are obtained in the +X, -X, +Y, and -Y directions. Here, the main spindle center coincides with the target ball center when the target ball 32 is positioned at the position (x0, y0). Therefore, as shown in Fig. 16, the respective compensation values ​​are obtained from a movement distance from the center point position and the target ball diameter. tc1=x0−xp2−d0 / 2tc2=x0−xm2+d0 / 2tc3=y0−yp2−d0 / 2tc4=y0−ym2+d0 / 2

[0081] As described above, in step S2, the center position (x0, y0, z0) of the target ball 32 is measured along with obtaining the probe diameter compensation value tc1, tc2, tc3 and tc4.

[0082] The probe is moved toward the center of the target sphere 32 so that the probe is brought into contact with the target sphere 32. The measured values ​​of the respective axes on the surface of the target sphere 32 at any given point are assumed to be (xs, ys, zs). Then, the following formula 6 can also be used to obtain the probe compensation values ​​(tax, tay, taz) at any given point. tax=x0−xs−d0 / 2tay=y0−ys+d0 / 2taz=z0−zs+d0 / 2

[0083] Next, the following describes details of step S5.

[0084] Under a measurement condition, one of the rotation axes is fixed, and the other is indexed to a plurality of angles, and the center position of the target sphere is measured. Difference vectors of the measured values ​​at the sphere center positions with respect to the command values ​​can be divided into a radial-direction component, an axial-direction component, and a tangential-direction component of an indexing axis under the measurement conditions. These respective components can be approximated as Fourier series of a zero-order component (radius error), a first-order component (a center deviation), and a second-order component (elliptical shape), namely an arc with an error, using, for example, the least-squares method.

[0085] A radial-direction component dRr i , an axial-direction component dRa i and a tangential direction component dRt iof the measured values ​​at a k-th switching angle θ ijk a j-th rotation axis under a measurement condition i can be expressed as the following formula 7. dRri=ra0i+ra1i∗cos(θijk)+rb1i∗cos(θijk)+ra2icos(2θijk)+rb2i sin(2θijk)dRai=aa0i+aa1i∗cos(θijk)+ab1i∗cos(θijk)+aa2icos(2θijk)+ab2i sin(2θijk)dRti=ta0i+ta1i∗cos(θijk)+tab1i∗cos(θijk)+ta2icos(2θijk)+tab2i sin(2θijk)

[0086] When the geometric error in the five-axis control machining center in Fig. 1, the perpendicularity between the X and Y axes is denoted as dCyx, the perpendicularity between the Y and Z axes is denoted as dAxz, the perpendicularity between the Z and X axes is denoted as dBxz, the X-direction error of the C-axis center position is denoted as dXca, the offset error between the C and A axes is denoted as dYca, the angular offset error of the A-axis is denoted as dAca, the perpendicularity between the C and A axes is denoted as dBca, the Y-direction error of the A-axis center position is denoted as dYay, the Z-direction error of the A-axis center position is denoted as dZay, the perpendicularity between the A and Z axes is denoted as dBay, and the perpendicularity between the A and Y axes is denoted as dCay.

[0087] When a first measurement condition is set as the A-axis at 0° and the C-axis from 0° to 360°, a second measurement condition is set as the C-axis at -90° and the A-axis from -90° to +90°, and a third measurement condition is set as the A-axis at -90° and the C-axis from 0° to 180°, the relationships between the respective coefficients in Formula 7 and the geometric error are the following Formula 8. Here, each of R1, R2, and R3 is a distance from a rotation center to a sphere center position on a plane in which the sphere center positions are placed under the first, second, and third measurement conditions, namely, a radius of an arcuate trajectory. A modification of Formula 8 can capture the respective geometric errors. ra11=−dXca−(dBca+dBay+dBxz)∗Hrb11=dYca+dYay−(dAca+dAxz)∗Hrb21=dCyx∗R1 / 2aa11=dBca+dBa yab11=dAcara12=−dYayrb12=dZayrb22=−dAxz∗R2 / 2aa12=dCayab12=−(dBay+dBxz)rb23=dBxz∗R3 / 2

[0088] The defect identification method and system with the above-described configuration enables the calibration of the length and diameter compensation values ​​of the probe 30 during a series of measurements for the identification of the geometric defect. The need for physical labor, except for preliminary preparatory work, is eliminated. Accordingly, the preparation of an additional gauge or similar preparation is not required, ensuring a reduction in the burden on a machine operator and the reliable calibration of the probe 30 when identifying the geometric defect. This does not degrade the measurement accuracy of the probe 30 even in a state where the probe 30 changes due to, for example, thermal displacement, ensuring highly accurate identification of the geometric defect.

