Abstract

We describe a closed-loop control system ensuring full penetration in welding by controlling the focus position and power of a 4-kW Nd:YAG laser. A focus position monitoring system was developed based on the chromatic aberration of the focusing optics. With the laser power control system we can determine the degree of penetration by analyzing the keyhole image intensity profile. We demonstrate performance in bead-on-plate welding of Inconel 718 and titanium. The focus control system maintained a focal position on tilted and nonflat workpieces, and the penetration monitoring technique successfully controlled the laser power to maintain the full-penetration regime in the presence of linear and step changes of thickness. Finally we discuss the performances and the limits of the systems when applied to a realistic complex aerospace component.

© 2005 Optical Society of America

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  1. J. Beersiek, “New aspects of monitoring with a CMOS camera for laser materials processing,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2002).
  2. P. Abels, S. Kaierle, C. Kratzsch, R. Poprawe, W. Schulz, “Universal coaxial process control system for laser material processing,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. E, pp. 99–108.
  3. J. Beersiek, R. Poprawe, W. Schulz, H. Gu, R. E. Mueller, W. W. Duley, “On-line monitoring of penetration depth in laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 30–39.
  4. M. Dahmen, S. Kaierle, P. Abels, C. Kratzsch, E. W. Kreutz, R. Poprawe, “Adaptive quality control for laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. D, pp. 29–38.
  5. F. M. Haran, D. P. Hand, C. Peters, J. D. C. Jones, “Focus control system for laser welding,” Appl. Opt. 36, 5246–5251 (1997).
    [CrossRef] [PubMed]
  6. M. D. T. Fox, D. P. Hand, D. Su, J. D. C. Jones, S. A. Morgan, M. A. McLean, W. M. Steen, “Optical sensor to monitor and control temperature and build height of the laser direct-casting process,” Appl. Opt. 37, 8429–8433 (1998).
    [CrossRef]
  7. A. Cobo, F. Bardin, P. Aubry, W. Knapp, O. Collin, J. D. C. Jones, D. P. Hand, J. M. López-Higuera, “Optical fibre-based focus control system for laser welding incorporating automatic setup,” in Proceedings of the Sixteenth International Conference on Optical Fiber Sensors (Institute of Electronics, Information and Communications Engineers, Tokyo, 2003), pp. 412–415.
  8. C. Dietz, M. Jurca, L. Schlichtermann, M. Kigel-Hollacher, S. Breitschwerdt, C. Schmid, L. Rowold, “Closed loop control system for laser welding of transmission parts,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1998), Vol. 85, Sect. C, pp. 178–186.
  9. S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Penetration control in laser welding of sheet metal,” J. Laser Appl. 14, 210–214 (2002).
    [CrossRef]
  10. S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Feedback control for optimal production speed in laser beam welding of mild steel,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2002).
  11. C. Bagger, F. O. Olsen, “Laser welding closed-loop power control,” J. Laser Appl. 15, 19–24 (2003).
    [CrossRef]
  12. H. Derouet, L. Sabatier, F. Coste, R. Fabbro, “Process control applied to laser surface remelting,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 85–92.
  13. H. Gu, W. W. Duley, “A novel detector for closed-loop focus control during laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1998), Vol. 85, Sect. C, pp. 69–75.
  14. H. K. Tonshoff, A. Ostendorf, W. Specker, “Quality assurance of laser welding processes by adaptive closed-loop process control,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2000), Sect. E, pp. 252–261.
  15. F. Bardin, A. Cobo, J. M. Lopez-Higuera, O. Collin, P. Aubry, T. Dubois, M. Högström, P. Nylen, P. Jonsson, J. D. C. Jones, D. P. Hand, “Optical techniques for real-time penetration monitoring for laser welding,” Appl. Opt. (submitted for publication).

2003 (1)

C. Bagger, F. O. Olsen, “Laser welding closed-loop power control,” J. Laser Appl. 15, 19–24 (2003).
[CrossRef]

2002 (1)

S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Penetration control in laser welding of sheet metal,” J. Laser Appl. 14, 210–214 (2002).
[CrossRef]

1998 (1)

1997 (1)

Aarts, R. G. K. M.

