JP4806093B1 - Method and measuring system for measuring locus of movement of rotation axis of rotating body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring a movement trajectory of a rotation axis of a rotating body.
SOLUTION: A rotating body is attached to a main shaft, and a set of three light emitting units and a light receiving unit facing each other with a part of the rotating body in a vertical plane perpendicular to the rotation axis of the rotating body. , Measuring the amount of edge light while rotating the rotating body integrally with the main shaft, and obtaining a virtual sectional shape different from the sectional shape of the rotating body based on the amount of edge light. And determining a trajectory of the rotation axis of the rotating body based on the amount of edge light and the virtual cross-sectional shape.
[Selection] Figure 1

Description

The present invention relates to a method for measuring a movement trajectory of a rotation axis of a rotating body, and a measurement system for measuring a movement trajectory of a rotation axis of a rotating body.

  A machine tool such as a milling machine for cutting a workpiece (workpiece) grips a table for fixing the workpiece, a cutter such as a milling machine for cutting the workpiece while moving relative to the workpiece fixed to the table, and the cutter And a spindle that rotates the chuck and the blade attached to the tip at high speed (for example, several thousand to several tens of thousands rpm).

When cutting the work surface of the workpiece, the tip of the blade of the blade that rotates at high speed as the spindle rotates (hereinafter simply referred to as the “tip of the blade”) is brought into contact with the work surface of the workpiece. At this time, if shaft runout occurs in the axis of the rotating blade, the tip of the blade rotates while drawing a locus deviating from a perfect circle. For example, when the blade is rotating while being microvibrated in a random direction within a plane perpendicular to the axis, the tip of the rotating blade draws a locus in which the microvibration is superimposed on a perfect circle. At this time, the locus drawn by the tip of the cutting tool is transferred to the work surface of the workpiece, that is, the work surface of the workpiece is formed with irregularities reflecting the locus drawn by the tip of the blade. In this way, since there is a clear correlation between the trajectory of the axis of the rotating blade and the machining accuracy (for example, surface roughness) of the workpiece machining surface, the workpiece machining accuracy can be evaluated. Therefore, it is required to accurately measure the trajectory of the movement of the axis of the cutting tool.

  As will be described in detail later, the shaft runout of the blade mainly occurs due to the rotation accuracy of the main shaft, chucking accuracy when the blade is attached to the chuck, and attachment accuracy when the chuck is attached to the main shaft. It has been known. Here, in Patent Document 1, while measuring the shaft runout of the spindle in real time, feedback control is performed on the attitude of the spindle center based on the measured shaft runout data to suppress the spindle runout of the spindle to be small. An axial shake correction control device is disclosed. Specifically, the shaft shake correction control device of Patent Document 1 includes a main shaft that is pivotally supported by an air bearing, a reference ring that has a high roundness, and is attached so as to rotate integrally with the main shaft. Are mainly provided with three non-contact displacement sensors arranged concentrically on the outside of the main body and a controller for performing feedback control on the attitude of the main shaft.

  In the shaft shake correction control device of Patent Document 1, three non-contact displacement sensors are used to measure the distance between the outer surface of the reference ring and each non-contact displacement sensor in real time. Then, from the measurement data obtained from the three non-contact displacement sensors, the actual shape component that faithfully reproduces the actual shape of the reference ring using the three-point method described later, and the radius of the spindle to which the reference ring is attached The vibration component in the direction (surface direction perpendicular to the axis of the main axis) is extracted. Here, based on the vibration component in the radial direction of the axis of the spindle, feedback control is performed to adjust the attitude of the axis of the spindle, thereby suppressing the shaft runout of the axis of the spindle. By using the three-point method, the actual shape component and the vibration component of the reference ring can be extracted independently. In other words, only the vibration component in the radial direction of the axis of the main shaft can be extracted regardless of the shape error and mounting error of the reference ring.

JP-A-6-235422

  As described above, it is known that the shaft runout of the blade mainly occurs due to the rotation accuracy of the main shaft, the chucking accuracy when the blade is attached to the chuck, and the attachment accuracy when the chuck is attached to the main shaft. However, in the shaft shake correction control apparatus of Patent Document 1, only the rotational accuracy of the main shaft is measured. Therefore, the machining accuracy of the workpiece cannot be evaluated unless the chucking accuracy and the mounting accuracy to the holder are further measured.

Here, as described above, the magnitude of the shaft runout of the axis of the cutting tool is caused by the rotation accuracy of the main shaft, chucking accuracy when the cutting tool is attached to the chuck, and mounting accuracy when the chuck is attached to the main shaft. Therefore, if the axial runout of the axis of the cutting tool can be measured, the machining accuracy of the workpiece can be accurately evaluated. However, the shaft shake correction control device of Patent Document 1 can only measure the shaft runout generated in a reference member having a high roundness such as a reference ring as shown below. It is not possible to measure the shaft runout (or the trajectory of the movement of the axis of the blade) of the blade having a complicated shape having such a large unevenness .

