JP7152171B2 - Plate thickness measuring device and plate thickness measuring method - Google Patents

Description

The present invention relates to a plate thickness measuring device and a plate thickness measuring method capable of measuring the thickness of a part machined by a machine tool with high accuracy. TECHNICAL FIELD The present invention relates to a plate thickness measuring device and a plate thickness measuring method that are incorporated in a machine tool such as a machining center that performs machining by replacement and that measures the thickness of a machined part with high precision.

Machine tools in recent years, for example, have adopted machining centers that automatically change cutting tools such as milling cutters, end mills, drills, boring, taps, etc., and machine parts. In order to achieve this, it is necessary to measure the dimensions of the processed part, such as width and thickness, with high precision.

This patent document 1 describes a taper shank having the same shape as the taper shank of an exchangeable tool selectively attached to the spindle of a machine tool, and an ultrasonic probe provided at the tip of the taper shank, which is attached to the surface of the workpiece W. Equipped with an ultrasonic plate thickness measurement unit that transmits ultrasonic waves while being in contact with, detects the echo sound waves and measures the thickness of the workpiece W, and measures the thickness of the workpiece such as a thin plate with high accuracy. Sonic thickness gauge technology is described.

Documents describing a touch probe that measures the outer shape of a processed part by coming into contact with the outer shape of the processed part include the following Patent Documents 2 and 3.

JP 2016-75584 A JP 2011-136390 A JP 2010-71775 A

The technique described in the aforementioned Patent Document 1 uses an ultrasonic probe that emits ultrasonic waves while in contact with the surface of a workpiece, detects the echoed sound waves, and measures the thickness of the workpiece. , a couplant that improves the contact between the ultrasonic probe and the surface of the work piece should be used during thickness measurement, and the table top should be used to detect echo sound waves and measure the thickness of the work piece. There was a problem that the thickness (also called width), which is the dimension in the plane direction of the work mounted on the machine, could not be measured.

In addition, the technology described in Patent Document 2 is limited to the effect of measuring the outer shape of a processed part using one touch probe, and the technology described in Patent Document 3 has two touch probe contacts. The effect remains that the position can be corrected and confirmed at the same time by press-contacting and abutting against the piece substantially at the same time.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art described above. It is an object of the present invention to provide a plate thickness measuring method, and an object of the present invention is to measure the thickness and clearance of a machined part with high precision even when a work is set obliquely.

To achieve the above object, the present invention provides a plate thickness measuring device for measuring the thickness of a work by means of a pair of sensors that face and contact the side surfaces of the work in the thickness direction with a predetermined pressing force, wherein the pair of sensors are: Equipped with a measuring device that moves vertically and in the thickness direction, which is the measurement direction, and an XY table that moves the pair of sensors to at least two different measurement points in the longitudinal direction of the work, and the pair of sensors measures The true thickness is determined based on the thickness at the measurement point, the distance between the two measurement points, and the difference in the measurement direction at the two measurement points by any of the sensors.

In the above, the thickness at the measurement point is C, the distance between the two measurement points is ba, and the difference in the measurement direction at the two measurement points by any of the sensors is the pushing amount S. , θ=tan−1(S/b−a), and the true thickness t=C·(cos θ).

Furthermore, in the above, it is desirable that the approximate thickness of the workpiece, which is the measurement standard, is 5 to 15 mm, and the distance between the two measurement points is 5 to 15 mm.

Further, in the above, instead of moving the pair of sensors to at least two different measurement points in the longitudinal direction of the workpiece on the XY table, two sets of the pair of sensors are installed in the measuring device in the longitudinal direction. It is desirable to fix a predetermined interval and make the predetermined interval the distance between the two measurement points.

Furthermore, in the above, let r be the radius of the contact of the pair of sensors that contacts the workpiece, D be the measurement value measured by the pair of sensors, x be the error due to positional deviation due to the difference in the contact position of the contact, and Let C be the thickness at the measurement point, b-a be the distance between the two measurement points, and S be the difference in the measurement direction at the two measurement points by any of the sensors,
θ=tan−1(S/b−a),
x=r·((1/cos θ)−1),
C = D - 2 · x, find,
It is desirable to set the true thickness t=C·(cos θ).

