This paper addresses in-process monitoring of weld penetration depth (WPD) during remote laser welding of battery tab connectors using optical coherence tomography (OCT). The research aims at studying the impact of welding process parameters on the accuracy of WPD measurements. In general, the highest measurement accuracy is achievable by positioning the OCT measuring beam toward the bottom of the keyhole. However, finding and maintaining the alignment between the OCT measuring beam and the bottom of the keyhole is a challenging task because of the dynamic changes in the size and shape of the keyhole itself. The paper addresses the above challenge by (1) developing welding process parameters for the Al-Cu thin foil lap joint (Al 1050 foil 450 μm and Ni-plated Cu foil 300 μm) using a novel adjustable ring mode (ARM) laser and (2) integrating OCT technology with two beams: one targeting the bottom of the keyhole and another as a reference to the part surface (TwinTec technology). The methodology is underpinned by the “Keyhole Mapping” approach, which helps one to identify the optimal placement of the OCT measuring beam with considerations to both measurement accuracy and stability of the keyhole. Findings indicated that welding with the ARM laser results in a more stable process, reduces fluctuations of the keyhole opening, and, therefore, helps one to improve the measurement accuracy by a factor of 50% (from the average error of 0.22 mm to 0.11 mm). Results further identified that the feasible operating window of the OCT measuring beam, corresponding to the highest measurement accuracy, is below 20 μm in length.

This study investigates the influence of hybrid laser-arc welding parameters on the microstructure and mechanical properties of the weld: namely, influence of welding speed and preheating temperature on the cooling rates, microstructure and hardness. In order to achieve the maximum productivity, optimum welding speed for the hybrid laser-arc welding X80 steel of 14mm thickness with and without preheating was defined

Remote laser welding (RLW) combines the positive features of tactile laser welding with additional benefits such as increased processing speed, reduced operational cost and service, and higher process flexibility. A leading challenge preventing the full uptake of RLW technology in industry is the lack of efficient closed loop in-process (CLIP) monitoring and weld quality control solutions. This underpins the need to fuse multiple sensor technologies and data analytics with predictive engineering simulations. Although the development and integration of a variety of sensors covers the radiation spectrum from ultraviolet to far-infrared, the flawless deployment of CLIP solutions is still challenged by the need for the following: signal denoising in the case of process instability; real-time data analytics; and adaptive control engineering architecture to cope with process variations induced by manufacturing tolerances. This paper focuses on the aspect of weld penetration depth control using optical coherence tomography (OCT) as a necessary step to enable adaptive penetration depth control during RLW of aluminum components in the fillet lap joint configuration with consideration to part-to-part gap variation. The approach entails decoupling the welding process parameters in two subsets: (1) in-plane control of the heat input on the upper part to facilitate the droplet formation; and (2) out-of-plane heat management to achieve the desired level of penetration control in the keyhole mode. This paper presents the results of finding the optimal placement of the OCT beam with variable part-to-part gap conditions. Results have shown that statistical signal processing of the raw OCT signal gives insight not only into the depth of the keyhole but can infer the shape of the keyhole itself. Current limitations and next phases of research and development are highlighted based on the experimental study.