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Development of Combined Seam Tracking and Process Monitoring for Laser Welding
C. Allen, A. Wallner, N. Wikström and J. Johansson

Light-emitting diode (LED)-based process zone illumination and coaxial imaging using a matching narrow bandpass filter give images of a sufficient quality to be used in a novel seam tracking and process monitoring laser welding tool. Features of the image can be determined every 10 ms. Variations in the features imaged (area, aspect ratio and centre position), along with changes in the noise levels of photodiode-monitored process emissions, allow for the detection of welding process defects, including contamination of the cover slide, joint gaps, incorrect settings of beam focus or gas shielding flow rate, and loss of full penetration on loss of power or an unexpected increase in material thickness.

Keywords: Laser welding, titanium alloy, nickel alloy, light-emitting diode (LED), photodiode, seam tracking, defects, aerospace

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