State of the art and new advances in process control for laser materials processing

Abstract

In laser beam materials processing, the high demands on the quality of the produced parts can only be guaranteed by a continuous supervision of the manufacturing process and by control of specific features of the manufactured product. By means of ISO 9000 ff. and other by law enforced rules it is sometimes even necessary to document the quality features of each manufactured part. This can only be achieved by reliable online process control systems. Process diagnostic devices commonly used in actual quality monitoring systems are spatially integrating plasma sensors. Evaluation of the data is performed in different ways which will be shown on the example of commercially available sensors. Experimental results have shown that the reliability of the quality prediction can significantly be increased by using an image processing system with a two-dimensional spatial resolution instead. Based upon these results a different kind of online process control system was developed. The system can be adapted for different applications like welding, cutting or surface treatment. In the case of welding the system can monitor the penetration depth, a full penetration weld, deviations from the desired welding path, the seam width, stability of the capillary and defects of the seam caused by ejection of molten material. The latest results obtained with the system will be presented.