Volkswagen has introduced an advanced, investment-secure non-destructive testing (NDT) solution for resistance spot welding (RSW) as part of its electric vehicle manufacturing operations at the Zwickau plant in Germany. Following a successful pilot phase, the automated thermographic inspection technology has now entered series production, supporting large-scale quality assurance for battery-electric vehicle bodies.
The solution is based on the modernisation of an existing INDU-SCAN test bench, originally deployed for thermographic quality control of laser welds. Developed in collaboration with InfraTec, the system has been upgraded with state-of-the-art infrared imaging, intelligent algorithms, and industrial robot integration to meet the demands of resistance spot welding used in Volkswagen’s modular electric drive kit platform.
Volkswagen Sachsen and InfraTec have worked together since 2007 on non-destructive inspection methods for car body construction. When Volkswagen transitioned its Zwickau-Mosel facility to electric vehicle production, the shift from laser welding to resistance spot welding raised the challenge of adapting existing NDT infrastructure to a fundamentally different joining process. Rather than replacing the system, the partners opted for a technology upgrade.
The modernised system incorporates a high-performance ImageIR 8300 hp infrared camera and an adapted flash excitation unit, enabling precise active thermography in transmissive mode. Intelligent data-processing algorithms were introduced to handle the large volumes of thermographic data generated during inspection and to deliver consistent, reliable weld quality evaluation.
In resistance spot welding, electrical current of several thousand amperes is applied through electrodes to generate localized heat at the joint, forming a molten weld nugget that solidifies to join the metal sheets. The quality of this connection is verified using active thermography, where thermal energy introduced by flash excitation propagates through the material and is measured on the opposite side. The infrared camera evaluates temperature distribution curves pixel by pixel, allowing defects such as inclusions, impurities, or incomplete fusion to be clearly identified.
To enable full-vehicle inspection, the INDU-SCAN measuring station has been equipped with two industrial robots mounted on traversing axes. One robot carries the infrared camera, while the second holds the flash unit and generator, allowing automated, contact-free positioning across the vehicle body.
“This is the world's first thermographic solution for testing resistance weld spots in large-scale automotive production in an automated, contact-free manner,” estimates the head of quality assurance in vehicle manufacturing. “This is a minor revolution for the industry.”
Compared with conventional ultrasonic testing, the thermographic NDT solution offers significant advantages. Ultrasonic inspection is typically manual, physically demanding, and limited to random sampling. Automation attempts have historically proven difficult. By contrast, the INDU-SCAN system delivers inspection times of five to ten seconds per weld spot, compared with 30 to 40 seconds using ultrasound, enabling up to 1,500 weld spots to be inspected per shift.
The increased inspection speed allows for broader sampling, more consistent quality control, and faster corrective action during production. Volkswagen and InfraTec are now focused on further development of the technology, with the long-term goal of achieving a fully inline NDT solution that enables real-time assessment of weld quality during ongoing vehicle production.
The thermographic inspection process is not limited to electric vehicles and can be applied across any manufacturing environment using resistance spot welding, reinforcing its relevance as a scalable NDT solution for modern automotive production.
