JP2006242605A - Method for measuring runout of rotating tool and its measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately measure runout of cutting edges of rotary tools since runout of rotary tools rotating at high speed cause accuracy degradation in machining shape and correct the runout. <P>SOLUTION: A light source module; the center of a cutting edge of a rotary tool; two lenses having a confocal point; and an imaging element are sequentially arranged on one common optical axis. The center of a ball of the cutting edge is arranged at the focal point on the side of the light source module among other two focal points of the lenses, the imaging element is arranged at the other focal point, and an anti-pinhole filter is arranged at the confocal point. Electric signals acquired by the imaging element are introduced to a personal computer to improve clarity of edge images of the cutting edge. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to precise measurement of runout of a rotary tool in precision machining using a rotary tool, and an object thereof is to suppress runout based on the measurement result of the runout.

Precise machining using a rotary tool is generally performed, but if there is runout due to eccentric error or chucking error of the rotary tool, it will cause deterioration in machining shape accuracy and tool life, etc. It is an obstacle to processing.
In response to this problem, for example, in Japanese Patent Laid-Open No. 10-141934, the shape accuracy and runout of the cutting edge of the ball end mill are obtained by non-contact measurement using laser light with reference to the motion accuracy of the processing machine. However, this method has problems such as time-consuming measurement and sequential measurement, and the measurement accuracy depends on the processing machine accuracy.

In Japanese Patent Laid-Open No. 2002-205246, a point on a cutting edge ridge line of a ball end mill is measured to detect a radius accuracy, and this measurement method can also be applied to the shake measurement aimed at by the present invention. However, this measuring method also has a problem that it takes time to measure with high accuracy because of sequential measurement, as in JP-A-10-141934. In addition to the above, many methods have been proposed in which the laser beam is irradiated onto the rotary tool, and the fluctuations in the position of the rotary tool accompanying the rotation are measured one by one to obtain the deflection.

However, in these conventional shake measurement methods using laser light, the coherence of the laser light is very good, so that the cutting edge ridge is caused by the mutual interference between the diffracted light generated at the cutting edge of the rotary tool and the transmitted light. There is a problem that the boundary of the image is unclear and the identification accuracy is lowered.
In addition, when the discriminating accuracy of the edge of the cutting edge is low as described above, when a severe machining shape accuracy such as micron or submicron is required, the runout of the one-rotating tool is measured and corrected, and two corrections are made. If the trial cutting using the rotary tool and the measurement and evaluation of the machining shape accuracy are not repeated many times, the required machining shape accuracy cannot be ensured.

  In particular, as the rotary tool becomes smaller in diameter and the machining shape accuracy becomes more severe, it is necessary to increase the measurement accuracy and correction accuracy of the cutting edge ridge runout of the rotary tool, which greatly increases the measurement of the machining shape accuracy and the correction of runout. Will have to spend a lot of time. Moreover, it is necessary to increase the rotation speed of the tool as the diameter of the rotating tool becomes smaller. However, there is a problem that the shape measurement of the cutting edge ridge becomes more difficult as the rotation speed becomes higher.

  The processed shapes targeted by the present invention are shown in FIG. 1, FIG. 2 and FIG. FIG. 1 shows a concave spherical surface 2 having a radius of curvature R and having a rotationally symmetric shape around a central axis 3. Further, the concave cylindrical surface 5 whose cross section shown in FIG. 2 is a part of the circle 6 and the concave elliptic cylindrical surface 7 which is a part of the ellipse 8 in FIG. When machining these concave spherical surface 2, concave cylindrical surface 5 or concave elliptic cylindrical surface 7, a ball end mill is used as a rotating tool.

  The AA cross section in FIG. 1 is shown in FIG. Here, the ball center Q ′ of the ball end mill having the ball radius R does not exist strictly on the rotational axis 4 of the tool due to the eccentricity of the cutting edge of the ball end mill or a chucking error. Have Here, if there is a distance from the rotation axis 4 of the tool to the ball center Q ′, that is, a tool runout ε, the ball end mill swings around the rotation axis 4. As a result, a concave spherical processed shape having a radius of curvature R ′ different from the design value R and a shape error Δe is obtained. In FIG. 4, these relationships are exaggerated for the sake of explanation. Similarly, the concave cylindrical surface 5 shown in FIG. 2 to the concave elliptic cylindrical surface 7 shown in FIG. 3 also have a problem that if the tool is shaken, a similar curvature radius error or shape error is caused.

