JP2020082231A - Measurement method - Google Patents

Abstract

To provide a measurement method related to machine accuracy of a machine tool which can be executed with less man hour and at low cost without using a reference unit.SOLUTION: A measurement method for measuring an accuracy of a machine tool comprises the steps of: setting a workpiece W on a machine tool 2 and performing processing; setting a sensor 30 on the machine tool 2; measuring a same point P on a target surface of the workpiece W on at least two measurement points S1, S2 in a field of view of the sensor 30; and detecting an accuracy of the machine tool 2 on the basis of a measurement result on at least two measurement points S1, S2.SELECTED DRAWING: Figure 2

Description

The present invention relates to a measuring method for machine accuracy of a machine tool.

It is important to grasp the machine accuracy of the machine tool and perform appropriate calibration in order to perform machining with high dimensional accuracy. In order to deal with this, there has been proposed a method for measuring the accuracy of a machine tool using a reference device such as a quadrangle master whose accuracy is compensated (for example, refer to Patent Document 1).

JP-A-2009-103599

In the measuring method described in Patent Document 1, the straightness and the squareness can be measured by measuring the reference device installed in the machine with the sensor attached to the tool spindle. However, it is necessary to separately own a standard device, and it is necessary to install a sensor inside the machine for each measurement, which causes problems in terms of cost and man-hours.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a measuring method for machine accuracy of a machine tool that can be implemented with a small number of steps and at low cost without using a standard.

In order to solve the above problems, a measurement method according to one embodiment of the present disclosure,
The process of setting the work on the machine tool and processing it,
Setting a sensor on the machine tool;
Measuring the same point on the machined surface of the workpiece at at least two measurement points within the field of view of the sensor;
Detecting the accuracy of the machine tool based on the measurement results at the at least two measurement points;
including.

According to the above-described embodiment, it is possible to provide a method for measuring the machine accuracy of a machine tool that can be implemented with a small number of steps and at low cost without using a standard.

FIG. 3 is a side view schematically showing a step of moving a sensor attached to a spindle to measure the same point on a machining surface of a work placed on a table at two measurement points within a field of view of the sensor, FIG. 5 is a diagram showing a case where the moving direction of the spindle is parallel to the reference direction of the mounting surface of the table. FIG. 3 is a side view schematically showing a step of moving a sensor attached to a spindle to measure the same point on a machining surface of a work placed on a table at two measurement points within a field of view of the sensor, FIG. 6 is a diagram showing a case where the moving direction of the main shaft has an inclination angle with respect to the reference direction of the mounting surface of the table. It is a side view which shows typically the process of rotating and moving the sensor attached to the main shaft, and measuring the same point of the processed surface of the workpiece mounted on the table at two measurement points within the visual field of the sensor. It is the figure which showed typically three measurement points in the visual field of a sensor. It is the figure which showed typically the machine precision which exists for every X, Y, and Z axis of a machine tool. It is a figure which shows the process which calculates|requires the inclination angle in an X-axis direction by moving a sensor attached to the main shaft one by one, making the same measurement point enter the same visual field.

Hereinafter, embodiments and examples for carrying out the present disclosure will be described with reference to the drawings. The measurement method described below is for embodying the technical idea of the present disclosure, and the present disclosure is not limited to the following unless specified otherwise.
In the drawings, members having the same function may be designated by the same reference numeral. Although there are cases in which the embodiments and examples are shown separately for the sake of convenience, in order to facilitate explanation and understanding of the points, partial replacement or combination of the configurations shown in different embodiments and examples is possible. In the later-described embodiments and examples, description of matters common to the above is omitted, and only different points will be described. In particular, similar effects obtained by the same configuration will not be sequentially described for each embodiment or example. In some cases, the size, positional relationship, etc. of the members shown in each drawing are exaggerated in order to clarify the explanation.

