Spectrum analysis of the arc for laser guided robot welding applications

In robot are welding applications, in order to overcome inaccuracies of the robot itself and the workpiece, the tracking of the seam is of primal importance. To detect the seam, a novel sensor based on a laser scanner and using triangulation methods has been developed. A definite problem of the development is the difference in the optical power emitted by the are which is in the range of hundreds of Watts and the power of the diode laser in the range of mW. In order to achieve good signal to noise ratio, it is necessary to select a wavelength where the glow of the are is minimal and design an appropriate interference filter. For this purpose detailed measurements and analysis of the spectrum of the welding are have been performed The measurements extend from the ultraviolet region of the spectrum (150 nm) to the near infrared region (970 nm). The study was concentrated on the welding of ferrous metals using as shielding gas a mixture of 80% Ar and 20% CO2 and welding currents in the range of 100A to 160A The measurements have revealed the presence of many strong emission lines in the spectrum.