Process control of laser beam welded small section aluminium sheets

Although in modern laser systems the monitoring of a large number of machine parameters is already state of the art structural, material and environmental disturbances, which dispossess themselves mostly from control, can lead to a deviation from the "optimum operating point" and in consequence to weld defects. Beyond that demands, which result in the context of the quality assurance, as well as manufacturer-specific requirements on the reliability and documentation of the component quality of welded parts, are the moving spirit for the use of quality assurance systems in all ranges of the industrial production. Therefore emphasis has to be put on to the process control in the sense of error recognition. Aim of the investigation discussed in the paper is to estimate the capabilities of a camera-based sensor system for the detection of welding failures. Failures which are detectable by surface monitoring will be selected by analysis of the dynamical processes in the weld ing zone. For imaging of the surface structure, melt pool shape and capillary shape an external illumination of the interaction zone and its neighbourhood is used.