JP2018030195A - Method for correction of thermal displacement of machine tool and reference gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to improve a process tolerance with a simple configuration and obtain a stable process tolerance.SOLUTION: According to a method for correction of a machine tool 1, a reference gauge 12 having a quality of material same as a work-piece W is fixed to a jig 4. The reference gauge 12 has a center point provided at a center hole which is provided on an intersection part of a first arm part 20 and a second arm part 21 which are orthogonal to each other. The reference gauge 12 measures a reference dimension of lengths of the first and second arm parts 20, 21 and a squareness between two axes as reference data under a reference temperature. The reference gauge 12 is fixed to the jig 4 under a processing temperature, and by a touch sensor 15 fixed to a main shaft 7, a length of the reference gauge 12 in a two axis direction is measured as length measurement data, and each included angle in the two axis direction is measured as angle measurement data. Errors in the length measurement data and the angle measurement data of the first and second arm parts 20, 21 to the reference data of the reference gauge 12 under the processing temperature are determined, whereby said errors are corrected by correction control means of an NC device when processing the work-piece W by the machine tool 1.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a thermal displacement correction method for a machine tool for correcting thermal displacement during machining by a machine tool, and a reference gauge used in the correction method.

In general, a machine tool is thermally deformed by a change in environmental temperature, friction, heat generated by a drive motor, or the like. In addition, the table of the machine tool on which the workpiece is installed is deformed due to changes in the environmental temperature, expansion / contraction due to the heat of the ball screw shaft that moves the table, thermal deformation of the structure, etc., leading to deterioration of workpiece machining accuracy. There was a problem.
As an improvement measure against such thermal displacement, a technique has been proposed in which a temperature sensor is attached to each part of a machine tool to detect a change in temperature and correct the position of the workpiece or the spindle.

  For example, in a thermal displacement compensation type machine tool described in Patent Document 1, a temperature sensor is provided on a main shaft to which a tool body is attached, and a bush with a heater is connected to a feed shaft of a table on which a workpiece is placed. The feed shaft is heated or cooled with a heater-equipped bush by the controller with respect to the temperature detected by the spindle temperature sensor, so that the spindle and the feed shaft are almost equally thermally displaced and the relative positional relationship is made substantially constant. Is maintained.

JP-A-8-267341

However, the above-described improvement measures have a drawback in that correction of thermal displacement is not accurate because the degree of temperature change of each part differs depending on the operating status of the machine tool, the surrounding environment, and the like. Further, in the machine tool described in Patent Literature 1, when the material of the workpiece is different from the material of the main shaft or the feed shaft, the thermal displacement cannot be corrected with high accuracy.
In order to improve positioning accuracy, a scale is attached to the stage over the stroke range in the X, Y, and Z axis directions of the machine tool, and the displacement in the relative stroke range of the spindle including thermal displacement is measured. A method of feeding back the change to the machine tool is also conceivable.
However, since the thermal expansion length of the workpiece itself and the thermal expansion length of the scale are different, there is a drawback that a thermal expansion error occurs and affects the machining accuracy.

  The present invention has been made in view of such circumstances, and a thermal displacement correction method for a machine tool and a thermal displacement correction method for the machine tool that can improve the machining accuracy with a simple configuration and obtain stable machining accuracy. The purpose is to provide a reference gauge for use in

The thermal displacement correction method for a machine tool according to the present invention has a first arm part and a second arm part in a biaxial direction intersecting each other with respect to a reference gauge made of the same material as the workpiece, and a preset reference temperature The reference dimension of the first arm part and the second arm part below and the angle between the first arm part and the second arm part are measured, and the reference gauge is a member that supports the workpiece or its vicinity under the processing temperature. And measuring the length of the first arm part and the second arm part of the reference gauge as length measurement data with a sensor attached to the spindle of the machine tool, and between the first arm part and the second arm part Measuring an angle as angle measurement data, and based on an error between a reference dimension and angle of the reference gauge at a reference temperature and a length measurement data and an angle measurement data at a processing temperature. , And it performs the correction during workpiece machining.
According to the present invention, the reference gauge is installed in or near a member that supports a workpiece such as a jig or a table in a machining environment, and the first arm portion and the first gauge of the reference gauge are detected by a sensor attached to the spindle at the machining temperature. The length of the two arm portions is measured as length measurement data, and the length at the time of workpiece machining is corrected based on an error from the reference dimensions of the first arm portion and the second arm portion at the reference temperature. In addition, the angle between the first arm part and the second arm part under the processing temperature is measured as angle measurement data, and the workpiece is processed due to an error from the angle between the first arm part and the second arm part at the reference temperature. By correcting the time, machining errors such as tilt due to the temperature of the machine tool can be corrected.