S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Penetration control in laser welding of sheet metal,” J. Laser Appl. 14, 210–214 (2002).
[CrossRef]

S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Feedback control for optimal production speed in laser beam welding of mild steel,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2002).

Abels, P.

P. Abels, S. Kaierle, C. Kratzsch, R. Poprawe, W. Schulz, “Universal coaxial process control system for laser material processing,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. E, pp. 99–108.

M. Dahmen, S. Kaierle, P. Abels, C. Kratzsch, E. W. Kreutz, R. Poprawe, “Adaptive quality control for laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. D, pp. 29–38.

Aubry, P.

A. Cobo, F. Bardin, P. Aubry, W. Knapp, O. Collin, J. D. C. Jones, D. P. Hand, J. M. López-Higuera, “Optical fibre-based focus control system for laser welding incorporating automatic setup,” in Proceedings of the Sixteenth International Conference on Optical Fiber Sensors (Institute of Electronics, Information and Communications Engineers, Tokyo, 2003), pp. 412–415.

F. Bardin, A. Cobo, J. M. Lopez-Higuera, O. Collin, P. Aubry, T. Dubois, M. Högström, P. Nylen, P. Jonsson, J. D. C. Jones, D. P. Hand, “Optical techniques for real-time penetration monitoring for laser welding,” Appl. Opt. (submitted for publication).

Bagger, C.

C. Bagger, F. O. Olsen, “Laser welding closed-loop power control,” J. Laser Appl. 15, 19–24 (2003).
[CrossRef]

Bardin, F.

A. Cobo, F. Bardin, P. Aubry, W. Knapp, O. Collin, J. D. C. Jones, D. P. Hand, J. M. López-Higuera, “Optical fibre-based focus control system for laser welding incorporating automatic setup,” in Proceedings of the Sixteenth International Conference on Optical Fiber Sensors (Institute of Electronics, Information and Communications Engineers, Tokyo, 2003), pp. 412–415.

F. Bardin, A. Cobo, J. M. Lopez-Higuera, O. Collin, P. Aubry, T. Dubois, M. Högström, P. Nylen, P. Jonsson, J. D. C. Jones, D. P. Hand, “Optical techniques for real-time penetration monitoring for laser welding,” Appl. Opt. (submitted for publication).

Beersiek, J.

J. Beersiek, “New aspects of monitoring with a CMOS camera for laser materials processing,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2002).

J. Beersiek, R. Poprawe, W. Schulz, H. Gu, R. E. Mueller, W. W. Duley, “On-line monitoring of penetration depth in laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 30–39.

Breitschwerdt, S.

C. Dietz, M. Jurca, L. Schlichtermann, M. Kigel-Hollacher, S. Breitschwerdt, C. Schmid, L. Rowold, “Closed loop control system for laser welding of transmission parts,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1998), Vol. 85, Sect. C, pp. 178–186.

Cobo, A.

F. Bardin, A. Cobo, J. M. Lopez-Higuera, O. Collin, P. Aubry, T. Dubois, M. Högström, P. Nylen, P. Jonsson, J. D. C. Jones, D. P. Hand, “Optical techniques for real-time penetration monitoring for laser welding,” Appl. Opt. (submitted for publication).

A. Cobo, F. Bardin, P. Aubry, W. Knapp, O. Collin, J. D. C. Jones, D. P. Hand, J. M. López-Higuera, “Optical fibre-based focus control system for laser welding incorporating automatic setup,” in Proceedings of the Sixteenth International Conference on Optical Fiber Sensors (Institute of Electronics, Information and Communications Engineers, Tokyo, 2003), pp. 412–415.

Collin, O.

A. Cobo, F. Bardin, P. Aubry, W. Knapp, O. Collin, J. D. C. Jones, D. P. Hand, J. M. López-Higuera, “Optical fibre-based focus control system for laser welding incorporating automatic setup,” in Proceedings of the Sixteenth International Conference on Optical Fiber Sensors (Institute of Electronics, Information and Communications Engineers, Tokyo, 2003), pp. 412–415.

F. Bardin, A. Cobo, J. M. Lopez-Higuera, O. Collin, P. Aubry, T. Dubois, M. Högström, P. Nylen, P. Jonsson, J. D. C. Jones, D. P. Hand, “Optical techniques for real-time penetration monitoring for laser welding,” Appl. Opt. (submitted for publication).

