JPH07294237A - Method for measuring profile of hole using three-dimensional measuring apparatus - Google Patents

Abstract

PURPOSE:To provide a method for measuring the profile of a hole using a three-dimensional measuring apparatus in which the profile of a hole can be measured accurately by determining the projection surface reliably at high rate. CONSTITUTION:The surface profile of a hole 32 in a predetermined surface 31 of a work 14 is measured by projecting a measuring point on the inner wall thereof onto a corresponding projection surface using a three-dimensional measuring apparatus with a touch probe. In such measuring method, the coordinate positions of two points A and B on the inner wall of the hole 32 are measured at a predetermined depth delta. Subsequently, the outer product (c) in two measuring directions (a) and (b) is determined in the measuring operation and a surface having a normal vector closest to the outer product (c) is determined as a projection surface 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the surface shape of a hole such as a circle or an ellipse on a predetermined surface of a work by using a coordinate measuring machine having a touch probe.

[0002]

2. Description of the Related Art When a work shape is measured by using a coordinate measuring machine having a touch probe, coordinate data of each surface of the work is obtained by a probe 50 as shown in FIG. The dimension calculation is performed on the basis of the workpiece coordinate system (x, y, z). However, as shown in FIG. 5, when measuring the surface shape of a hole 52 such as a circle or an ellipse that is perpendicular to the surface 51 on which the work is present, in principle, a hole is not formed on the surface 51 where the hole 52 is open. It is not possible to obtain the necessary coordinate data to calculate the shape.

Therefore, as shown in FIG. 6, the surface 51 of the hole 52 is
The coordinate data will be obtained from the inner wall which is deviated from the position of by δ. Even if the coordinate data of the three points A, B, and C are obtained, since the coordinate data has the deviation amount δ, the measurement points A, B, and C are projected on the projection surface 61 corresponding to the surface 51, It is necessary to perform the shape calculation (element calculation) after eliminating the deviation amount δ.

As a method of determining the projection plane 61, there is a method of designating the projection plane in advance before obtaining the coordinate data on the inner wall of the hole, but the coordinate data obtained by the measurement operation of the hole is used for projection. A method of automatically determining the surface has also been proposed. This is because, as shown in FIG. 6, when three measurement points A, B, and C are obtained, a plane including these measurement points is determined. Therefore, the plane is first calculated and its normal vector P is calculated.
Is obtained, and the surface having the normal vector closest to the normal vector P is determined as the projection surface.

[0005]

However, the conventional method described with reference to FIG. 6 requires the measurement data of three points to determine the projection plane. If the three points A, B, and C are at positions where the deviation amounts from the work surface 51 are different from each other as shown in FIG. 7, the normal vector P of the surface determined by the three points A, B, and C is As shown in the drawing, the projection plane having the closest normal vector to this may not correspond to the surface 51 of the workpiece actually required.

The present invention has been made in consideration of such circumstances, and the hole shape measurement using a coordinate measuring machine capable of obtaining the projection surface at high speed and reliably and accurately measuring the hole shape. It is intended to provide a way.

[0007]

According to the present invention, a three-dimensional measuring machine having a touch probe is used to determine the surface shape of a hole on a predetermined surface of a workpiece and the measurement point on the inner wall of the hole to correspond to the predetermined surface. And measuring the coordinate positions of two points on the inner wall of the hole, obtaining the outer products of the two measurement directions in the measurement operation, and determining the normal vector closest to the outer product. The feature is that the plane that has is obtained as the projection plane.

[0008]

According to the present invention, the determination of the projection plane used for the calculation of the element of a circle or an ellipse is performed based on the measurement data of two points in the hole, so that the conventional method requiring the measurement data of three points is used. Compared with this, a faster projection plane determination is possible. Also, 2
According to the method of the present invention for calculating the vector cross product of the measurement points of the measurement points, even if the depth positions (deviation amounts) of the two measurement points are different, they are not affected and the correct projection plane determination is made. You can

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of a coordinate measuring machine used in an embodiment of the present invention. Although the control drive unit is omitted in the coordinate measuring machine main body 11, it is possible to perform three-dimensional movement in the (X, Y, Z) coordinate system on the table 13. CMM main unit 1
A touch-type probe 12 is detachably provided at the tip of the workpiece 1, so that the three-dimensional coordinate value of the workpiece 14 placed on the table 13 is measured. The measured coordinate values are sent to the data processing device 15, where necessary data processing such as element calculation is performed, and the measurement result is displayed on the display device 16.

