Apparatus and method for automatically aligning a welding device for butt welding workpieces

• US 5,045,668 A
• Filed: 04/12/1990
• Issued: 09/03/1991
• Est. Priority Date: 04/12/1990
• Status: Expired due to Term

• Current Assignee: Armco Inc. (Cleveland-Cliffs Steel Holding Corp.)
• Original Assignee: Armco Inc. (Cleveland-Cliffs Steel Holding Corp.)
• Inventors: Nagle, William W., Justice, Robert J., Neiheisel, Gary L., Hoover, Bradley R.
• Primary Examiner(s): ALBRITTON, CLARENCE
• Application Number:
  US07/508,904
• Time in Patent Office: 509 Days
• Field of Search: 219/121.83, 219/121.63, 219/121.64, 219/121.67, 219/121.72, 219/124.34
• US Class Current: 219/121.83
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/0344 Observing the speed of the workpiece
• CPC Class Codes: B23K 26/04 Automatically aligning, aiming or focusing the laser beam, e.g. using the back-scattered light
• CPC Class Codes: B23K 26/044 Seam tracking
• CPC Class Codes: B23K 26/0643 comprising mirrors
• CPC Class Codes: B23K 26/147 Features outside the nozzle for feeding the fluid stream towards the workpiece
• CPC Class Codes: B23K 26/348 in combination with arc heating, e.g. TIG [tungsten inert gas], MIG [metal inert gas] or plasma welding laser beam for starting a welding or cutting arc B23K9/067
• CPC Class Codes: B23Q 35/128 Sensing by using optical means

Abstract

Apparatus and method for aligning a welding device along the center of a gap defined by confronting edges of at least two workpieces to be joined, wherein relative motion between the welding device and the workpiece gap occurs along a longitudinal axis substantially parallel to the gap such that the proximal edges of the workpieces can be joined by forming a weld seam along the gap during the relative motion. The apparatus preferably includes an imaging system for determining the location of the gap center relative to a predetermined two dimensional coordinate system by monitoring an image of a vision area along the gap downstream of the welding zone. In a preferred embodiment, the imaging system is effectively isolated from the welding zone through use of a high magnification optics system, a shroud structure, an independent light source, and a vectored jet of inert gas supplied to the welding zone.

Claims

1. An apparatus for automatically and continuously aligning a welding device along approximately the center of a continuous gap defined by confronting proximal edges of at least two workpieces to be joined, wherein relative motion between said welding device and said workpieces along a longitudinal axis substantially parallel to said gap permits joining of said confronting edges of said workpieces by said welding device by application of welding energy at a welding zone along said edges, said aligning apparatus comprising:

(a) an imaging system for determining the location of said gap center relative to a predetermined two dimensional coordinate system, wherein an image of a vision area spaced downstream of said welding zone along said longitudinal axis is produced, said vision area designed to span said gap and include said confronting edges of said workpieces;

(b) means for receiving and transforming said image of said vision area into an output signal defining the location of said gap center relative to said welding device;

(c) means for automatically adjusting the relative positions of said welding device and said center of said gap in response to said output signal such that said welding device and said center are continuously aligned at all times; and

(d) means for effectively isolating said vision area from said welding zone, said isolating means including a jet of inert gas provided adjacent said welding zone to divert weld plume, smoke, spatter and other welding debris from said vision area.

2. The apparatus of claim 1, further comprising an independent source of illumination which transmits light to said vision area by means of a coherent fiber optics bundle.

3. The apparatus of claim 2, wherein illumination of said vision area is provided coaxially with said imaging system.

4. The apparatus of claim 1, wherein said adjusting means further comprises a translation table for supporting said workpieces, said translation table being movable substantially perpendicular to said longitudinal axis in response to control signals derived from said output signal, wherein movement of said translation table results in adjustment of said gap center in a direction substantially perpendicular to said longitudinal axis.

5. The apparatus of claim 1, further including means for directing a laser beam of said welding device to said welding zone, said directing means comprising at least one reflecting mirror which reflects said laser beam through laser focusing optics to said zone.

6. The apparatus of claim 5, said adjusting means comprising means for moving said at least one reflecting mirror, wherein said laser beam is movable substantially perpendicular to said longitudinal axis in response to control signals derived from said output signal.