Coste, F.

H. Derouet, L. Sabatier, F. Coste, R. Fabbro, “Process control applied to laser surface remelting,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 85–92.

Dahmen, M.

M. Dahmen, S. Kaierle, P. Abels, C. Kratzsch, E. W. Kreutz, R. Poprawe, “Adaptive quality control for laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. D, pp. 29–38.

Derouet, H.

H. Derouet, L. Sabatier, F. Coste, R. Fabbro, “Process control applied to laser surface remelting,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 85–92.

Dietz, C.

C. Dietz, M. Jurca, L. Schlichtermann, M. Kigel-Hollacher, S. Breitschwerdt, C. Schmid, L. Rowold, “Closed loop control system for laser welding of transmission parts,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1998), Vol. 85, Sect. C, pp. 178–186.

Dubois, T.

F. Bardin, A. Cobo, J. M. Lopez-Higuera, O. Collin, P. Aubry, T. Dubois, M. Högström, P. Nylen, P. Jonsson, J. D. C. Jones, D. P. Hand, “Optical techniques for real-time penetration monitoring for laser welding,” Appl. Opt. (submitted for publication).

Duley, W. W.

H. Gu, W. W. Duley, “A novel detector for closed-loop focus control during laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1998), Vol. 85, Sect. C, pp. 69–75.

J. Beersiek, R. Poprawe, W. Schulz, H. Gu, R. E. Mueller, W. W. Duley, “On-line monitoring of penetration depth in laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 30–39.

Fabbro, R.

H. Derouet, L. Sabatier, F. Coste, R. Fabbro, “Process control applied to laser surface remelting,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 85–92.

Fox, M. D. T.

Gu, H.

J. Beersiek, R. Poprawe, W. Schulz, H. Gu, R. E. Mueller, W. W. Duley, “On-line monitoring of penetration depth in laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 30–39.

H. Gu, W. W. Duley, “A novel detector for closed-loop focus control during laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1998), Vol. 85, Sect. C, pp. 69–75.

Hand, D. P.

M. D. T. Fox, D. P. Hand, D. Su, J. D. C. Jones, S. A. Morgan, M. A. McLean, W. M. Steen, “Optical sensor to monitor and control temperature and build height of the laser direct-casting process,” Appl. Opt. 37, 8429–8433 (1998).
[CrossRef]

F. M. Haran, D. P. Hand, C. Peters, J. D. C. Jones, “Focus control system for laser welding,” Appl. Opt. 36, 5246–5251 (1997).
[CrossRef] [PubMed]

F. Bardin, A. Cobo, J. M. Lopez-Higuera, O. Collin, P. Aubry, T. Dubois, M. Högström, P. Nylen, P. Jonsson, J. D. C. Jones, D. P. Hand, “Optical techniques for real-time penetration monitoring for laser welding,” Appl. Opt. (submitted for publication).

A. Cobo, F. Bardin, P. Aubry, W. Knapp, O. Collin, J. D. C. Jones, D. P. Hand, J. M. López-Higuera, “Optical fibre-based focus control system for laser welding incorporating automatic setup,” in Proceedings of the Sixteenth International Conference on Optical Fiber Sensors (Institute of Electronics, Information and Communications Engineers, Tokyo, 2003), pp. 412–415.

Haran, F. M.

Högström, M.

F. Bardin, A. Cobo, J. M. Lopez-Higuera, O. Collin, P. Aubry, T. Dubois, M. Högström, P. Nylen, P. Jonsson, J. D. C. Jones, D. P. Hand, “Optical techniques for real-time penetration monitoring for laser welding,” Appl. Opt. (submitted for publication).

Jones, J. D. C.

