WO1991015731A1

WO1991015731A1 - Process and device for measuring and/or checking the contours or edges of workpieces

Info

Publication number: WO1991015731A1
Application number: PCT/EP1990/000534
Authority: WO
Inventors: Christian Lippuner
Original assignee: Aurotec System Gmbh Industrieautomation
Priority date: 1990-04-05
Filing date: 1990-04-05
Publication date: 1991-10-17

Abstract

A process and device for measuring and/or checking the contours or edges of workpieces (10), preferably for detecting and evaluating edge defects and/or edge notches of cutting disks with an optoelectronic test device, are described. The test workpiece (10) is rotated about a stationary axis (2), and as it rotates at least one rotating edge of the workpiece is scanned with a light beam (8, 8') at a predetermined angle. Simultaneously a projected profile of the edge is formed on a light-sensitive layer and the measured values are compared with the reference values of a tested edge profile by means of an electronic computer.

Description

Method and device for measuring and / or checking the outline shapes or edges of workpieces

The invention relates to a method for measuring and / or checking the outline shapes or edges of workpieces, preferably for detecting edge defects and / or edge breakouts of cutting inserts, with an optoelectronic test device.

Workpieces, the precision and accuracy of which must meet special requirements, must be subjected to a quality control after they have been manufactured, which today is still mostly carried out by persons entrusted with quality control. In order to rule out errors due to fatigue and carelessness of the people involved in quality control, efforts are being made to use computer-aided quality assurance systems (CAQ).

The problem of quality control exists, for example, with indexable inserts, which usually consist of sintered hard metal and have geometrically easy to describe shapes such as cuboids or disks, or consist of disk-shaped bodies with plane-parallel top and bottom sides in the form of squares, rectangles, circles, triangles, rhombuses or polygons . Such indexable inserts place special demands on the cutting edges and the radii of the cutting corners. These indexable inserts may only leave the manufacturing company after thorough quality control, whereby the indexable inserts are divided into tolerance classes according to the accuracy of the cutting edges and cutting radii. Thorough quality control is especially necessary for indexable inserts because cutting edge chipping cannot be avoided.

The object of the invention is therefore a method of the beginning to create specified type, according to which the edges and / or radii and part geometry of workpieces and in particular of indexable inserts can be checked automatically and without contact for breakouts or other errors. This automatic test should be able to be carried out in the shortest possible time so that the test time is adapted approximately to the cycle time of the production of the workpieces.

According to the invention, this object is achieved in a method of the type specified at the outset in that the workpiece to be tested is rotated about a spatially fixed axis and at least one circumferential edge of the workpiece is scanned with a light beam during the rotation so that the light beam, the diameter of which is so large, that it constantly detects at least a portion of the edge during rotation, on a picture of electrical signals generating image n, existing photo-sensitive layer of a camera maps a projected profile of the edge, that the electrical signals corresponding to the edge profile as actual values in a computer, in which the target values of the checked edge profile are stored, are subjected to a target-actual value comparison and that the quality of the workpiece is evaluated in accordance with the result of the target-actual value comparison.

The method according to the invention is suitable for rapid quality control of workpieces with high accuracy. In particular, the method according to the invention is suitable for quality control of indexable inserts, which are currently manufactured in approximately 2400 different shapes and geometries. A high level of test accuracy can be achieved by using so-called "CCD cameras", which are semiconductor cameras whose light-sensitive plates consist of light-sensitive diodes arranged in rows and columns. The CCD cameras are connected to evaluation electronics, which generate electrical signals according to the profile shown on the plate, which are then evaluated in an electronic computer. The light beam creates on

REPLACEMENT LEAF the light-sensitive plate of the camera when rotating, an image of the edges and corners to be checked, which change according to the rotation and thus allow a control at small angles during the rotation. A rotation can take place in about 3 to 4 seconds, so that the entire test process, including the delivery and removal of the test specimens, does not take longer than about 2 to 5 seconds. The measuring light beam consists of a beam of preferably parallel light. Parallel light can preferably be generated, for example, by a laser diode or else by a quartz lamp with appropriate filters and diaphragms.

