Product Code: ICA11_204

Novel Monitoring System for Spatially Resolved Topographical Measurement of Laser-Based Processes
Authors:
Peter Berger, Institut fuer Strahlwerkzeuge (IFSW); Stuttgart Germany
Jan-Philipp Weberpals, Institut fuer Strahlwerkzeuge (IFSW); Stuttgart Germany
Thomas Graf, Institut fuer Strahlwerkzeuge (IFSW); Stuttgart
Johannes Trein, Silicon Software GmbH; Mannheim Germany
Holger Singpiel, Silicon Software GmbH; Mannheim Germany
Presented at ICALEO 2011

Particularly the automation and industrialization of thermal material processing makes high demands on monitoring and controlling the resulting quality. Indeed, current laser systems with strong focusability and wavelengths of about 1 micrometer exhibit a high innovation potential in many application ranges, for example the possibility of adjusting the welding depth to even small material thicknesses. However, the usability of these advantages is limited because the suitable process windows are considerably constricted at increased welding speed. In some applications even more than for lasers emitting 10 micrometer-radiation. Therefore, a reliable real-time monitoring of thermal material processing is of vital importance. A new promising approach is the exploitation of the polarization-dependent emission characteristics of hot radiating surfaces to get detailed information about geometrical surface structures.
In addition to the dimensions of the melt pool, the raised welding bead or its underfill are important quality characteristics for industrial applications. Generally melt pool structures or seam imperfections result from the geometry and the dynamics of the capillary. This paper introduces a novel monitoring system to determine the inclination of a keyhole or cutting front along its circumference based on the polarized thermal emission of the hot surfaces. Besides the possibility to ascertain the spatial inclination of capillaries, this sensor can be used to monitor melt pool structures or upcoming seam imperfections during laser material processing or to prevent the latter by an in-process control as well.