The reference gauge has a first arm part and a second arm part in two axial directions intersecting each other across the center hole, and measures four points on the inner wall of the center hole that are orthogonal to each other. The center point is obtained, and both end portions in the longitudinal direction of the first arm portion and the second arm portion are respectively formed in an arc shape, and the length between the both end portions of the first arm portion and the second arm portion is defined as a reference dimension and You may make it measure as length measurement data.
The center point of the center hole is obtained from the coordinates of the two intermediate points in the direction perpendicular to the center hole inner wall of the reference gauge, and the center point of the center hole and the arc-shaped ends of the first arm part and the second arm part Since the length to the outer diameter can be measured as the length measurement data with respect to the part, the length at the time of workpiece machining can be corrected from the error between the reference dimension at the reference temperature and the length measurement data at the machining temperature.

Further, the sensor measures the squareness as the angle between the first arm part and the second arm part from the two measurement points on each side of the first arm part and the second arm part, and the first arm part The squareness of the second arm portion with respect to one axial direction as a reference may be measured to correct an error from the angle under the reference temperature.
Since the reference gauge does not change the perpendicularity of the crossing angle between the first arm and the second arm even if the temperature changes, the straightness between the first arm and the second arm determined from each of the two measurement points. As for the angle, an error from the squareness under the reference temperature can be corrected at the time of machining as a result of thermal displacement of the machine tool.

The reference gauge according to the present invention is a reference gauge for measuring the thermal displacement of a machine tool, and includes a first arm part and a second arm part, a first arm part and a second arm which intersect each other at right angles. It is provided with the crossing part which is provided in the crossing part of an arm part, and has a central hole, and each both ends of the 1st arm part and the 2nd arm part are formed in circular arc shape, It is characterized by the above-mentioned.
According to the reference gauge of the present invention, the longest length can be measured as the length measurement data between the center hole and the arc-shaped ends of the first arm portion and the second arm portion. The change in length can be measured.

Moreover, it is preferable that the center point provided in the center hole is set to be equal in length to both end portions of the first arm portion and the second arm portion.
Thereby, the outer diameter length of a 1st arm part and a 2nd arm part can be measured by measuring the length from a center point to the both ends of a 1st arm part and a 2nd arm part.

According to the thermal displacement correction method for a machine tool according to the present invention, using the reference gauge made of the same material as the workpiece, the length measurement data of the first arm portion and the second arm portion of the reference gauge is obtained by the sensor at the processing temperature. The length at the time of workpiece processing can be corrected by measuring and error from the reference length dimension of the first arm part and the second arm part at the reference temperature.
Moreover, the angle between the first arm part and the second arm part is measured as angle measurement data under the processing temperature, and the workpiece is processed due to an error from the angle between the first arm part and the second arm part at the reference temperature. By correcting for time, machining errors such as tilt due to thermal displacement of the machine tool can be corrected.

  In addition, according to the reference gauge of the present invention, since both end portions of the first arm portion and the second arm portion are formed in an arc shape, an error in length due to thermal displacement can be corrected when the workpiece is processed. Since the deviation of the angle between the second arm parts can be corrected as an error due to the thermal displacement of the machine tool at the time of processing the workpiece, it is possible to perform highly accurate processing.