[0089] Furthermore, the measuring system with the CCD camera or a similar system is not required, and thus a comparatively low price can be achieved.

[0090] To obtain the reference block position, the configuration brings the reference tool into indirect contact with the reference block using the block gauge. However, the reference tool can be brought into direct contact with the reference block without the block gauge.

[0091] Furthermore, in the configuration, the steps from the tool sensor position acquisition step to the geometric error identification step are performed once. However, the steps from the tool sensor position acquisition step to the relative position calculation step may be executed once, and the steps from the reference tool position acquisition step to the geometric error identification step may be executed multiple times.

[0092] The following describes the fault identification method and the fault identification system according to claims 8 to 14. It should be noted that the following describes the measurement preparation work based on the flowchart in Fig. 17, since the configurations are identical to the configurations described above except for the measurement preparation work.

[0093] First, step SQ1 is identical to step SR1 in Fig. 7. This means that the reference tool 8, as shown in Fig. 8, is installed on the main spindle 2 and measured by the laser sensor 40. Here, the Z-axis is moved so that the reference tool 8 approaches the laser light 14, and the Z-axis position at the time when the distal end of the reference tool 8 intersects the laser light 14 and the light reception ratio is the threshold or less, or the time taking the signal delay into account, is acquired. The storage unit (not shown) in the controller stores the acquired Z-axis position Z1 (the tool sensor position acquisition step and the tool sensor position acquisition means). The storage unit also stores the length Td of the reference tool 8 in advance.

[0094] Next, in step SQ2, a position of any given reference surface, such as the upper surface of the table or the gauge, is obtained with the reference tool 8 (a reference tool measurement position obtaining step and a reference tool measurement position obtaining means). For example, with the reference tool 8 installed on the main spindle 2, as shown in Fig. 18, the reference tool 8 is brought into contact with the upper surface of the table 3 via the block gauge 43 to obtain a Z-axis position Za at that time. The storage unit (not shown) in the controller stores a value Za' obtained by subtracting the thickness Hb of the block gauge 43 from the Z-axis position Za (= Za-Hb). The block gauge 43 need not be a block gauge, but may be a block with a previously known thickness dimension or a similar block.

[0095] In step SQ3, the probe head 30 is installed on the main spindle 2 to measure the position of any given reference surfaces by the probe head 30 in the same manner as in step SQ2 (a position measuring sensor measurement position obtaining step and a position measuring sensor measurement position obtaining means). For example, as in Fig. 19, the Z-axis is moved so that the probe head 30 approaches the upper surface of the table 3. The Z-axis position Zp at the time when the probe of the probe head 30 touches the upper surface and the probe head 30 transmits the trigger signal, or at the time taking the signal delay into account, is obtained. The storage unit (not shown) in the controller stores the obtained Z-axis position Zp.

[0096] In step SQ4, the probe-in-contact length is calculated. A probe-in-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 the storage unit stores the probe-in-contact length Tp (a position measurement sensor length calculation step and a position measurement sensor length calculation means).

[0097] In step SQ5, the reference block 42 is measured by the probe 30 (a first reference block position obtaining step and a first reference block position obtaining means). That is, as shown in Fig. 10, the Z-axis is moved so that the probe head 30 approaches the reference block 42, and the Z-axis position Zp at the time the probe of the probe head 30 touches the reference block 42 and the probe head 30 transmits the trigger signal, or at the time taking the signal delay into account, is obtained. The storage unit in the controller (not shown) stores the obtained Z-axis position Zp.

[0098] In step SQ6, the relative position dZb (= Z1 - Td - Zp + Cp) of the reference block 2 with respect to the laser sensor 40 is calculated from the Z-axis position Z1 stored in step SQ1, the length of the probe 30 in contact Tp calculated in step SQ4, the Z-axis position Zp stored in step SQ5, and the reference tool length Td, and stored in the storage unit in the controller (the relative position calculation step and the relative position calculation means).

[0099] While the corresponding procedure of geometric error identification is identical to the one described above in Fig. 11 to Fig. 16 described configurations, step S1-2 in Fig. 13 a second reference block position obtaining step and second reference block position obtaining means according to claim 8 and claim 14.

[0100] Moreover, also in the modified example, the steps from the tool sensor position acquisition step in step SQ1 to the relative position calculation step in SQ6 may be executed once, and the steps from the subsequent reference tool position acquisition step to the geometric error identification step may be executed multiple times.

