JP3025413B2 - Method and apparatus for measuring contour shape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour shape for tracing the contour of a work with a stylus and detecting the displacement of the stylus at that time to obtain a contour shape including the surface roughness and undulation of the work. The present invention relates to a measuring method and an apparatus therefor. A surface roughness measuring device is known as a measuring device for measuring the surface roughness and undulation of a work, and a contour shape measuring device is known as a measuring device for measuring the contour shape of a work. The contour shape includes the contour shape.

[0002]

2. Description of the Related Art Since a surface roughness measuring instrument and a contour measuring instrument have the same basic configuration, the contour measuring instrument will be described here as an example. As shown in FIG. 7, a measuring unit 10 of a general contour shape measuring machine is provided with a horizontal feeder 13 on a column 12 erected on a base 11, and has a stylus 15, ) Detector 14 for detecting displacement in direction
Are provided on the horizontal feeder 13 so as to be movable in the horizontal (X) direction. The horizontal feeder 13 has a built-in scale for detecting the amount of movement of the detector 14 in the horizontal direction. Accordingly, when the detector 14 is moved in the X direction while the stylus 15 is in contact with the measurement position of the workpiece W, the vertical displacement of the stylus 15 is detected by the detector 14, and the horizontal movement of the detector 14 is detected. The amount of movement in the direction is detected by the scale of the horizontal feeder 13, and measurement data of the workpiece is obtained. The measurement data of the work is calculated by a data processing device (not shown), and a contour shape including the surface roughness and waviness of the work (hereinafter referred to as “work contour shape”) is output.

In this case, as shown in FIG. 5, a work measurement trajectory 34, which is a trajectory of a specific portion (reference point 15b) near the tip of the stylus 15, is obtained from the measurement data of the work. The shape 15a of the tip of the stylus in contact with the workpiece is not a “point” but an arc of a certain size, so that the workpiece measurement trajectory 34 does not match the contour Wa of the workpiece. Therefore, the stylus 1 represented by a virtual line on the right side of FIG.
As shown in FIG. 5, in the data processing device, the workpiece measurement trajectory 3
The arc radius S of the stylus tip shape 15a for each normal direction 4
Only by moving the workpiece measurement trajectory 34 in the normal direction,
The work outline shape is assumed.

[0004]

However, the stylus tip shape 15a is not a perfect circle, the radius S differs depending on the position, the normal direction of the point where the stylus 15 contacts the work, and the work measurement trajectory at that time. 34 is different from the normal direction. Therefore, the work contour shape 36 obtained by correcting the work measurement trajectory 34 does not match the work contour Wa.
In particular, when the tip of the stylus 15 becomes worn, the tendency becomes remarkable. Therefore, in order to improve the measurement accuracy, the stylus tip shape 15a is processed with high accuracy, and
5 has to be replaced, and there is a problem that the measurement cost is high.

The present invention has been made in view of such circumstances, and in a method and an apparatus for measuring a contour including a surface roughness and undulation of a workpiece, the tip 15a of a stylus is different from a perfect circle. Can measure with high accuracy,
An object of the present invention is to provide a method and an apparatus for measuring a contour shape in which it is not necessary to process the stylus 15 with high precision or replace it frequently.

[0006]

In order to achieve the above object, the present invention provides a method for measuring a contour shape, comprising the steps of: (a) measuring a knife edge or a reference gauge 17 on which a perfect circle of a known radius is formed; 15 stylus tip shapes 15
a is calculated, and a correction value δ is calculated for each normal direction of the stylus tip shape 15a. (B) Work is measured to obtain a work measurement trajectory 34 which is a trajectory of a stylus, and for each normal direction of the work measurement trajectory 34,
The work measurement trajectory 34 is corrected using the correction value δ, and the work outline shape 35 is calculated. I did it as above.