Further, in the above, it is desirable that the approximate thickness of the workpiece, which is the measurement standard, is 5 to 15 mm, the distance between the two measurement points is 5 to 15 mm, and the radius r of the contact is 4 to 8 mm.

Further, in the above, instead of moving the pair of sensors to at least two different measurement points in the longitudinal direction of the workpiece on the XY table, the measurement points are moved to at least two different measurement points in the vertical direction. It is desirable to move the sensor of

Further, the present invention is a plate thickness measuring method for measuring the thickness of the work by a pair of sensors that face and contact side surfaces of the work in the thickness direction with a predetermined pressing force. Moving the pair of sensors to at least two different measurement points, the thickness at the measurement points measured by the pair of sensors, the distance between the two measurement points, and the two measurement points by any of the sensors and the difference in the measurement direction at .

INDUSTRIAL APPLICABILITY The plate thickness measuring device and plate thickness measuring method according to the present invention can measure the thickness and gap of a machined part with high accuracy even when a workpiece to be measured is placed obliquely.

1 is a diagram for explaining the overall structure and operation of a plate thickness measuring device according to an embodiment of the present invention; FIG. FIG. 1 is a plan view showing a measuring section of a plate thickness measuring device according to an embodiment of the present invention; A plan view showing the details of the measuring unit according to the present embodiment. A plan view showing a plate thickness measuring device of another embodiment Furthermore, the side view which shows the measuring apparatus of board thickness which is another Example

An embodiment of a machine tool having a thickness measuring section to which the thickness measuring method according to the present invention is applied will be described below.

[Constitution]
As shown in FIG. 1(a), a machine tool 100 to which the thickness measuring unit according to the present embodiment is applied measures, for example, A working section 30 for automatically exchanging cutlery tools for milling, end milling, drilling, boring, tapping, etc., for machining parts, and a workpiece 10 for checking the machining accuracy during the work machining process in the working section 30. and a measuring device 40 for measuring the thickness t in the plane direction (X direction) with high accuracy. In this embodiment, the workpiece 10 is a rectangular flat plate, and is freely mounted so that its four sides are parallel to the XY axes of the XY table 20, but it may be fixed.

The measuring device 40 according to this embodiment includes two arms 41 that can move vertically toward the plane of the XY table 20 and in the measurement direction (thickness t direction in this example), and the lower ends of the arms 41 face each other. The thickness t of the workpiece 10 is determined by optically detecting the positions of the sensors 42a and 42b, which are arranged in the X direction and contact the side surface of the object to be measured of the workpiece 10 with a predetermined pressure, and the positions of the sensors 42a and 42b. and an optical measuring unit (not shown) for measuring. Further, the sensors 42a and 42b according to the present embodiment have contacts that are hemispherical contacts facing each other, and the hemispherical contacts contact the parallel sides of the workpiece 10 to be measured with a predetermined pressure. Although it is an optical type that optically detects the position of the contact when it is pressed against the coil, it may be a differential transformation type that electrically detects a change in the insertion amount of the core inserted into the coil.

The machine tool 100 according to this embodiment includes a machining process in which the machining unit 30 performs cutting while automatically exchanging cutting tools with respect to the workpiece 10, and a machining dimension to the workpiece 10 is set to a predetermined value during this machining process. The workpiece 10 is machined while repeating a measuring step of measuring whether or not the range (several μm to several tens of μm) is measured by the measuring device 40 .

The measurement process according to this embodiment is as follows.
(1) From the state in which the working part 30 and the measuring device 40 are positioned on the workpiece 10 mounted on the XY table 20 shown in FIG. A first step in which the working part 30 and the measuring device 40 are lowered to a position where the sensors 42a and 42b arranged facing each other at the lower ends of the pair of arms 41 extending from the measuring device 40 face both sides of the work 10. In this example, an example in which the working part 30 and the measuring device 40 are moved up and down at the same time will be described. 40 may be configured to move up and down in the Z-axis (gravity) direction.

(2) Next, as shown in FIGS. 1(d) to 1(e), the sensors 42a and 42b of the pair of arms 41 are brought closer to the side of the work 10 on the XY table 20 in the thickness direction, and the work 10 is A second step of moving so as to come into contact with a side surface in the thickness direction (for example, the measurement point a shown in FIG. 2A) with a predetermined pressure.