[0101] It is explicitly stated that all features disclosed in the description and / or the claims are intended to be disclosed separately and independently of one another for the purpose of original disclosure and for the purpose of limiting the claimed invention, regardless of the composition of the features in the embodiments and / or the claims. It is explicitly stated that all value ranges or indications of groups of units disclose every possible intermediate value or possible intermediate unit for the purpose of original disclosure and for the purpose of limiting the claimed invention, in particular as limits of value ranges.

Claims

[1] An error identification method for measuring a position of a measured gauge (32) in a three-dimensional space and for identifying a geometric error in a machine tool in which the measured gauge (32) is mounted on a table (3), from a value of the position measured by a position measuring sensor (30) installed on a spindle (2) in the machine tool, wherein the machine tool includes three or more translation axes, one or more rotation axes, the rotatable spindle (2) to which a tool (9) is to be installed, the table (3), and a control device configured to control the respective translation axes, the rotation axis, and the spindle (2), the error identification method comprising: a tool sensor position acquiring step of installing a reference tool (8) as a length reference of the tool (9) on the spindle (2) and acquiring a sensing position of a distal end of the reference tool (8) with a tool sensor (40, 50); a reference block position acquiring step of acquiring positions of the translation axes when the reference tool (8) installed on the spindle (2) is brought into contact directly or indirectly with a reference block (42, 53) arranged on the side of the tool sensor (40, 50); a relative position calculation step of calculating a relative position of the reference block (42, 53) with respect to the perception position from the perception position obtained in the tool sensor position obtaining step and the positions of the translation axes obtained in the reference block position obtaining step; a reference tool position acquiring step of installing the reference tool (8) on the spindle (2) and acquiring a reference tool position with the tool sensor (40, 50), the reference tool position being a distal end position of the reference tool (8); a position measuring sensor measuring step of installing the position measuring sensor (30) on the spindle (2) and measuring a position of the reference block (42, 53) with the position measuring sensor (30); a length compensation value calculation step of calculating a compensation value of the position measuring sensor (30) in a longitudinal direction from the reference tool position obtained in the reference tool position obtaining step, the position of the reference block (42, 53) measured in the position measuring sensor measuring step, the relative position calculated in the relative position calculation step, and the length of the reference tool (8); a diameter compensation value obtaining step of obtaining a compensation value of the position measuring sensor (30) in a radial direction with the measured gauge (32); a position measuring step of indexing the rotation axis to a plurality of arbitrary given angles and measuring respective positions of the measured gauge (32) by the position measuring sensor (30); a position compensation step of compensating the position measurement value in the position measuring step using the compensation value in the longitudinal direction and the compensation value in the radial direction; and a geometric error identification step of identifying the geometric error from the compensation of a plurality of position measurement values ​​in the position compensation step. [2] The error identification method of a machine tool according to claim 1, wherein the steps from the tool sensor position obtaining step to the relative position calculating step are configured to be executed once, and the steps from the reference tool position obtaining step to the geometric error identifying step are configured to be executed a plurality of times. [3] A fault identification method of a machine tool according to claim 1 or 2, wherein the positions measured by the position measuring sensor (30) are positions of the translation axes when the position measuring sensor (30) detects contact with a measuring object. [4] A fault identification method of a machine tool according to any one of claims 1 to 3, wherein the positions measured by the tool sensor (40, 50) are positions of the translation axes when the tool (9) installed on the spindle (2) moves in the translation axes and the tool sensor (40, 50) detects contact with the tool (9) or passing of the tool (9). [5] A fault identification method of a machine tool according to any one of claims 1 to 4, wherein the measured gauge (32) has a spherical shape. [6] A fault identification method of a machine tool according to claim 5, wherein the diameter compensation value obtaining step includes measuring an initial position of the measured gauge (32) by the position measuring sensor (30), wherein the diameter compensation value obtaining step includes obtaining a compensation value of the position measuring sensor (30) in a radial direction. [7] An error identification system for measuring a position of a measured gauge (32) in a three-dimensional space and for identifying a geometric error in a machine tool in which the measured gauge (32) is mounted on a table (3), from a value of the position measured by a position measuring sensor (30) installed on a spindle (2) in the machine tool, wherein the machine tool includes three or more translation axes and one or more rotation axes, the rotatable spindle (2) on which a tool (9) is to be installed, the table (3), and a control device configured to control the respective translation axes, the rotation axis, and the spindle (2), the error identification system comprising: a reference tool (8) as a length reference of the tool (9); a tool sensor (40, 50) configured to detect a remote end position of the reference tool (8) installed on the spindle (2); a reference block (42, 53) installed on the side of the tool sensor (40, 50); a tool