M. D. T. Fox, D. P. Hand, D. Su, J. D. C. Jones, S. A. Morgan, M. A. McLean, W. M. Steen, “Optical sensor to monitor and control temperature and build height of the laser direct-casting process,” Appl. Opt. 37, 8429–8433 (1998).
[CrossRef]

F. M. Haran, D. P. Hand, C. Peters, J. D. C. Jones, “Focus control system for laser welding,” Appl. Opt. 36, 5246–5251 (1997).
[CrossRef] [PubMed]

F. Bardin, A. Cobo, J. M. Lopez-Higuera, O. Collin, P. Aubry, T. Dubois, M. Högström, P. Nylen, P. Jonsson, J. D. C. Jones, D. P. Hand, “Optical techniques for real-time penetration monitoring for laser welding,” Appl. Opt. (submitted for publication).

A. Cobo, F. Bardin, P. Aubry, W. Knapp, O. Collin, J. D. C. Jones, D. P. Hand, J. M. López-Higuera, “Optical fibre-based focus control system for laser welding incorporating automatic setup,” in Proceedings of the Sixteenth International Conference on Optical Fiber Sensors (Institute of Electronics, Information and Communications Engineers, Tokyo, 2003), pp. 412–415.

Jonker, B.

S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Penetration control in laser welding of sheet metal,” J. Laser Appl. 14, 210–214 (2002).
[CrossRef]

S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Feedback control for optimal production speed in laser beam welding of mild steel,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2002).

Jonsson, P.

F. Bardin, A. Cobo, J. M. Lopez-Higuera, O. Collin, P. Aubry, T. Dubois, M. Högström, P. Nylen, P. Jonsson, J. D. C. Jones, D. P. Hand, “Optical techniques for real-time penetration monitoring for laser welding,” Appl. Opt. (submitted for publication).

Jurca, M.

C. Dietz, M. Jurca, L. Schlichtermann, M. Kigel-Hollacher, S. Breitschwerdt, C. Schmid, L. Rowold, “Closed loop control system for laser welding of transmission parts,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1998), Vol. 85, Sect. C, pp. 178–186.

Kaierle, S.

M. Dahmen, S. Kaierle, P. Abels, C. Kratzsch, E. W. Kreutz, R. Poprawe, “Adaptive quality control for laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. D, pp. 29–38.

P. Abels, S. Kaierle, C. Kratzsch, R. Poprawe, W. Schulz, “Universal coaxial process control system for laser material processing,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. E, pp. 99–108.

Kigel-Hollacher, M.

C. Dietz, M. Jurca, L. Schlichtermann, M. Kigel-Hollacher, S. Breitschwerdt, C. Schmid, L. Rowold, “Closed loop control system for laser welding of transmission parts,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1998), Vol. 85, Sect. C, pp. 178–186.

Knapp, W.

A. Cobo, F. Bardin, P. Aubry, W. Knapp, O. Collin, J. D. C. Jones, D. P. Hand, J. M. López-Higuera, “Optical fibre-based focus control system for laser welding incorporating automatic setup,” in Proceedings of the Sixteenth International Conference on Optical Fiber Sensors (Institute of Electronics, Information and Communications Engineers, Tokyo, 2003), pp. 412–415.

Kratzsch, C.

P. Abels, S. Kaierle, C. Kratzsch, R. Poprawe, W. Schulz, “Universal coaxial process control system for laser material processing,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. E, pp. 99–108.

M. Dahmen, S. Kaierle, P. Abels, C. Kratzsch, E. W. Kreutz, R. Poprawe, “Adaptive quality control for laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. D, pp. 29–38.

Kreutz, E. W.

M. Dahmen, S. Kaierle, P. Abels, C. Kratzsch, E. W. Kreutz, R. Poprawe, “Adaptive quality control for laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. D, pp. 29–38.

Lopez-Higuera, J. M.

F. Bardin, A. Cobo, J. M. Lopez-Higuera, O. Collin, P. Aubry, T. Dubois, M. Högström, P. Nylen, P. Jonsson, J. D. C. Jones, D. P. Hand, “Optical techniques for real-time penetration monitoring for laser welding,” Appl. Opt. (submitted for publication).

López-Higuera, J. M.

A. Cobo, F. Bardin, P. Aubry, W. Knapp, O. Collin, J. D. C. Jones, D. P. Hand, J. M. López-Higuera, “Optical fibre-based focus control system for laser welding incorporating automatic setup,” in Proceedings of the Sixteenth International Conference on Optical Fiber Sensors (Institute of Electronics, Information and Communications Engineers, Tokyo, 2003), pp. 412–415.