(3) A third step of measuring the position coordinate values of the sensors 42a and 42b in contact with both sides of the work 10 at the measurement point a of the work 10 shown in FIG.

(4) Next, the sensors 42a and 42b, which are in contact with both sides of the work 10, are moved from both sides of the work 10 in the direction opposite to the second step, and are separated from each other in the direction of the arrow (Y The sensor 42a and the sensor 42b of the pair of arms 41 are moved toward the side surface of the work 10 in the thickness direction again, and the thickness of the work 10 A fourth step of moving so as to come into contact with a side surface in the vertical direction (for example, the measurement point b shown in FIG. 2A) with a predetermined pressure. Alternatively, without moving in the direction opposite to the second step, it moves to the measurement point b as it is.

The measuring device 40 according to this embodiment measures the position coordinate values at the measurement point a and the measurement point b of the pair of sensors 42a and 42b in contact with both sides of the workpiece 10 with a predetermined pressure. A true thickness t of the workpiece 10 is calculated from the value. That is, the thickness based on the difference between the position coordinate values of the sensors 42a and 42b at the measurement point a and the thickness based on the difference between the position coordinate values of the sensors 42a and 42b at the measurement point b are measured.

In the thickness measurement of the workpiece 10 at this measurement point ab, if the four sides of the workpiece 10 are completely aligned with the XY directions of the XY table 20, the measured values at both measurement points are logically the same. However, in an actual machine, the four sides of the workpiece 10 do not always match the Y direction of the XY table 20 in micron units, and it is assumed that the workpiece 10 is mounted obliquely as shown in FIG. 2(b). be. When this work 10 is mounted obliquely, the contact points of the pair of contacts of the sensors that move simultaneously come into contact with the XY table 20 at the coaxial position in the Y direction (see FIG. 2A), and the thickness C at this measurement point is differs from the true thickness t by the amount that the workpiece 10 is tilted.

Therefore, in the present embodiment, in order to deal with the fact that the workpiece 10 is arranged obliquely, the following correction for the oblique arrangement of the workpiece is performed, and the correction calculation method will be explained below.

First, when the aforementioned workpiece 10 is arranged obliquely by an angle θ, the thicknesses measured at the measurement points a and b are different from the true thickness t of the workpiece 10 as shown in FIG. The thickness C at the measurement point becomes the measured value.

The thickness C at the measurement point, the true thickness t, and the positional relationship with each sensor are expressed as shown in FIG. When the pushing amount S in the X direction of the sensor 42b at the reference measurement point b (the difference in the position in the measurement direction between the measurement point a and the measurement point b by either sensor) and the thickness at the measurement point C , the true thickness t=C·(cos θ). However, θ=tan−1(S/b−a), b−a is the distance from measurement point a to measurement point b.

That is, the true thickness t is obtained by measuring the thickness of the workpiece 10 at least at two different measurement points, measurement point a and measurement point b, with a pair of sensors 42a and 42b, and measuring the thickness C at the measurement points. Correction may be performed based on the distance from the point a to the measurement point b (the distance between the two measurement points a and b) and the pressing amount S. Also, if the error δ is (C−t), δ=C(1−cos θ). Table 1 shows an example in which the inclination angle θ is calculated when the distance b−a from the measurement point a to the measurement point b is 10 mm and the true thickness t is 10 mm=10000 μm.

If the distance ba from the measurement point a to the measurement point b is increased, the tilt angle θ can be calculated more accurately. However, since the distance in the Y direction to be moved from the measurement point a to the measurement point b is increased, the effect of errors such as linearity in the XY table 20 to be moved is increased. Therefore, it is preferable to appropriately determine the distance ba from the measurement point a to the measurement point b depending on the thickness of the workpiece 10 .

For example, it is preferable to make the approximate thickness of the workpiece 10 and the distance ba, which are the measurement standards, substantially equal. In Table 1, the approximate thickness of the workpiece 10 is 10 mm, and the distance ba is 10 mm. As a result of actual measurement under these conditions, the inclination angle θ is Above 3°, the correction was found to be effective up to at least 10°. Further, when the thickness of the workpiece 10 to be measured is 5 to 15 mm, it is appropriate to set the distance ba to 5 to 15 mm.

