Process control in laser materials processing - Combined sensor technologies for secure quality assurance

For any manufacturing process the high demand on the quality of the produced parts can only be guaranteed by continuous supervision. In particular this is a fact in laser materials processing. It is for this reason, that process monitoring systems become more and more standard devices in modern automotive laser applications. The task for reliable on-line process monitoring systems is to gain significant indicators for the instantaneous condition of the interaction zone and/or neighbouring areas. Depending on the application it is essential to select the most reliable system configuration. As presented by Precitec in former publications, there is a possibility to monitor processes with various kinds of sensors, starting from photo diode based sensors to a camera as a sensor to extract as much information as possible from the interaction zone between the laser and the work piece. Precitec is following this strategy since several years now and was very successful in integrating numerous monitoring systems into industrial production lines. This paper will describe new approaches in the field of process monitoring, the combination of various sensor technologies. It is for sure, that future production plants will try to reduce the factor human resources dramatically, which in the end means a higher degree of automation. This degree of automation can only be reached by closed loop control and the basis is absolutely reliable, industrial proofed monitoring systems. The paper will show, how one can increase the degree of reliability by the intelligent fusion of sensor systems. By using this sensor configuration the monitoring system will mainly focus on typical seam irregularities, which can occur in the specific application because of material or laser related problems, in TWB applications e.g. pinholes, undercut, missing laser power, etc. All the possible welding problems because of misalignment can be neglected.