It is explanatory drawing which shows the spindle and workpiece of a machine tool by embodiment of this invention. In the machine tool shown in FIG. 1, it is a principal part perspective view which shows the state which measures the reference | standard gauge attached to the jig | tool with the touch sensor. The reference | standard gauge is shown, (a) is a front view, (b) is a center sectional drawing. It is a figure which shows the measuring point by the touch sensor of the reference | standard gauge fixed to the jig | tool. It is a flowchart which shows the process of measuring the measurement point of a reference | standard gauge, correct | amending a thermal displacement with a machine tool, and processing a workpiece | work. It is a figure which shows the result of having measured the inclination of the reference gauge with the three-dimensional measuring device under reference temperature. The 1st Example is shown, (a) is a figure which shows the result of having measured the inclination of the reference gauge in a processing environment with a touch sensor, (b) is a 2nd arm part by making a 1st arm part into an X-axis reference | standard. FIG. The second embodiment is shown, in which (a) shows the result of measuring the inclination of the reference gauge with a touch sensor under the processing environment, and (b) shows the second arm part with the first arm part as the X-axis reference. FIG.

Hereinafter, a machine tool and a thermal displacement correction method thereof according to an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows a configuration of a main part of a machine tool 1 according to an embodiment. A table 3 is installed on the upper surface of a bed 2 so as to be movable in the X-axis direction, and a workpiece W is placed on the upper surface of the table 3 via a jig 4. Is installed. On the upper surface of the bed 2, a column 5 is installed on the bed 2 so as to be movable in the Z-axis direction at a position facing the workpiece W, and the Z-axis is a direction orthogonal to the X-axis in the horizontal plane. A spindle head 6 is supported on the column 5 so as to be movable up and down in the Y-axis direction (vertical direction) perpendicular to the X-axis and Z-axis. On the front side of the spindle head 6, a spindle 7 that holds a tool is installed. As shown in FIG. 2, the workpiece W may be turnable and indexable by a rotary table 9 provided at the lower part (or upper part) of the table 3.

  In the machine tool 1 according to the present embodiment, the machine tool 1 itself is thermally expanded or heated by the heat of the drive motor or the temperature of the machining environment in the environment (hereinafter referred to as the machining environment or machining temperature) where the workpiece W is machined. There is a case of contraction (hereinafter sometimes referred to as thermal displacement). In addition, the workpiece W installed on the table 3 may be thermally expanded or contracted due to the temperature of the processing environment or the heat generated during cutting with a tool. The machine tool 1 according to the present embodiment takes into account that the machine tool 1 and the workpiece W that are subject to such thermal displacement affect the machining accuracy of the workpiece W. The heat shrinkage was corrected so that stable high processing accuracy was obtained.

In the present embodiment, as shown in FIG. 2, a reference gauge 12 and a touch sensor 15 are used as a jig for measuring such a thermal displacement.
FIG. 2 shows a measurement method for measuring the amount of thermal expansion (or amount of thermal shrinkage) due to the thermal influence of the machine tool 1 or the workpiece W. The spindle 7 has a fixed portion 16 of the touch sensor 15 instead of a tool. The probe 17 extends from the fixed portion 16 to the distal end side. A reference gauge 12 is fixed to the side of the table 3 or the jig 4 on the table 3 with a fixing screw or a clamp member as a thermal displacement measuring jig.
Then, the mutual position is sequentially measured as, for example, three-dimensional coordinate data (coordinates) by bringing the probe 17 of the touch sensor 15 into contact with the side surface in the thickness direction of the reference gauge 12.

3 (a) and 3 (b) show a reference gauge 12, which has a substantially cruciform plate shape when viewed from the front. For example, a lateral first arm portion 20 made of a rectangular plate shape having the same dimensions, The second arm portion 21 in the vertical direction is integrally formed perpendicular to each other. The intersecting portion 23 of the first arm portion 20 and the second arm portion 21 is formed, for example, widened in a substantially square shape (or disk shape), and its corner portion is integrated with the first arm portion 20 and the second arm portion 21. It has become. A circular center hole 22 is formed at the center of the intersection 23.
Both longitudinal ends 20a, 21a of the first arm portion 20 and the second arm portion 21 form a partial arc of a virtual circle R in which the arm portions 20, 21 of the reference gauge 12 are inscribed. The center point O of the virtual circle R is also the center point of the center hole 22 of the reference gauge 12, and the line connecting the center point O and both ends 20a of the first arm portion 20 is the diameter L1 of the virtual circle R. Similarly, a line connecting the center point O and both end portions 21a of the second arm portion 21 is also the diameter L2 of the virtual circle R. The first arm portion 20 and the second arm portion 21 have center axis lines O1 and O2 orthogonal to each other at the center point O.