(Measurement method according to the first embodiment of the present disclosure)
First, the measurement method according to the first embodiment of the present disclosure regarding the machine accuracy of a machine tool will be described with reference to FIGS. 1 and 2. First, a basic description of the measurement method will be given with reference to FIG. FIG. 1 schematically shows a process in which a sensor attached to a spindle (tool spindle) is moved to measure the same point on a machining surface of a workpiece placed on a table at two measurement points within the field of view of the sensor. It is a side view shown. In particular, FIG. 1 shows a case where the main shaft moves in a direction parallel to a reference direction (for example, the X-axis direction, but not limited to this) of the mounting surface of the table.

In this embodiment, after the work W is set on the mounting surface 10a of the table 10 of the machine tool 2 for processing, the sensor 30 is set on the spindle 20 of the machine tool without removing the work W from the table 10. .. As the sensor 30 used here, a three-dimensional sensor that can obtain a three-dimensional profile, such as a fringe projection area sensor, can be exemplified. Further, it is possible to obtain a three-dimensional profile by scanning in the direction perpendicular to the longitudinal direction of the line light using the optical cutting type sensor. A two-dimensional sensor such as an image sensor may be used depending on the direction of detection.

Whichever sensor is used, the calibration is performed for the sensor alone (calibration within the measurement range of the sensor), and the measurement is performed with the coordinates in the two-dimensional field of view calibrated.
Further, the measurement is performed in the state where the attachment of the sensor to the spindle is calibrated near the reference position of the machine tool (for example, the center of rotation of the table). The calibration related to this attachment is for making a reference, and for example, the same point may be measured at two points S1 and S2 on the visual field in the vicinity of the center of rotation of the table to give an apparent inclination. Due to the nature of this measurement, it is necessary for the sensor to be able to guarantee accuracy within a certain plane (within the measurement range).

In the present embodiment, as an example of measurement of the machine accuracy of the machine tool 2, a case will be described in which the tilt angle of the moving direction of the spindle 20 with respect to the reference direction of the mounting surface of the table is detected. In this embodiment, the work W is fixed on the table 10, and the sensor 30 is moved by the movement of the main shaft 20 to perform the measurement. FIG. 1 shows a case where the main shaft 20 moves in the X-axis direction.
However, the invention is not limited to this, and the sensor side may be fixed and the work side may be moved. For example, the table on which the work is placed can be moved without moving the member to which the sensor is attached. Further, both the sensor and the work can be moved. Any mode can be adopted as long as the sensor and the workpiece can be moved in translation relative to each other.

<When the moving direction of the spindle is parallel to the reference direction of the table mounting surface>
In FIG. 1, the optical axis of the sensor 30 (axis of the main shaft 20) is orthogonal to the mounting surface 10a of the table 10, and the moving direction of the main shaft 20 is parallel to the reference direction of the mounting surface 10a of the table 10. Indicates that That is, the case where a predetermined machine precision is obtained is shown.

After setting the sensor 30 on the spindle 20, the point A provided on the processing surface of the workpiece W, which is a measurement mark, is measured at two measurement points S1 and S2 in the visual field 32 of the sensor 30. Specifically, the point A is measured at the position shown by the solid line in FIG. 1 to obtain the measurement point S1 in the visual field 32, and then the spindle 20 to which the sensor 30 is attached is moved by the distance L (thick arrow). (See FIG. 1), the point A is measured again at the position indicated by the broken line in FIG. As a result, the measuring point S2 is obtained within the visual field.

If a punch or marking is attached to the work, it can be used as the point A on the work W to be the measurement mark. Further, a convex portion, a concave portion, an edge portion, a corner portion or the like formed on the work W by machining can also be used as the measurement mark.

When a three-dimensional profile is obtained by the sensor 30, the coordinate Z1 of the measurement point S1 in the Z-axis direction and the coordinate Z2 of the measurement point S2 in the Z-axis direction are measured, and based on the deviation ΔZ (=Z2-Z1). The inclination angle θ of the moving direction of the spindle 20 with respect to the reference direction of the mounting surface 10a of the table 10 can be obtained. In the case shown in FIG. 1, since the deviation ΔZ=0, it can be determined that the moving direction of the spindle 20 is parallel (not inclined) to the reference direction of the mounting surface 10a of the table 10. ..

