JPH07159147A - Three-dimensional measuring system - Google Patents

Abstract

PURPOSE:To easily recognize the error distribution and carry out the automatic correction work by obtaining the error quantity defined by the difference between the displacement quantity detected by a displacement detection type measuring head and the reference displacement quantity, in a prescribed timing along the locus of the relative shift, and visibly displaying the obtained error quantity. CONSTITUTION:As for a displacement detection type measuring head 14, a feeler shifts along the measuring locus prescribed by a measuring program, in contact with the surface of a workpiece. An error calculation part 61 calculates the error quantity defined by the difference between the displacement quantity of the head 14 and the standard displacement quantity, and if a previously determined allowable value is exceeded, an alarm part 63 generates an alarm. Further, the obtained displacement data and the coordinate data are stored, together with the error, in a recording part 62. When recording completes, a coordinate conversion part 71 converts the coordinates which are stored 62, into the CRT coordinate data, and an error quantity drawing part 72 magnifies the error quantity, and a drawing/printing part 73 displays the error quantity at each measuring point of the measuring locus. Accordingly, the working precision is confirmed, and can be corrected automatically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional measuring system, and more particularly to a three-dimensional measuring system for measuring a deviation error amount of an object shape from a reference shape.

[0002]

2. Description of the Related Art Conventionally, when a workpiece is machined into an arbitrary three-dimensional shape, an NC machining program is created using a digitizer or CAD, and a machining center is controlled according to the created NC machining program. To inspect the machining accuracy, the shape and dimensions of the workpiece thus processed and N
The amount of error, which is the difference from the shape and dimensions specified by the C program, is measured. To measure this error amount, a so-called displacement detection type measuring head is attached on the main axis of the machining center, and the reference shape or the displacement based on displacement data obtained by moving the feeler while contacting the surface of the workpiece. The difference between the dimensional value and the measured value is obtained as the amount of error. An example of a machining center having such a processing accuracy inspection function is disclosed in Japanese Patent Laid-Open No. 5-253800 and used as a three-dimensional measuring system.

[0003]

As described above, in the conventional three-dimensional measuring system for measuring the three-dimensional shape accuracy and dimensions of the work, the surface of the work is measured using the displacement detection type measuring head. . However, in the measurement process, the measurement head is brought close to the work surface, the displacement data is obtained only under a specific condition in which the two come into contact with each other, then the head is retracted, and the work surface is again brought close to the next measurement point. Since the stepwise operation measurement is performed by repeating the point measurement operation sequence such as obtaining the data of 1), it takes time to complete the measurement.

Further, the dedicated measurement program required for the three-dimensional measurement usually has to be created by a dedicated CAT system, and a separate CAM or the like is used to obtain the shape error amount from the measurement result. The system requires calculation, making quick measurement difficult.

Further, although the above-mentioned conventional three-dimensional measuring system can obtain an error amount, the obtained error amount is only obtained as numerical data, so that the error distribution of the machined workpiece and However, there is a problem in that it is difficult to visually recognize and grasp the identification of a part having a large error.

Therefore, an object of the present invention is to provide a three-dimensional measuring system for promptly measuring the shape accuracy and dimensional error of a work and displaying the measurement result in a visually recognizable manner. Another object of the present invention is to provide a three-dimensional measurement system capable of creating an NC machining program for modifying a workpiece based on the obtained measurement result.

[0007]

In order to solve the above-mentioned problems, a three-dimensional measuring system according to the present invention has a displacement detecting type measuring head and an object to be measured and the measuring head which are moved relative to each other. It is defined by an NC device for commanding, a position detecting means for detecting a relative movement position of the object to be measured and the measuring head, and a difference between a displacement amount obtained from the measuring head and a predetermined reference displacement amount. Error amount calculating means for obtaining an error amount at a predetermined timing along the relative movement locus, and display means for visually displaying the error amount obtained by the error amount calculating means with respect to the relative movement locus. It is configured with.