The image that the light beam generates on the light-sensitive plate of the camera consists of a sequence of shadows that change in intensity, a sinusoidal curve being formed in particular. Starting from the incidence of the light beam on an edge of the test specimen, the test specimen rotates according to its angle of rotation on the driven ring through the incident light beam, with all edges of the test specimen passing through one after the other with more or less darkening of the light beam, as a result of which the shadows formed create one a characteristic curve is formed for the test object, which is in particular sinusoidal. This sine curve, which is fed to the computer during registration in the camera, is then compared with an ideal curve, which means that deviations of the test object in the area of its edges can be immediately recorded by calculation.

The signals supplied by the electronic camera in accordance with the illustrated profiles in successive steps are processed as actual values in the electronic computer in which the edge profiles, radii and possibly other values scanned by the light beam are stored as target values, so that by means of a corresponding target / actual value comparison, record the quality of the test object and have it classified into certain tolerance classes.

SPARE BLADEΓ Geometry errors as well as positioning errors of the test object are eliminated by the suitable calculation algorithm. In the computer di forms are stored the workpieces to be inspected, so that the can be adjusted in each case to the ^{'corresponding} workpiece to be tested to the test program Bewertun of the specimen. After the evaluation, the workpieces are sorted into the corresponding tolerance classes or sorted out as rejects if they can no longer be classified into a tolerance class.

The rotation of the workpiece is carried out so that it occurs bumplessly, for example in the form of a sinusoidal characteristic. The

Angular steps between the individual measurements can range from 0.01 to 0.05 degrees.

The workpieces are expediently placed on a rotatable carrier in such a way that the axis of rotation is approximately aligned with the central axis of the workpiece. This central axis is basically the axis of symmetry or the axis running perpendicularly through the center of gravity.

In an embodiment of the invention it is provided that in the case of workpieces with plane-parallel sides, the upper and lower edges are simultaneously scanned by two light beams, provided that the workpiece rests on a horizontal support. Of course, the workpiece can also be evaluated on a vertical support.

In a particularly advantageous manner, the light beams enclose angles of 45 degrees with the side surfaces adjoining the edges. If edges are not rectangular, for example because the edges have a free cut, the light beam, e.g. stand perpendicular to the bisector of the edges or take another suitable angle to the edge to be tested. The optimum angle for the incidence of light on the edge to be examined is obtained when the light beam strikes the edge to be examined such that the angle of the light beam to the one edge delimitation surface exactly corresponds to the angle de

REPLACEMENT LEAF Corresponds to the light beam, which this encloses to the other edge boundary surface.

A device for carrying out the method according to the invention is characterized according to the invention in that a ring rotatably mounted in a frame and driven by a servo motor is provided, which frame-like surrounds a pane of translucent glaze, the light sources emitting parallel light on one side of the pane and on on the other hand, semiconductor cameras are arranged with light-sensitive layers consisting of light signals generating electrical signals, and that an electronic computing unit is provided which, on the basis of the signals from the semiconductor cameras, carries out the target / actual comparison using suitable algorithms. Glass is preferred because of its low coefficient of thermal expansion, so that the measurement accuracy is maintained even when the support is heated.

The ring is shock-proof and vibration-free, so that no shocks or vibrations can be transmitted to the body lying on the glass. The drive should also be smooth and with such suitable accelerations and decelerations that the position of the test specimen relative to the glass pane is not changed during its rotation.

The drive is therefore expediently slip-free and jerk-free with the required gear ratio.

The ring or the motor is expediently connected to an incremental encoder, which is the clock generator for the transmission of the measurement signals.

The glass pane is expediently provided with a plane-parallel, plastic support in the area of the ideal axis of rotation of the ring. This support prevents the pane from scratching and increases in addition, the friction between the test specimen and the support. In addition, a mechanical and / or magnetic holder of the test specimen can also be provided on the pane.

In a further embodiment of the invention it is provided that the CCD camera is provided with adjustable optics with which the imaging scale of the edge on the CCD sensor can be changed.