<When the moving direction of the main shaft is inclined with respect to the reference direction of the table mounting surface>
Next, referring to FIG. 2, the optical axis of the sensor 30 is orthogonal to the mounting surface 10a of the table 10, and the movement direction of the main shaft 20 is an angle with respect to the reference direction of the mounting surface 100a of the table 10. A case of inclining by θ will be described. FIG. 2 is a side view schematically showing a case where the sensor attached to the main shaft is moved to measure the same point on the machining surface of the workpiece placed on the table at two measurement points within the field of view of the sensor. In particular, it is a diagram showing a case where the movement direction of the main shaft has an inclination angle with respect to the reference direction of the mounting surface of the table.

After the sensor 30 is set on the spindle 20, the point A is measured at the position shown by the solid line in FIG. 2 to obtain the measurement point S1 in the visual field, and then the spindle to which the sensor 30 is attached is moved by the distance L. (Refer to the thick arrow) and measure the point A again at the position shown by the broken line in FIG. As a result, the measuring point S2 is obtained within the visual field.

When a three-dimensional profile is obtained by the sensor 30, the coordinate Z1 of the measurement point S1 in the Z-axis direction and the coordinate Z2 of the measurement point S2 in the Z-axis direction are measured, and based on the deviation ΔZ (=Z2-Z1). The inclination angle θ of the moving direction of the spindle 20 with respect to the reference direction of the mounting surface 10a of the table 10 can be obtained. In the case shown in FIG. 2, the deviation ΔZ has a predetermined value other than zero, so that the moving direction of the spindle 20 is not parallel (inclined) to the reference direction of the mounting surface 10a of the table 10. You can judge. Then, based on the value of the deviation ΔZ, the inclination angle θ of the movement direction of the spindle 20 with respect to the reference direction of the mounting surface 10a of the table 10 can be obtained. Specifically, the inclination angle θ can be calculated by the angle θ=ARCSIN(ΔZ/L).

As described above, in the first embodiment, the sensor 30 and the workpiece W are moved in translation relative to each other, so that the same point on the machined surface of the workpiece W is measured at two measurement points S1 in the visual field of the sensor 30. It is possible to detect the inclination angle θ of the moving direction of the spindle 20 with respect to the reference direction of the mounting surface 10a of the table 10 as the accuracy of the machine tool 2 based on the measurement result in S2.

(Measurement method according to the second embodiment of the present disclosure)
Next, a measurement method according to the second embodiment of the present disclosure will be described with reference to FIG. FIG. 3 is a side view schematically showing a case where the sensor mounted on the spindle is rotated and moved to measure the same point on the machined surface of the workpiece placed on the table at two measurement points within the field of view of the sensor. It is a figure.

In the first embodiment described above, the sensor 30 and the workpiece W are moved in translation relative to each other,
The measuring point S1 and the measuring point S2 are obtained within the visual field 32 of the sensor 30 to detect the accuracy of the machine tool 2. In the present embodiment, the sensor 30 and the work W are relatively rotationally and translationally moved to obtain the measurement point S1 and the measurement point S1′ within the field of view 32 of the sensor 30 to detect the accuracy of the machine tool 2. ..

In the visual field 32 of the sensor 30, the measurement point S1 is arranged such that the line connecting to the rotation center CL of the sensor 30 (spindle 20) coincides with the moving direction of the spindle 20. Further, the measurement point S1 is arranged at a distance M from the rotation center CL of the sensor 30.
In this state, the point A is measured at the position shown by the solid line in FIG. 3 to obtain the measurement point S1 in the field of view, and then the spindle 32 to which the sensor 30 is attached is rotated 180 degrees and the spindle 32 is moved by the distance 2 The point A is measured again at the position shown by the broken line in FIG. 3 after moving by ×M (see the thick arrow). As a result, the measurement point S1′ is obtained within the visual field.

When a three-dimensional profile is obtained by the sensor 30, the coordinate Z1 of the measurement point S1 in the Z-axis direction and the coordinate Z1′ of the measurement point S1′ in the Z-axis direction are measured, and the deviation ΔZ (=Z1′−Z1). Based on the above, the tilt angle θ of the moving direction of the spindle 20 with respect to the reference direction of the mounting surface 10a of the table 10 can be obtained. Specifically, the inclination angle θ can be calculated by the angle θ=ARCSIN(ΔZ/L).
Since the other points are the same as those of the first embodiment, further description will be omitted.