7. The apparatus of claim 5, said adjusting means comprising:

(a) a gantry structure having a cross member;

(b) a mechanical carriage connected to said cross member and linearally movable thereacross, said directing means and said vision system being attached to said mechanical carriage;

(c) means for moving said mechanical carriage across said cross member;

(d) means for providing a control signal to move said mechanical carriage in response to said output signal, wherein adjustment of said laser beam normal to said longitudinal axis occurs to maintain alignment with said gap center.

15. The apparatus of claim 1, including a source of illumination which illuminates said gap from below said workpieces.

8. An apparatus for automatically and continuously aligning a laser beam along approximately the center of a continuous gap defined by confronting proximal edges of at least two workpieces, wherein relative motion between said laser beam and said workpieces occurs along a longitudinal axis substantially parallel to said gap to permit welding or cutting of said workpieces by said laser beam, said aligning apparatus comprising:

(a) a vision system for determining the location of said center relative to a predetermined two dimensional coordinate system, said vision system further comprising;

(1) a line scan camera for producing an image of a vision area spaced downstream of said laser beam along said longitudinal axis, said vision area designed to span said gap and to include said confronting edges of said workpieces;

(2) an optics system operably attached to said line scan camera, wherein said line scan camera may be substantially spaced from said vision area while maintaining the reception of said vision area;

(3) a fiber optic ring illuminator connected to the lowermost portion of said optics system; and

(4) an independent source of illumination connected to said fiber optic illuminator by means of a coherent fiber optics bundle, wherein illumination is supplied to said vision area coaxial to said optics system;

(b) means for receiving said image and transforming it into an output signal defining the location of said gap center relative to said laser beam;

(c) a first translation table movable parallel to said longitudinal axis for providing said relative motion between said laser beam and said workpieces, said workpieces being fixtured to said first translation table so that said workpieces move in accordance therewith;

(d) means for automatically adjusting the relative locations of said laser beam and said gap center in response to said output signal such that said laser beam and said gap center are continuously maintained in alignment.

9. The apparatus of claim 8, wherein said adjusting means further comprises a second translation table being movable substantially perpendicular to said longitudinal axis in response to control signals derived from said output signal, said second translation table being movable in conjunction with said first translation table, said workpieces being fixtured to said translation tables so that said workpieces move in accordance with said first and second translation tables.

10. The apparatus of claim 8, wherein said receiving means has an adjustable field of view to selectively transform only a predetermined portion of said image into an output signal.

11. The apparatus of claim 8, further including means for directing said laser beam to a defined zone along said longitudinal axis, said directing means comprising at least one reflecting mirror which reflects said laser beam through laser focusing optics to said zone.

12. The apparatus of claim 11, further including:

(a) a gantry structure having a cross member;

(b) a mechanical carriage connected to said cross member and linearally movable thereacross, said directing means and said vision system being attached to said mechanical carriage;

(c) means for moving said mechanical carriage across said cross member;

(d) means for providing a control signal to move said mechanical carriage in response to said output signal, wherein adjustment of said laser beam normal to said longitudinal axis occurs to maintain alignment with said gap center.

13. The apparatus of claim 8, including a means for monitoring said output signal.

14. The apparatus of claim 8, wherein said adjusting means is not responsive to an output signal below a predetermined threshold level.

16. The apparatus of claim 8, wherein said workpieces are substantially planar.

17. The apparatus of claim 8, said adjusting means including a computer for automatically adjusting the velocity of said first translation table adjustments.

18. A method of automatically and continuously aligning a welding device along approximately the center of a continuous gap defined by confronting proximal edges of at least two workpieces to be joined, wherein relative motion between said welding device and said workpieces along a longitudinal axis substantially parallel to said gap permits joining of said confronting edges of said workpieces by said welding device, said method including the steps of:

(a) providing a vision system for determining the location of said center of said gap along said longitudinal axis during said relative motion, said vision system monitoring said gap within a vision area spaced downstream of said welding device along said longitudinal axis;

(b) automatically adjusting the relative positions of said welding device and said center of said gap such that said welding device and said gap center are maintained in alignment;

(c) providing a jet of inert gas adjacent the zone where said welding device applies welding energy along said gap during joining procedures, said jet being effectively oriented such that its resultant vector is through said zone and away from said vision area.

