DE3613096A1 - Method for machining workpieces - Google Patents

Abstract

The invention relates to a method for machining workpieces by means of a programmed multi-axial robot which guides a machining tool, preferably a laser beam along a three-dimensional workpiece contour, a marking, cutting line or the like being applied to a pattern or workpiece in order to mark the position to be machined and a three-dimensional profile NC programme being generated by scanning the marking by means of a sensor guided by the multi-axial robot, which sensor controls the axes of the robot in such a manner that the sensor always follows the markings and the coordinates of the sensor at predetermined points are input into the NC controller as programme points and then the workpieces are machined on the basis of this NC programme. To create a simple programming method for three-dimensional workpieces in which the markings, cutting lines or the like are optically detected and can be input as coordinates into the controller, a TV camera sensor (32) is used for scanning the markings (30), which sensor determines the normal of the tool and/or the tool height with respect to the workpiece surface so that the TV camera sensor (32) is oriented normally and/or at the nominal tool distance (vertically) to the workpiece surface at least at the predetermined points. <IMAGE>

Description

The invention relates to a method for processing Workpieces according to the preamble of claim 1 and one Device for performing the method according to the Ober Concept of claim 4.

The machining of workpieces with a particular complicated workpiece contour is preferably on a programmable multi-axis robot that can be used in every arbitrary position within its travel range move the path information stored in the control can be. The preparation of a given bear processing sequence into a data sequence (program) which is from Computer or the controller can be processed complicated with three-dimensional workpiece contours and time consuming. Often there are analytical or exact drawings neric data to describe the machining contour in  Do not give space as this includes tool orientation are at least five coordinates. This is especially true for processing on prototype parts.

In today's common processes, the workpiece is made by Hand torn and with the processing machine the points relevant to the machining contour by hand Control approached and transferred to the control. Here, for example, instead of the tool the so-called "teach-in sensor" attached to the tool holder, which is aligned with the marking with a pointer. The The machine operator observes the exact position by eye nation of the pointer.

However, problems arise in the exact orientation of the "teach-in sensor" normal to the workpiece contour as well in the accuracy of the reading. Another essential The disadvantage of such methods lies in their accessibility the workpiece or the machining contour is founded when the workpieces are several square meters in size.

From DE-OS 32 26 448 it is known to work piece of a marker to mark the one to be processed Mark position and a three-dimensional profile program by scanning the marking with an In to create industrial robots and then the workpieces based on this program.

Furthermore, a special print from the "Industrial Anzeiger ", No. 8 from 01/27/84 a contactless work the NWAL seam tracking sensor for welding technology described with which the positional guidance of a laser  welding device can be achieved.

It is known from the earlier patent application No. 34 43 340 for example, this sensor NWAL as a "teach-in sensor" clog.

With the help of these facilities, an accurate Orientation on the markings, cutting lines or the like. achieve the problem of inaccessibility of the workpiece and thus the observation of the sensor remains stand. It can when using such facilities errors always occur when, on the one hand, the position of the sensor not observed by the machine operator can be, so that the data of the sensor at wrong Po sitions in the controller and others the workpiece has a three-dimensional workpiece contour with gradations, recesses, grooves or the like. that cannot be passed through with the sensor.

The invention has for its object a simple Programming method for three-dimensional workpieces create where the markings, cutting lines, flaws or the like. optically detected and as coordinates in the control can be entered.

This task is carried out in a generic method by the characterizing features of claim 1 and in a generic device by the kenn Drawing features of claim 4 solved.  

The advantages achieved with the invention are essential lichen that the problem is inaccessible speed by, for example, showing the TV camera sensor is solved in the beam path of a laser, so that the "Teach-in sensor" no longer moved in grooves or the like must become. The TV camera sensor is advantageous here stationary to, for example, a beam manipulator arranges. Via the TV camera sensor with evaluation electronics becomes the specified three-dimensional machining contour converted into a data sequence (signals) and the controller entered the processing machine. Preferably that Overall system an appropriate resolution to a thread cross a cutting line, marking, marking or the like. with an accuracy of less than ± 0.05 millimeters to be able to lead. Furthermore, the location of the working point tes on the workpiece surface on a TV monitor be shown what a simple monitoring at esp special large workpieces.