Table 2 shows an example of calculation of the pushing amount S under the same conditions as in Table 1, with the distance ba from the measurement point a to the measurement point b being 10 mm, and the true thickness t being 10 mm.

To detect a small tilt angle .theta., the larger the distance ba, the better, but the XY table 20 needs to be highly accurate. In response to this, the two sensors 42a and 42b are changed to four, and two sensors are used for measurement at the measurement point a and the measurement point b. and

That is, instead of moving the pair of sensors 42a and 42b to at least two different measurement points in the longitudinal direction of the workpiece 10 on the XY table 20, the measuring device 40 is provided with two pairs of the sensors 42a and 42b in the longitudinal direction. A predetermined interval is fixed, and this predetermined interval is defined as the distance between the two measurement points a and b. As a result, the distance ba can be made independent of the movement of the XY table 20, contributing to higher accuracy. In addition, since the measurement can be performed simultaneously from the measurement point a to the measurement point b without moving, the measurement time can be shortened.

FIG. 3 is a plan view showing the details of the measuring section, taking into consideration the influence of the contact radius r. In actual measurement, since the contacts of the sensors 42a and 42b have a finite radius r, the contact point with the workpiece 10 is shifted in the X direction. From FIG. 3, as the measured value D measured by the sensors 42a and 42b, the thickness C at the measurement point is C=D−2·x, where x is the error due to the positional deviation due to the difference in the contact position of the contact. . Also, x becomes x=r·((1/cos θ)−1).

Therefore, if the radius r of the contact is known, the error x due to positional deviation is obtained as θ=tan-1 (S/b-a), and from the measured value D in the same manner as described above, C=D-2 x as the measurement point By obtaining the thickness C at , the true thickness t=C·(cos θ) can be obtained.

Table 3 shows the error x due to positional deviation and the total error 2x for each tilt angle θ, with the radius r of the contact being 6000 μm (mm).

Compared with Table 1, for example, when the tilt angle θ is 3°, the error is 13.723 μm from Table 1, whereas the total error in Table 3 is 16.4682 μm, which is sufficiently small. However, it can be seen that the value cannot be ignored when the inclination angle θ increases. Also, if the contact radius r is large, the error cannot be ignored. it was appropriate to

FIG. 4 is a plan view showing another embodiment, in which, compared with the embodiment shown in FIG. 2, there are three measurement points in the Y direction: measurement point a, measurement point b, and measurement point c. be. 2 and 3, at the measurement points a and b, the true thicknesses can be obtained as t=C·(cos θ) and θ=tan-1 (S/L). C is the thickness C at the measurement point, and L is the distance ba from the measurement point a to the measurement point b.

Also, at the measurement points b and c, if L in the above equation is the distance c−b from the measurement point b to the measurement point c, the true thickness t can be similarly obtained. Further, at the measurement points a and c, if L is the distance c−a from the measurement point a to the measurement point c, the true thickness t can be similarly obtained. The average of the true thicknesses obtained at measurement points a and b, the true thicknesses obtained at measurement points b and c, and the true thicknesses obtained at measurement points a and c a more accurate value is calculated. Hereinafter, the true thickness t can be similarly calculated even when three or more measurement points are used.

In addition, when there are three measurement points, measurement point a, measurement point b, and measurement point c, if the thickness of the workpiece 10 is constant, the sum of the pushing amounts by the sensors 42a and 42b at each measurement point , or the difference between the position coordinate values of the sensor 42a and the sensor 42b is the same. Therefore, the parallelism of the workpiece 10 in the Y direction and the machining accuracy can be detected from the total value of the pressing amount at each measurement point or the deviation amount of the difference between the position coordinate values.

FIG. 5 is a side view showing still another embodiment, in which the measurement points are set to measurement points f and g in the Z direction, compared with the other embodiment shown in FIG. 2 and 3, at the measurement point f and the measurement point g, the true thickness t=C.(cos .theta.) and .theta.=tan-1 (S/f-g) can be obtained. C is the thickness C at the measurement point, and fg is the distance in the Z direction from the measurement point f to the measurement point g.