  In the shaft shake correction control device of Patent Document 1, the distance between the outer surface of the reference ring coaxially attached to the axis of the main shaft and the proximity sensor is measured by using the non-contact displacement sensor as described above. is doing. Here, the reference ring has a high roundness and its outer surface is mirror-finished. That is, no irregularities having a height exceeding the irregularities (for example, about several μm) corresponding to the surface roughness due to the processing accuracy of the outer surface are formed on the outer surface of the reference ring. Therefore, the non-contact displacement sensor can be disposed close to the outer surface of the reference ring, and the distance between the non-contact displacement sensor and the outer surface of the reference ring can be accurately measured.

Here, since the detection range of the non-contact displacement sensor is generally about 0 mm to several mm, when measuring the axial runout of the axis of the blade using the non-contact displacement sensor, it surrounds the outside of the blade, and The at least three non-contact displacement sensors must be arranged so as to be within a few mm from the blade. However, it is virtually impossible to dispose a non-contact displacement sensor that must be disposed close to the outside of the cutting tool and close to the measurement target so as not to interfere with the work when cutting the work. Is possible. In addition, for example, the cross section of a cutting tool such as an end mill has a complicated shape greatly deviating from a perfect circle, and irregularities of several mm or more may be formed. In this way, when the cross-sectional shape of the cutting tool has irregularities exceeding the detection range of the non-contact displacement sensor, even if the non-contact displacement sensor can be arranged close to the cutting tool outside the cutting tool, It is impossible to accurately measure the cross-sectional shape of the cutting tool, and it is not possible to measure the axial runout of the axial center of the cutting tool (or the locus of movement of the axial center of the cutting tool ) .

An object of the present invention is to provide a method for measuring a trajectory of the rotation axis of a rotating body, regardless of the shape of the rotating body, and a rotating body such as a cutting tool attached to a machine tool. It is to provide a measurement system for measuring a movement trajectory of a rotation axis.

According to the first aspect of the present invention, there is provided a method for measuring a locus of movement of a rotation axis of a rotating body having irregularities , wherein the rotating body is attached to a main shaft that is rotatably provided at a predetermined rotation speed. Mounting, disposing a set of three light emitting units and a light receiving unit facing each other across a part of the rotating body in a vertical plane perpendicular to the rotation axis of the rotating body, and the rotating body Irradiating light from each light emitting part toward each light receiving part while rotating integrally with the main shaft at the predetermined rotation speed, and the light is not blocked by the rotating body. Measure the amount of edge light received by each light receiving unit, and create a virtual cross-sectional shape in which the depth of the concave portion is shallower than the vertical cross-sectional shape of the rotating body by the edge light. , calculated on the basis of the to the amount of the edge light measured by the light receiving portions And Rukoto, based on the amount and the virtual cross-sectional shape of the edge light method and a determining the trajectory of movement in the vertical plane of the rotation axis of the rotating body is provided.

According to the first aspect of the present invention, it is possible to measure the trajectory of the rotation axis of the rotating body without accurately measuring the cross-sectional shape in the cross section perpendicular to the rotating axis of the rotating body. Therefore, it is not necessary to arrange a measuring device for measuring the distance to the rotating body around the rotation axis of the rotating body. Instead, the locus of motion of the rotation axis of the rotating body is measured by irradiating a part of the rotating body with light and measuring the amount of light (edge light) that passes without being blocked by the rotating body. Therefore, the degree of freedom of arrangement of the light emitting unit and the light receiving unit is increased, and the locus of movement of the rotation axis can be easily measured even for a rotating body having large unevenness.

In the method of measuring the movement locus of the rotation axis of the rotating body according to the present invention, the rotating body may be a cutting tool having a cutting edge portion formed on a surface around the rotating axis. In this case, for example, even in a cutting tool having a complicated shape such as an end mill, a drill, a reamer, or a face mill, the trajectory of the rotation axis can be measured.

In the method for measuring a motion trajectory of the rotational axis of the rotating body of the present invention, the light emitting unit may be a laser irradiation device that irradiates a laser beam, and the light receiving unit may be a photodiode. In this case, since the laser beam is used, the directivity of the light is very high. Therefore, it is easy to dispose the set of the light emitting unit and the light receiving unit away from the rotating body such as a cutting tool. The degree of freedom of arrangement becomes high.

In the method of measuring a motion trajectory of the rotation axis of the rotating body according to the present invention, the cross-sectional shape of the vertical surface of the rotating body has a first convex portion having the longest distance from the rotation axis. The virtual cross-sectional shape may have a second protrusion corresponding to the first protrusion, and a distance between the rotation axis and the first protrusion may be the rotation axis. It may be the same as the distance between the second convex portions. In this case, the virtual cross-sectional shape extracted based on the measurement of the amount of edge light is different from the actual cross-sectional shape (actual cross-sectional shape). Can be accurately reproduced even in a virtual cross-sectional shape. Therefore, for example, when measuring the shape of a cutting tool, the length (radial length) of the blade tip can be accurately determined from the virtual cross-sectional shape, and the degree of wear of the blade tip can be determined. Can do.

  Further, the cross-sectional shape of the vertical surface of the rotating body may have a first recess having a shortest distance from the rotation axis, and the virtual cross-sectional shape corresponds to the first recess. There may be two recesses, and the distance between the rotation axis and the second recess may be longer than the distance between the rotation axis and the first recess. In this case, the virtual cross-sectional shape is a shape with shallow irregularities as compared with the actual cross-sectional shape. That is, the virtual cross-sectional shape has fewer high-frequency components when Fourier-expanded than the real cross-sectional shape. Therefore, when the virtual cross-sectional shape is Fourier-expanded, the virtual cross-sectional shape can be accurately extracted without taking a large number of peaks.