sensor position acquisition unit configured to move the reference tool (8) installed on the spindle (2) in the translation axes and to acquire and store a perception position of the distal end of the reference tool (8) with the tool sensor (40, 50); a reference block position acquisition unit configured to move the reference tool (8) installed on the spindle (2) in the translation axes to bring the reference tool (8) into contact directly or indirectly with the reference block (42, 53), the reference block position acquisition unit being configured to acquire and store positions of the translation axes at the contact; a relative position calculation unit configured to calculate and store a relative position of the reference block (42, 53) with respect to the perception position from the perception position obtained in the tool sensor position acquisition unit and the positions of the translation axes obtained in the reference block position acquisition unit; a reference tool position acquisition unit configured to move the reference tool (8) installed on the spindle (2) in the translation axes, wherein the reference tool position acquisition unit is configured to acquire and store a reference tool position with the tool sensor (40, 50), and wherein the reference tool position is the remote end position of the reference tool (8); a measurement position acquisition unit configured to measure and store a position of the reference block (42, 53) with the position measuring sensor (30) installed on the spindle (2); a length compensation value calculation unit configured to calculate and store a compensation value of the position measuring sensor (30) in a longitudinal direction from the reference tool position obtained in the reference tool position acquisition unit, the position of the reference block (42, 53) obtained in the measurement position acquisition unit, the relative position obtained in the relative position calculation unit, and the length of the reference tool (8); a diameter compensation value acquisition unit configured to acquire and store a compensation value of the position measuring sensor (30) in a radial direction with the measured gauge (32); a position compensation unit configured to index the rotation axis to a plurality of arbitrary given angles, and to compensate and store the arbitrary position measurement values ​​of the gauge (32) measured by the position measuring sensor (30) using the compensation value in the longitudinal direction and the compensation value in a radial direction; and a geometric error identification unit configured to identify the geometric error from the plurality of position measurement values ​​compensated in the position compensation unit. [8] An error identification method for measuring a position of a measured gauge (32) in a three-dimensional space and for identifying a geometric error in a machine tool from a value of the position measured by a position measuring sensor (30) installed on a spindle (2) in the machine tool, in which the measured gauge (32) is mounted on a table (3), the machine tool including three or more translation axes, one or more rotation axes, the rotatable spindle (2) on which a tool (9) is to be installed, the table (3), and a control device configured to control the respective translation axes, the rotation axis, and the spindle (2), the error identification method comprising: a tool sensor position acquiring step of installing a reference tool (8) as a length reference of the tool (9) on the spindle (2) and acquiring a sensing position of a distal end of the reference tool (8) with a tool sensor (40, 50); a reference tool measurement position obtaining step of obtaining any given tool measurement position with the reference tool (8) installed on the spindle (2); a position measuring sensor measuring position acquiring step of acquiring any given sensor measuring position with the position measuring sensor (30) installed on the spindle (2); a position measuring sensor length calculation step of obtaining a difference between the tool measuring position and the sensor measuring position and obtaining a length of the position measuring sensor (30) based on the difference and the length of the reference tool (8); a first reference block position obtaining step of measuring a position of a reference block (42, 53) arranged on the side of the tool sensor (40, 50) with the position measuring sensor (30) installed on the spindle (2); a relative position calculation step of calculating a relative position of the reference block (42, 53) with respect to the perception position from the perception position obtained in the tool sensor position acquisition step, the position of the reference block (42, 53) obtained in the first reference block position acquisition step, the length of the position measuring sensor (30) calculated in the position measuring sensor length calculation step, and the length of the reference tool (8); a reference tool position acquiring step of installing the reference tool (8) on the spindle (2) and acquiring a reference tool position with the tool sensor (40, 50), the reference tool position being a remote end position of the reference tool (8); a second reference block position acquiring step of installing the position measuring sensor (30) on the spindle (2) and measuring a position of the reference block (42, 53) with the position measuring sensor (30); a length compensation value calculation step of calculating a compensation value of the position measuring sensor (30) in a longitudinal direction from the reference tool position obtained in the reference tool position acquisition step, the position of the reference block (42, 53) measured in the second reference block position acquisition step, the relative position calculated in the relative position calculation step, and the length of the reference tool (8); a diameter compensation value obtaining step of obtaining a compensation value of the position measuring sensor (30) in a radial direction with the measured gauge (32); a position measuring step of indexing the rotation axis to a plurality of arbitrary given angles and measuring respective positions of the measured gauge (32) by the position measuring sensor (30); a position compensation step of compensating the