When measuring the shape of a circle or an ellipse opened perpendicularly to a surface of the work 14, a projection surface for element calculation is required as described above. The projection plane determination method in this embodiment is as follows. As shown in FIG. 3, the probe is inserted into the hole 32 formed in the surface 31 of the work 14 to a predetermined depth δ, and the coordinate values of two points A and B on the inner wall of the hole 32 are measured. The two measurement directions a and b in the coordinate measuring operation for moving the probe tip inserted into the hole 32 until it contacts the inner wall of the hole 32 are, for example, the directions perpendicular to the axis of the hole 32 and the angles formed by them. It may be selected so that θ does not become 0 ° or 180 °. These two measurement directions a and b are taken into the data processor 15 as input data for determining the projection plane.

In the data processor 15, first, the cross product of the two input measurement directions a and b is obtained. As shown in FIG. 3, the outer product c is represented by a vector that is perpendicular to both of these two measurement directions a and b. That is, if the angle θ formed by the two measurement directions a and b is not 0 ° or 180 °, one plane including these two measurement directions a and b is uniquely determined, and the outer product c is perpendicular to this plane. become.
Then, the surface having the normal vector that is closest to the obtained outer product c is determined as the projection surface 33, and element calculation for determining the shape of the hole 32 on the determined projection surface 33 is performed.

FIG. 2 shows a processing block configuration of the above-described projection plane determination and element calculation in the data processing device 15.
The outer product of the two input measurement directions a and b is the outer product calculation unit 2
The surface having the normal vector that is obtained in 1 and closest to the outer product obtained by the normal vector determination unit 22 is selected as the projection surface, and the element calculation unit 23 performs element calculation on the projection surface. The projection plane obtained by the normal vector determination unit 22 is preferably displayed on the display device 16 so that the operator can confirm it.

According to this embodiment, the projection plane determination process becomes faster than the conventional method of measuring three coordinates. Moreover, in the case of this embodiment, as shown in FIG. 4, depths (deviation amounts) δ1 and δ from the surface 31 of the two measurement points A and B are measured.
There is no problem even if 2 is different. That is, if the two measurement directions a and b are both perpendicular to the axis of the hole, the outer product c of them is the same vector as in the case of FIG. 3, and as in the case of the conventional method described in FIG. There is no risk of making an incorrect projection plane determination.

[0014]

As described above, according to the present invention, the projection surface determination process used for element calculation in the case of measuring the shape of a hole of a work by using a coordinate measuring machine having a touch probe. , Is performed at high speed based on the measurement data of two points in the hole. Further, according to the method of the present invention for calculating the vector cross product of the measurement directions of the two measurement points, even if the depth positions of the two measurement points are different, they are not affected, and
The correct projection plane can be determined.

[Brief description of drawings]

FIG. 1 shows a schematic configuration of a coordinate measuring machine used in an embodiment of the present invention.

FIG. 2 shows a block configuration of a projection plane determination processing system of the same embodiment.

FIG. 3 is a diagram for explaining a projection plane determination processing method according to the embodiment.

FIG. 4 is a diagram for explaining the effectiveness of the projection plane determination of the embodiment.

FIG. 5 is a diagram for explaining the principle of hole shape measurement of a work by a coordinate measuring machine.

FIG. 6 is a diagram for explaining a projection plane determination method according to a conventional method.

FIG. 7 is a diagram for explaining a problem of the conventional method.

[Explanation of symbols]

11 ... CMM main body, 12 ... Touch probe, 1
3 ... table, 14 ... work, 15 ... data processing device,
16 ... Display device, 21 ... Outer product calculation unit, 22 ... Normal vector determination unit, 23 ... Element calculation unit, 31 ... Surface, 32 ... Hole, 3
3 ... Projection plane, A, B ... Measuring point, a, b ... Measuring direction, c ...
Cross product.

Claims (1)

[Claims] 1. A coordinate measuring machine having a touch probe is used to measure the surface shape of a hole on a predetermined surface of a workpiece by projecting a measurement point on the inner wall of the hole onto a projection surface corresponding to the predetermined surface. Measuring the coordinate positions of two points on the inner wall of the hole, obtaining the outer products of the two measurement directions in the measurement operation, and obtaining the surface having the normal vector closest to the outer product as the projection surface. A method for measuring the shape of a hole using a coordinate measuring machine.