According to the second aspect of the present invention, there is provided a measurement system for measuring a movement trajectory of a rotation axis of a rotating body having irregularities , extending in a predetermined axial direction, and fixing the rotating body to one end. A main shaft provided with a fixed portion, a main shaft head connected to the other end of the main shaft and having a motor that rotates the main shaft about the shaft, and a vertical plane perpendicular to the rotation axis of the rotating body In addition, three sets of light emitting units and light receiving units arranged so as to face each other with a part of the rotating body interposed therebetween, and the rotating body are rotated integrally with the main shaft at the predetermined rotation speed. the by irradiating light toward the respective light receiving portions from the light emitting portion, of the light, to measure the amount of light received by the edge light at each light receiving portion without being blocked by the said rotary body, said edge The depth of the recess compared to the cross-sectional shape of the vertical surface of the rotating body by light Virtual cross-sectional shape was a shallow gentle shape, the with determined Mel based on the amount of said measured edge light in each light receiving section, based on the amount and the virtual cross-sectional shape of the edge light, the rotator And a control unit that obtains a trajectory of movement of the rotation axis in the vertical plane.

By using the measurement system of the present invention, for example, in a cutting tool such as a milling machine, the trajectory of the rotation axis of a cutting tool having a complicated shape that rotates at high speed is measured with high accuracy (for example, accuracy of 1 μm or less). can do.

FIG. 1 is a schematic diagram of a shaft runout measurement system according to the first embodiment. FIG. 2A is a side view of the end mill 30, and FIG. 2B is a top view of the end mill 30. FIG. 3 is a schematic diagram showing the arrangement of the end mill 30 and the optical measurement system 120. FIG. 4 is an arrangement diagram when performing calibration measurement for examining the correlation between the position of the calibration reference tool 300 and the light amount of the laser beam 121a. It is a flowchart which shows the measuring method of the axial deflection which concerns on 1st Embodiment . It is a figure which shows the relationship between real cross-sectional shape and virtual cross-sectional shape. Fig.7 (a) is the movement locus | trajectory of the axial center of the end mill 30 obtained by simulation, FIG.7 (b) shows virtual cross-sectional shape. FIG. 8 is a diagram showing wear at the tip of the end mill 30. FIG. 9 is a graph showing the correlation between the wear of the end mill 30 and the actual wear of the end mill 30 obtained by simulation. FIG. 10 is a graph showing the Fourier series coefficients of the actual cross-sectional shape and the virtual cross-sectional shape of the end mill 30. FIG. 11 (a) is a view corresponding to FIG. 7 (b) relating to a four-blade end mill, and FIG. 11 (b) is a view corresponding to FIG. 7 (a) relating to a four-blade end mill.

<First Embodiment>
As an example of a measurement system for measuring the movement trajectory of the rotational axis of a rotating body according to the present invention, an axial runout measurement system 1 for measuring the axial runout of an end mill attached to a milling machine which is a kind of machine tool. Will be described. As shown in FIG. 1, the shaft runout measurement system 1 mainly includes a milling machine 10 that cuts a workpiece with an end mill 30, and a control unit 110 that measures a motion trajectory and a shaft runout of an axis 30 a of the end mill 30. .

The milling machine 10 includes a spindle head 13 having a table 11 on which a workpiece is placed, a vise 12 for fixing the workpiece on the table 11, and a spindle 13a and a motor 13b that rotates the spindle 13a around its axis (rotation axis). When, by an unillustrated ball screw mechanism, the moving mechanism moves the spindle head 13 relative to the table 11 to the axial direction of the main shaft 13a (Z direction) and / or the side surface direction of the table 11 (X, Y direction) 14 And a chuck portion 40 (corresponding to a fixing portion of the present invention) for gripping the end mill 30, and the chuck portion 40 is attached to the tip of the main shaft 13a. A rotary encoder (not shown) is provided around the spindle 13 a of the spindle head 13, and data on the rotation angle of the spindle 13 a is sent to a measurement control unit 130 described later. Further, the motor 13b of the spindle head 13 is controlled by a control unit 110 described later. In addition, as the chuck | zipper part 40, the well-known collet chuck which hold | grips and fixes the end mill 30 inserted in the collet not shown can be used, for example. Alternatively, other types of chuck mechanisms can be used.