19. The method of claim 18, further including the step of providing illumination to said vision area.

20. The method of claim 18, further comprising the step of maintaining a constant rate of adjustment of the relative positions of said welding device and said gap center at the end of said gap once said vision area passes the distal end of said gap, said constant rate being determined by a controller for maintaining alignment once said vision area passes the end of said gap.

21. The method of claim 18, further including the step of initially aligning said gap center with the direction of relative motion between said welding device and said workpieces.

22. The method of claim 21, wherein said initial alignment step includes:

(a) pulsing said welding device at a plurality of predetermined points along the longitudinal axis of said gap;

(b) locating a line connecting said points;

(c) comparing said line with the current direction of relative motion; and

(d) compensating for any misalignment between said line and the current direction of relative motion.

23. An apparatus for automatically and continuously aligning a welding device along approximately the center of a continuous gap defined by confronting proximal edges of at least two workpieces to be joined, wherein relative motion between said welding device and said workpieces along a longitudinal axis substantially parallel to said gap permits joining of said confronting edges of said workpieces by said welding deice by application of welding energy at a welding zone along said edges, said aligning apparatus comprising:

(a) an imaging system for determining the location of said gap center relative to a predetermined two dimensional coordinate system, wherein an image of a vision area spaced downstream of said welding zone along said longitudinal axis is produced, said vision area designed to span said gap and include said confronting edges of said workpieces;

(b) means for receiving and transforming said image of said vision area into an output signal defining the location of said gap center relative to said welding device;

(c) means for automatically adjusting the relative positions of said welding device and said center of said gap in response to said output signal such that said welding device and said center are continuously aligned to all times; and

(d) means for effectively isolating said vision area from said welding zone, said isolating means comprising a jet of inert gas provided adjacent said welding zone during joining procedures, said jet effectively oriented in a direction such that its resultant vector is away from said vision area.

24. The apparatus of claim 23, wherein said jet is provided via a supply line having a first end connected to a sources of inert gas, and a nozzle, wherein a vectored jet of inert gas is applied adjacent said welding zone, such that smoke, spatter and other welding debris are directed away from said vision area.

25. The apparatus of claim 24, wherein said supply line and nozzle are positioned downstream of said vision area such that said vectored jet of inert gas is applied to said welding zone substantially along said longitudinal axis.

26. An apparatus for automatically and continuously aligning a welding device along approximately the center of a continuous gap defined by confronting proximal edges of a at least two workpieces to be joined, wherein relative motion between said welding device and said workpieces along a longitudinal axis substantially parallel to said gap permits joining of said confronting edges of said workpieces by said welding device by application of welding energy at a welding zone along said edges, said aligning apparatus comprising:

(a) an imaging system for determining the location of said gap center relative to a predetermined two dimensional coordinate system, wherein an image of a vision area spaced downstream of said welding zone along said longitudinal axis is produced, said vision area designed to span said gap and include said confronting edges of said workpieces;

(b) means for receiving and transforming said image of said vision area into an output signal defining the location of said gap center relative to said welding device;

(c) means for automatically adjusting the relative positions of said welding device said center of said gap in response to said output signal such that said welding device and said center are continuously aligned at all times;

(d) means for effectively isolating said vision area from said welding zone; and

(e) a shroud connected to the lowermost portion of said imaging system adjacent said vision area, said shroud effectively protecting said imaging system from welding debris and facilitating concentration of illumination onto said vision area.

27. An apparatus for automatically and continuously aligning a laser beam long approximately the center of continuous gap defined by confronting proximal edges of at least two workpieces, wherein relative motion between said laser beam and said workpieces occurs along a longitudinal axis substantially parallel to said gap to permit welding or cutting of said workpieces by said laser beam, said aligning apparatus comprising:

(a) a vision system for determining the location of said center relative to a predetermined two dimensional coordinate system, said vision system further comprising;

(1) a line scan camera for producing an image of a vision area spaced downstream of said laser beam along said longitudinal axis, said vision area designed to span said gap and to include said confronting edges of said workpieces;

(2) an optics system operably attached to said line scan camera, wherein said line scan camera may be substantially spaced from said vision area while maintaining the reception of said vision area;

(3) a fiber optic illuminator connected to the lowermost portion of said optics system; and

