The demands placed on laser welding by the production of battery systems for electric vehicles in particular are high. Their quality plays a crucial role for safety. Continuous monitoring of the production laser process is needed for the millions of welded joints in order to ensure long-term quality and to produce safe and efficient battery systems.

An 'early view' article in PhotonicsViews presents several proprietary non-contact optical sensors for the monitoring of automated laser welding of batteries in e-automotive production. Along the battery production chain, there are a multitude of different laser processing utilization in the electrode, cell, module, and pack sectors: the welding of can-caps, busbars, and housings are some application examples. Lessmüller Lasertechnik provides an appropriate sensor for each application to ensure the required welding precision: the OCT interferometric imaging system, the WELDCHECK photodiode or the WELDEYE camera-based sensor. Either single sensors or several different sensors can be integrated into diverse configurations.

Seam tracking and seam quality can be controlled online with OCT during the sealing of the battery cells. OCT can be also utilized to measure changes in keyhole depth, which in turn can be used to control laser power while welding the busbars. OCT as a sensor tool offers many benefits in terms of process flexibility, enhanced component reproducibility, precision and productivity.

Radiation emitted by the plasma or metal vapor plume during laser materials processing is  considered as an important aim for the monitoring of busbar welding that can be achieved by the WELDCHECK. It is a photodiode-based, cost-effective design system, which can be easily integrated into different types of laser processing setups.

When the cells have been packed into the module, and several battery modules are then combined into a block, WELDEYE can perform process monitoring and seam inspection during the welding of the battery housing. A camera with a high pass filter is used to obtain live images of the solidified seam. Also, the behavior of the emission created by the laser process provides feasible information on the laser welding process.

The application of Lessmüller Lasertechnik optical sensors makes the laser process accurate, repeatable, and reliable, enabling their wide deployment by industries that utilize laser processing for both material modification and fabrication. Nataliya Deyneka Dupriez

The article appears in print in the October/November issue of PhotonicsViews and is available online as an early view article. To subscribe or apply for a free qualified subscription, please download and return the attached PDF form.

Reference: N. Deyneka Dupriez: Smart monitoring of battery welding processes – Sensor systems for laser welding applications along the battery production chain: from cell to package, PhotonicsViews, published online 16 June 2021; DOI: 10.1002/phvs.202100045