The image of the professional image is enlarged or reduced in accordance with the desired resolution or part size by means of an appropriate adjusting device, which can also be operated automatically. In the same way, the camera can be approached or removed from the test specimen by an automatic control, so that adaptation to different test specimens is ensured in a simple manner.

In a further embodiment of the invention, at least one gripper or slide is provided for the delivery and removal of the test specimen, which takes the workpieces to be tested from a cassette, places them in the test position on the glass pane and, after the test, reinserts, sorts or, according to the test result, into the cassette is eliminated. The test specimens consisting of indexable inserts are expediently held in specially designed cutting element cassettes, as are known, for example, from DE-GMS 84 22 631. The test specimens are removed from the cassette by a suitable robot system and fed to the measuring system. The test specimens are usually taken upright, rotated by one or more grippers, possibly with a clipboard, by 90 degrees in order to be placed in this position in their test position.

Before the workpieces are removed from the glass pane, the test specimens are expediently rotated back into their position in which they have been loaded, so that the return transport by the grippers can take place in the same manner as the delivery.

REPLACEMENT LEAF The test specimens must be placed on the glass pane by the robot gripper system within predefined tolerances, which can be, for example, + 0.1 mm. The test program can make corrections within this tolerance range. For example, when the test specimen rotates, the test program detects one or more edges or corners of the test object and recognizes them as the zero point of the entire test process, to which the program then adjusts itself.

An embodiment is explained below with reference to drawings in which a test device is shown schematically.

Show it:

FIG. 1 shows the test device with the test specimen and cameras directed at the edges of the test specimen in a schematic illustration,

FIG. 2 shows the test specimen with an arrangement on the test device in a top view,

FIG. 3 shows a detail of the clamping of the glass plate on the driven ring,

FIG. 4 shows the rotating ring with the glass plate in cross section clamped by clamping claws,

FIG. 5 shows an image of the edges of the test specimen generated in the cameras in the manner of a sine curve,

6 shows a test piece shown as an example in a cuboid design.

In a machine frame, not shown, a frame-shaped ring 1 is rotatably mounted about its central axis 2. The ring is on

LATT provided on the outside with a toothing 3 over which a toothed belt 11 runs. The endless toothed belt 10 is driven by the drive wheel 4, a servo motor 5, which also rotates the incremental encoder in the embodiment.

The diameter of the ring 1 and the drive gear 4 are matched to one another in accordance with the desired transmission ratio.

The ring 1 forms the holding frame for a glass plate 6 made of refraction-free glass.

Below the glass plate 6, two lamps 7, preferably parallel light emitting by suitable optical systems, are arranged.

The light rays 8,8 'cut the glass plate 6 at 45 degrees. The light rays 8, 8 'are aligned in the manner shown on the central axes of the semiconductor cameras 9, 9'. The light rays 8, 8 'are set on the edges of a test body 10 placed centrally on the glass plate 6 in such a way that they each capture an edge section to be tested.

When determining the edges of the test specimen, it is important that the glass plate 6 according to FIG. 3 is seated in a holder 15 in an external ring 16 which is driven in rotation. The bracket 15 between the glass plate 6 and the ring 16 consists of a clamping system, which is formed from springs 17 and clamping claws 13. The springs 17 are directed radially inward in a spring-loaded manner, axial displacement of the glass plate 6 upwards and downwards being avoided by the fact that a lower stop 18 is present on the ring 16, the springs 17 pressing the glass plate 6 downwards against this stop 18 preload. In connection with this, the glass plate 6 is thus clamped against a cone 19 of the clamping claws 13 on the inner circumference of the circumferential ring 16.

REPLACEMENT LEAF According to Figure 3, for example, three clamping elements 13 are provided, which clamp the glass plate 6 against the lower circumferential stop 18 of the ring 16, the claws 13 being mounted in the manner of a one-armed lever in a groove 20 of the ring 16 and from there resiliently at an angle Attack the circumference of the glass plate 6.

