High-speed stereo X-ray imaging system for the analysis of laser materials processing

• Subject Area: Production Technology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 584896134

In laser material processes such as welding, cutting and drilling, the efficiency and quality of the process are directly connected with the geometry of the interaction zone. The geometry of the interaction zone between laser beam and material is to be measured by the proposed stereo X-ray imaging system in a time-resolved and three-dimensional manner during welding, cutting or drilling processes. Since 2009, a mono-X-ray imaging system has been in operation at the IFSW at the University of Stuttgart, which can be used to determine the two-dimensional geometry of the cavities in the interaction zone of laser material processing. Based on the location-dependent absorption of X-rays, the local extent of the cavity in the direction of X-ray irradiation can be determined, assuming a symmetrical cavity. However, its actual three-dimensional shape remains unknown. Recent work by various international groups uses highly brilliant synchrotron X-rays to measure the two-dimensional geometry of the cavity. The significantly higher intensities of synchrotron X-rays enable significantly higher temporal and spatial resolutions of the image sequences. However, even the simplified three-dimensional reconstruction of the cavity mentioned above is not possible. For the investigation of laser material processing, the exact three-dimensional determination of the cavity geometry is of utmost importance in order to understand the origin of fluctuations and instabilities that occur and to improve the processes. Based on the determined three-dimensional cavity geometries, the distribution of the local absorbed irradiance can be calculated by means of ray tracing of the laser radiation and, in a further step, the vapour flows within the cavity and the melt flow around it. In particular, the exact three-dimensional geometry is necessary for investigating asymmetric effects that occur when using the latest beam shaping technologies. The highly dynamic geometry fluctuations of the cavities in laser material processing require a temporal resolution of at least 10 kHz with a spatial resolution of 10 µm. The central elements of the proposed stereo X-ray imaging system are two X-ray tubes and two imaging systems, including scintillators, optical imaging systems, image intensifiers and high-speed cameras. In addition, 19 NC axes with a corresponding control system are required to examine the laser material processes and to adjust the X-ray sources and all imaging elements. A laser and x-ray-proof enclosure is necessary to ensure the safe operation of the system.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Hochgeschwindigkeits-Stereoröntgenbildgebungsanlage zur Diagnostik von Laserbearbeitungsprozessen
• Instrumentation Group: 4020 Röntgenkameras für Feinstruktur und Topographie
• Applicant Institution: Universität Stuttgart
• Leader: Professor Dr. Thomas Graf