Apparatus for regulating welding parameters during laser beam welding

• US 6,311,099 B1
• Filed: 10/15/1998
• Issued: 10/30/2001
• Est. Priority Date: 04/18/1997
• Status: Expired due to Fees

• Current Assignee: Daimler AG (Mercedes-Benz Group AG)
• Original Assignee: Daimler Chrysler Company LLC (Stellantis NV)
• Inventors: Jasper, Knut, Breitschwerdt, Sven, Schmid, Carlo
• Primary Examiner(s): Grant, William
• Assistant Examiner(s): Hartman, Jr., Ronald D
• Application Number:
  US09/172,600
• Time in Patent Office: 1,111 Days
• Field of Search: 700/166, 700/258, 700/195, 700/95, 219/121.83, 219/121.64, 706/900, 706/904
• US Class Current: 700/166
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/04 Automatically aligning, aiming or focusing the laser beam, e.g. using the back-scattered light
• CPC Class Codes: H04N 7/183 for receiving images from a single remote source
• CPC Class Codes: Y10S 706/90 Fuzzy logic
• CPC Class Codes: Y10S 706/904 Manufacturing or machine, e.g. agricultural machinery, machine tool

Abstract

An apparatus for regulating welding parameters during laser beam welding includes a camera for detecting the geometry of a melt bath formed during the welding process. The camera is connected with an image-data-processing unit. The welding depth is regulated by the processing unit as a function of the detected melt bath length or melt bath area. The focus position of the laser beam is regulated as a function of the geometric similarity factor, which is calculated as the quotient of the melt bath area and the distance between the geometric centers of gravity of the laser beam keyhole and the melt bath area. Detection and regulation of gaps between the workpieces of height offset between the workpieces and/or lateral offset of the laser beam is also provided for.

Claims

1. An apparatus for regulating welding parameters during laser beam welding, comprising:

a CCD camera for detecting a geometry of a melt bath formed during a welding process, and

an image data processing unit,

wherein the camera is operably connected with the image-data-processing unit such that a welding depth is regulated as a function of a melt bath length or melt bath area detected and wherein at least one of a gap offset and a weld position of the laser beam is regulated as a function of the detected geometry of the melt bath.

2. The apparatus of claim 1, wherein recognition of melt bath ejections takes place via detection of the melt bath length.

3. The apparatus of claim 1, wherein the camera records electromagnetic radiation in a range between 800 nm and 1,100 nm.

4. The apparatus of claim 3, wherein the camera detects electromagnetic radiation in a range between 820 nm and 1,050 nm.

5. The apparatus of claim 4, wherein a sharp-edged interference filter as well as a gray filter of optical density are placed ahead of the camera.

6. The apparatus of claim 1, wherein gray value assignment of the pixels of a melt bath image detected by the camera is effected by the image data processing unit.

7. The apparatus of claim 6, wherein a three-stage gray value assignment including white, gray and black is effected by the image data processing unit.

8. The apparatus of claim 2, wherein the camera records electromagnetic radiation in a range between 800 nm and 1,100 nm.

9. The apparatus of claim 8, wherein the camera detects electromagnetic radiation in a range between 820 nm and 1,050 nm.

10. The apparatus of claim 9, wherein a sharp-edged interference filter as well as a gray filter of optical density are placed ahead of the camera.

11. The apparatus of claim 2, wherein gray value assignment of the pixels of the melt bath image detected by the camera is effected by the image data processing unit.

12. The apparatus of claim 4, wherein gray value assignment of the pixels of a melt bath image detected by the camera is effected by the image data processing unit.

13. The apparatus of claim 12, wherein a three-stage gray value assignment including white, gray and black is effected by the image data processing unit.

14. An apparatus for regulating welding parameters during laser beam welding, comprising:

a CCD camera for detecting a geometry of a melt bath formed during a welding process, and

an image data processing unit,

wherein the camera is operably connected with the image-data-processing unit such that a focus position of the laser beam is regulated as a function of a geometric similarity factor, which is calculated as the quotient of the melt bath area and the distance between the geometric centers of gravity of a laser beam keyhole and the melt bath area.

15. The apparatus according to claim 14, wherein the camera records electromagnetic radiation in a range between 800 nm and 1,100 nm.

16. The apparatus according to claim 15, wherein the camera detects electromagnetic radiation in a range between 820 nm and 1,050 nm.

17. The apparatus according to claim 14, wherein a sharp-edged interference filter as well as a gray filter of optical density are placed ahead of the camera.

18. The apparatus according to claim 16, wherein a sharp-edged interference filter as well as a gray filter of optical density are placed ahead of the camera.

19. The apparatus according to claim 14, wherein gray value assignment of the pixels of a melt bath image detected by the camera is effected by the image data processing unit.

20. The apparatus according to claim 19, wherein a three-stage gray value assignment including white, gray and black is effected by the image data processing unit.

21. A method of manufacturing a structure by laser beam welding parts together, comprising:

projecting a laser beam onto the parts to weld them with formation of a melt bath having a melt bath geometry including a melt bath length, a melt bath area, and a melt bath depth,

detecting the melt bath geometry utilizing a CCD camera and supplying a melt bath geometry signal from the camera to an image processing unit,

and controlling the projection of the laser beam to control the melt bath depth as a function of at least one of the melt bath length and the melt bath area wherein at least one of a gap offset and a weld position of the laser beam is regulated as a function of the detected geometry of the melt bath.

22. A method according to claim 21, wherein the control of the melt bath depth is made as a function of the melt bath length.

23. A method according to claim 21, wherein the camera records electromagnetic radiation in a range between 800 nm and 1,100 nm.

24. A method according to claim 21, wherein gray value assignment of the pixels of a melt bath image detected by the camera is effected by the image data processing unit.

25. A method according to claim 24, wherein a three-stage gray value assignment including white, gray and black is effected by the image processing unit.

26. A method of manufacturing a structure by laser beam welding parts together, comprising:

projecting a laser beam onto the parts to weld them with formation of a melt bath having a melt bath geometry including a melt bath length, a melt bath area, and a melt bath depth,

detecting the melt bath geometry utilizing a CCD camera and supplying a melt bath geometry signal from the camera to an image processing unit,

and controlling the projection of the laser beam such that a focus position of the laser beam is regulated as a function of a geometric similarity factor calculated as a quotient of the melt bath area and the distance between the geometric centers of gravity of a laser beam keyhole and the melt bath area.

27. A method according to claim 26, wherein the camera records electromagnetic radiation in a range between 800 nm and 1,100 nm.