position measurement value in the position measuring step using the compensation value in the longitudinal direction and the compensation value in the radial direction; and a geometric error identification step of identifying the geometric error from the plurality of position measurement values ​​compensated in the position compensation step. [9] The error identification method of a machine tool according to claim 8, wherein the steps from the tool sensor position obtaining step to the relative position calculating step are configured to be executed once, and the steps from the reference tool position obtaining step to the geometric error identifying step are configured to be executed multiple times. [10] A fault identification method of a machine tool according to claim 8 or 9, wherein the positions measured by the position measuring sensor (30) are positions of the translation axes when the position measuring sensor (30) detects contact with a measuring object. [11] A fault identification method of a machine tool according to any one of claims 8 to 10, wherein the positions measured by the tool sensor (40, 50) are positions of the translation axes when the tool (9) installed on the spindle (2) moves in the translation axes and the tool sensor (40, 50) detects contact with the tool (9) or passing of the tool (9). [12] A fault identification method of a machine tool according to any one of claims 8 to 11, wherein the measured gauge (32) has a spherical shape. [13] A fault identification method of a machine tool according to claim 12, wherein the diameter compensation value obtaining step includes measuring an initial position of the measured gauge (32) by the position measuring sensor (30), and the diameter compensation value obtaining step includes obtaining a compensation value of the position measuring sensor (30) in a radial direction. [14] An error identification system for measuring a position of a measured gauge (32) in a three-dimensional space and for identifying a geometric error in a machine tool from a value of the position measured by a position measuring sensor (30) installed on a spindle (2) in the machine tool, in which the measured gauge (32) is attached to a table (3), the machine tool including three or more translation axes, one or more rotation axes, the rotatable spindle (2) on which a tool (9) is to be installed, the table (3), and a control device configured to control the respective translation axes, the rotation axis, and the spindle (2), the error identification system comprising: a reference tool (8) as a length reference of the tool (9); a tool sensor (40, 50) configured to detect a remote end position of the reference tool (8) installed on the spindle (2); a reference block (42, 53) installed on the side of the tool sensor (40, 50); a tool sensor position acquisition unit configured to move the reference tool (8) installed on the spindle (2) in the translation axes, and to acquire and store a sensing position of the distal end of the reference tool (8) with the tool sensor (40, 50); a reference tool measurement position acquisition unit configured to acquire and store any given tool measurement position with the reference tool (8) installed on the spindle (2); a position measuring sensor measurement position acquiring unit configured to acquire and store any given sensor measurement position with the position measuring sensor (30) installed on the spindle (2); a position measuring sensor length calculation unit configured to obtain a difference between the tool measuring position and the sensor measuring position, wherein the position measuring sensor length calculation unit is configured to calculate and store a length of the position measuring sensor (30) based on the difference and the length of the reference tool (8); a first reference block position acquisition unit configured to measure and store a position of the reference block (42, 53) with the position measuring sensor (30) installed on the spindle (2); a relative position calculation unit configured to calculate and store a relative position of the reference block (42, 53) with respect to the perception position from the perception position obtained in the tool sensor position acquisition unit, the position of the reference block (42, 53) obtained in the first reference block position acquisition unit, the length of the position measuring sensor (30) calculated in the position measuring sensor length calculation unit, and the length of the reference tool (8); a reference tool position acquisition unit configured to move the reference tool (8) installed on the spindle (2) in the translation axes, wherein the reference tool position acquisition unit is configured to acquire and store a reference tool position with the tool sensor (40, 50), wherein the reference tool position is the remote end position of the reference tool (8); a second reference block position acquisition unit configured to measure and store a position of the reference block (42, 53) with the position measuring sensor (30) installed on the spindle (2); a length compensation value calculation unit configured to calculate and store a compensation value of the position measuring sensor (30) in a longitudinal direction from the reference tool position obtained in the reference tool position acquisition unit, the position of the reference block (42, 53) obtained in the second reference block position acquisition unit, the relative position calculated in the relative position calculation unit, and the length of the reference tool (8); a diameter compensation value acquisition unit configured to acquire and store a compensation value of the position measuring sensor (30) in a radial direction with the measured gauge (32); a position compensation unit configured to index the rotation axis to a plurality of arbitrary given angles and to compensate and store the respective position measurement values ​​of the measured gauge (32) measured by the position measurement sensor (30) using the compensation value in the longitudinal direction and the compensation value in the radial direction; and a geometric error identification unit configured to identify the geometric error from the plurality of position measurement values ​​compensated in the position compensation unit.

Images