The fact that the measuring workpiece on the same machine in the same place as the workpieces to be machined is provided and is a workpiece to be machined and the TV camera sensor after program creation is exchanged for a processing tool there are the advantages of editing the program machine with its own kinematics and dynamics, so without transmission errors, and that the TV Sensor and tool (laser beam) adjusted to each other can be. It is advantageous further that immediately after the program creation without Um clamp or reload a test run or immediately start processing process can begin.  

However, the procedure is not based on programming limited to the processing machine, but it can ge the program was opened in the same way on a programming machine be taken and then transferred to the processing machine be.

The device for performing the method is thereby characterized in that the sensor is a TV camera, the one directions for keeping the distance constant and / or normals control or setting are assigned.

TV cameras with the outline of two-dimensional drawing can be scanned are from DE-OS 19 04 664 known in principle.

The TV camera sensor is opposite this state of the art according to the invention as a "teach-in sensor" for three-dimensional onal workpieces. Because the TV camera Sensor connected to a TV monitor, it will be advantageous possible, the position of the working point on the workpiece surface figuratively on the possibly removed Display TV monitor. The machine operator is thus easy monitoring of the working point, even with large ones Workpieces from his stationary work place possible.

The TV camera sensor is preferably used in a CO ₂ laser. The TV camera sensor is faded into the beam path of the CO ₂ laser by means of a pivotable mirror, with the advantages that the mirror can be partially transparent and a light source present in the machining center, for example a HeNe laser, for illuminating the Working point can be used.

The CO ₂ laser advantageously has a stationary laser resonator and a beam manipulator with a stationary portal under which a workpiece manipulator carrying the workpiece can be moved in the X direction, a carriage that can be moved on the portal in the Y direction, a vertical guide , which is attached to the carriage so that it can be moved in the Z direction above the workpiece, a swivel joint with a vertical axis of rotation at the end of the vertical guide in the C direction, and a laser head attached to the swivel joint that rotates about an axis in A -Direction can be swiveled to where the swiveling mirror can be faded into the beam path running in the Z direction. With this arrangement above the endless rotary movement of the C-axis, the connecting lines to the TV camera sensor do not have to be routed via slip rings.

The TV camera sensor is preferably on the tool holder of the machining head, i.e. along the A axis. At this arrangement, the conditions at the working point at the disturbance least observed. Furthermore, this one Training the highest accuracy because of working with the TV camera sensor either the electronic company cross must be superimposed on the picture or a mechanical crosshairs at the working point of the workpiece contour must be placed. This crosshair will open the tool tip, preferably on the focus point of the Lasers adjusted. Then the machines axes are moving, this is caused by incorrect adjustment itself the deflecting mirror with this training is not a mistake the teach-in programming. The smallest distance between The objective and workpiece are 20 millimeters.

The tool, in particular the machining, is preferred Fix the laser head in a tool change holder  igt, which is designed for example as a magnet holder. With a tool change holder designed in this way, as described in patent application 38 23 887.9, it is advantageously possible to use the TV camera sensor quickly and exchange it exactly for the tool. The TV camera sensor as a very compact structural unit, ins especially designed as a CCD camera sensor.

Further developments of the invention are in the subclaims shown.

An embodiment of the invention is in the drawing shown and is described in more detail below.

Show it:

Figure 1 is a perspective view of the device according to the invention.

Fig. 2 is a schematic representation of the superimposable in the beam path of a laser TV camera sensor;

Fig. 3 is a schematic representation of the arranged on the tool holder TV camera sensor and the field of view of the TV camera sensor relative to the crack or the like. On the workpiece contour;

Fig. 4 is a schematic representation of the arranged on the tool holder TV camera sensor electronics with Auswertelek and light source;

Figure 5 is a schematic representation of the image of the workpiece surface with light spot.

Fig. 6 is a schematic representation of a measurement error in the distance measurement with light point.

In Fig. 1, a workpiece and beam manipulator with five axes is designated by 10 in its entirety. The five axes are formed from three linear axes X , Y , Z and two axes of rotation A, C. The manipulator 10 consists essentially of a coordinate table 11 on which the workpiece 12 ( FIG. 2) can be moved in the X direction and a portal 13 projecting above the coordinate table 11 , which is arranged in a stationary manner. On the double girder bridge 14 of the portal 13 there are lanes 15 , 16 on which a carriage 17 can be moved in the Y direction. On the carriage 17 , a ver vertical guide 18 is attached in height in the Z direction above the workpiece 12 . At the work piece 12 facing the end of the vertical guide 18 , a rotary joint 19 which is rotatable in the C direction and has a vertical rotary axis 20 is arranged. On the swivel 19 , the laser head 21 is attached, which is pivotable about an axis perpendicular to the axis of rotation 20 in the A direction.