[0007] Further, the contour shape measuring device is provided with (a) a stylus 1
The measuring section 10 detects workpiece measurement data by tracing the contour of the workpiece at 5 and detecting the displacement of the stylus 15 at that time, and (b) a reference on which a knife edge or a perfect circle of a known radius is formed. A gauge 17; and (c) a correction value calculating unit 21 for measuring the reference gauge 17 to obtain a stylus tip shape 15a of the stylus 15 and calculating a correction value δ for each normal direction of the stylus tip shape 15a. (D) Calculated correction value δ
And a correction value storage unit 22 for storing the workpiece measurement trajectory 34, which is the trajectory of the stylus 15, from the measurement data of the workpiece detected by measuring the workpiece. The workpiece measurement trajectory 34 is corrected using the stored correction value δ,
, An output unit 24 that outputs the calculated work contour shape 35, and (g) the operator corrects the measurement content of the reference gauge 17 or the work. And an input unit 25 for instructing the value calculation unit 21 and the contour shape calculation unit 23.

[0008]

According to the present invention, since the stylus tip shape 15a of the stylus 15 can be obtained by measuring the reference gauge 17, a correction value δ is calculated from this for each normal direction of the stylus tip shape 15a. The correction value δ is the tangential distance P and the normal direction distance Q between each point on the stylus tip shape 15a and the reference point 15b set near the tip of the stylus 15. Next, for each normal direction of the workpiece measurement trajectory 34 obtained by measuring the workpiece, the workpiece measurement trajectory 34 is moved and corrected by P in the tangential direction and Q in the normal direction to obtain a workpiece contour shape 35. .

[0009]

FIG. 2 is a block diagram showing the configuration of an embodiment of a contour shape measuring apparatus according to the present invention. In FIG. 2, the measuring unit 10 is the same as that described in the related art (shown in FIG. 7). The correction value calculation unit 21 is a reference gauge 17
Is calculated for each normal direction of the stylus tip shape 15a from the stylus tip shape 15a of the stylus 15 obtained by measuring. The correction value storage unit 22 stores the calculated correction value δ. The contour shape calculation unit 23 obtains a work measurement trajectory 34 which is a trajectory of the stylus 15 from measurement data of the work detected by measuring the work, and uses a correction value δ for each normal direction of the work measurement trajectory 34. Work measurement trajectory 34
Is corrected, and the workpiece contour shape 35 is calculated. Output unit 2
4 displays the calculated work contour shape 35 on a CRT or outputs it to an XY plotter. The input unit 25 is used by the operator to instruct the correction value calculation unit 21 and the contour shape calculation unit 23 about the measurement of the reference gauge 17 or the measurement of the work, or the content of the measurement.

FIG. 1 shows a flowchart of an embodiment of a contour shape measuring method according to the present invention. First, the operator indicates from the input unit 25 that measurement of the reference gauge 17 is to be performed (step 41), and the measurement unit 10 measures the reference gauge 17 (step 42). The stylus tip shape 15a is required, and the stylus tip shape 1
The correction value δ is calculated for each normal direction of 5a, and the correction value δ
Is stored in the correction value storage unit 22 (step 43). Next, the operator instructs the measurement of the work from the input unit 25 (step 44), and measures the work by the measuring unit 10 (step 45), whereby measurement data of the work is obtained.
The contour shape calculation unit 23 calculates the stylus 15 from the work measurement data.
The work measurement trajectory 34 which is the trajectory of the work measurement trajectory is obtained, and the work measurement trajectory 34 is corrected using the correction value δ for each normal direction of the work measurement trajectory 34 to calculate the work contour shape 35 (step 46). Then, the measurement result is output from the output unit 24 (step 47).

Next, a method of calculating the correction value δ of the stylus tip shape 15a will be described. FIG. 3 shows the stylus 15 and the reference gauge 1.
7 shows a contact state. In FIG. 3, reference gauge 1
7 has a knife edge 17a at the tip. The reference point 15b is a calculated point set near the tip of the stylus 15. θ is the contact 15c between the stylus 15 and the reference gauge 17
Is a tangential distance between the contact point 15c and the reference point 15b, and Q is a tangential distance between the contact point 15c and the reference point 15b.
5b with respect to the normal direction. L is the contact 15c
M is the distance in the Z direction between the contact point 15c and the reference point 15b, M is the measured value detected by the detector 14, and L is the horizontal movement of the detector 14. It corresponds to the measured value detected on the scale as a quantity.