McLean, M. A.

Meijer, J.

S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Penetration control in laser welding of sheet metal,” J. Laser Appl. 14, 210–214 (2002).
[CrossRef]

S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Feedback control for optimal production speed in laser beam welding of mild steel,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2002).

Morgan, S. A.

Mueller, R. E.

J. Beersiek, R. Poprawe, W. Schulz, H. Gu, R. E. Mueller, W. W. Duley, “On-line monitoring of penetration depth in laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 30–39.

Nylen, P.

F. Bardin, A. Cobo, J. M. Lopez-Higuera, O. Collin, P. Aubry, T. Dubois, M. Högström, P. Nylen, P. Jonsson, J. D. C. Jones, D. P. Hand, “Optical techniques for real-time penetration monitoring for laser welding,” Appl. Opt. (submitted for publication).

Olsen, F. O.

C. Bagger, F. O. Olsen, “Laser welding closed-loop power control,” J. Laser Appl. 15, 19–24 (2003).
[CrossRef]

Ostendorf, A.

H. K. Tonshoff, A. Ostendorf, W. Specker, “Quality assurance of laser welding processes by adaptive closed-loop process control,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2000), Sect. E, pp. 252–261.

Peters, C.

Poprawe, R.

J. Beersiek, R. Poprawe, W. Schulz, H. Gu, R. E. Mueller, W. W. Duley, “On-line monitoring of penetration depth in laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 30–39.

M. Dahmen, S. Kaierle, P. Abels, C. Kratzsch, E. W. Kreutz, R. Poprawe, “Adaptive quality control for laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. D, pp. 29–38.

P. Abels, S. Kaierle, C. Kratzsch, R. Poprawe, W. Schulz, “Universal coaxial process control system for laser material processing,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. E, pp. 99–108.

Postma, S.

S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Penetration control in laser welding of sheet metal,” J. Laser Appl. 14, 210–214 (2002).
[CrossRef]

S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Feedback control for optimal production speed in laser beam welding of mild steel,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2002).

Rowold, L.

C. Dietz, M. Jurca, L. Schlichtermann, M. Kigel-Hollacher, S. Breitschwerdt, C. Schmid, L. Rowold, “Closed loop control system for laser welding of transmission parts,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1998), Vol. 85, Sect. C, pp. 178–186.

Sabatier, L.

H. Derouet, L. Sabatier, F. Coste, R. Fabbro, “Process control applied to laser surface remelting,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 85–92.

Schlichtermann, L.

C. Dietz, M. Jurca, L. Schlichtermann, M. Kigel-Hollacher, S. Breitschwerdt, C. Schmid, L. Rowold, “Closed loop control system for laser welding of transmission parts,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1998), Vol. 85, Sect. C, pp. 178–186.

Schmid, C.

C. Dietz, M. Jurca, L. Schlichtermann, M. Kigel-Hollacher, S. Breitschwerdt, C. Schmid, L. Rowold, “Closed loop control system for laser welding of transmission parts,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1998), Vol. 85, Sect. C, pp. 178–186.

Schulz, W.

P. Abels, S. Kaierle, C. Kratzsch, R. Poprawe, W. Schulz, “Universal coaxial process control system for laser material processing,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1999), Sect. E, pp. 99–108.

J. Beersiek, R. Poprawe, W. Schulz, H. Gu, R. E. Mueller, W. W. Duley, “On-line monitoring of penetration depth in laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 30–39.

Specker, W.

H. K. Tonshoff, A. Ostendorf, W. Specker, “Quality assurance of laser welding processes by adaptive closed-loop process control,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2000), Sect. E, pp. 252–261.

Steen, W. M.

Su, D.

Tonshoff, H. K.

H. K. Tonshoff, A. Ostendorf, W. Specker, “Quality assurance of laser welding processes by adaptive closed-loop process control,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2000), Sect. E, pp. 252–261.

Appl. Opt. (2)

J. Laser Appl. (2)

C. Bagger, F. O. Olsen, “Laser welding closed-loop power control,” J. Laser Appl. 15, 19–24 (2003).
[CrossRef]

S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Penetration control in laser welding of sheet metal,” J. Laser Appl. 14, 210–214 (2002).
[CrossRef]

Other (11)

S. Postma, R. G. K. M. Aarts, J. Meijer, B. Jonker, “Feedback control for optimal production speed in laser beam welding of mild steel,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2002).