  As shown in FIGS. 2A and 2B, the end mill 30 is a cylindrical cutting tool, and includes a cylindrical shank portion 31 and a cutting edge portion 32 formed on one end side of the shank portion 31. Have. The central axis of the shank portion 31 is called an axis 30a of the end mill 30. Here, the cutting blade portion 32 is formed as a so-called two-blade on the side surface of the shank portion 31 and the end surface 31 a on one end side of the shank portion 31. Specifically, the cutting edge portion 32 has two end face blades 33a and 33b extending from the axial center side toward the outer peripheral side on the end face 31a, and outer peripheral blades 34a and 34b extending spirally on the side surface of the shank part 31. Have

  As shown in FIG. 1, the control unit 110 is based on three sets of optical measurement systems 120 (only one set of optical measurement systems 120 is shown in FIG. 1) and the measurement results of the optical measurement system 120. And a measurement control unit 130 for extracting the magnitude of the shaft runout of the shaft center 30a of the end mill 30 by a three-point method described later. Here, the three sets of optical measurement systems 120 are arranged in the same plane, and a plane defined by the three sets of optical measurement systems 120 is referred to as a measurement reference plane S. As shown in FIG. 1, the measurement reference plane S is a plane perpendicular to the axis 30 a of the end mill 30 and is a plane that perpendicularly intersects the region where the cutting edge portion 32 of the end mill 30 is formed. Each optical measurement system 120 includes a laser light emitting unit 121 that emits a laser beam 121a (see FIG. 3), and a photodiode 122 that outputs an output signal corresponding to the amount of the received laser beam 121a. The laser light emitting unit 121 is controlled by the control unit 110. The measurement control unit 130 receives an output signal (current signal or voltage signal) of the photodiode 122, and performs an A / D conversion 131 on the input signal of the photodiode 122, and an A / D converter 131. A computer (analysis unit) 132 that performs analysis processing based on a three-point method described later based on data from the D converter 131 and data on the rotation angle of the main shaft 13a is provided.

  Next, a method for measuring the shaft runout of the axis 30a of the end mill 30 using the shaft runout measurement system 1 will be described with reference to FIG. First, the chuck part 40 is fixed to the tip of the main shaft 13a. Further, the shank portion 31 of the end mill 30 is fixed to the chuck portion 40 (end mill fixing step SS1). At this time, the shaft center 30a of the end mill 30, the center of the chuck portion 40, and the shaft center of the main shaft 13a substantially overlap with each other within a range of attachment errors.

  Next, as shown in FIG. 3, the laser emission unit 121 and the photodiode 122 of each optical measurement system 120 are opposed to each other with the end mill 30 sandwiched in the tangential direction of the end mill 30 in the measurement reference plane S (see FIG. 1). (Optical measurement system arrangement step SS2). Here, when the end mill 30 is rotated, a part of the laser light 121a emitted from the laser light emitting unit 121 is always incident on the photodiode 122 without being blocked by the end mill 30, and a part of the laser light 121a. Adjusts the positions of the laser light emitting part 121 and the photodiode 122 so that they are not blocked by the end mill 30 and enter the photodiode 122. In other words, of the laser light 121 a emitted from the laser light emitting unit 121, the edge light that travels straight without being blocked by the edge of the end mill 30 is incident on the photodiode 122. Adjust the position. Here, it is conceivable that a part of the laser light 121 a emitted from one of the laser light emitting units 121 is scattered by the end mill 30 and enters the other set of photodiodes 122. In such a case, in order not to affect the measurement of the amount of edge light, it is preferable that the wavelengths of the laser beams 121a emitted from the three laser emitting units 121 are different wavelengths. In this way, when the three laser light emitting units emit laser beams having different wavelengths, the laser light emitted from the laser light emitting unit is transmitted between each laser light emitting unit and each photodiode, It is preferable to arrange a wavelength filter that cuts off the laser light emitted from the other laser light emitting section.

In addition to the measurement of the axial runout of the axis 30a of the end mill 30 ( measurement of the movement locus of the rotation axis) , as shown in FIG. 4, the laser beam 121a is interposed between the laser light emitting unit 121 and the photodiode 122. Is inserted in the insertion direction perpendicular to the optical axis of the laser beam 121a, the position of the tip 300a of the calibration reference tool 300 in the insertion direction, and the photodiode without being blocked by the calibration reference tool 300. The correlation between the amount of laser light 121a received by 122 and the amount of light is examined. By performing such measurement (calibration measurement), the position in the insertion direction of the calibration reference tool that blocks the laser beam 121a can be specified from the light amount of the laser beam 121a received by the photodiode 122.

  Next, in a state where the motor 13b of the spindle head 13 is driven and the spindle 13a is rotated, a laser beam is emitted from the laser light emitting unit 121 of each optical measurement system 120 in a region of the side surface of the end mill 30 where the cutting edge portion 32 is formed. The laser beam 121a (edge light) that has been irradiated with the light 121a and passed without being blocked by the end mill 30 is received by the photodiode 122 (edge light measurement step SS3).

Output signals from the three photodiodes 122 are respectively input to the A / D converter 131 of the measurement control unit 130, and a signal related to the rotation angle of the main shaft 13a is also input to the measurement control unit 130. Based on the signals from the three photodiodes 122 and the signal related to the rotation angle of the main shaft 13a, an analysis process, which will be described later, is performed, so that the actual cross-sectional shape of the cross section on the measurement reference plane S of the end mill 30 from the measurement data. A virtual cross-sectional shape, which will be described later, is extracted (virtual cross-sectional shape extraction step SS4), and the trajectory of the axis 30a of the end mill 30 and the magnitude of the axial runout are extracted (axial runout information extraction step SS5).