Further, a three-dimensional measuring system according to another aspect of the present invention is an NC for instructing relative movement while bringing a displacement detection type measuring head into contact with an object to be measured and the measuring head.
A device, a position detecting means for detecting a relative movement position of the object to be measured and the measuring head, and an error amount defined by a difference between a displacement amount obtained from the measuring head and a predetermined reference displacement amount. An error amount calculating means for obtaining at a predetermined timing along the path of the relative movement, and a correcting means for correcting the processing program of the object to be measured based on the error amount obtained by the error amount calculating means. To be done.

[0009]

In the present invention, the error amount defined by the difference between the displacement amount detected by the displacement detection type measuring head that moves relatively while contacting the object to be measured and the predetermined reference displacement amount, By visually determining the error amount obtained at each predetermined timing with respect to the path of the relative movement, the error amount obtained visually at the predetermined timing along the path of the relative movement is visually displayed. Facilitates recognition of accurate measurement results (error distribution). Further, by correcting the NC processing program of the NC device based on the obtained error amount, automatic correction processing is also possible.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a system configuration diagram showing an embodiment of a three-dimensional measuring system according to the present invention. In the present embodiment, the NC device memory 11 of the machining center 1
The NC measurement program is stored in. The NC measuring program is, for example, a program for tracing the shape of an object to be measured, which is created by using a normal CAM system, and is a radius of a tip spherical portion of a feeler of a displacement type measuring head used for measurement (hereinafter, (Referred to as feeler) and the amount of generated displacement are taken into consideration to provide an NC measurement program that is offset. In this example, the NC measurement program is CAD /
Program data from the CAM system 9A or the digitizing unit 9B is transmitted via the DNC device 8,
It is stored in the NC device memory 11. This NC measurement program can be replaced with an NC machining program that machined the workpiece to be measured.

From the NC device memory 11, each axis motor 1
A command program for controlling the motor of each axis is supplied to 2. Displacement type measurement head 14 according to rotation of each axis motor 12
Moves, but the position coordinates are x, x from the scale 13.
It is output as y, z coordinate reference data. The position coordinates may be output as coordinate value data by counting the pulses output from the encoder of each axis motor 12 with the pulse counter 2B.

A pulse as a coordinate value reference signal is output from the scale 13 for each x, y, z coordinate, these pulses are counted by the pulse counter 2B, output as coordinate value data, and a coordinate data acquisition section 3B. Is taken into.

The pulse of x, y, z coordinates as the displacement data reference signal obtained from the displacement detection type measuring head 14 is counted by the pulse counter 2A, and the count value is the displacement data Ex, Ey, Ez. Capture part 3
It is taken in by A.

Measurement of displacement data by the displacement detection type measuring head 14 will be described with reference to FIG. FIG. 2 shows the cross-sectional shape of the machined work, the solid line part of the oblique line boundary shows the outer part of the work after machining, and the smooth arc part (consisting of the solid line part and the broken line part) is defined by the NC machining program. It is a reference part showing an ideal processed surface. Actually, the processing surface is uneven because the processing is insufficient or the processing is performed too deeply. For example, the X1 portion of FIG. 2 indicates a convex portion that is not sufficiently processed, and the X2 portion indicates a concave portion. In FIG. 2, the generated displacement, which is the amount of error from the reference portion, is indicated by the length of a thick arrow in the direction of the normal to the processing surface (reference surface).

The displacement detection type measuring head 14 is moved according to the measurement locus defined by the measurement program while its feeler is in contact with the surface of the work. First, in the non-displacement contact state, the measuring head 14 (1) and the feeler 141 (1)
Is in the position shown. The movement locus of the feeler as a measurement locus is a locus offset by a distance determined by the radius of the feeler from a locus along the machining surface defined by the NC measurement program. This locus is represented by the feeler 141.
(1), 141 (2), ..., 141 (k), ..., 141
It is a locus connecting the centers C1, C2, ..., Ck, ..., Cn of (n). The actual trajectory of the center of the feeler is
Move to the black circle position on the uneven part.