In the central longitudinal section of the reference gauge 12 shown in FIG. 3B, the intersecting portion 23 of the reference gauge 12 has a substantially rectangular tube shape (or a thickness greater than the thickness of the first and second arm portions 20 and 21) (or And a sealing portion 23 a having a predetermined thickness is provided at the bottom of the central hole 22. An insertion hole 23b is formed coaxially with the center point O in the sealing portion 23a. A plurality of insertion holes 23 c are also formed at predetermined intervals around the central hole 22 in the intersection 23.
The reference gauge 12 is mounted on the table 3 by screwing a fixing screw into a screw hole (not shown) formed in the side surface of the table 3 or the workpiece mounting portion on the side of the jig 4 through the insertion holes 23b and 23c. Fix to the jig 4.

Moreover, the reference gauge 12 is made of the same material as the workpiece W to be processed. Accordingly, the reference gauge 12 is thermally expanded (or thermally contracted) to the same extent at the same temperature as that of the workpiece W, so that it is possible to measure the thermal displacement at any temperature in the processing environment. In addition, the reference gauge 12 can also measure thermal displacement such as a tilt due to a thermal influence of a drive motor of the machine tool 1 and a temperature change in a processing environment.
For example, with a temperature of 20 ° C. as the reference temperature, the outer diameter dimensions (full length length) L1, L2 (L1 = L2) of the first arm portion 20 and the second arm portion 21 of the reference gauge 12, the first arm portion 20 and the second arm portion 20 The perpendicular angles A1, A2, A3, and A4, which are the four crossing angles of the arm portion 21, are measured in advance with a three-dimensional measuring device (not shown) and used as reference data.

Then, the outer diameters L1a and L2a (length measurement data) of the first arm portion 20 and the second arm portion 21 that are thermally expanded (or thermally contracted) of the reference gauge 12 fixed to the table 3 in the processing environment and the first If the perpendicular angles A1a to A4a (angle measurement data) of the arm part 20 and the second arm part 21 are respectively measured by the touch sensor 15, thermal displacement due to thermal expansion or thermal contraction can be calculated as an error with respect to the reference data. This error is fed back to the NC device of the machine tool 1 as a correction value, and is calculated by a known correction control means (not shown) that is set in advance, and the gradient (pitch) correction is performed when the workpiece W is machined. The reduced and highly accurate work W can be processed.
Although the lengths L1 and L2 of the first arm portion 20 and the second arm portion 21 are the same and the diameter of the virtual circle R, they may be different.

Further, the measurement points by the touch sensor 15 with respect to the reference gauge 12 are shown in FIG. In order to determine the position of the center point O of the center hole 22, the intermediate points of the two points d2-d4 and d1-d3 on the inner wall of the center hole 22 that are orthogonally opposed to each other, for example, on the X axis and the Y axis are measured. Then, the coordinates of the center point O are determined based on the coordinates of each intermediate point. In order to measure the total length of the first arm part 20 and the second arm part 21, the distance from the center point O to the four points e1 to e4 of the arcuate ends 20a and 21a is measured.
Moreover, the squareness which is the crossing angle of the first arm part 20 and the second arm part 21 is measured as follows. That is, four points f1 to f4, which are intersections of the virtual circle Q having a radius h / 2 from the center point O and the one side surfaces 20b and 21b of the first arm part 20 and the second arm part 21, are used as measurement points. taking measurement. Then, from the positional relationship between the two points f1 and f2 on the side surface 20b of the first arm unit 20 and the two points f3 and f4 on the side surface 21b of the second arm unit 21 and the center point O, the first arm unit 20 and the first The errors of the perpendicular angles A1, A2, A3, and A4 of the intersection angles of the two arm portions 21 can be measured.