  Here, in order to remove a component resulting from the cross-sectional shape of the measurement reference surface S of the end mill 30 from the measured data according to the three-point method described later, the actual shape of the cross-section of the measurement reference surface S of the end mill 30 ( It has been believed that the actual cross-sectional shape) must be accurately extracted and the contribution from this real cross-sectional shape removed. In other words, in order to remove the component due to the cross-sectional shape of the measurement reference surface S of the end mill 30 from the measured data by the three-point method, the actual cross-sectional shape of the rotating end mill 30 on the measurement reference surface S is measured. Therefore, it has been believed that the measuring device must be arranged so that the actual cross-sectional shape can be measured accordingly.

Specifically, in order to measure the actual cross-sectional shape of the object to be measured on the measurement reference plane, for example, as shown in Patent Literature 1, the object to be measured is positioned outside the rotating object to be measured. It has been believed that a displacement measuring device such as a non-contact displacement sensor that measures distance must be arranged. However, it is difficult to measure the distance between the object to be measured having a complicated cross-sectional shape such as the end mill 30 and the object to be rotated at a high speed of several thousand rpm or more. For this reason, up to now, the measurement of the axial run-out of the rotating object to be measured (the movement trajectory of the rotation axis) has been performed using the three-point method while measuring the actual cross-sectional shape of the object to be measured. In other words, the magnitude of the axial runout can be extracted only when the measurement object is a reference measurement object having a substantially circular actual cross-sectional shape such as a reference ring. Therefore, the measurement of shaft run-out ( measurement of the movement trajectory of the rotation axis) for a cutting tool having a complicated shape actually used such as the end mill 30 has not been performed.

However, as a result of diligent study, the present inventor has replaced the extraction of the actual cross-sectional shape of the measurement object rotating at high speed by measuring the distance to the measurement object rotating at high speed as described above. By measuring the amount of edge light and extracting a virtual cross-sectional shape, which will be described later, different from the actual cross-sectional shape, the trajectory of the rotation axis of the object to be measured can be obtained, and the magnitude of the shaft runout can be obtained. I found. Hereinafter, this finding found by the inventors will be described in detail.

First, it is examined whether or not the amount of edge light is a measurement amount that reflects the axial runout (the locus of motion of the rotational axis) of the object to be measured such as the end mill 30. Here, the amount of edge light of the end mill 30 varies depending on the position (edge position) of the tip of the end mill 30 when the end mill 30 is viewed from the tangential direction (the optical axis direction of the laser light 121a). Since the cutting edge portion 32 is formed on the side surface of the end mill 30, the cross section of the measurement reference surface S of the end mill 30 is not a perfect circle but has a shape with large irregularities. Therefore, when the end mill 30 is viewed from the tangential direction, the edge position of the end mill 30 varies depending on the rotation (rotation angle) of the end mill 30. In other words, the edge position of the end mill 30 changes due to the cross-sectional shape on the measurement reference surface S of the end mill 30.

Note that the axis 30a of the end mill 30 and the axis of the main shaft 13a are not completely coincident with each other. The chucking accuracy when the end mill 30 is attached to the chuck portion 40 and the chuck portion 40 to the main shaft 13a are not limited. It is thought that it is eccentric due to the mounting accuracy at the time of mounting. As described above, when the axis 30a of the end mill 30 and the axis of the main shaft 13a are arranged so as to be shifted from each other, the end mill 30 rotates while being eccentric, and as a result, the shaft of the end mill 30 is rotated. The core 30a swings. Furthermore, it is considered that the shaft center 30a of the end mill 30 is shaken due to the rotational accuracy of the main shaft 13a. Since the main shaft 13a is supported by a bearing (not shown), the rotation axis of the main shaft 13a is considered to vibrate slightly due to the working accuracy of the bearing and the main shaft 13a. Further, depending on the chucking accuracy when the end mill 30 is attached to the chuck portion 40, blurring (vibration) occurs between the end mill 30 and the chuck portion 40 when the end mill 30 rotates, and thereby the axis 30 a of the end mill 30. There is also a possibility that the shaft runout will occur. The same can be said for the connecting portion between the chuck portion 40 and the main shaft 13a. Due to such various causes, while the end mill 30 rotates, the axis 30a of the end mill 30 constantly vibrates in a plane perpendicular to the axis 30a. The edge position of the end mill 30 also changes due to the shaft runout (movement trajectory) of the shaft center 30a of the end mill 30.

Thus, it has been found that the edge position of the end mill 30 changes due to the shaft runout (movement locus) of the axis 30a of the end mill 30. However, as described above, the edge position of the end mill 30 changes due to the cross-sectional shape of the measurement reference plane S. Therefore, the shaft runout (movement) of the axis 30a of the end mill 30 is determined from the measured amount of edge light. In order to extract only the information of the trajectory of () , it is necessary to extract a component due to the cross-sectional shape on the measurement reference plane S of the end mill 30 and remove it. Here, the cross-sectional shape extracted in the measurement of the amount of edge light is different from the actual cross-sectional shape, and in the present application, this is called a virtual cross-sectional shape.

  Next, the relationship between the virtual cross-sectional shape and the real cross-sectional shape will be described by taking two measured objects 401 and 402 having a real cross-sectional shape as shown in FIG. 6 as an example. The DUT 401 has a substantially star-shaped actual cross-sectional shape, and includes five convex portions 401a that are equally disposed in the circumferential direction and five concave portions 401b that are respectively disposed between the convex portions. The DUT 402 has five convex portions 402a formed at the same height as the convex portion 401a and five concave portions 402b formed deeper than the concave portion 401b.