At the position of the measuring head 14 (2), the feeler is at the feeler 141 (2) position, and the feeler 141 (2) is displaced in the normal direction of the measuring point P on the processing surface. At this time, as is well known, when the generated displacement amount is E, the feeler radius is R, and the reference displacement amount is E0, the relationship of E = E0 = R is established. That is, the feeler is traced along the surface of the work so that the generated displacement amount of the measuring head maintains a reference displacement amount that is theoretically equal to the feeler radius. At the feeler 141 (k) position, the processed surface is finished in a convex shape, and the protrusion amount in the normal direction is ΔE.
Then, the generated displacement amount E is obtained by E = E0 + ΔE.
Further, at the feeler 141 (n) position, the machined surface is finished in a concave shape, and if the amount of concave in the normal direction is ΔE, the generated displacement amount E is obtained by E = E0−ΔE.

Returning to FIG. 1, the automatic measurement start / end determination unit 4 determines the measurement start and end timings based on the supplied displacement data and the coordinate data of the measuring head. , Output the data taken in by the end timing. The error amount calculation unit 61 that constitutes the error amount processing unit 6 obtains the error amount defined by the difference between the displacement amount obtained by the above measurement and the reference displacement amount by the calculation process shown in FIG. 3 described later. Further, when this error amount exceeds a predetermined error allowable amount, the alarm unit 63 is caused to issue an alarm. Further, the obtained displacement data and coordinate data are recorded in the memory of the recording unit 62 together with the error amount.

The process of obtaining the error amount will be described with reference to FIG. 3. In step S1, displacement amounts Ex, Ey and Ez in the x, y and z directions are obtained, and step S3 is performed.
, The generated displacement amount E is E = √ (Ex ² + Ey ² + E
z ² ) At this time, a predetermined error allowance d
The above parameters are read from the parameter file in which parameters such as e, the reference displacement amount E0, and the drawing magnification Gg of the error are stored (step S2), and are used for the subsequent processing.

Next, the error amount d is calculated by d = E−E ₀ (step S4), and it is determined whether the absolute value of the obtained error amount is smaller than the error allowable amount de (step S).
5). If the absolute value of the error amount is smaller than the error allowable amount de, the coordinate values (x, y, z) at that time and the displacement amounts Ex, Ey, Ez are recorded (step S6). After performing the alarm processing such as the buzzer sounding for (step S7), the process proceeds to step S6.
After the processing of step S6 is executed, the current coordinate value,
Based on the displacement amount data, it is determined whether or not the measurement process is completed (step S8). This determination is determined to be completed, for example, when it is confirmed from the coordinate value data that the mechanical axis movement has stopped and from the displacement amount data that there is no change in displacement. If it is determined in step S8 that the process is completed,
If the measurement is finished and it is not judged to be finished, step S1
Then, the process returns to the next process of capturing the displacement amount.

In FIG. 1, when the recording unit 62 finishes recording the displacement data and the coordinate data obtained by a series of measurement processes, the drawing unit 7 draws the measurement results. First, for display on a CRT screen used as a monitor screen of a personal computer or the like, the coordinate conversion unit 71 converts the coordinate data recorded in the memory of the recording unit 62 into CRT coordinate data.

The error amount drawing unit 72 enlarges the error amount for each position of the coordinate data converted by the coordinate conversion unit 71 by a predetermined magnification Gg read from the parameter file and designates a specified plane (for example, xz). Create drawing data projected on a plane. The creation of this drawing data is obtained by the following calculation.

FIG. 4 shows a display example of the error amount at the measurement point P of the measurement trajectory S along the processed work on the xz plane. Since the error amount is a very small value, it is difficult to visually recognize the size of the error amount even when it is displayed as it is when it is displayed on a CRT or printed by a printer. Therefore, the error amount is multiplied by the predetermined drawing magnification Gg as described above to be enlarged and displayed. Based on the reference displacement amount E0, the enlargement error amount D is calculated by D = (E−E0) × Gg calculation. Further, the x-axis projection amount ex and the z-axis projection amount ez of the error amount D are obtained by ex = D × Ex / E ez = D × Ez / E.

As is apparent from FIG. 4, the error amount Dxz projected on the xz plane at the measurement point P is the vector amount e.
It is obtained as a composite vector of x and ez. The error amount thus obtained is magnified and displayed on the CRT or output by the printer.