As described above, in order to precisely process the concave spherical surface, the concave cylindrical surface, or the concave elliptical cylindrical surface, it is indispensable to measure the tool runout ε with high accuracy and correct the runout ε to 0 as much as possible. .
In order to cope with the above-mentioned problems, the object of the present invention is to measure the runout of the cutting edge of a rotating tool with high accuracy on the micron or submicron level in a wide rotational speed range from very low speed to several hundred thousand revolutions per minute. It is to provide a measurement method that can be used and to enable correction of runout of a cutting edge of a rotary tool.

By using a transmission optical system, the shape of the cutting edge ridge can be measured with high accuracy.

FIG. 9 is an explanatory diagram of the effect of the present invention.
The single-crystal diamond single-blade ball end mill 17 is chucked on the rotation axis 18 of the rotating tool of the inclined machining unit 39 of the portal jig boring machine 35 shown in FIG. 7, and the ball end mill rotates. FIG. 9 shows a micrograph of the processed surface of the workpiece 1 when the workpiece 1 is first cut by applying a down feed, then revolved to 180 ° around the main axis, and then retracted. FIG. 9A is a result of cutting without correcting the shake, and the shake is large.
1) It has a large diameter in the lateral direction, and 2) At the first 0 ° position and the 180 ° cutting end position, there is a marked radial boundary in the lower half.
That is confirmed.

Incidentally, the tool runout at this time was measured by the runout measuring apparatus of the present invention and found to be 70.5 μm. On the other hand, when the concave spherical shape in FIG. 9A is measured with a three-dimensional shape measuring instrument and the geometric processing shape error of the concave spherical surface is calculated based on the measurement data, the tool runout is about 70 μm. Thus, the measurement results obtained by the shake measuring device of the present invention are in good correspondence.

  Based on the measurement result of the runout, the runout of the tool was corrected to 1 μm or less by a self-revolving unit described in JP-A-2002-361510. The processing result cut in this state is shown in FIG. It is clear that the concave spherical surface does not have a boundary due to run-out, and the tool run-out is small. As described above, when the tool runout was calculated from the geometric processing shape error based on the measurement data of the three-dimensional shape of the concave spherical surface, it was confirmed that the runout was suppressed to 1 μm or less. .

  FIG. 10 shows the relationship between the run-out of the ball end mill measured using the run-out measuring device of the present invention and the rotational run-out obtained from the measurement data of the three-dimensional shape of the concave spherical surface cut by the ball end mill. Both show a very good linear relationship. By using the run-out measuring device, the run-out of the tool can be accurately measured to 1 μm or less, and a good concave spherical surface can be obtained by correcting the measured run-out. It is clear that can be processed.

In addition, it has been confirmed that, even in a single blade ball end mill with a radius of 0.5 mm rotating at 100,000 / min, the deflection measurement is possible by using the deflection measuring device.
As described above, by using the runout measurement apparatus of the present invention, it is possible to measure runout of a rotary tool even with a rotary tool that rotates at high speed. Further, by correcting the runout ε in the direction in which the runout ε decreases while viewing the visualized edge image as shown in FIG. 11, the runout of the rotary tool can be corrected.
In addition, when measuring shake using an anti-pinhole as described above, compared to when measuring shake using a diffraction image,
1) In the case of the former diffraction image, as shown in FIG. 12, a plurality of bright and dark stripes appear, and the edge image to be obtained is a disordered image in which it cannot be distinguished, whereas the latter anti-pinhole is used. In this case, as shown in FIG. 13, the fringes that wrap around inward are not observed, and the edge image is obtained as one line. In the case of the diffraction image, the interference fringes constituting the diffraction image are fringes. Since a sinusoidal luminance distribution is shown in the width direction, shape errors are likely to occur when binarizing or arc fitting after binarization. On the other hand, in the case of anti-pinholes, a sharp single edge image as shown in FIG. 11 is obtained, so that a measurement error is unlikely to occur. In the case of a diffraction image, a plurality of bright and dark images are provided as shown in FIG. Since stripes appear, when adjusting the tool displacement while viewing the visualized image of the tool, a plurality of light and dark stripes move with the tool so that the stripes are sucked into the tool edge or spring out as shown in FIG. Skill and feeling are required for fine adjustment. On the other hand, in the case of using anti-pinholes, a sharp single edge image as shown in FIG. 13 is obtained, so that it is easy to finely adjust the tool displacement and the amount of calculation for calculating runout is small. There are advantages such as.