H. Derouet, L. Sabatier, F. Coste, R. Fabbro, “Process control applied to laser surface remelting,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1997), Vol. 83, Part 1, Sect. C, pp. 85–92.

H. Gu, W. W. Duley, “A novel detector for closed-loop focus control during laser beam welding,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 1998), Vol. 85, Sect. C, pp. 69–75.

H. K. Tonshoff, A. Ostendorf, W. Specker, “Quality assurance of laser welding processes by adaptive closed-loop process control,” in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (Laser Institute of America, Orlando, Fla., 2000), Sect. E, pp. 252–261.

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Figures (11)

Fig. 1
Fig. 1

Schematic of the experimental arrangement.

Fig. 2
Fig. 2

Images of the keyhole and their corresponding intensity profile. The intensity profile represents the average profile along the three lines.

Fig. 3
Fig. 3

Schematic of the laser power controller architecture.

Fig. 4
Fig. 4

Focal error signal obtained in the open-loop test when 2-mm-thick Inconel was welded at 1.2 m/min with 2.5 kW of a Nd:YAG laser beam (left-hand scale). The laser head was moved from 0 to −5 mm and then to +5 mm as shown on the right-hand scale.

Fig. 5
Fig. 5

Welding of a 2-mm-thick Inconel workpiece tilted at an angle of 5° for a laser power of 2.5 kW and a speed of 1.2 m/min. (a) Longitudinal cross section, (b) photographs of rear seams obtained for welds generated with open-loop and closed-loop controls, (c) focal error signals obtained in each case.

Fig. 6
Fig. 6

(a) Keyhole opening as function of the laser power for different workpiece thicknesses. (b) Optimum laser power (i.e., giving the optimum full penetration) as a function of the workpiece thickness at a constant speed of 1.2 m/min.

Fig. 7
Fig. 7

Welding of a tapered and stepped Inconel workpiece for a speed of 1.2 m/min. (a) Longitudinal cross section (note that scales are different in the two axes), (b) photographs of top and bottom surfaces, (c) closed-loop laser power control signal, (d) keyhole opening parameter H calculated from the image processing at 100 Hz.

Fig. 8
Fig. 8

Welding of a tapered and stepped Inconel workpiece for a speed of 1.2 m/min. (a) Longitudinal cross section. Photographs of bottom surfaces of a weld realized (b) with and (c) without (4-kW) closed-loop laser power control.

Fig. 9
Fig. 9

Welding of a stepped Inconel workpiece at a speed of 1.2 m/min. (a) Longitudinal cross section. (b) Photographs of top and bottom surfaces of a weld realized without and with closed-loop laser power control. (c) Laser power signal controlled by the closed-loop controller and without the controller (constant value of 4 kW). Keyhole opening parameter H for the weld realized (d) without closed-loop control and (e) with closed-loop control.

Fig. 10
Fig. 10

Welding of a stepped Inconel workpiece tilted at an angle of 5° for a speed of 1.2 m/min. (a) Longitudinal cross section. (b) Photographs of top and bottom surfaces of the weld without closed-loop focus and laser power control (constant value of 2.8 kW). (c) Photographs of top and bottom surfaces of the weld in the closed-loop control regime (focus and laser power). (d) Focal error of uncontrolled and controlled weld (left-hand scale) and displacement of the laser head recorded by the vertical translation stage during the focus control weld (right-hand scale). (e) Laser power signal for both welds.

Fig. 11
Fig. 11

Welding of an Inconel airfoil for a speed of 1.2 m/min. (a) Photograph of the entire airfoil. (b) Photograph of left internal airfoil edge. Photographs of (c) top and (d) bottom surfaces of the weld. (e) Focal error signal obtained in the closed-loop system (left-hand scale) and vertical displacement of the laser head recorded by the vertical translation stage and measure of the height change of the top surface of the airfoil (right-hand scale). (f) Closed-loop laser power control signal.

Equations (1)

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H = 100 ( I max - I min ) / ( I max ) ,

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