Since the reference gauge 12 has a symmetrical shape in the vertical and horizontal directions, changes in the perpendicularity A1, A2, A3, and A4 of the first arm portion 20 and the second arm portion 21 due to heat from the reference data are considered. The error of the measured value, which is a change in squareness, is a thermal displacement of the machine tool 1.
Further, in FIG. 4, the side surfaces 20b and 21b in the vicinity of the end portions 20a and 21a of the first arm portion 20 and the second arm portion 21 are slightly narrower toward the distal end side. It is easy to position the contact portion. The distance (diameter) h between the two measurement points f1, f2 and f3, f4 of the first arm unit 20 is set to be slightly shorter than the diameters L1, L2 of the virtual circle R. The length of the distance h can be determined as appropriate.

The correction mechanism using the reference gauge 12 of the machine tool 1 according to the present embodiment has the above-described configuration. Next, FIG. 5 illustrates a thermal displacement correction method using the reference gauge 12 and the touch sensor 15 that form a mounting jig. It demonstrates along the flowchart shown.
In addition, the workpiece | work W used by this embodiment is a disk-shaped flange, for example, and shall drill a hole with high precision in the center of a flange and its circumference | surroundings. This thermal displacement correction method is performed at a stage after roughing the workpiece W and before finishing, so that the heat of the roughing process remains in the machine tool 1, and the finishing accuracy of the workpiece W is stably improved. Preferred above.

  First, prior to processing the workpiece W with the machine tool 1, a reference gauge 12 made of the same material as the workpiece W is prepared. And, for example, a total length L1 passing through the center point O of the center hole 22 of the reference gauge 12 and the center point O of the first arm part 20 and the second arm part 21 using a three-dimensional measuring machine under a reference temperature of 20 ° C. L2 (reference dimension) and the perpendicular angles A1 to A4, which are the included angles of the four positions of the first arm part 20 and the second arm part 21, are measured in advance and used as reference data (S101).

Next, the reference gauge 12 is fixed to the jig 4 of the table 3 or the attachment portion of the workpiece W in the machine tool 1 shown in FIGS. 1 and 2 using a fixing screw (not shown) (S102). At this time, the reference gauge 12 is set so that the surface thereof faces the main shaft 7, but the parallelism with the main shaft 7 and the level of the first arm portion 20 (or the second arm portion 21) may be somewhat rough, Strictness is not required. The reference gauge 12 is fixed such that the entire reference gauge 12 is within a range in which the main shaft 7 strokes relatively in the X-axis direction and the Y-axis direction.
The above is a measurement for preparatory preparation, and once each dimension of the reference gauge 12 and its mounting position on the jig 4 are determined, it is not necessary to measure again even if the workpiece W of the same material to be measured changes. Also good.

Next, a thermal displacement correction method corresponding to each workpiece W is executed. First, the touch sensor 15 is attached and fixed to the spindle 7 (S103). As for the Z-axis direction, in this example of the workpiece W, since a through-hole is formed in the flange, it is only necessary to have a stroke that can penetrate the flange, so an error in the Z-axis direction is not considered. Note that the temperature of the processing environment is arbitrary, and is different from the reference temperature (20 ° C.).
Next, in the processing environment, the coordinates of the center point O of the reference gauge 12 at the mounting position are obtained, and the length error and the squareness error due to the thermal effect of the reference gauge 12 in the processing environment are determined as the reference of the reference gauge 12. Calculate as the error of the measured value for the data. Then, these error data are evenly distributed by the correction control means of the NC device in the machine tool 1 and corrected by adjusting the machining ratio of the workpiece W by the tool.

(Length adjustment)
That is, as shown in FIGS. 2 and 4, the column 5 is relatively moved in the Z-axis direction, the touch sensor 15 is relatively moved, and the tip of the probe 17 is pressed into contact with the inner wall in the central hole 22 of the reference gauge 12. . Next, in FIG. 4, an intermediate point between a line connecting one point d2 on the inner wall of the central hole 22 and another point d4 on the horizontal X axis is taken, and the other one point d1 and the Y axis perpendicular thereto are taken. The middle point of the line connecting the other one point d3 above is taken. The intermediate point of the coordinates of these two intermediate points is determined as the coordinate of the central point O of the central hole 22 (S104).