A laser resonator 22 , in which the laser beam 23 is generated, is preferably arranged in alignment with the double-beam bridge 14 . The laser resonator 22 is preferably arranged above the control and supply devices 24 .

Of course, any other arrangement of the laser resonator 22 is also possible. The laser beam 23 is then adjusted to the optical axis of the beam manipulator 10 via mirrors.

The laser beam 23 emerging from the laser resonator 22 is deflected in the Z direction via a mirror 26 ( FIG. 2) arranged at 45 ° and fed to the laser head 21 in the center through the vertical guide 18 . For this purpose, mirrors 27 and 28 ( FIG. 2) are arranged in the swivel joint 19 and the laser head 21 .

Coordinate table 11 , carriage 17 , vertical guide 18 , rotary joint 19 and laser head swivel device 25 are preferably moved before by means of a CNC control, the drive motors are not shown for reasons of clarity.

Fig. 2 shows a schematic representation of the beam path of the laser beam 23 which is directed onto the workpiece 12 via the mirrors 26 , 27 , 28 . The Ar beitpunkt 29 of the laser beam 23 is on a machining contour 30 corresponding outline. A pivotable mirror 31 is preferably arranged above the C axis of rotation in the beam path of the laser beam, via which the working point 29 (corresponds to the tool tip) can be observed by the TV camera sensor 32 . For this purpose, the mirror can be faded into the Z-linear axis at an angle of 45 °. This can take place, for example, via a mirror drive assigned to the mirror 31 , with which the mirror 31 is moved into or out of the beam path of the laser beam 23 . At right angles to the Z linear axis, the TV camera sensor 32 is fastened in the optical axis of the mirror 31 , preferably to a holder of the carriage 17 , not shown in detail.

According to a further advantageous embodiment, the pivotable mirror 31 is designed to be partially transparent, so that a light source 33 present in the processing system, preferably before a HeNe laser, can be used to illuminate the working point 29 . Here, the light beam 34 of the light source 33 is faded into the beam path of the laser beam 23 emerging from the laser resonator 22 via a further pivotable mirror 35 .

In Fig. 3, the TV camera sensor 32 is attached below the axis of rotation in a tool holder 36 , as described, for example, in patent application 35 23 887.9. By installing the TV camera sensor 32 instead of a tool, for example a lens or a cutting head, the conditions at the working point 29 can advantageously be observed at the most trouble-free. On the tool holder 36 a device for constant spacing 37 and a device for tilt control or adjustment 38 is arranged.

In Fig. 3, the distance sensor is designed as an annular grinding shoe 39 which is attached to a linear potentiometer 40 . About the linear potentiometer 40 a proportional to the distance between the TV camera sensor 32 and workpiece 12 linear analog signal is given to the CNC Steuerein device 24 . The measuring or reference point on the workpiece 12 is the working point 29 . The distance control to the target distance is controlled by the CNC control via the X, Y , Z linear axes using the "Constant distance" function.

The ring-shaped grinding shoe 39 is articulated via the linear potentiometer 40 on a guide rod 41 to the tool holder 36 . The swivel joint is designated 42 with net. The guide rod 41 are assigned two potentiometers 43 , via which the angular deviations from the machine axes are measured and the inclination of the tool axis relative to the workpiece surface is determined. In Fig. 3 only Dar potentiometer 43 is drawn for reasons of position. A signal proportional to the inclination is sent from the two potentiometers 43 to the CNC control device 24 and the machine axes are corrected by the CNC control.

With all devices for constant distance maintenance or to adjust or adjust the inclination instead of potentiometers ometer capacitive, inductive etc. measuring systems used will.  

A very compact CCD camera can be expanded particularly advantageously as a TV camera sensor 32 with sensors 37 , 38 if, for example, the sensor NWAL mentioned in the prior art is used as the sensor. This sensor gives, for example, analog signals about the distance and angular deviations. According to these signals, a zero adjustment can either be made manually or corrected automatically via the CNC control. The operator can carry out the entire teach-in programming from a stationary work station. For this purpose, the TV camera sensor 32 is connected via a line 45 to a TV monitor 46 which is installed in the CNC control device 24 . Preferably, the TV camera sensor 32 sits an optical or electronic crosshair 47 , which together with a part of the workpiece 12 on which the machining contour 30 is located, is visible on the TV monitor. The axes of the crosshairs 47 are permanently assigned to the axes of the TV camera sensor 32 and can be adjusted to the working point 29 or the workpiece tip. This advantageously ensures that the center of the image of the TV camera sensor ( 32 ) does not have to coincide with the working point 29 . The crosshair 47 always has the same position on the TV monitor 46 , even if the TV camera sensor 32 is rotated in or by the CO ₂ laser. Of course, it is also possible to install additional electronics that rotate the image with the crosshairs 47 in accordance with the rotation of the machine axes.

