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Soldagem & Inspeção

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MOTA, Carolina Pimenta; MACHADO, Marcus Vinícius Ribeiro; FINZI NETO, Roberto Mendes  and  VILARINHO, Louriel Oliveira. Near-infrared vision system for arc-welding monitoring. Soldag. insp. [online]. 2013, vol.18, n.1, pp.19-30. ISSN 0104-9224.

Vision, the human being's favorite sense, and its great capacity to obtain, to process and to interpret great amount of visual nature data has been throughout the years a great inspiration for development of techniques and technological devices that reproduce it into a computational system. In welding processes, vision can supply information in inspection and welded joint's quality, in the parameters' monitoring, in trajectory correction and even, finally, in the study of the phenomena involved in the process. However, the luminosity/radiation emitted from the weld arc represents a barrier for these studies based in the process visualization. One of the forms currently used to visualize the process, without the interference of the arc's light, consists of illuminating the process with the near infrared light and, using band pass (interference) filters, around this exactly wave length, during the acquisition of the images. A solution for the near infrared illumination, of increasing application, involves the use of laser diodes of high power, with low cost and less complex installation than conventional lasers. Therefore, the proposal of this work is the project, construction and assessment of a vision system for welding processes with low cost and high flexibility. It is based on characterization of the spectrum of the weld arc, definition of a drive topology for the laser diode within its limitations of use and maximizing the emitted luminous power, built of control circuits, selection of optics equipment and components and, finally, project and application of a prototype for visualization of different arc-welding processes. The final assessment of the whole vision system was carried out during TIG and MIG/MAG welding. Although, during the welding, the system was not capable of overcoming the arc radiation, it provides a homogenous illumination in synchronism with the camera, whereby the main limitation was large shutter time. Eventually, it is suggested to employ the developed vision system for helping joint tracking.

Keywords : Image System; laser diode; NIR; data acquisition; welding.

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