Micrometer-Scale Seal Defects Detected During Packaging

Optical coherence tomography is being adapted for inline quality control of film packaging through the publicly funded OCTInline project. Fraunhofer Institute for Ceramic Technologies and Systems IKTS has integrated the inspection technology into a packaging machine from Kallfass Verpackungsmaschinen GmbH, targeting applications where seal integrity is critical, including food and medical packaging.

Inline Inspection Addresses Seal Integrity
Sealed film packaging can contain pores, air pockets or incompletely bonded regions that compromise seal integrity. The challenge becomes more significant with recyclable mono-material films, which can be more susceptible to sealing defects than multilayer composite structures.

Fraunhofer IKTS is addressing this problem using optical coherence tomography (OCT), an imaging technique based on near-infrared light. Light is directed into transparent or semitransparent material, and reflected signals are processed to generate three-dimensional information about subsurface structures.

This enables internal defects to be identified without opening or damaging the packaging.

Integration Into Packaging Machinery
Within OCTInline, Fraunhofer IKTS researchers integrated the OCT inspection system directly into the sealing process of an industrial packaging machine. The system performs continuous inspection while production is running at speeds of up to 25 meters per minute.

The system can detect and visualize pores in the seal down to eight micrometers. Achieving this resolution at production speed requires coordination between imaging depth, exposure time, data processing and film movement. Mechanical vibration must also be controlled because small movements of the film can affect measurement accuracy.

Kallfass Verpackungsmaschinen provides the industrial environment in which the inspection approach can be evaluated under packaging-machine operating conditions. A demonstration system has been operating at the company's site in Nürtingen, Germany, since July 2026.

Inspection Data Supports Process Control
The OCT data can provide information beyond pass-or-fail defect detection. Changes in seal quality can indicate unsuitable combinations of sealing pressure and temperature or progressive wear of tooling.

Continuous monitoring therefore allows deviations to be identified during production rather than through downstream sampling. Earlier detection can reduce the quantity of defective packaging produced before corrective action is taken and can provide information for maintenance decisions such as tool replacement.

Applications Beyond Film Packaging
The inspection principle can also be adapted to other transparent and semitransparent materials where internal structures or thin layers require non-destructive examination.

Potential industrial quality assurance applications include functional coatings, ceramic components and additive manufacturing. The underlying OCT approach is particularly relevant where micrometer-scale internal defects must be detected without sectioning or otherwise damaging the component.

Edited by Sucithra Mani, Induportals editor – adapted by AI.

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