  Here, although the measured objects 401 and 402 have completely different actual cross-sectional shapes, the measured amounts of edge light are measured for the measured objects 401 and 402, and the measured object 401 is measured by a three-point method described later. , 402, the virtual sectional shape 403 having five convex portions 403 a and five concave portions 403 b arranged between the convex portions 403 a is obtained in any case. That is, here, when the actual cross-sectional shape of the measured objects 401 and 402 is compared with the virtual cross-sectional shape 403, the height of the convex portion 403a of the virtual cross-sectional shape 403 is the same as the height of the convex portions 401a and 402a of the real cross-sectional shape. However, the depth of the recess 403b of the virtual cross-sectional shape 403 is shallower than the recesses 401b and 402b of the actual cross-sectional shape. In other words, the virtual cross-sectional shape 403 reproduces the height of the convex portion of the real cross-sectional shape, but does not reproduce the depth of the concave portion. Therefore, when the object to be measured has a convex part that is long in the radial direction and a concave part that is shorter in the radial direction than the convex part, the edge position of the measured object is easily affected by the convex part, but the influence of the concave part Is difficult to receive.

  Next, a three-point method used when extracting a virtual cross-sectional shape from data obtained by measuring the amount of edge light will be described. As shown in FIG. 3, the origin O is set so that the distances from all the optical axes are equal for the laser beams 121a emitted from the three laser light emitting sections 121. Further, the x-axis and the y-axis are set so that the displacement direction of the edge light is zero for one of the three photodiodes 122. Then, it is assumed that the remaining two photodiodes 122 are arranged at angles of φ [rad] and ψ [rad], respectively. At this time, the virtual cross-sectional shape of the object to be measured, the vibration component in the x-axis direction of the object to be measured, and the vibration component in the y-axis direction are respectively R (θ) and x (θ) as an angle θ from the x-axis. , Y (θ), the outputs Sa, Sb, and Sc of the three photodiodes 122 are expressed as Equation 1.

  Here, variable transformation is performed as Φ = φ + π / 2 and ψ = ψ + π / 2, and the function S (θ) is defined as in Equation 2. At this time, if constants a, b, Φ, and Ψ are selected so as to satisfy Formula 3, the function S (θ) is expressed as Formula 4.

Further, the virtual cross-sectional shape R (θ) is expanded in Fourier series with the number of peaks as k as in Equation 5, and constants α _k and β _k are defined as in Equation 6. Substituting these into Equation 4, the function S (θ) can be expressed as Equation 7.

As shown in Equation 2, S (θ) can be derived from the outputs of the three photodiodes 122. The Fourier coefficients A _k and B _k of the virtual cross-sectional shape R (θ) can be determined by Fourier transforming this and comparing the coefficients of the respective orders with the mathematical formula 7, and the virtual cross-sectional shape R ( θ) can be obtained. If the virtual cross-sectional shape R (θ) is determined, the vibration component x (θ) in the x direction and the vibration component y (θ) in the y direction can also be obtained from Equation 1. In this manner, the virtual cross-sectional shape R (θ), the vibration component x (θ) in the x direction, and the vibration component y (θ) in the y direction are extracted from the measured outputs from the three photodiodes 122, respectively. Can do.

As described above, the inventor of the present application measures the light amount of the edge light and extracts the virtual cross-sectional shape R (θ) different from the actual cross-sectional shape, so that the trajectory (x (θ ), Y (θ)) was found. Next, on the basis of this knowledge, in order to confirm that the trajectory of the axial center of the end mill 30 and the magnitude of the axial runout can be actually obtained, the measurement of the axial runout of the axial center 30a of the end mill 30 described above is performed. A simulation was performed.

  In this simulation, the data sampling rate was 512 times per revolution. The three photodiodes 122 were arranged at an angle of φ = 149.8 ° and ψ = 210.23 °.

FIGS. 7A and 7B show simulation results. Here, as shown in FIG. 7A, the motion trajectory 233 of the axis 30a of the end mill 30 obtained by the simulation and the motion trajectory 234 given to the end mill 30 in this simulation are very good. The standard deviation was found to be 0.0058 μm. From this, it was found that the method of measuring the shaft runout of the shaft center 30a of the end mill 30 based on the above-described method (the method of measuring the motion track of the shaft center ) is effective.

As shown in FIG. 7B, the virtual cross-sectional shape 232 of the end mill 30 extracted in this simulation is different from the real cross-sectional shape 231 . In particular, partial solid cross-section shape 231, the outer peripheral edge 34a of the end mill 30, respectively corresponding to the tip of 34b, the tip 232a of the convex portion of the virtual cross section 232, but overlap the 232b, the recessed actual cross-sectional shape 231 It does not overlap the virtual cross section 232 at. It can also be seen that even if the actual cross-sectional shape has an acute shape such as the vicinity of the tip of the convex portion, the virtual cross-sectional shape 232 is reflected as a gentle shape.

