Method of and apparatus for monitoring and positioning a radius in machining femi-finished products

The subject of the invention is a method and device for controlling and setting the laser beam in the process of welding semi-finished products, especially in mass production, for example in the construction of cars.

In many, primarily industrial machining methods, it is necessary to control or set the radius, for example for laser radiation or an aqueous cutting stream. In both cases, the beam path was mainly determined by the electrical device. The ray would later follow this path. The quality of the cut depends, among other things, on whether the radius stops exactly on the specified route.

A similar situation occurs with larger dimensions, when welding with a ray, in particular when welding with a laser beam. However, the advantages of the butt joint process, machined sheet metal parts, carried out by laser beam welding, appear directly in mass production, for example in the construction of cars, as "tolerated blanks" and are relevant only when they meet the high requirements of this process, geometric tolerance parts, edge cut quality and laser radiation properties.

With a normal focal diameter of 0.2 to 0.4 mm, accurate laser beam alignment and a high-quality weld connection on the connecting line between the two blanks to be joined can be achieved. The maximum setting tolerance should not exceed 0.1 mm with a technological gap. If this gap must be flooded with a metal pool, tolerance is still limited.

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Appearing deficiencies of smelting resulting from defective radius setting are particularly harmful for covered welds because they are covered by a wider weld face. Also with remelting, widespread weld penetration can be made to invisible internal melting deficiencies.

Sufficiently high positioning accuracy was achieved by means of optoelectronic sensors or photo-machining systems that convey the actual course of the line connecting the parts, i.e. the contact line of both blanks, before the radius as a consequence of the correction coordinate directly to the machine control device. In this way, the laser head can be pointed at the weld with an accuracy of approximately 0.05 mm. A similar weld search system is shown, for example, in DE-OS 43 12 241.

The main disadvantage with these methods is that the search system for lines connecting parts must come out of a well-defined position of the laser beam. The reference coordinate measurement cannot be referenced to the actual radius position. Temporarily one exemplary course will be carried out at least after one radius path check, which implies a production break. The changes in the position of the laser beam caused by the thermal operation of the ray generator and the beam guidance are completely ignored. The result is a reduction in the accuracy of the welding process.

A possible solution to this problem could function in adapting the computer program to detect the position of the ray in the beam guidance system that already exists, thanks to the search system. Similar detection, however, is usually inappropriate for on-line work, or at least a significant amount of work is to be expected.

A solution is also known in which the welding weld is controlled by a radius. However, the position of the line connecting the parts is not taken into account, but only the quality of the weld weld is detected.

The subject of the invention is a method for controlling and setting the radius for machining of blanks, in which the first sensor (weld search system) located in front of the radius or the set value determines the path following the radius. A second sensor behind the beam controls its activity.

The essence of the invention is that the set value or indication of the first sensor over the set position is compared with the indications of the second sensor over the actual position of the ray. The relation between velocity of relative radius displacement (blank) and correcting at the deviation of the actual position to the given radius position at the basic position are taken into account.

Preferably, the set position of the ray is detected in a light cutting method or in a combination of a light cutting method and a method of assessing the gray of an image. The actual position of the ray is detected by assessing the gray of the image or in a combination of a method of cutting with light and a method of assessing the gray of the image and compares each other.

The invention also relates to a device for controlling and setting the radius for machining semi-finished products, in which the first sensor (weld search system) located in front of the radius or the set value determines the path following the radius, and the second sensor after the radius controls its activity.

The essence of the invention is that the first and second sensors are connected to a control device for comparing the indications of both sensors; The control device is connected to a displacement device for realizing the relative movement of the radius displacement towards the blank.

Both sensors can work in any way. The method of the invention is used for cutting with a radius, so a radius sensor is usually superfluous. In this case, the set value present in the electronic memory is assumed as the sensor supply for determining the set position and appropriate beam management.

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The system of the invention is not limited to the production of a welded joint between two blanks, in particular for laser welding, but can be used in all methods involving guiding a beam along a certain path. First of all, they include cutting methods using high-energy radiation.

The object of the invention is illustrated in the embodiment in the drawing, in which Fig. 1 partially shows a top view of the radius setting control device for machining of blanks, and Fig. 2 shows a top view of the device according to Fig. 1 with a schematic representation of the radius position.

The method of functioning of the present invention is described in particular in detail on the basis of Fig. 2.

Sensor 7, which precedes ray 3, also works in the so-called light cutting process. The radius is projected at an angle to the optical band pattern of the detection axis, in the present case over five existing parallel bands 10, over the area of ​​the line connecting the parts 4. The bands 10 in fact run across the weld seam, but can also be arranged in different intervals. In the area of ​​the connecting line, parts 4 of the bands have been interrupted, but slips occur that have been detected by sensor optics. The course of the line connecting the parts can then be determined from the band numbers corresponding to the number of points.

According to Fig. 2, the second sensor 9 also works in the same way, the welding weld 5 being displayed here by a corresponding band pattern 11.

Thus, radius 3 deviates over time, e.g. as a result of a thermally caused shift from its constantly indicated position to its limit position, and thus can be unnoticed by sensor 7, because sensor 7 is always set to the fact that the radius 3 is in the basic position . On the other hand, the sensor 9 downstream of the sensor 7 detects a different course of the welding weld 5, because the measurement results fed to the control device 8, which, for example, consist of the position coordinates achieved by drawing analysis, do not match. This is also schematically indicated by dashes. By means of the control device 8 only the offset unit is moved according to the correction value obtained, so that the radius 3 is brought back to the basic position.

According to Fig. 1, two blanks 1 and 2 should be connected with a radius 3. The connection area between both blanks 1 and 2 located before the radius 3 is marked as the connecting line of the parts 4, the area after the radius 3 as the welding weld 5.

The radius 3 comes from an unspecified ray source located in the displacement device 6, which can, for example, constitute a cross slide. In this case, the offset device 6 is shifted in two dimensions in the x or y direction. However, it is also possible to use three-dimensional offset. It is only important that the radius 3 can be guided through the displacement device 6 along the line connecting the parts 4 and set on it.

In order for the radius 3 to be routed along the connecting line of the parts 4, a sensor 7 is switched on before the radius 3, which is also marked as a weld search system. The sensor 7 detects the current course of the connecting line of parts 4, and based on the speed dependence, the offset time of the blank - or the offset time of the beam, if this is shifted relative to the blank - is detected, and the route of the connecting line of 4 through the control device 8, the control device being 8 actuates the displacement device 6 according to the measurement results of the sensor 7 so that the radius 3 is always directed exactly at the line connecting the parts 4, first, in the not represented center line of the line connecting parts 4.

According to the invention, the further sensor 9 should be switched on behind the radius 3 and also connected to the control device 8. This second sensor 9 observes the weld 5.

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UP Department of Publications. Circulation of 60 copies

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