Abstract

A nonintrusive optical sensor system is applied to real-time process control of the recently developed laser direct-casting process, in which a stream of metal powder is introduced into the beam of a high-power (500-W) cw laser to fabricate complex three-dimensional structures. The sensor system allows two critical parameters, temperature and build height, associated with this process to be monitored and controlled continuously. We achieved a height-sensing resolution of ±0.25 mm and temperature control with a resolution of ±10 °C at a typical working temperature of 1500 °C with an evident improvement in process quality, especially for complex workpieces comprising relatively high, thin walls at which the conductive heat transfer varies substantially as the process proceeds.

© 1998 Optical Society of America

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References

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  1. M. Murphy, C. Lee, W. M. Steen, “Studies in rapid prototyping by laser surface cladding,” in Laser Materials Processing Conference (ICALEO’93, P. Denney, I. Miyamoto, B. L. Mordike, eds., (Laser Institute of America, Orlando, Fla., 1993), Vol. 77, pp. 882–891.
  2. M. A. McLean, G. J. Shannon, W. M. Steen, “Laser generating metallic components,” in Eleventh International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference, D. R. Hall, H. J. Baker, eds., Proc. SPIE3092, 753–756 (1996).
    [CrossRef]
  3. F. Meriaudeau, F. Truchetet, “Image processing applied to the laser cladding process,” in High-Power Lasers: Applications and Emerging Applications, M. R. Osborne, G. Sayegh, eds., Proc. SPIE2789, 93–103 (1996).
    [CrossRef]
  4. 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]
  5. J. P. Bentley, Principles of Measurement Systems (Longman Scientific and Technical, London, 1983), p. 342.

1997

Bentley, J. P.

J. P. Bentley, Principles of Measurement Systems (Longman Scientific and Technical, London, 1983), p. 342.

Hand, D. P.

Haran, F. M.

Jones, J. D. C.

Lee, C.

M. Murphy, C. Lee, W. M. Steen, “Studies in rapid prototyping by laser surface cladding,” in Laser Materials Processing Conference (ICALEO’93, P. Denney, I. Miyamoto, B. L. Mordike, eds., (Laser Institute of America, Orlando, Fla., 1993), Vol. 77, pp. 882–891.

McLean, M. A.

M. A. McLean, G. J. Shannon, W. M. Steen, “Laser generating metallic components,” in Eleventh International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference, D. R. Hall, H. J. Baker, eds., Proc. SPIE3092, 753–756 (1996).
[CrossRef]

Meriaudeau, F.

F. Meriaudeau, F. Truchetet, “Image processing applied to the laser cladding process,” in High-Power Lasers: Applications and Emerging Applications, M. R. Osborne, G. Sayegh, eds., Proc. SPIE2789, 93–103 (1996).
[CrossRef]

Murphy, M.

M. Murphy, C. Lee, W. M. Steen, “Studies in rapid prototyping by laser surface cladding,” in Laser Materials Processing Conference (ICALEO’93, P. Denney, I. Miyamoto, B. L. Mordike, eds., (Laser Institute of America, Orlando, Fla., 1993), Vol. 77, pp. 882–891.

Peters, C.

Shannon, G. J.

M. A. McLean, G. J. Shannon, W. M. Steen, “Laser generating metallic components,” in Eleventh International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference, D. R. Hall, H. J. Baker, eds., Proc. SPIE3092, 753–756 (1996).
[CrossRef]

Steen, W. M.

M. A. McLean, G. J. Shannon, W. M. Steen, “Laser generating metallic components,” in Eleventh International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference, D. R. Hall, H. J. Baker, eds., Proc. SPIE3092, 753–756 (1996).
[CrossRef]

M. Murphy, C. Lee, W. M. Steen, “Studies in rapid prototyping by laser surface cladding,” in Laser Materials Processing Conference (ICALEO’93, P. Denney, I. Miyamoto, B. L. Mordike, eds., (Laser Institute of America, Orlando, Fla., 1993), Vol. 77, pp. 882–891.

Truchetet, F.

F. Meriaudeau, F. Truchetet, “Image processing applied to the laser cladding process,” in High-Power Lasers: Applications and Emerging Applications, M. R. Osborne, G. Sayegh, eds., Proc. SPIE2789, 93–103 (1996).
[CrossRef]

Appl. Opt.

Other

J. P. Bentley, Principles of Measurement Systems (Longman Scientific and Technical, London, 1983), p. 342.

M. Murphy, C. Lee, W. M. Steen, “Studies in rapid prototyping by laser surface cladding,” in Laser Materials Processing Conference (ICALEO’93, P. Denney, I. Miyamoto, B. L. Mordike, eds., (Laser Institute of America, Orlando, Fla., 1993), Vol. 77, pp. 882–891.

M. A. McLean, G. J. Shannon, W. M. Steen, “Laser generating metallic components,” in Eleventh International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference, D. R. Hall, H. J. Baker, eds., Proc. SPIE3092, 753–756 (1996).
[CrossRef]

F. Meriaudeau, F. Truchetet, “Image processing applied to the laser cladding process,” in High-Power Lasers: Applications and Emerging Applications, M. R. Osborne, G. Sayegh, eds., Proc. SPIE2789, 93–103 (1996).
[CrossRef]

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Figures (11)

Fig. 1
Fig. 1

Laser direct casting.

Fig. 2
Fig. 2

Optical arrangement to gather light for temperature and height control.

Fig. 3
Fig. 3

Blackbody curve showing the relative change in amplitude at two wavelengths.

Fig. 4
Fig. 4

Experimental setup.

Fig. 5
Fig. 5

IR and visible signals obtained when we laid a 100-mm track of stainless steel using 500 W of CO2 laser radiation. The focal stand-off was increased from 4.5 to 9.5 mm as the plate traversed through the laser beam at a speed of 0.5 m min-1. An argon shield gas was used.

Fig. 6
Fig. 6

Error signal ∊ for the signals shown in Fig. 5. The visible signal was subtracted from the IR signal to produce an error signal that could be used to adjust the focal stand-off.

Fig. 7
Fig. 7

Wall built with and without focus control with the nozzle stand-off set incorrectly.

Fig. 8
Fig. 8

Residual error signal for a 50-mm track with a focal stand-off increase from 4.5 to 9.5 mm and a feed rate of 5 m min-1.

Fig. 9
Fig. 9

Measured temperature and error signals for a 40 mm high × 5 mm wide wall with the temperature control loop open.

Fig. 10
Fig. 10

Measured temperature and laser power for a 40 mm × 5 mm wide wall with the temperature control loop closed.

Fig. 11
Fig. 11

Tall narrow wall built with laser power set too high, with and without temperature control.

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