The fact that the actual cross-sectional shape 231 overlaps the tips 232a and 232b of the convex portions of the virtual cross-sectional shape 232, but does not overlap the depressed portion of the real cross-sectional shape 231 is, as described above, the amount of edge light. This corresponds to the fact that the virtual cross-sectional shape extracted by this measurement is easily affected by the convex portion of the object to be measured, but is not easily affected by the concave portion. Conversely, a virtual cross section 232 that is extracted by measuring the amount of edge light, an outer peripheral edge 34a of the end mill 30, since it faithfully reproduces the height of the tip of 34b, the virtual cross-section 232, The amount of wear of the outer peripheral blades 34a and 34b of the end mill 30 can be determined by accurately determining the height of the portion corresponding to the tips of the outer peripheral blades 34a and 34b.

  Here, as shown in FIG. 8, when the heights of the tips of the outer peripheral blades 34a and 34b of the end mill 30 are gradually lowered, the same simulation as described above is performed, and the tips of the outer peripheral blades 34a and 34b of the end mill 30 are The correlation between the height and the height of the tips of the outer peripheral blades 34a and 34b obtained from the virtual cross-sectional shape obtained as a result of the simulation was obtained. As shown in FIG. 9, the heights of the tips of the outer peripheral blades 34 a and 34 b obtained from the virtual cross-sectional shape are substantially the same as the heights of the tips of the outer peripheral blades 34 a and 34 b of the actual end mill 30. I understood. Thus, it was found that the wear amount of the outer peripheral blades 34a and 34b of the end mill 30 can be obtained from the height of the portion of the virtual cross-sectional shape 232 corresponding to the tips of the outer peripheral blades 34a and 34b.

Note that, as described above, in FIG. 7B, even if the actual cross-sectional shape has an acute shape such as the vicinity of the tip of the convex portion, the virtual cross-sectional shape 232 is reflected as a gentle shape. Is considered to correspond to the fact that the virtual cross-sectional shape 232 (R (θ)) does not contain many high-frequency components. In order to confirm this, as shown in FIG. 10, the magnitudes of the coefficients A _k and B _{k in} the number of peaks when the actual cross-sectional shape 231 is Fourier-expanded and the number of peaks when the virtual cross-sectional shape 232 is Fourier-expanded The coefficients A _k and B _k were compared with each other. Even if it sees, it turns out that the virtual cross-sectional shape 232 (R ((theta))) has few high frequency components compared with the real cross-sectional shape 231. FIG. From this, it was found that when extracting the virtual cross-sectional shape 232, it is not necessary to have a large number of peaks, and about 256 samplings per rotation are sufficient.

Second Embodiment
Next, a second embodiment of the present invention will be described. Here, this embodiment is the same as the first embodiment except that a four-blade end mill 430 is used as a measurement object instead of the two-blade end mill 30 in the first embodiment. In the description, only differences from the first embodiment will be described.

  As shown in FIG. 11 (a), the actual cross-sectional shape 431 on the measurement reference plane S of the four-blade end mill has four convex portions 431a to 431d corresponding to the four outer peripheral blades of the four-blade end mill. . A simulation similar to that described above was performed using such a four-blade end mill as a measurement target, and a virtual cross-sectional shape 432 was extracted. When the virtual sectional shape 432 and the actual sectional shape 431 are compared, it can be seen that the portions corresponding to the four convex portions 431a to 431d are very well matched. Further, as in the case of the first embodiment, it can be seen that the virtual cross-sectional shape 432 is a gentle shape with less unevenness (the depth of the recessed portion is shallower) than the actual cross-sectional shape 431.

Also, as shown in FIG. 11B, the locus 433 of the axial center of the four-blade end mill obtained from the simulation and the locus 434 of the movement given to the end mill in this simulation are very good. The standard deviation was found to be 0.0071 μm. For this reason, the shaft runout measurement method ( measurement method of the movement of the shaft center) based on the above-described method is effective even for an object having a complicated shape such as a 4-flute end mill. I understood.

  In the embodiment described above, a two-blade, four-blade end mill has been measured. Here, the cross-sectional shapes of the two-blade and four-blade end mills are 180 ° symmetrical and 90 ° symmetrical, respectively, but the present invention is not limited to this. The cross-sectional shape of a rotating body such as a cutting tool to be measured according to the present invention may be a rotationally symmetric shape at an arbitrary angle, or may be a shape that is not rotationally symmetric. In addition, the cutting tool to be measured in the present invention is not limited to an end mill, and can be applied to a cutting tool having an arbitrary shape such as a drill, a reamer, or a face mill.

  In the above-described embodiment, the optical measurement system for measuring the amount of edge light has been described by taking the laser light emitting unit and the photodiode that irradiate the laser light as examples. However, the present invention is not limited to this. As long as it is a light emitting device that can irradiate a predetermined region with parallel light with a stable output and a light amount measuring device that can measure the light amount of the irradiated light, optical measurement having an arbitrary light emitting device and light amount measuring device A system may be used. In addition, for example, an LED device with high directivity can be used instead of the laser light emitting unit. Further, a CCD or the like may be used instead of the photodiode. The number of optical measurement systems may be at least three. In the embodiment described above, one end of the cutting tool is irradiated with laser light, and the amount of edge light at the end is measured. However, the present invention is not limited to this. For example, a laser beam wider than the width of the cutting tool (the length in the direction perpendicular to the optical axis of the laser beam) is irradiated, and cutting is performed using a two-divided photodiode. You may measure the light quantity of edge light simultaneously in the both ends of the tool width direction. At this time, when the cutting tool is displaced in one direction, the light quantity of one of the two divided photodiodes increases and the light quantity of the other decreases, so that the measurement sensitivity can be improved.

