Weld depth dynamics measured with optical coherence tomography during remote laser beam oscillation welding of battery system

This paper represents nondestructive quality monitoring technique using optical coherence tomography (OCT). It addresses online monitoring of weld depth during laser beam oscillation welding and aims at the application in joining cells in large battery assemblies. The weld depth was continuously detected with OCT while the OCT beam position was adjusted highly dynamically in accordance with the scanning optics position. By displacing the OCT measurement beam according to the current machining direction, the correlation between the position of the laser beam in an oscillating circular pattern along the circular feed direction and the periodic fluctuations of the measured weld depth was explored. It was found that the deepest part of the keyhole is located at the trailing position of the laser beam. This effect can be attributed to the large heat input due to the overlapping circular movements. The results confirm once again that instant weld depth monitoring with OCT ensures superior weld quality.