As described above, in the measuring methods according to the first and second embodiments described above,
The sensor 30 is attached to the spindle 20,
The work W is placed on the table 10,
Based on the difference between the measurement results at the two measurement points S1 and S2 (S1 and S1′) within the field of view of the sensor 30, the tilt angle θ with respect to the moving direction of the spindle 20 and the reference direction of the mounting surface 10a of the table 10 is detected. can do.

This makes it possible to reliably measure the accuracy of inclination using the machined workpiece W without installing a reference device or the like inside the machine tool 2 with a small number of steps.

In particular, the sensor 30 and the workpiece W are moved in translation relative to each other, whereby the same point P on the machining surface of the workpiece W is measured at at least two measurement points S1 and S2 in the field of view 32 of the sensor 30, and the machine tool is machined. The accuracy of 2 can be detected (first embodiment). Further, the sensor 30 and the workpiece W are relatively rotated and translated, so that the same point P on the processing surface of the workpiece W is measured at at least two measurement points S1 and S1′ in the visual field 32 of the sensor 30. The accuracy of the machine tool 2 can be detected (second embodiment). In any case, the function of the machine tool 2 can be effectively used to efficiently detect the accuracy of the machine tool 2.

Further, the sensor 30 and the workpiece W are relatively rotationally and translationally moved to measure the same point on the machined surface of the workpiece W at at least two measurement points within the field of view of the sensor 30. The accuracy of can be detected. Also in this case, the accuracy of the machine tool 2 can be efficiently detected by effectively utilizing the function of the machine tool 2.
In particular, since it is possible to detect the error in translational movement based on the deviation between the two measurement points and the error in rotational movement based on the sum of the two measurement points, separate estimation of the rotational movement error and the translational movement error can be performed. Will be easier.
In addition, although the main shaft 20 to which the sensor 30 is attached is rotated here, the present invention is not limited to this, and the table 10 side may be rotated. At this time, the surface of the workpiece W processed into a flat surface by grinding is processed not along the table 10 but along the moving direction of the spindle 20. Therefore, the surface of the work W is tilted in the opposite direction by rotating the table 10 by 180°, and the tilt of the X axis can be detected with higher sensitivity than when the reference device is used.

In the above description, the detection of the tilt angle θ in the moving direction of the main shaft 20 has been described as an example, but the mechanical accuracy of detection is not limited to this. For example, the same point P on the machined surface of the workpiece W is measured at at least two measurement points S1 and S2 in the field of view 32 of the sensor 30, and the table 10 is placed on the optical axis of the sensor 30 (axis of the main shaft 20). It is also possible to detect the tilt angle with respect to the surface 10a. Specifically, based on the deviation between the coordinates of the measurement point 2 and the coordinates when the optical axis of the sensor 30 (axis of the main shaft 20) is orthogonal to the mounting surface 10a of the table 10, the sensor 30 The inclination angle of the optical axis (the axis of the main axis 20) can be obtained.

(Measurement method according to the third embodiment of the present disclosure)
Next, a measurement method according to the third embodiment of the present disclosure will be described with reference to FIG. Figure 4
It is the figure which showed typically three measurement points in the visual field of a sensor.
By performing the measurement method according to the first or second embodiment described above not only in the X-axis direction but also in the Y-axis direction, three measurement points T1 to T3 in the field of view of the sensor as shown in FIG. Can be obtained. Thereby, based on the difference between the measurement results at the two measurement points within the field of view 32 of the sensor 30, the tilt angle of the mounting surface 10a of the table 10 with respect to the reference direction in the movement direction of the spindle 20 in the X-axis direction and the Y-axis direction. θ can be detected. Similarly, the tilt angle of the optical axis of the sensor 30 (axis of the main shaft 20) with respect to the mounting surface 10a of the table 10 can also be detected.

