04 December 2009
Using vision for direct observation of laser or arc welding melt pool
Vision-guided seam tracking is commonly used in automatic welding robots, but the strong flare from the welding spot has made it very difficult to apply vision technology to directly observe the melt pool for on-line control of weld quality.
In an article in trade magazine Teknisk Nyt nr 13, October 2009 (in Danish), Finn Mengel and Simon Hoffgaard from welding automation specialist Migatronic Automation discuss two major innovations which makes it possible to apply vision for on-line optimization and control of welding processes.
The first innovation is high-dynamic range CMOS sensors like those developed by Swiss camera manufacturer Photonfocus. Cameras using these sensors are able to look through the strong thermal and plasma radiation from a laser welding process and directly observe the melt pool for measuring the key parameters that determine the weld quality. Cameras from Photonfocus are currently used in several CO2 and YAG laser welding machines.
The second innovation is the Cavilux laser flash that produces very intense, short-duration infrared laser pulses for illumination of the weld pool and surrounding metal. With a Cavilux flash, a vision camera is able to look through even the blinding light from a high-current arc welding process and produce crisp, sharp images of the weld pool for automatic on-line measurement of melt pool geometry.
 Read article (in Danish)
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