Observation of Laser Materials Processing by Means of High-Speed Imaging

High-speed imaging is a valuable tool for investigations on laser processes. The high temporal resolution of high-speed imaging allows a detailed observation of different laser processes which helps to understand process mechanisms like e.g. the formation of spatters during laser welding or the formation of a heat affected zone during laser cutting of carbon fiber reinforced plastics (CFRP). In the following the potential of high-speed imaging as a tool for laser process development is shown using different applications as an example. Initially it is described how high-quality images can be achieved during laser processing although the laser beam itself and process emissions make this a challenging task. Subsequently different applications like laser welding, laser drilling of metals with ultra-short pulsed lasers and laser processing of CFRP are introduced. During laser welding, the formation of spatters and hot cracks can be observed. Furthermore the influence of spatial beam modulation on the welding process can be investigated by means of high-speed imaging. The capillary dynamics during laser welding of metals can be studied using high-speed X-rays imaging while in transparent materials the capillary dynamics can be directly observed. During laser drilling the drilling process can be immediately seen using a suitable experimental setup. With the help of high-speed imaging it was revealed that the formation of a heat affected zone during laser processing of CFRP with ultra-short pulses is caused by heat accumulation. Furthermore the dynamics of process emissions like particles or hot vapor generated during laser processing of CFRP was investigated.