Accordingly, the normal angle θ, the tangential distance P, and the normal distance Q are calculated from the measured values L and M according to the following equations. However, in this equation, the reference point 15b is the origin in the X direction, the right side of the reference point 15b is minus, and the left side is plus. tan (90−θ) = dM / dL (dM / dL is a value obtained by differentiating M with L) P = L sin θ−M cos θ Q ² = L ² + M ² −P ²

When the correction value δ is represented by a vector having a magnitude of R and a direction of α, R and α are calculated by the following equations. tan (θ−α) = P / Q R ² = L ² + M ²

Note that, as shown in FIG.
Is measured (in the range of about 120 degrees in angle), reference gauge measurement data 31 is obtained. However, since the reference gauge measurement data 31 is a shape 32 obtained by inverting the stylus tip shape 15a, the reference gauge measurement data 31 is inverted. By doing so, the stylus tip shape 15a is obtained. In this case, although the reference gauge measurement data 31 includes the shape of the knife edge 17a of the reference gauge 17, the size of the knife edge 17a is extremely small (when viewed as an arc shape, the radius is 0.5 μm).
m), the radius of the stylus tip shape 15a (2
(About 5 μm), which is negligible in size, and a shape 32 obtained by inverting the stylus measurement data 31 and a stylus tip shape 15 a
And almost match.

The reference gauge 17 is a knife edge 17.
Instead of a, a perfect circle having a known radius may be formed.
In this case, when the reference gauge 17 is measured (in the range of about 120 degrees in angle), the reference gauge measurement data 33 shown in FIG.
Is obtained, but if the reference gauge measurement data 33 is corrected in the normal direction by the radius r of a perfect circle, the reference gauge measurement data 3
Since the same reference gauge measurement data as that of No. 1 is obtained, the stylus tip shape 15a can be obtained in the same manner as in the case of the reference gauge 17 having the knife edge 17a.

FIG. 5 shows an example in which the workpiece measurement trajectory is corrected using the correction value δ of the stylus tip shape 15a thus obtained.
Shown in In FIG. 5, Wa is the contour of the work, and the stylus 1
5 is in contact with the contour Wa of the work at the contact point 15d. When the stylus 15 moves in the X direction in such a state, a work measurement trajectory 34 which is a trajectory of the reference point 15b is obtained. The work measurement trajectory 34 is calculated by correcting an error in the detection mechanism from the work measurement data. Next, for each normal angle θ of the obtained work measurement trajectory 34, the correction value δ of the stylus tip shape 15a corresponding to the same normal angle θ is called from the correction value storage unit 22 and moved by R in the α direction. I do. The locus of the moved reference point 15b becomes the workpiece contour shape 35.

In this case, strictly speaking, as shown in FIG. 6, the normal angle θo at the contact point 15d where the tip of the stylus 15 is in contact with the contour Wa of the work, and the work measurement trajectory 34 at that time. Does not always coincide with the normal angle θ of the reference point 15b. Therefore, the contact 15d is originally required.
The correction value δ based on the normal angle θ in the workpiece measurement trajectory 34 is used in the place where the correction value δo based on the normal angle θo should be used.
The contact point 15e is used instead of 5d, and an error occurs. However, when the contour Wa of the workpiece is a smooth continuous shape, the difference between the normal angle θo and the normal angle θ is so small as to be negligible, so that the above-mentioned error does not become a value that causes a problem in measurement accuracy. Therefore, in FIG. 5, the calculated work outline shape 35 and the work outline Wa are shown in agreement.

FIG. 5 also shows, for comparison, a workpiece contour shape 36 obtained by the above-described conventional correction method. The more the stylus tip shape 15a deviates from a perfect circle, the more the calculated workpiece shape. It can be seen that the contour shape 36 deviates from the contour Wa of the work.

