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BMW adopts terahertz measurement for plastic coatings
Ther Leipzig site in Germany has introduced a terahertz-based inline measurement system for plastic exterior components, enabling non-destructive inspection of paint layer thickness in series production.
As part of the ongoing digitalisation of its production processes, BMW Group Plant Leipzig, Germany has integrated a terahertz-based measurement system into the series production of plastic exterior components. The technology determines paint layer thickness without destroying the part and has now been scaled up to deliver automated, reproducible quality inspections directly within the production line.
“Terahertz measurement technology replaces complex manual inspection with a fully automated solution, taking quality assurance to an entirely new level,” says Christoph Theiselmann, Head of Exterior Plastics, Production at Plant Leipzig. The system at the core of the project, “Irys”, was developed by technology partner das-Nano for industrial inline use. It allows contactless measurement of multi-layer paint systems and provides results in real time.
From manual inspection to inline paint layer measurement
Until now, paint layer thickness on plastic exterior components at the Leipzig site was checked manually using scalpels and microscopy, a method that destroyed the inspected parts. Deviations from specifications were often only identified at a later stage in the process, and the procedure generated avoidable waste.
The new method changes this approach. Sensors mounted on two robots within the existing end-of-line measurement cell are positioned automatically relative to the component. The thickness of the individual paint layers is determined by analysing the time-of-flight of reflected terahertz waves. Each measurement takes only seconds and reaches accuracy in the micrometre range.
According to the company, the system delivers objective and reproducible results and supports the early detection of process deviations. As destructive testing is no longer required, waste and material consumption are reduced. The digital measurement data also create a basis for data-driven process control.
“The combination of higher measurement accuracy, direct process integration and full digitalisation delivers tangible benefits across the entire production chain, strengthening quality, economic efficiency and resource conservation in equal measure,” Theiselmann adds.
Step towards a digital paint shop
Following the introduction of automated surface inspection in 2024, the new measurement technology marks a further step towards a fully digital paint shop for plastic components in Leipzig. All measurement and quality data are generated in digital form and will in future be analysed using AI-based methods to identify deviations early, evaluate trends and refine process parameters.
“In 2020, we pioneered the first robotic inspection cell for car bodies, a milestone that has now resulted in 20 systems in production for 10 OEMs worldwide. This year, 2026, we’re replicating that leadership in the plastic components industry. Our mission goes beyond measurement: we’re digitizing precision to elevate industry excellence, reducing costs and protecting the environment,” statet Israel Arnedo, Director of das-Nano, the supplier of the new meassuring system.
First application within the BMW Group
By scaling the technology for industrial use, the Exterior Plastics unit in Leipzig is the first BMW Group site to integrate the method into in-house production, and the first to apply terahertz measurement to paint layer thickness on plastic components more broadly.
Following piloting and ramp-up, the system can now be used with all component carrier systems, or “skids”, and is currently being enabled for all colour variants. The company sees potential for further rollout at other plants, particularly in painted body shops, as well as within the supplier network.
The Exterior Plastics team forms part of the Purchasing and Supplier Network division at the Leipzig site. Its 450 employees produce injection-moulded plastic exterior body components – including bumpers, side sills and spoilers – which are supplied to the Leipzig plant as well as to the BMW Group sites in Dingolfing and Regensburg.
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