  Insert an anti-pinhole filter that blocks the amount of 0th-order light into the incident optical system so that the transmitted light emitted from the light source does not reach the image sensor directly. A Fraunhofer image is obtained. Thereby, the discrimination accuracy of the boundary of the cutting edge of the rotary tool can be remarkably improved, and the runout of the cutting edge of the rotary tool can be obtained with high accuracy.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 5 shows an embodiment of the shake measuring device of the present invention, FIG. 6 is a diagram for explaining the principle thereof, and FIG. 7 is a portal jig boring machine equipped with the shake measuring device shown in FIG. A board 35 is shown.

  The shake measuring device includes a shake measuring unit 9, a light source module 11, and a personal computer 20. In the shake measurement unit 9, a light source module 11, a lens barrel module 13, and a detection module 14 are arranged on a base 10 in this order with a common optical axis 16, and these are covered with a cover 15 as a whole. ing. A window is opened in a part of the upper surface of the cover, and a ball end mill 17 to be measured passes through the window, and the ball center of the ball end mill is assembled so as to substantially coincide with the optical axis 16. It has been. Further, the detection end of the origin angle detector 19 is arranged close to the outer periphery of the ball end mill 17 and the other end is fixed to a stand standing on the base 10 to detect the origin of the ball end mill 17 in the rotation angle direction. It is possible.

The light source power source 12 is electrically connected to the light source module 11 and supplies power to the light source module. The image signal from the detection module 14 and the origin signal from the origin angle detector 19 are electrically connected to the personal computer 20.
FIG. 7 shows a case where the optical axis 16 of the shake measuring device is taken parallel to the X-axis direction of the portal jig boring machine 35, and the center of the ball of the ball end mill 17 described above is shown in FIG. The predetermined position of the measuring device is matched with NC control commands in the X-axis, Y-axis, and Z-axis directions of the portal jig boring machine 35.

Next, the measurement principle of the present invention will be described.
FIG. 6 shows an optical system in which key parts of the shake measurement unit 9 shown in FIG. 5 are arranged on a plane in order to explain the measurement principle of the present invention. A laser oscillator 21 and a lens group A built in the light source module 11, a lens B built in the lens barrel module 13, an anti-pinhole filter 25 and a lens C, and an image pickup device 26 built in one end of the detection module 14. In order, they are arranged on the optical axis 16 common to the laser light emitted from the laser oscillator 21. Here, the rear focal point 28 of the lens B coincides with the front focal point 28 ′ of the lens C, which is called confocal here. At this confocal position, an anti-pinhole filter 25 having a filter function for shielding the transmitted light 30 that has been focused on the rear focal point 28 through the lens B is disposed. The rear focal point 26 ′ of the lens C coincides with the detection surface of the image sensor 26. Further, the cutting edge ridge 27 of the ball end mill 17 to be measured is made to coincide with the front focal point 27 ′ of the lens B.

With the configuration of such an optical system, when the laser beam 31 emitted from the laser oscillator 21 is collimated through the lens group A and irradiated onto the cutting edge ridge 27 of the ball end mill 17, the cutting edge ridge is obtained. From 27, diffracted light 29 of various orders is generated. In addition, the transmitted light 30 of the 0th-order light component that passes through the portion of the laser light 31 away from the cutting edge ridge 27 is incident on the lens B as parallel light. Since the cutting edge ridge 27 coincides with the front focal point 27 ′ of the lens B, the transmitted light 30 and the diffracted light 29 passing through the periphery of the cutting edge ridge 27 are reflected by the lens B by the Fourier transform action of the lens B. At the rear focal point 28, it is resolved into spatial frequencies. That is, the transmitted light 30 is collected, but the diffracted light 29 is not collected. Since the anti-pinhole 25 that functions as a filter that blocks only the zero-order light component is provided at the position of the rear focal point 28 of the lens B, the collected transmitted light 30 is completely blocked.

