Method and system for the remote laser welding of two coated sheets

Abstract

A method is provided for the remote laser welding of two coated sheets, wherein by way of a scanner, a laser beam is directed at the sheets to be connected to each other and guided on the sheets. The sheets are connected to each other by producing an end fillet weld on a lap joint. The continuous production of the weld is recorded by a camera and, if necessary, the path of the laser beam is corrected and adapted to a target weld course on the basis of an automatic evaluation of the recorded images.

Claims

1. A method for laser remote welding of two coated sheets, the method comprising the acts of: directing a laser beam onto the two coated sheets to be joined to one another and guiding the laser beam on the two coated sheets by way of a scanner; producing an end fillet weld on a lap joint between the two coated sheets in order to join the two coated sheets to one another; continuously recording images of a production of the end fillet weld, via a camera; comparing the continuously recorded images to a desired weld course by identifying a position of the generated end fillet weld on the recorded images and comparing a course of the generated end fillet weld to a step offset that is formed by an abutment between the two coated sheets that have not yet been welded; determining an actual position of the laser beam; calculating a correction movement amount; correcting a path of the laser beam to match it to the desired weld course, based on the correction movement amount to ensure continuous production of the end fillet weld; and checking a quality of the produced end fillet weld.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows two sheets joined to one another by way of an end fillet weld in a plan view;

(2) FIG. 2 shows a section through the end fillet weld from FIG. 1; and

(3) FIG. 3 shows a system according to an embodiment of the invention for laser remote welding in a schematic view.

DETAILED DESCRIPTION OF THE DRAWINGS

(4) FIG. 1 shows two coated flat sheets 10 and 20, which are arranged overlapping one another or with a lap joint and are joined to one another by material-to-material bonding by way of a straight end fillet weld 30. According to the diagram shown in FIG. 1, the sheet 10 can be designated as the bottom sheet and the sheet 20 as the top sheet. The top sheet 20 can rest completely on the bottom sheet 10 and be joined to the bottom sheet 10 by way of peripheral end or side fillet welds. An end fillet weld 30 can also have a course which is curved in one plane and, if necessary, also curved spatially.

(5) FIG. 2 shows a section through the end fillet weld 30. The form of the weld, which is formed between the edge surface or side surface of the top sheet 20 and the adjacent contact surface of the bottom sheet 10, can be clearly seen in this diagram.

(6) Before welding, the top sheet 20 is positioned and aligned on the bottom sheet 10. The coated sheets 10 and 20 are then welded with a laser beam, which can be carried out on the system explained below in conjunction with FIG. 3.

(7) FIG. 3 shows a system for laser remote welding which is designated as a whole by 100. The system 100 includes a scanner 110, which is known as such from the prior art and is fixed to a robot arm 120 of a robot by way of a flange 125. The scanner 110 can be moved in space by the robot, which is illustrated by the double arrows. This enables welding on the fly to be carried out as explained above. Further, the system 100 includes an illumination device 130 which is fixed to the scanner 110, and an imaging device 140, such as a camera which is likewise fixed to the scanner 110. The system 100 also includes a control unit 150 which is connected by way of interfaces (not shown) to the scanner 110, the illumination device 130, the camera 140 and the robot.

(8) In order to weld the two coated sheets 10 and 20, they are positioned together. A laser beam L is then directed by way of the scanner 110 onto the sheets 10 and 20, which are arranged below the scanner 110, and guided along a specified path (desired weld course) over the sheets 10 and 20 (see arrow in FIG. 3), wherein an end fillet weld 30 as described above is formed. The formation of an end fillet weld 30 leads to good degassing conditions for the coating material, which vaporizes due to the heat introduced by the laser beam (as explained in detail above). Further possible ways of removing the coating from the sheets 10 and 20 are described above. Further, the end fillet weld allows the sheets 10 and 20 to be joined without a gap (as likewise explained in detail above).

(9) The distance between the scanner 110 and the sheets 10/20 is, for example, 0.5 m or more, which increasingly leads to position errors. During the production of the weld, the end fillet weld 30 produced is continuously recorded by the camera 140, wherein the recorded region (this is typically the process zone directly and the zone immediately following the process zone) can be additionally illuminated by the illumination device 130. On the basis of the images or video sequences recorded by the camera 140, the actual weld course is automatically evaluated by the control unit 150, for example by comparison with the step offset between the sheets 10 and 20. In the event of a deviation from the desired weld course, the path of the laser beam L is corrected and matched to the desired weld course, which is likewise initiated by the control unit 150, which actuates the scanner 110 and/or the robot appropriately for this purpose. The path can be matched with an accuracy of +/100 m.

(10) A quality control or quality check of the generated end fillet weld 30 can be undertaken on the basis of the images recorded by the camera 140 as already explained.

(11) Instead of the arrangement of the illumination device 130 and the camera 140 shown by way of example in FIG. 3, these can also be coupled within the scanner 110, which can take place with the help of mirrors, for example.

LIST OF REFERENCES

(12) Method and device for the laser remote welding of two coated sheets 10 Coated sheet (bottom sheet) 20 Coated sheet (top sheet) 30 End fillet weld (weld) 100 System 110 Scanner 120 Robot arm 125 Fixing flange 130 Illumination device 140 Camera 150 Control unit (control module) L Laser beam

(13) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.