The overall dimensional accuracy of the arrangement is defined in that the glass plate 6 rests with its lower base on the radially inwardly projecting ring projection or stop 18 of the ring. In this way, also according to FIG. 1, a radially inwardly projecting stop is formed on the ring 1, on which the glass plate 6 rests true to size and is held laterally by the ring surface.

When determining the edges of the test specimen, it is important that the table or ring 1, 16 according to FIGS. 1 and 2 runs absolutely smoothly, in particular without a stroke, since otherwise the measurement result in the pattern recognition of the CCD cameras is falsified.

In this context, it is also important that the tester body 10 according to FIGS. 2 and 4 is placed on a support 12 of the glass pane in order to protect the glass pane itself from injuries caused by the test body 16, since otherwise irregularities in the light throughput could result.

According to Figures 2 and 4, it is essential that the support 12 is always smaller than the outer circumference of the test specimen 10, so that it is ensured that the support 12 does not protrude in any area beyond the test specimen and thus the light rays 8,8 'only Can touch test specimen 10 itself, but not hit the pad 12. These measures ensure the required dimensional accuracy for pattern recognition in the respective CCD cameras.

The support 12 according to FIG. 4 consists e.g. a hard metal disk which has an axial, central pin 21,

ZBLATT which engages in an associated central bore in the glass plate 6. Instead of a hard metal disc, a plastic disc or the like can also be used.

In connection with the dimensional accuracy of the arrangement, it is also important that the glass pane 6 is flat. It must also be ensured that the underside of the support 12, which rests on the glass pane 6, is also flat and runs exactly parallel to the surface of the glass plate. In order to achieve this, it is provided that the glass plate and the support 12 are processed together in order to produce the required plane parallelism.

The prerequisite here is, of course, that the glass plate 6, in turn, rests with its lower contact surface on a plane-parallel circumferential support ring 1, 16 according to FIGS. 1 and 3, a stop being formed in the manner of a circumferential ring, which is formed by the inner circumference of the support ring 1, 16 protrudes radially inwards.

It is also important that the test specimen 10 is placed on the support 12 on the glass plate 6 with a close tolerance in order to avoid eccentricity during the rotation of the entire ring 16 during the test process. The tolerance here is in the range of several hundredths of a millimeter.

However, the orientation of the placement of the test specimen is not essential, which is a considerable advantage of the present application. In this context, it is also provided that the device is used to test gemstones and optical glasses, the edge profile or refractive index of which is recorded in connection with the translucent light beam by means of CCD cameras.

Here, gemstones or optical glasses represent test specimens, which create a characteristic pattern in the CCD cameras, which also includes an ideal case can be compared, in order to be able to classify the test objects in certain quality classes.

The test specimens are placed in particular in an automated process by grippers, the gripper being programmed so that it positions the test specimen in the correct position, i.e. not twisted, placed on the support 10 of the glass pane 6.

However, it is permissible and possible according to the present invention to also twist the test specimen 10, i.e. so in another zero position on the support 12 centered on the glass plate 6. It is only important here that the CCD cameras 9, 9 ', with their associated evaluation electronics, detect such a twisted support of the test specimen.

In this context, software can be used to record that the test specimen winke! Has been placed rotated on the support and that there is no defect in the cutting edge to be tested.

A test procedure of the type described above proceeds as follows:

The test specimen 10 is placed on the stationary carrier plate or ring 1, 16 according to FIGS. 1 and 2 with the internal glass plate 6 using a robot gripper. The test specimen 10 can consist of hard metal, a ceramic plate or a sintered hard metal or a plastic material, where correspondingly arranged cutting edges are provided. However, gemstones or optical glasses can also be used as test specimens.

A distinction is made between test specimens of different accuracy classes. The highest accuracy class requires that the test specimen have absolutely parallel edges and parallel contact surfaces, and this accuracy class is in the computer of the pattern recognition system entered, after which this detects deviations in inclination in the edges and assigns the test specimens to certain accuracy classes.

If e.g. a lower class is entered, then in these lower classes it is permitted that the examiner body e.g. has inclined cutting edges or inclined contact surfaces and these permitted errors are recognized and tolerated by the program of the pattern recognition system.