On the other hand, the high-frequency component diffracted light 29 that has passed through the anti-pinhole 25 forms an image on the image sensor 26 disposed at the rear focal point 26 ′ of the lens C by the inverse Fourier transform action of the lens C. At this time, from the concentric interference image generated by the cutting edge ridge 27, only the first-order diffracted light of the interference image, that is, the edge image 32 giving the shape of the cutting edge ridge 27 is extracted by the anti-pinhole. With such an optical system configuration, the edge image 32 having a sharp boundary between the cutting edge ridges 27 of the ball end mill 17 can be identified with high accuracy without being affected by the interference image.

Next, how to obtain the maximum value of the deflection of the rotating cutting edge ridge 27 and the rotation angle at which the deflection becomes the maximum value will be described with reference to procedures 1 to 3.
An edge image 32 ′ detected at a certain time interval and an edge image 32 ″ at a rotation angle of 180 ° are extracted.
For the arc portions of the two edge images, base circles 41 ′ and 41 ″ that are best fitted by the least square method are obtained.
3 Find the distance between these two ball centers.
In this way, the distance between the ball centers for each fixed rotation angle is sequentially obtained in steps 1 to 3, and the value at which the distance between the ball centers becomes the maximum, that is, the shake and the rotation at which the shake becomes the maximum. Find the angle.

  Since the origin in the rotational direction of the ball end mill is detected by the origin angle detector 19, the rotational angle from the origin reaches the maximum value for the rotation angle to the edge images 32 ′ and 32 ″ where the maximum value of the shake is detected. It can be calculated from the rotation time of the rotating tool up to.

Here, the edge image obtained from the image sensor 26 is captured by a high-speed electronic shutter having a sampling rate of 1 μs or less, and the measurement error of shake due to digitization can be ignored.
Even when the sampling rate is slow, the maximum value of the shake is obtained by approximating the shake obtained at the sampling interval with a sine wave and interpolating the shake data based on the digital data of the intermittent edge image. Can be calculated.

FIG. 7 shows an example in which the run-out measuring device shown in FIG. 5 is mounted on the portal jig boring board 35. The shake measurement unit 9 is fixed to the X-axis table 36 so that the optical axis 16 is parallel to the X-axis direction.
On the other hand, an inclination machining unit 39 capable of alignment correction with an accuracy within 1 μm is coupled to the main shaft 37 of the portal jig boring machine 35 as described in JP-A-2002-361510. Revolution around 38 is possible. In addition, the inclined machining unit has a built-in tool rotation shaft 18 ′ having a rotation axis 18 of the tool inclined with respect to the main shaft axis 38 and capable of rotating, and one blade at one end of the tool rotation shaft. A ball end mill 17 having a cutting edge ridge 27 made of single crystal diamond is chucked, and minute alignment correction is possible in a direction perpendicular to the tool rotation axis 18 ′.

Here, a procedure for measuring and correcting the shake is shown in FIG.
First, the runout measurement unit 9 is installed on the X-axis table 36 of the portal jig boring board 35. Next, the ball center of the ball end mill 17 is aligned with the front focal point of the lens B on the optical axis of the shake measuring unit. Subsequently, the projected image and origin angle of the cutting edge of the rotary tool are taken into a personal computer. Based on the projection image data and the origin angle data, the rotation angle at which the shake is at a maximum value and the maximum shake value at that time are obtained by analysis, and the shake is zero at the obtained rotation angle position. Correct the shake.

  The concave cylindrical surface 5 in FIG. 2 can be processed by applying a feed to the rotary tool and portal jig boring machine that are the same as the processing of the concave spherical surface 2 shown in FIG. Further, the concave elliptic cylindrical surface 7 in FIG. 3 is arranged so that the rotational axis 4 of the tool in the feed direction in the set-up state between the rotary tool and the portal jig boring machine similar to the processing of the concave spherical surface shown in FIG. It can be processed by tilting and feeding it. This can be achieved, for example, by feeding a rotating tool that rotates in a state where the inclined machining unit attached to the main shaft of the portal type boring machine is rotated at a certain angle in the revolving direction. .