Next, in FIG. 4, the probe 17 is brought into contact along the arcuate ends 20a on both sides of the first arm portion 20 with the center point O as a reference, and the maximum distance from the coordinates of the contact points e1, e2 and the center point O is reached. Are respectively determined as radii (L1a / 2) to obtain the diameter L1a. Similarly, the probe 17 is brought into contact with the center point O along the arc-shaped end portions 21a on both sides of the second arm portion 21, and the maximum distance from the coordinates of the contact points e3 and e4 and the center point O is set to the radius ( L2a / 2) to obtain the diameter L2a (S105).
The error between the diameters L1a and L2a of the first arm portion 20 and the second arm portion 21 of the obtained reference gauge 12 and the diameters L1 and L2 of the reference data is a machine tool including the temperature error of the machining environment and the spindle 7. 1 and the X-axis and Y-axis length correction values including thermal displacement errors due to thermal expansion and contraction caused by environmental temperature, heat, and the like.

(Adjustment of squareness)
Next, under the processing environment, as shown in FIG. 4, measurement points f <b> 1 and f <b> 2 on one side surface 20 b of the first arm portion 20 of the reference gauge 12 and measurement point f <b> 3 on one side surface 21 b of the second arm portion 21. , F4 are measured by the probe 17 (S106). And the error with respect to the reference data of these measurement points f1, f2, f3, f4 is calculated. Here, since the reference gauge 12 is made of the same material as the workpiece W and has a symmetrical shape in the vertical and horizontal directions, it can be said that there is no change in the squareness even if the environmental temperature changes.

  Therefore, it can be said that the error of the measurement points f1, f2, f3, and f4 is an error due to the thermal displacement of the machine tool 1 provided with the spindle 7. Then, in relation to the reference data, the error between the two measurement points f1 and f2 on the side surface 20b of the first arm portion 20 (X axis direction) and the two on the side surface 21b of the second arm portion 21 (Y axis direction). Straightness correction (tilt correction) is applied to the error at the two measurement points f3 and f4. That is, the posture of the second arm portion 21 is adjusted based on the posture of the first arm portion 20. These errors can be corrected by the correction control means of the NC device (S107).

The error that occurs in the squareness of the reference gauge 12 is not a phenomenon of the reference gauge 12 itself but a phenomenon of thermal displacement such as tilting of the machine tool, so two measurement points f1, f2 in the X-axis direction and two measurements in the Y-axis direction. By comparing the points f3 and f4, the inclination of the squareness can be corrected.
At that time, even if the X-axis reference by the virtual line connecting the measurement points f1 and f2 of the first arm unit 20 is inclined with respect to the horizontal line, the relationship between the X-axis and the Y-axis connecting the measurement points f3 and f4 is obtained. So there is no problem.
Further, when the reference gauge 12 is fixed to the jig 4 or the like, even if the horizontal arrangement of the first arm portion 20 is slightly deviated, it is obtained by the touch sensor 15 based on the coordinates of the center point O of the center hole 22. In addition, since the tilt angle of the first arm 20 is calculated and the direction of the Y axis is set based on the tilted X axis, there is no problem because the measurement error does not increase.
Note that the degree of correction can be confirmed by measuring the length and perpendicularity of the workpiece W corrected based on the reference gauge 12 with a three-dimensional measuring device at a reference temperature.

(Example)
In the reference gauge 12, the length adjustment by the temperature change of the first arm portion 20 and the second arm portion 21 is simply the difference between the reference temperature and the processing temperature in the X-axis direction of the spindle 7 of the machine tool 1 and the Y-axis. By distributing by the relative stroke in the axial direction, machining correction of the workpiece W can be performed.
Next, Embodiments 1 and 2 of the method for correcting the perpendicularity of the first arm portion 20 and the second arm portion 21 of the reference gauge 12 will be described with reference to FIGS.
FIG. 6 shows the measurement of the squareness of the reference gauge 12 fixed to the jig 4 at a reference temperature of 20 ° C. The first arm part 20 and the second arm part 21 have, for example, outer diameter lengths L1 = L2 = φ300 mm. Since the first arm portion 20 is based on the X axis, the first arm portion 20 is tilted by 0 μm. On the other hand, the second arm portion 21 has a characteristic that it is inclined to the right by 2 μm with respect to the Y axis.