(4) an independent source of illumination connected to said fiber optic illuminator by means of a coherent fiber optics bundle, wherein illumination is supplied to said vision area coaxial to said optics system;

(b) means for receiving said image and transforming it into an output signal defining the location of said gap center relative to said laser beam;

(c) a first translation table movable parallel to said longitudinal axis for providing said relative motion between said laser beam and said workpieces, said workpieces being fixtured to said first translation table so that said workpieces move in accordance therewith;

(d) means for automatically adjusting the relative locations of said laser beam and said gap center in response to said output signal such that said laser beam and said gap center are continuously maintained in alignment; and

(e) a jet of inert gas provided adjacent the point of impingement of said laser beam with said gap and effectively oriented such that its resultant vector is away from said vision area.

28. The apparatus of claim 27, wherein said jet of inert gas is provided by a supply line having a first end connected t a supply of inert gas and a nozzle, said nozzle attached adjacent said optics system and downstream of said vision area adjacent said gap center.

29. An apparatus for automatically and continuously aligning a laser beam along approximately the center of a continuous gap defined by confronting proximal edges of at least two workpieces, wherein relative motion between said laser beam and said workpieces occurs along a longitudinal axis substantially parallel to said gap to permit welding or cutting of said workpieces of said laser beam, said aligning apparatus comprising:

(a) a vision system for determining the location of said center relative to a predetermined two dimensional coordinate system, said vision system further comprising;

(1) a line scan camera for producing an image of a vision area spaced downstream of said laser beam along said longitudinal axis, said vision area designed to span said gap and to include said confronting edges of said workpieces;

(2) an optics system operably attached to said line scan camera, wherein said line scan camera may be substantially spaced from said vision area while maintaining the reception of said vision area;

(3) a fiber optic illuminator connected to the lowermost portion of said optics system; and

(4) an independent source of illumination connected to said fiber optic illuminator be means of a coherent fiber optics bundle, wherein illumination is supplied to said vision area coaxial to said optics system;

(b) means for receiving said image and transforming it into an output signal defining the location of said gap center relative to said laser beam;

(c) a first translation table movable parallel to said longitudinal axis for providing said relative motion between said laser beam and said workpieces, said workpieces being fixtured to said first translation table so that said workpieces move in accordance therewith;

(d) means for automatically adjusting the relative locations of said laser beam and said gap center in response to said output signal such that said laser beam and said gap center are continuously maintained in alignment; and

(e) a shroud attached to the lowermost portion of said optics system to protect said optics system frog debris, smoke and the like.

30. An apparatus for automatically and continuously aligning a laser beam long approximately the center of a continuous gap defined by confronting proximal edges of at least two workpieces, wherein relative motion between said laser beam and said workpieces occurs along a longitudinal axis substantially parallel to said gap to permit welding or cutting of said workpieces by said laser beam, said aligning apparatus comprising:

(a) a vision system for determining the location of said center relative to a predetermined two dimensional coordinate system, said vision system further comprising;

(1) a line scan camera for producing an image of a vision area spaced downstream of said laser beam along said longitudinal axis, said vision area designed to span said gap and to include said confronting edges of said workpieces;

(2) an optics system operably attached to said line scan camera, wherein said line scan camera may be substantially spaced from said vision area while maintaining the reception of said vision area;

(3) a fiber optic illuminator connected to the lowermost portion of said optics system; and

(4) an independent source of illumination connected to said fiber optic illuminator by means of a coherent fiber optics bundle, wherein illumination is supplied to said vision area coaxial to said optics system;

(b) means for receiving said image and transforming it into an output signal defining the location of said gap center relative to said laser beam;

(c) a first translation table movable parallel to said longitudinal axis for providing said relative motion between said laser beam and said workpieces, said workpieces being fixtured to said first translation table so that said workpieces move in accordance therewith;

(d) means for automatically adjusting the relative locations of said laser beam and said gap center in response to said output signal such that said laser beam and said gap center are continuously maintained in alignment;

(e) means for directing said laser beam to a defined zone along said longitudinal axis, and directing means comprising at least one reflecting mirror which reflects said laser beam through laser focusing optics to said zone; and

(f) a motor operably connected to said reflecting mirror, wherein said reflecting mirror may be rotated to allow slight adjustments in the direction or said laser beam.