The present invention can be applied to a square end mill, a grindstone, or a drill instead of the ball end mill 17 as a rotating tool, and the same runout measurement and runout correction are possible.

Even if an encoder is used instead of the origin angle detector 19, it is possible to detect the rotation angle at which the maximum value of the shake is obtained, and the same effect can be obtained.

The run-out measuring apparatus of the present invention can be mounted not only on the portal jig boring machine 35 described above but also on a general-purpose milling machine, a multi-axis machine, a jig grinder, etc., and the same effects as described above can be obtained.

Example of concave spherical surface to be processed Example of concave cylindrical surface to be machined Example of concave elliptic cylinder surface to be machined Illustration of shape error due to runout of rotating tool The figure which shows one Example of the shake measuring apparatus of this invention Explanatory drawing showing the principle of the present invention FIG. 5 is an explanatory diagram of a gate-type jig boring machine equipped with the embodiment of FIG. Flow chart showing run-out measurement / correction procedure Comparison of concave spherical surfaces due to runout differences Explanatory drawing which shows the effect of this invention Visualized edge image example An example of an edge image disturbed by a diffraction image An example of a sharp edge image according to the present invention Explanatory drawing of the difficulty of adjusting the tool displacement due to the movement of light and dark stripes

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Workpiece 2 Concave spherical surface 3 Center axis of concave spherical surface 4 Rotation center 5 of a tool 5 Concave cylindrical surface 6 Circle 7 Concave elliptical cylindrical surface 8 Ellipse 9 Shaking measurement unit 10 Base 11 Light source module 12 Light source power supply 13 Lens barrel 14 Detection Module 15 Cover 16 Optical axis 17 Ball end mill 18 Rotating tool axis 18 ′ Tool rotating axis 19 Origin angle detector 20, 20 ′ PC 21 Laser oscillator 22 Lens group A
23 Lens B
24 Lens C
25 Anti-pinhole filter 26 Image sensor 26 ′ Rear focal point 27 of lens C Cutting edge ridge 27 ′ Front focal point 28 of lens B Rear focal point 28 ′ of lens B Front focal point 29 of lens C Diffracted light 30 Transmitted light 31 Laser light 32, 32 ′, 32 ″ edge image 35 portal jig boring machine 36 X-axis table 37 spindle 38 spindle axis 39 inclined machining unit 40 40 ′, 40 ″ interference fringe 41 41 ′, 41 ″ tool edge 42 Interference fringe movement 43 Interference fringe movement 44 seen by humans as an illusion 44 Tool movement

O The center of the projection circle of the concave sphere P The apparent center of curvature of the concave sphere with an eccentric error
Q Center of curvature of concave sphere Q ', Q "Tool ball center R Concentric radius of concave spherical surface R' Apparent radius of curvature of concave spherical surface with eccentric error ε Eccentricity of tool ball center with respect to tool rotation axis That is, the deflection Δe Shape error θ The inclination angle of the rotation axis in the cross section 42

Claims (2)

A light source module that emits parallel light, a lens barrel and an image sensor that share the optical axis and axis of the parallel light, and a microcomputer having an arithmetic processing function, and a rotation placed at a position that blocks the parallel light In a measurement system for measuring tool deflection, the lens barrel includes at least two lenses having a confocal and an anti-pin that shields the amount of 0th-order light out of incident light disposed in the vicinity of the confocal. The image sensor is composed of a Hall filter, the cutting edge of the rotary tool is disposed at the focal point on the light source module side of the remaining two focal points of these two lenses, and the other focal point is orthogonal to the optical axis. The two edge images showing the maximum shake at the rotational angle positions different from each other by taking in the electric signal of the edge image of the cutting edge ridge projected on the image sensor by the microcomputer From the difference, runout measuring method and measuring apparatus of the rotary tool, characterized in that to be able to calculate the deflection of the cutting edge ridge of the rotary tool The measuring system according to claim 1, further comprising an angle detector or an origin angle detector, wherein the rotational angle of the rotary tool can be detected.

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