A mark is advantageously placed on the workpiece 12 with the laser beam 23 before the start of teach-in programming. Then, the machining head of the laser against the TV camera sensor is exchanged 32 and the reticle 47 to the tool tip adjusted (eg. As the focal point of the laser).

If the machine axes of the workpiece and beam manipulator 10 are now moved, even an incorrect adjustment of the mirrors 26 , 27 , 28 does not result in an error in the teach-in programming.

However, the distance between the lens and the workpiece 12 and the inclination of the tool axis with respect to the workpiece surface are preferably determined via a TV camera sensor 32 with evaluation electronics.

For distance measurement, a light source 48 is attached to the TV camera sensor 32 or at a fixed (adjustable) angle to the camera, which generates the smallest possible point-shaped light spot 49 on the workpiece 12 .

If the TV camera sensor 32 is removed from the workpiece 12 in accordance with the desired distance 50 , the light point 48 should hit the working point 29 or the tool tip as precisely as possible in order to rule out inclination errors. If the desired distance increases or decreases to an actual distance 51 or 52 , other points of impact 53 , 54 on the workpiece 12 result (subject to the sign). In the field of view of the camera, the light point 49 lies in a defined pixel 56 (or - depending on the light source - in a number of pixels) of the CCD array 55 .

If light source 48 , working point 29 or tool tip and cross hair 47 - as described above - are adjusted to one another, then at target distance 50, light point 49 points exactly to cross hair 47 . In the event of a change in distance, the light point 49 migrates from its target position.

For flat (or almost flat surfaces and small deflections kung) and normal to the surface of the camera Emigration is a direct measure of the change in distance.  

It can be counted by changing the coordinates of the light point 49 on the CCD array 55 and thus measured.

In the case of strongly curved workpieces 12 , an apparent ble error 61 results, which is composed of a measurement error 57 and a height error 62 . The measurement error 57 depends on the angle of inclination 59 of the light beam 58 and the angle of inclination 60 of the workpiece surface.

This error is irrelevant for the use as described here, since the signal tends to be preserved (signed), the signal is only slightly distorted and the signal is not used as the actual measurement signal but only as a control signal, ie a control process (manual or automatic) restores the target distance 50 and here the measured value is independent of the inclination of the workpiece surface.

It makes sense to evaluate the CCD image 55 (digital counting of pixels, change of coordinates) for further processing, e.g. B. prepare for the transfer to a CNC control as an anal signal or as for conventional interfaces ( V 24 or similar) suitable digital signal.

A measuring routine can be used to determine the inclination. The distances from several points are preferred wise from three points, close to the working point measure and the inclination is calculated and corrected. The device for inclination re described above gelung or setting 38 can ent in this process fall. The points are added via the Detected image generated by camera sensor.  

If one does not want to use the method "measuring three points and calculating the plane in space from this", one can install three of the light sources 48 described above with three light points 49 on the CCD array 55 . The average inclination of the workpiece surface can be determined from the actual coordinates of the light points 49 in relation to the target coordinates.

With this method of inclination measurement the result is Advantage that only one point can be approached for measuring must (not three points). This saves time and easy handling.

Depending on the arrangement (angle of inclination, spacing of the light points 49 ) and the required accuracy, either three light points 49 or four light points 49 can be used for the distance and inclination measurement.

With three light points 49 , the average distance is calculated, which is therefore subject to errors (see above).

In the case of four light points 49 , the fourth light point 49 is only used for measuring the distance and thus provides an exact result for the adjustment to the desired distance 50 .

For security monitoring and possibly for the rough position a second TV system can be installed.

If the minimum predetermined distance between the lens and the workpiece is undershot and reaches, for example, a distance of 10 millimeters, an alarm signal is generated by the TV camera sensor 32 . In addition, in the event of errors in the sensor system (ie overall system from lens to monitor) which could lead to the destruction of the sensor or the beam manipulator 10 , an interference signal is given to the machine control, which triggers an emergency stop of the processing machine.