On the other hand, in Example 1 shown in FIG. 7, in FIG. 7A, the reference gauge 12 is attached to the jig 4 after rough machining of the workpiece W fixed on the table 3 in the machining environment and before finishing machining. In the fixed state, the measurement result by the touch sensor 15 is that the first arm part 20 is inclined 2 μm to the right side, and the lower part of the second arm part 21 is inclined 2 μm to the left side. Assuming that the first arm portion 20 in this posture is on the X axis (referred to as the X axis reference) as shown in FIG. 7B, the inclination of the first arm portion 20 is 0 μm. The second arm portion 21 has a posture in which the upper side is inclined to the right by 2 μm, and has the same shape as that of the reference gauge 12 at the time of three-dimensional measurement.
Therefore, when the workpiece W is machined, the squareness of the machine tool 1 need not be corrected by the correction control means of the NC device.

Next, in Example 2 shown in FIG. 8, the measurement result by the touch sensor 15 in FIG. 8A in a state where the reference gauge 12 is fixed to the jig 4 before finishing the workpiece W in the machining environment. The first arm portion 20 is inclined 4 μm on the right side, and the lower portion of the second arm portion 21 is inclined 2 μm on the left side. Assuming that the first arm portion 20 in this posture is on the X-axis reference as shown in FIG. 8B, the second arm portion 21 is inclined to the right side by 4 μm and the lower side is 2 μm on the left side. Inclined posture. Therefore, as a result, the Y axis of the second arm portion 21 is tilted to the right by 6 μm, and the reference gauge 12 is tilted to the right by 2 μm at the reference temperature.
Therefore, the machine tool 1 can recognize that it has fallen to the right by 4 μm at the distance h between the measurement points f1-f2 and f3-f4 of the reference gauge 12. By correcting this by converting to the length of the full stroke range of the spindle 7 by the correction control means of the NC device, the processing accuracy of the workpiece W can be improved and stabilized.

As described above, according to the reference gauge 12 and the thermal displacement correction method for the machine tool 1 according to the present embodiment, the first arm portion 20 and the first arm portion 20 of the reference gauge 12 at the machining temperature are compared with the reference data of the reference gauge 12. By measuring the total length of the two arm portions 21 and the squareness of the first arm portion 20 and the second arm portion 21 to obtain an error, the amount of thermal expansion or contraction due to the temperature change of the workpiece W and the spindle 7 can be obtained. Machining can be performed by correcting the inclination due to the thermal displacement of the machine tool, and the machining accuracy of the workpiece W can be improved. In addition, machining correction can be performed without installing a temperature sensor or scale. Therefore, the machining accuracy of the workpiece W can be stably improved regardless of changes in the installation environment of the machine tool 1 and the workpiece W.
Further, since the reference gauge 12 made of the same material as the workpiece W is used, thermal expansion and thermal contraction occur at the same level, so that highly accurate machining correction can be performed in this respect as well.

In addition, since the reference gauge 12 according to the present embodiment is provided with the central hole 22 at the intersecting portion 23 of the first arm portion 20 and the second arm portion 21, the coordinates of the center point O can be easily detected by the touch sensor 15 and the second. Since both ends 20a, 21a of the one arm part 20 and the second arm part 21 are formed in an arc shape of a virtual circle R inscribed therein, the total length and perpendicularity of the first arm part 20 and the second arm part 21 can be easily measured. .
Moreover, since the measurement by the touch sensor 15 and the machining correction are performed immediately before the finishing process after the roughing, the heat during the roughing remains in the machine tool 1 and the table 3, and the heat effect is applied to the reference gauge 12 and the machine tool 1. It can be transmitted and is realistic, and the machining correction according to the machining environment and the operating status of the machine tool 1 can be greatly improved.

