TY - JOUR A1 - Maiwald, Frederik A1 - Roider, Clemens A1 - Schmidt, Michael A1 - Hierl, Stefan T1 - Optical Coherence Tomography for 3D Weld Seam Localization in Absorber-Free Laser Transmission Welding T2 - Applied Sciences N2 - Quality and reliability are of the utmost importance for manufacturing in the optical and medical industries. Absorber-free laser transmission welding enables the precise joining of identical polymers without additives or adhesives and is well-suited to meet the demands of the aforementioned industries. To attain sufficient absorption of laser energy without absorbent additives, thulium fiber lasers, which emit in the polymers’ intrinsic absorption spectrum, are used. Focusing the laser beam with a high numerical aperture provides significant intensity gradients inside the workpiece and enables selective fusing of the internal joining zone without affecting the surface of the device. Because seam size and position are crucial, the high-quality requirements demand internal weld seam monitoring. In this work, we propose a novel method to determine weld seam location and size using optical coherence tomography. Changes in optical material properties because of melting and re-solidification during welding allow for weld seam differentiation from the injection-molded base material. Automatic processing of the optical coherence tomography data enables the identification and measurement of the weld seam geometry. The results from our technique are consistent with microscopic images of microtome sections and demonstrate that weld seam localization in polyamide 6 is possible with an accuracy better than a tenth of a millimeter. KW - image processing KW - laser transmission welding KW - optical coherence tomography KW - process monitoring KW - transparent polymers Y1 - 2022 UR - https://opus4.kobv.de/opus4-oth-regensburg/frontdoor/index/index/docId/3242 N1 - Corresponding author: Frederik Maiwald VL - 12 IS - 5 SP - 1 EP - 11 PB - MPDI CY - Basel ER -