(Measurement method according to the fourth embodiment of the present disclosure)
In the measurement method according to the fourth embodiment of the present disclosure, the sensor 30 and the work W are relatively rotationally moved to measure the same point on the processed surface of the work W at at least two measurement points within the field of view of the sensor. To do. Using this measuring method, it is possible to detect the tilt angle of the optical axis of the sensor 30 (the axis of the main shaft 20) with respect to the mounting surface 10a of the table 10 as the mechanical accuracy.

When the sensor 30 and the work W are rotationally moved 360 degrees relative to each other, if the rotation axis of the sensor 30 (spindle 20) is perpendicular to the mounting surface 10a of the table 10, a point on the field of view 32 is detected. The projected image on the work W will draw a perfect circle. On the other hand, if the rotation axis of the sensor 30 (main shaft 20) is tilted with respect to the mounting surface 10a of the table 10, a deviation occurs with respect to the projected image of the perfect circle. Therefore, based on this deviation, the inclination angle of the rotation axis of the sensor 30 (main shaft 20), that is, the optical axis of the sensor 30 (axis of the main shaft 20) with respect to the mounting surface 10a of the table 10 can be obtained. If the measurement is performed at least at three points on the work, the tilt angle of the rotation axis of the sensor 30 (spindle 20) with respect to the mounting surface 10a of the table 10 can be obtained.

Further, after the sensor 30 measures the point A on the work to obtain the measurement point S1 in the visual field 32, the sensor 30 is rotated by a predetermined angle. Then, when the rotation axis CL of the sensor 30 (spindle 20) is perpendicular to the mounting surface 10a of the table 10, the sensor 30 moves with such a movement amount that the measurement point S1′ after rotation returns to the position of the point A. Let At this time, the inclination angle of the optical axis of the sensor 30 can be obtained based on the obtained deviation of the coordinates between the measurement points S1 and S1'. By measuring the same point A on the machined surface of the work W at at least three measurement points (three rotation angles) within the field of view of the sensor 30, the inclination angle of the optical axis of the sensor 30 with respect to the mounting surface 10a of the table 10 is measured. Can be asked.

Table 10
(Measurement method according to the fifth embodiment of the present disclosure)
Next, a measurement method according to the fifth embodiment of the present disclosure will be described with reference to FIGS. 5 and 6. FIG. 5 is a diagram schematically showing the machine accuracy that exists for each of the X, Y, and Z axes of the machine tool. FIG. 6 is a diagram showing a process of sequentially moving a sensor attached to a main shaft to obtain an inclination angle in the X-axis direction while keeping the same measurement point in the same visual field.

As shown in FIG. 5, the machine accuracy of the machine tool 2 includes position in the axial direction, straightness in the horizontal direction, straightness in the vertical direction, rolling around the axis, yawing, and pitching for each axis. Further, there is a squareness between the axes (a squareness between the XY axis, the XZ axis, and the YZ axis). Therefore, the machine accuracy of the machine tool 2 is 6 elements×3 axes+3 elements (between axes)=21 elements.
Each element of these machine precisions can be calculated by using the measuring method described in the above-mentioned embodiment by using a predetermined position on the work W as a reference.

In order to obtain the above-mentioned elements, as shown in FIG. 6, a step of obtaining the inclination angle in the X-axis direction by sequentially moving the sensor 30 attached to the spindle 20 while keeping the same measurement point in the same visual field. repeat. That is, it is possible to employ a so-called sequential three-point method in which the whole measurement is connected like a scale depending on the accuracy within the field of view. FIG. 6 shows that steps 1 and 2 are performed so that at least two of the measurement points in the visual field are measured at the same position in the visual field.

For example, when there are measurement marks T1 and T2 that are separated by a distance of 2/3 (hereinafter 2/3FOV) of the field of view (see step 1), the stage is moved by 2/3FOV and the measurement mark T2 is changed in step 2. The measurement is performed so as to come to the position of the measurement mark T1 in step 1. In this way, by measuring the same point at two points within the field of view that has been calibrated in advance, the accuracy of the sensor 30 can be connected in a scale-like manner, and the entire workpiece W can be measured.