In the embodiment, the case where the surface roughness and the contour shape including the waviness are measured by the surface roughness measuring device and the contour shape measuring device has been described. However, the present invention is not limited to this. The present invention can be applied to correct the tip shape of the probe of the displacement probe even when measuring the contour shape of the workpiece with a coordinate measuring machine equipped with an electronic probe capable of measurement).

[0020]

As described above, according to the present invention, a contour shape measuring method for determining a contour shape including surface roughness and waviness of a work is provided by a reference gauge 17 having a knife edge or a perfect circle of a known radius. And measure the stylus tip shape 15
a, a correction value δ is calculated for each normal direction of the stylus tip shape 15a, and a workpiece measurement trajectory is calculated using the correction value δ for each normal direction of the workpiece measurement trajectory 34 obtained by measuring the workpiece. 34 is corrected, and the workpiece contour shape 35 is calculated. Accordingly, it is possible to provide a contour shape measuring method and a contour shape measuring method which can perform measurement with high accuracy even when the stylus tip shape 15a is different from a perfect circle, and does not need to process the stylus 15 with high accuracy or frequently replace it. it can.

[Brief description of the drawings]

FIG. 1 is a flowchart of an embodiment of a contour shape measuring method according to the present invention.

FIG. 2 is a block diagram of an embodiment of a contour shape measuring apparatus according to the present invention.

FIG. 3 is an explanatory diagram of a calculation method of a correction value of a stylus tip shape according to the present invention.

FIG. 4 is an explanatory diagram of a method for obtaining a stylus tip shape according to the present invention.

FIG. 5 is an explanatory diagram of an example of a workpiece measurement trajectory correction according to the present invention and an example of a conventional workpiece measurement trajectory correction.

FIG. 6 is a supplementary explanatory diagram of an example of correcting a workpiece measurement trajectory according to the present invention.

FIG. 7 is an explanatory view of a measuring section of a general contour shape measuring instrument.

[Explanation of symbols]

 41: Reference gauge measurement instruction step 42: Reference gauge measurement step 43: Correction value calculation / storage step 44: Workpiece measurement instruction step 45: Workpiece measurement step 46: Contour shape calculation step 47: Output of measurement results Steps

Claims (2)

(57) [Claims] 1. A contour of the workpiece traced by a stylus, by detecting the displacement of the stylus at that time, the contour shape measuring method for determining a contour shape including a surface roughness and waviness of the workpiece, the knife edge The reference gauge on which the stylus is formed is measured to determine the stylus tip shape of the stylus, a correction value is calculated for each normal direction in a range of approximately 120 ° of the stylus tip shape, and the workpiece is measured and A work measurement trajectory which is a trajectory of a stylus is obtained, and the work measurement trajectory is corrected using the correction value for each normal direction of the work measurement trajectory, and a contour shape including surface roughness and undulation of the work is calculated. A contour shape measuring method. 2. A measuring section for tracing a contour of a work with a stylus and detecting a displacement of the stylus at that time to detect measurement data of the work; a reference gauge having a knife edge formed therein; from stylus tip shape of the probe obtained by measuring the reference gauge by the measuring unit, a correction value calculation unit for calculating a correction value for each <br/> normal direction about the substantially 120 DEG A correction value storage unit that stores the calculated correction value, and obtains a work measurement trajectory that is the trajectory of the stylus from the measured measurement data of the work, and for each normal direction of the work measurement trajectory, A contour shape calculation unit that corrects the workpiece measurement trajectory using the stored correction value to calculate a contour shape including the surface roughness and undulation of the workpiece; and calculates the calculated surface roughness and undulation of the workpiece. Contours included An output unit for outputting a shape, and an input unit for instructing the correction value calculation unit and the contour shape calculation unit by the operator about measurement of the reference gauge, measurement of the work, or measurement contents. Characteristic contour shape measurement device.