When the test specimen 10 is placed on the glass plate, the lamps 7, 7 'are always switched on. The lamps can be designed either as quartz emitters or as laser spot emitters.

A parallel light beam with a diameter of approximately 5 mm is generated by the laser light source. This light beam thus initially strikes a certain edge of the test specimen 10 when the glass plate 6 is stationary, the test specimen also being able to have any edges in connection with precious stones or optical glasses, such as e.g. a rhombus outer circumference, or a square, rectangular or triangular outer circumference.

The light beam 8, 8 'of the laser light source is directed onto the glass pane 6 in such a way that it is ensured that, with a full rotation of 360 °, all edges of the test specimen to be tested are touched by this laser light beam.

ATT DRAWING LEGEND

Ring center axis toothing drive wheel servo motor glass plate lamp, 8 'light beam camera 0 test specimen 1 toothed belt 2 support 3 clamping claw light bundle holder ring spring stop cone groove 1 pin 2 sine curve

Claims

Patent claims

1. Method for measuring and / or checking the outline shapes or edges of workpieces, preferably for detecting and evaluating edge defects and / or edge chipping of cutting inserts, with an optoelectronic test device, characterized in that the workpiece to be tested is rotated about a fixed axis and during the rotation, at least one circumferential edge of the workpiece is scanned with a light beam at a predetermined angle such that the light beam, the diameter of which is so large that it continuously detects at least a portion of the edge during the rotation, on a pixel which generates electronic signals existing light-sensitive layer of a camera maps a projected profile of the edge, which is subjected to a target-actual comparison in the electronic signals corresponding to the edge profile as actual values in an electronic computer in which the target values of the tested edge profile are stored n and that the quality of the workpiece is evaluated in accordance with the result of the target / actual value comparison.

2. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the rotation is carried out incrementally in small angular steps.

3. The method of claim 2, d a d u r c h g e k e nn z e i c h n e t that the angular steps are in the range of 0.01 to 0.05 °.

4. The method according to any one of claims 1 to 3, so that the workpiece is placed on a rotatable carrier such that the axis of rotation is approximately aligned with the central axis of the workpiece.

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5. The method according to any one of claims 1 to 4, that the upper and lower edges of the workpiece are simultaneously scanned by two light beams.

6. The method according to any one of claims 1 to 5, that the light beams enclose an angle with the side faces adjoining the edges.

7. The method according to any one of claims 1 to 6, that the workpieces falling out of predetermined tolerance ranges on the basis of the target / actual value comparison are separated out or assigned to coarser tolerance classes.

8. Device for performing the method according to one of claims l to 7, dadurchgeke nn characterized in that a rotatably mounted in a frame and driven by a stepper motor ring (1,16) is provided which frames a disk made of light-refractive glass that frame on one side of the pane, light-emitting light sources and on the other side of the pane, semiconductor cameras with light-sensitive layers consisting of light signals generating electrical signals are arranged, and that an electronic computing unit is provided which compares the target / actual value based on the signals from the semiconductor cameras makes.

9. The device according to claim 8, d a d u r c h g e k e nn z e i c h n e t that the glass plate in the region of the ideal axis of rotation of the ring (1,16) is provided with a plane-parallel, made of plastic pad.

10. Device according to one of claims 8 to 9, characterized in that the light source with an adjustable Optics is provided with which the diameter of the parallel light beam can be enlarged or reduced.

11. The device according to one of claims 8 to 10, characterized in that at least one gripper of a robot gripper system is provided, which takes the workpieces to be tested from a cassette, places them in the test position on the glass pane and after the tester according to the test result back into the cassette or another cassette is replaced or eliminated.

12. Device according to one of claims 8 to 11, d a d u r c h g e k e n n z e i c h n e t that the stepper motor brings the workpiece back into its starting position before the workpiece is removed.

13. The apparatus of claim 8, d a d u r c h g e k e n n z e i c h n e t that the ring (16) has a support (18) for the glass plate (6) and thereby attack resilient clamping claws (13) on the circumference of the glass plate (6).

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