At this time, it is necessary to make a large number of measurement marks on the work W at intervals such that a plurality of them are within the visual field of the sensor 30. For example, if the work W is a rack and pinion rack, a large number of measurement marks can be obtained along the longitudinal direction of the rack. Using this common mark as an intermediary, it is possible to detect a relative coordinate change of a long stroke.
By performing this not only in the X-axis direction but also in the Y-axis direction, it is possible to detect each element of the above-described machine accuracy and perform appropriate calibration. The shape of the work W used for the measurement is preferably a shape that allows the points as the measurement marks to be specified. Therefore, it can be said that a part of a polygonal cone, a cone, a convex sphere, or a concave sphere is preferable.

In the above embodiment, the case where the sensor 30 is attached to the spindle 20 of the machine tool 2 has been described as an example, but the present invention is not limited to this. If the sensor 30 can be moved relative to the work W, the sensor 30 can be attached to any other member of the machine tool 2.

As described above, in the measurement method according to the above embodiment,
A step of setting the work W on the machine tool 2 and performing machining,
A step of setting the sensor 30 on the machine tool 2,
Measuring the same point on the machined surface of the work W at at least two measurement points within the field of view of the sensor 30;
Detecting the accuracy of the machine tool 2 based on the measurement results at at least two measurement points;
including.

As a result, the accuracy of the machine tool 2 is measured using the machined work W without installing a reference device or the like inside the machine tool 2, so that the accuracy of the machine tool can be measured with a small number of steps and at low cost. be able to. In particular, by measuring the same point on the machined surface of the workpiece at at least two measurement points within the field of view of the sensor, the accuracy of the machine tool can be measured efficiently and reliably.
The standard device needs to be verified every year, and a large amount of cost is required for one test. Also, if it is deformed due to some accident, it will be in an unusable state. Further, the reference device can be used as a reference because the temperature condition must be constant (for example, 20° C.±0.5° C.), and it may be difficult to use it on a machine tool. Thus, the use of no scale provides a great advantage.

Even if the sensor 30 is an optical cutting type sensor, it is possible to obtain a three-dimensional profile by scanning in the direction perpendicular to the longitudinal direction of the line light.
When a three-dimensional sensor such as a fringe projection area sensor is used as the sensor 30, it can be expected that the measurement will be completed in a shorter time.

Although the embodiments and modes of the present invention have been described, the disclosure may change in details of the configuration, and combinations of elements in the embodiments and modes, changes in order, etc. are claimed. It can be realized without departing from the scope and the idea of.

2 machine tool 10 table 10a mounting surface 30 sensor 32 field of view W work

Claims (7)

The process of setting the work on the machine tool and processing it,
Setting a sensor on the machine tool;
Measuring the same point on the machined surface of the workpiece at at least two measurement points within the field of view of the sensor;
Detecting the accuracy of the machine tool based on the measurement results at the at least two measurement points;
A method for measuring the accuracy of a machine tool, comprising:
The translational movement of the sensor and the workpiece relative to each other allows the same point on the machined surface of the workpiece to be measured at at least two measurement points within the field of view of the sensor. How to measure the accuracy of machine tools.
The relatively same rotational movement and translational movement of the sensor and the workpiece measure the same point on the machined surface of the workpiece at at least two measurement points within the field of view of the sensor. The method for measuring the accuracy of machine tools described in.
The said sensor is an optical cutting|disconnection type sensor, The measuring method of the precision of the machine tool in any one of Claim 1 to 3 characterized by the above-mentioned.
The method for measuring the accuracy of a machine tool according to claim 1, wherein the sensor is a fringe projection area sensor.
The sensor is attached to the spindle,
The work is placed on the table,
The tilt angle of the moving direction of the spindle and the tilt angle of the mounting surface of the table with respect to the reference direction is detected based on a difference between measurement results at two measuring points in the field of view of the sensor. The method for measuring the accuracy of machine tools described in.
7. The whole work is measured by repeating a step of measuring at least two of the calibration measurement points at the same position in the field of view in advance, to measure the entire work. A method for measuring the accuracy of the described machine tool.

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