Penetration-depth control in a remote laser-welding system based on an optical triangulation loop

摘要

Remote laser-welding systems are being used more frequently because of their larger working areas, shorter down-times and ability to weld different seam types with high accuracy at greater speeds in comparison to conventional welding. Therefore, precise process-monitoring methods are needed in order to achieve weld traceability and good process and quality control to accompany different welding situations. This paper proposes the use of optical triangulation feedback on a remote laser-welding system that makes it possible to monitor a larger working area. This configuration means we can monitor the interaction zone itself, analyze the 3D position of the laser beam and key process estimators as a result of laser welding. AISI steel plates were welded in a lap configuration to show that stable partial penetration can be achieved. First, a dependency matrix was constructed for the different welding parameters (material thicknesses, welding speeds and laser powers) in order to describe the change of the weld's penetration depth with respect to the key estimators. An approximation was used to characterize the change of the weld's depth according to the change of the estimators. The experimental results demonstrate that the interaction zone's area can be used to successfully control the laser's power output in order to achieve a stable partial penetration with an error of less than 7 % of the desired target weld depth. Longitudinal macrographies show a significantly more constant weld penetration depth and laser-induced plume reduction during welding.