In FIG. 1, the drawing / printing unit 73 displays or prints the error amount obtained by the error amount drawing unit 72 and enlarged, at each measurement point of the measurement locus. In this display or printing process, the measurement locus range is enlarged or reduced corresponding to the CRT display screen or the print output range, and the desired measurement locus range is displayed or printed. Also, along with that,
The error magnification magnification Gg can also be adjusted.

In FIG. 4, when the error amount is +, the enlarged error amount extending in ten directions is displayed as shown, and when the error amount is −, the enlarged error amount extending in the opposite direction to that in FIG. 4 is displayed. .

FIG. 5 shows an example of an error amount display on the xz plane displayed on the CRT screen in this way or printed out by a laser beam printer or the like. In this measurement example, the number of measurement points is 158 and the sampling time is 300 m.
s, reference displacement 0.6 mm, maximum error amount is 38 μm,
It is a display example when the minimum value of −156 μm is obtained.

Returning to FIG. 1, the correction machining NC program creating unit 10 reads the displacement data and coordinate data error amount recorded in the memory of the recording unit 62, and corresponds to the read error amount. In order to correct and compensate for the machining error of the work, the amount of correction machining is calculated, and the NC machining program for correction machining is calculated from the obtained amount of chasing data and the NC machining program of the workpiece stored in the DNC device. Is created and fed back to the DNC device 8. Then, the data is transmitted from the DNC device 8 to the machining center 1 and the work is corrected and processed. Although the machining center is used as the measuring machine in the measuring system of the present embodiment, other machines such as an NC milling machine, a copying milling machine, a digitizing machine, and a three-dimensional measuring machine can be used.

[0028]

As described above, in the three-dimensional measuring system according to the present invention, the error amount obtained by the measurement is displayed or printed so that it can be easily visually recognized. And the processing result can be confirmed at a glance. Further, since the correction and compensation processing is performed based on the obtained error amount, it is possible to improve the processing accuracy and speed.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of a three-dimensional measurement system according to the present invention.

FIG. 2 is a diagram showing a cross-sectional shape of a processed work.

FIG. 3 is a calculation processing flowchart for obtaining an error amount.

FIG. 4 is a diagram showing a display example on an xz plane of an error amount at a measurement point of a measurement locus along a processed work.

FIG. 5 is a diagram showing an example of an error amount display on an xz plane displayed on a CRT screen or printed out by a laser beam printer or the like.

[Explanation of symbols]

 1 Machining center 2A, 2B Pulse counter 3A Displacement data acquisition part 3B Coordinate data acquisition part 4 Measurement start / end automatic judgment part 5 Parameter file 6 Error amount processing part 7 Output part 8 DNC device 9A CAD / CAM 9B Digitizing 10 Correction NC program creation part for machining 11 NC device memory 12 Each axis motor 13 Scale 14 Displacement type measurement head 61 Error amount calculation part 62 Recording part 63 Alarm part 71 Coordinate conversion part 72 Error amount drawing part 73 Drawing / printing part 141 Feeler

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G01B 5/20 101 Z 8605-2F

Claims (2)

[Claims] 1. A displacement detection type measuring head, an NC device for instructing relative movement while bringing the object to be measured and the measuring head into contact with each other, and detecting a relative movement position between the object to be measured and the measuring head. Position detecting means, and an error amount calculating means for obtaining an error amount defined by a difference between a displacement amount obtained from the measuring head and a predetermined reference displacement amount at a predetermined timing along the relative movement locus, A three-dimensional measurement system comprising: a display unit that visually displays an error amount obtained by the error amount calculation unit with respect to the locus of the relative movement. 2. A displacement detection type measuring head, an NC device for instructing relative movement while bringing the object to be measured and the measuring head into contact with each other, and detecting a relative movement position between the object to be measured and the measuring head. Position detecting means, and an error amount calculating means for obtaining an error amount defined by a difference between a displacement amount obtained from the measuring head and a predetermined reference displacement amount at a predetermined timing along the relative movement locus, A correction means for correcting the processing program of the object to be measured based on the error amount obtained by the error amount calculating means.