Billions of products are shrink-wrapped in plastic film every year, particularly in the medical and food industries, where the tightness of the packaging is crucial. As part of the ‚OCTInline‘ project, the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) has developed an innovative testing system that uses optical coherence tomography (OCT) to detect flaws in heat-sealed seams in real time during the packaging process. This method enables non-destructive testing with a resolution down to the micrometre range.
Optical coherence tomography is an imaging technique originally developed for ophthalmology. It uses infrared light to image the structure of a wide variety of materials beneath the surface in three dimensions and make defects visible. Conner Phillips, a researcher at the Fraunhofer IKTS, explains: „The system sends near-infrared light into the material and captures the reflected signals, which are used to create high-resolution three-dimensional images of the internal structure.“ This technology makes it possible to identify material flaws, air pockets or insufficiently welded areas without damaging the packaging or the product.
Continuously detect smallest defects
In the ‚OCTInline‘ project, researchers have integrated OCT technology directly into the sealing process of a packaging machine. This enables continuous, non-destructive quality inspection at a production speed of up to 25 metres per minute. According to Ralf Schallert, group manager at Fraunhofer IKTS, pores down to a size of eight micrometres can be detected and visualised in the seal seam. The combination of high resolution and production speed presented the team with challenges, particularly regarding data processing and integration into the industrial process. „We had to find a balance point between depth of field, exposure time and the movement of the film,“ says Phillips.
Fewer rejects, greater process reliability
The rising demands on sustainable packaging are increasing the importance of reliable seal seam testing. A growing number of manufacturers are relying on recyclable mono-films, which are ecologically advantageous but more frequently exhibit faulty seal seams. Schallert emphasises: „This increases the need for continuous monitoring.“ Real-time testing offers manufacturers several advantages, including the reduction of waste and material consumption, as well as information on the condition of machines and tools. „Many errors occur because pressure and temperature are not optimally matched to the material, or because the tool wears out over time,“ explains Schallert. „With the OCT data, we can make such changes visible and also identify at an early stage when, for example, a tool change becomes necessary.“
Versatile application possibilities
A demonstrator of the system has been in use at Kallfass Verpackungsmaschinen in Nürtingen since July 2026 and is being presented to potential customers. Schallert emphasises that the packaging industry is just one of many application areas for the technology. The systems can be individually adapted to different materials and requirements, making them usable for various industrial challenges. In addition to packaging, functional coatings, ceramic components or additively manufactured parts can also be inspected. „Wherever thin layers, internal structures or the smallest of defects need to be reliably detected, OCT can make an important contribution – from medical technology and functionalised surfaces to industrial 3D printing,“ says Schallert.
Source: Fraunhofer IKTS