The rough positioning can also be carried out with the TV camera sensor 32 . For this purpose, the TV camera sensor is equipped with a zoom lens and has a remote-controlled focus. The operator moves the tool to a large distance from the workpiece 12 . If he has the contour to be programmed in view, he can use the "move on the tool axis" function to approach the workpiece 12 at the desired distance.

Claims (12)

1. A method for machining workpieces with a programmed multi-axis robot, which leads a machining tool, preferably a laser beam, along a three-dimensional workpiece contour, a marking, cutting line or the like being applied to a pattern or workpiece in order to mark the position to be machined and a three-dimensional profile NC program is created by scanning the marking by means of a sensor guided by the multi-axis robot, which controls the axes of the robot so that the sensor always follows the markings and the coordinates of the sensor in the NC at predetermined points Control can be entered as program points and then the workpieces can be processed on the basis of this NC program, characterized in that a TV camera sensor ( 32 ) is used to scan the markings ( 30 ), which the tool standards and / or the tool height to the workpiece surface is determined so that at least on the given the TV camera sensor ( 32 ) is oriented normally and / or at the desired tool distance (perpendicular) to the workpiece surface. 2. The method according to claim 1, characterized in that the orientation to the workpiece surface via at least one light beam ( 58 ) and an optical crosshair ( 47 ) it follows, the target distance ( 50 ) of the TV camera sensor ( 32 ) to a working point ( 29 ) can be adjusted. 3. The method according to claim 1 or 2, characterized in that the measuring workpiece on the same machine ( 10 ) at the same place as the workpieces to be machined ( 12 ) is provided and a workpiece to be machined ( 12 ) and the TV camera Sensor is exchanged for a processing tool after the program has been created. 4. Device for carrying out the method according to one of claims 1 to 3, with a multi-axis machining machine and a teach-in control, the processing machine being assigned a sensor which controls the traversing drives in such a way that the sensor relates to the individual positions predetermined three-dimensional processing tool path, characterized in that the sensor is a TV camera ( 32 ), the facilities for distance constant maintenance ( 37 ) and / or normal control or setting (38) are assigned. 5.Device according to claim 4, characterized in that the TV camera sensor ( 32 ) is connected to a TV monitor ( 46 ) and on the TV monitor ( 46 ) by the TV camera sensor ( 32 ) captured image is shown. 6. Apparatus according to claim 4 or 5, characterized in that the processing machine is a CO ₂ laser ( 10 ) and the TV camera sensor ( 32 ) via a pivotable mirror ( 31 ) in the beam path of the laser beam ( 23 ) can be faded in is. 7. Device according to one of claims 4 to 6, characterized in that the CO ₂ laser ( 10 ) has a stationary laser resonator ( 22 ) and a beam manipulator

• - a stationary gantry (13) at which a workpiece (12) supporting the workpiece manipulator (11) is movable in the X direction,
• - A carriage ( 17 ) which can be moved on the portal ( 13 ) in the Y direction,
• - A vertical guide ( 18 ) which is attached to the carriage in its height in the Z direction above the workpiece ( 12 ),
• - At the end of the vertical guide ( 18 ) arranged in the C-direction rotatable swivel ( 19 ) with a vertical axis of rotation ( 20 ),
• a laser head ( 21 ) attached to the swivel joint ( 19 ), which can be pivoted in the A direction about an axis running perpendicular to the axis of rotation,

having
and the mirror ( 31 ) can be faded into the beam path of the laser beam ( 23 ) extending in the Z direction. 8. Apparatus according to claim 6 or 7, characterized in that the mirror ( 31 ) is partially transparent and the beam manipulator ( 10 ) is assigned a light source ( 33 ), preferably a HeNe laser, for illuminating the working point ( 29 ). 9. The roof of claim 4 or 5, characterized in that the processing machine is a CO ₂ laser and the TV camera sensor ( 32 ) is arranged on a tool holder ( 36 ) of the processing head. 10. Device according to one of claims 1 to 9, characterized in that the TV camera sensor ( 32 ) has an optical crosshair ( 47 ) which is adjustable to the working point ( 29 ) and which the axes of the TV camera Sensor ( 32 ) is assigned. 11. Device according to one of claims 1 to 10, characterized in that the means for maintaining a constant distance ( 37 ) and inclination control or adjustment (38) are designed as capacitive or inductive or eddy current sensors or light sources ( 48 ).