Also in this case, as in FIG. 4, the total value of the pushing amounts by the sensors 42a and 42b or the difference between the positional coordinate values of the sensors 42a and 42b is the same at each measurement point. Therefore, the parallelism of the work 10 in the Z direction and the machining accuracy can be detected from the total value of the pressing amount at each measurement point or the amount of deviation of the difference between the position coordinate values.

The workpiece 10 to be measured in this embodiment has a parallelogram shape parallel to the XY directions. However, it is sufficient to correct the error due to the angle of the trapezoidal shape of the workpiece.

Further, in the above-described embodiments, an example was described in which the contact was in contact with the side surface of the workpiece having parallel sides to measure the thickness. By widening the gap, it is possible to accurately measure the thickness of the gap (gap) that has been bored or the like. In addition, although the contact according to this embodiment has been described as having a semicircular shape protruding inward from the tip of the arm, a spherical contact provided at the tip of the thin linear arm like a general touch probe can be used. You can be a child.

C thickness at measurement point, t true thickness, S push amount, r contact radius, D measurement value, 10 workpiece, 20 XY table, 30 work part, 40 measuring device,
41 arm, 42a sensor A, 42b sensor B, 100 machine tool

Claims (6)

A plate thickness measuring device for measuring the thickness of a work by a pair of sensors having a pair of contacts that face and contact side surfaces in the thickness direction of the work with a predetermined pressing force,
a measuring device that moves the pair of sensors in the vertical direction and the thickness direction, which is the measurement direction;
an XY table that moves the pair of sensors to at least two different measurement points in the Y direction that intersects the vertical direction and the measurement direction ;
with
Let r be the radius of each of the pair of contacts that come into contact with the work, D be the measured value measured by the pair of sensors, and x be the error in the measurement direction due to the positional deviation due to the difference in the contact position of the pair of contacts. C is the thickness of the workpiece at a measurement point among the at least two different measurement points, b-a is the distance in the Y direction between two measurement points among the at least two different measurement points, and the pair The difference in the measurement direction at the two measurement points by any one of the sensors is the pushing amount S,
θ=tan ⁻¹ (S/b−a),
x=r·((1/cos θ)−1),
C = D - 2 · x, find,
A plate thickness measuring device characterized in that the true thickness of the work is t=C·(cos θ) . Instead of moving the pair of sensors to the at least two different measuring points on the XY table, the measuring device is arranged in two sets of the pair fixed in the Y direction with a spacing of ba. 2. The plate thickness measuring device according to claim 1, further comprising a sensor. 2. The method according to claim 1 , wherein the workpiece has an approximate thickness of 5 to 15 mm, a distance between the two measurement points is 5 to 15 mm, and a radius r of the contact is 4 to 8 mm. Thickness measuring device. 2. The plate thickness measuring device according to claim 1, wherein the measuring points are three or more in the Y direction. Instead of moving the pair of sensors to the at least two different measurement points in the Y direction on the XY table, the pair of sensors is moved to the at least two different measurement points in the vertical direction. 2. The plate thickness measuring device according to claim 1, wherein the sensor is moved. The thickness of the workpiece is measured by a pair of sensors having a pair of contacts that face and contact the side surfaces in the thickness direction of the workpiece with a predetermined pressing force, and the pair of sensors are measured in the vertical direction and the thickness direction, which is the measurement direction. A plate thickness measuring method applied to a plate thickness measuring device having a measuring device that moves to
moving the pair of sensors to at least two different measurement points in a Y direction that intersects the vertical direction and the measurement direction ;
Let r be the radius of each of the pair of contacts that come into contact with the work, D be the measured value measured by the pair of sensors, and x be the error in the measurement direction due to the positional deviation due to the difference in the contact position of the pair of contacts. C is the thickness of the workpiece at a measurement point among the at least two different measurement points, b-a is the distance in the Y direction between two measurement points among the at least two different measurement points, and the pair The difference in the measurement direction at the two measurement points by any one of the sensors is the pushing amount S,
θ=tan ⁻¹ (S/b−a),
x=r·((1/cos θ)−1),
C = D - 2 · x, find,
A method for measuring the plate thickness , wherein the true thickness of the work is t=C·(cos θ) .

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