  In the above-described embodiment, the side surfaces 20b and 21b in the thickness direction of the first and second arm portions 20 and 21 with which the probe 17 of the touch sensor 15 abuts in order to measure the squareness are set on either side. May be. The position where the probe 17 abuts is not limited to the intersection with the virtual circle Q, and an appropriate position in the longitudinal direction on the side surfaces 20b and 21b of the first and second arm portions 20 and 21 can be selected.

In the above-described embodiment, since the position and interval of the through-holes to be machined into the disk-shaped flange as the workpiece W are precisely machined, only the X-axis and Y-axis directions are corrected and machining in the Z-axis direction is performed. Although the position correction method was not considered, depending on the workpiece W, measurement and correction of the machining position in the Z-axis direction can also be performed. In short, the present invention can be applied to a method for correcting machining points of appropriate two or more axes in the X, Y, and Z axis directions.
In the machine tool 1, in the embodiment, the table 3 of the workpiece W is moved in the X-axis direction and the spindle 7 is movable in the Y-axis direction and the Z-axis direction. The moving structure in the Z-axis direction can be appropriately combined.

The sensor for measuring the length and perpendicularity of the reference gauge 12 is not limited to the contact sensor such as the touch sensor 15, and a non-contact sensor such as an optical sensor may be used.
In the above-described embodiment, the first arm portion 20 and the second arm portion 21 in the reference gauge 12 are measured as the biaxial directions of, for example, the X axis direction and the Y axis direction. Is not necessarily set to a right angle, and an appropriate included angle can be set.
In the embodiment, the reference gauge 12 is made of the same material as that of the work W. However, the reference gauge 12 may be made of a member having a different material as long as the work W has substantially the same thermal expansion coefficient as that of the work W.

1 Machine tool 3 Table
4 Jig 6 Spindle head 7 Spindle 12 Reference gauge 15 Touch sensor 17 Probe 20 First arm portion 20a, 21a End portion 20b, 21b Side surface 21 Second arm portion 22 Central hole 23 Intersection W Work d1, d2, d3, d4 Measurement points e1, e2, e3, e4 Measurement points f1, f2, f3, f4 Measurement points

Claims (5)

A reference gauge made of the same material as the workpiece has a first arm part and a second arm part in two axial directions intersecting each other, and the first arm part and the second arm part at a preset reference temperature. Measure the angle between the reference dimension and the first arm part and the second arm part,
A step of attaching the reference gauge to a member supporting the workpiece or the vicinity thereof under a processing temperature;
A sensor attached to the spindle of the machine tool measures the lengths of the first arm part and the second arm part of the reference gauge as length measurement data and determines the angle between the first arm part and the second arm part. A step of measuring as angle measurement data,
A method for correcting a thermal displacement of a machine tool, comprising: performing correction at the time of workpiece processing based on an error between a reference dimension and angle at a reference temperature of the reference gauge and measurement data and angle measurement data at a processing temperature. The reference gauge has the first arm portion and the second arm portion in two axial directions intersecting each other across a central hole,
While measuring four points of the inner wall of the central hole that are orthogonal to each other and obtaining the central point,
Both end portions in the longitudinal direction of the first arm portion and the second arm portion are respectively formed in an arc shape, and the length between the both end portions of the first arm portion and the second arm portion is determined by the reference dimension and the measurement. The thermal displacement correction method for a machine tool according to claim 1, wherein the method is measured as data.   The sensor measures a squareness as an angle between the first arm part and the second arm part from two measurement points on each side of the first arm part and the second arm part, and the first arm 3. The machine tool according to claim 2, wherein a square angle with the other axial direction is measured with respect to one axial direction of the first arm portion and the second arm portion, and an error from the angle of the reference temperature is corrected. Thermal displacement correction method. A reference gauge for measuring thermal displacement of a machine tool,
A first arm part and a second arm part intersecting at right angles to each other;
An intersection portion provided at the intersection of the first arm portion and the second arm portion and having a central hole,
The reference gauge according to claim 1, wherein both end portions of the first arm portion and the second arm portion are formed in an arc shape.   5. The reference gauge according to claim 4, wherein the center point provided in the central hole is set to have equal lengths to both end portions of the first arm portion and the second arm portion.

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