Image processing improves laser seam welding
Roland Roux
An electro-optic kit that makes laser welding more accurate and reliable has been developed by SESO (Aix en Provence, France) and Servo Robot (Boucherville, Quebec, Canada). The device is designed to address key problems associated with the CO2 laser-welding process, including controlling the position of the focused spot of a laser beam relative to the seam being welded and optimizing the speed of the beam and beam-delivery system.
During system operation, an electronic camera provides a digitized image of the weld seam. Customized image processing develops control information from the image, based on the seam position in terms of ga¥and mismatch. The control signals guide the dual-axis scanner mirror in the motorized optical head so that the mirror deflects the laser spot to the correct location. An optical sensor monitors the scanner mirror position in real time and provides additional feedback. An optional double camera can also be installed that enables an operator to see both the laser spot and the weld pool simultaneously, so the user can make real-time adjustments to the welding parameters.
The adapter kit includes a focusing-optic assembly--incorporating the dual-axis scanning mirror--to replace any existing one on the user`s system, a six-axis motor drive for the camera, and the electronic camera with image-processing electronics. The standard focal length of the system, which works independently of the numerical control that drives the laser, is 500 mm. The maximum input beam diameter is 50 mm, with a maximum 15-kW CW laser. At a beam-scanning frequency of 30 H¥(at 500-mm focal length), the spot motion at the seam (x and y axes) is 䔸 mm.