In the above embodiment, a rotating cutting tool is a measurement object, and the cross-sectional diameter of the measurement reference plane is about 10 mm to several tens of mm. However, the present invention is not limited to a thin rod-shaped rotating body such as a cutting tool, and can be applied to measure axial runout in a rotating body of any size and arbitrary shape. For example, the present invention can also be applied to measuring the axial runout of a large rotating body having a cross-sectional diameter of about several tens of centimeters to several meters, such as a propeller. Note that, as in the case where the measurement target is a relatively large rotating body, a part of the laser light emitted from one of the laser emission units may be scattered by the rotating body and enter another set of photodiodes. In the case where there is no laser beam, it is not always necessary to set the wavelength of the laser light emitted from each laser light emitting unit to a different wavelength, and a laser light emitting unit that emits laser light having the same wavelength may be used. Alternatively, the present invention can also be applied to a lathe that performs cutting by rotating at high speed while holding a workpiece and abutting against a fixed cutting tool. In this case, by measuring the amount of edge light with respect to the workpiece, not the cutting tool, by the same method as described above, it is possible to extract the movement locus and the shaft runout of the rotation center of the workpiece. Moreover, the cross-sectional shape on the measurement reference plane of the rotating body to be measured may be an arbitrary shape, and is not necessarily in the radial direction, like the two-blade and four-flute end mills exemplified in the above embodiment. A sharp notch may not be formed. For example, the rotating body to be measured may have a circular cross-sectional shape on the measurement reference plane. Even in this case, the actual cross-sectional shape on the measurement reference plane of the rotating body to be measured is not a perfect circle, but has irregularities due to the work accuracy. At this time, the virtual cross-sectional shape obtained by measuring the edge light as described above is a shape different from the real cross-sectional shape, and specifically, extracted as a gentle shape having a shallower depth of the recess than the real cross-sectional shape. Is done.

Even if a rotating body having a complicated shape is rotating at a high speed of several thousand rpm or more, the motion trajectory and axial runout of the rotating shaft center are measured with high accuracy (for example, accuracy of 1 μm or less). Can do.

1 Axis run-out measurement system 10 Milling machine 13a Spindle 30 End mill 110 Control unit 120 Optical measurement system

Claims (6)

A method for measuring a trajectory of a rotation axis of a rotating body having irregularities ,
Attaching the rotating body to a main shaft rotatably provided at a predetermined rotation speed;
Disposing three sets of light emitting units and light receiving units facing each other across a part of the rotating body in a vertical plane perpendicular to the rotational axis of the rotating body;
While rotating the rotating body integrally with the main shaft at the predetermined rotation speed, light is irradiated from the light emitting units toward the light receiving units, and the light is blocked by the rotating body. Without measuring the amount of edge light received by each light receiving unit without,
The virtual cross section the depth of the recess compared to the cross-sectional shape of the vertical surface is a shallow gentle shape of the rotating body, based the on light intensity of the edge light measured by the light receiving portion by the edge light and asked Mel,
Obtaining a trajectory of movement in the vertical plane of the rotation axis of the rotating body based on the light quantity of the edge light and the virtual cross-sectional shape.   The method according to claim 1, wherein the rotating body is a cutting tool having a cutting edge portion formed on a surface around a rotation axis.   The method according to claim 1, wherein the light emitting unit is a laser irradiation apparatus that irradiates laser light, and the light receiving unit is a photodiode. The cross-sectional shape of the vertical surface of the rotating body has a first convex portion having the longest distance from the rotational axis,
The virtual cross-sectional shape has a second convex portion corresponding to the first convex portion,
The method according to any one of claims 1 to 3, wherein a distance between the rotation axis and the first protrusion is the same as a distance between the rotation axis and the second protrusion. The cross-sectional shape of the vertical surface of the rotating body has a first recess having a shortest distance from the rotation axis,
The virtual cross-sectional shape has a second recess corresponding to the first recess,
The method according to claim 4, wherein a distance between the rotation axis and the second recess is longer than a distance between the rotation axis and the first recess. A measurement system for measuring a trajectory of a rotation axis of a rotating body having irregularities ,
A main shaft having a main shaft extending in a predetermined axial direction and provided with a fixing portion for fixing the rotating body at one end, and a motor connected to the other end of the main shaft and rotating the main shaft about the shaft Head,
A set of three light emitting units and a light receiving unit disposed so as to face each other across a part of the rotating body in a vertical plane perpendicular to the rotation axis of the rotating body;
While rotating the rotating body integrally with the main shaft at the predetermined rotation speed, light is irradiated from the light emitting units toward the light receiving units, and the light is blocked by the rotating body. The virtual cross-sectional shape in which the amount of edge light received by each of the light-receiving units is measured without being reduced, and the concave portion has a shallower depth than the cross-sectional shape of the vertical surface of the rotating body by the edge light. , it said with determined Mel based on the amount of the light receiving portion and the edge light measured by, on the basis of the edge light quantity and the virtual cross-section, the rotating body the rotation axis of the vertical plane of the And a control unit for obtaining a trajectory of movement in the measurement system.

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