The challenge
The packaging lines operate at high speed and process up to 80 packages per minute, weighing between 450 and 2500 grams. PE film in various thicknesses is used, both printed and transparent. At those speeds and with such a wide variation in film and packaging format, reliable manual inspection of the long seal is practically impossible.
Moreover, the problem is that a seal defect occurs in several ways, and not every defect can be recognized with the naked eye. Vision Partners distinguished several conditions that the inspection must be able to distinguish, including:
- Good seal – overlap and seam profile are nominal.
- Cold seal – the seal temperature is too low, the foils do not completely fuse together.
- Hot seal – the seal temperature is too high. The foil around the seam is deformed and the seam profile is deformed.
- Unsealed – no seal has been applied; the packaging is only held together by the foil overlap, without a seam profile.
The core of the challenge: can one sensor technology, in-line and at full line speed, reliably distinguish all these errors – across different film types and packaging formats?
The approach
Vision Partners carried out the feasibility tests on-site, directly on a production machine. A 3D Laser Profile Sensor was temporarily mounted on the heating element of the long seal, at the inspection position immediately after the side film was formed, sealed and cooled, but before filling and the cross seal.
The sensor measures the height differences in the seal using laser triangulation and builds a detailed 3D point cloud of the seam area using a line scan method. Specifically, the tested 3D profile sensor achieved the following:
- High resolution (z-axis) of approximately 4 µm (0.004 mm) over a measurement range (FOV) of approximately 60 mm;
- X resolution of approximately 0.03 mm – which means that a seal width of 3 mm yields approximately 100 measuring points in width alone;
- Measuring frequency of 660 Hz, which guarantees a y-resolution of at least 0.75 mm at the maximum line speed of 500 mm/s.
This measurement density makes it possible to not only see the seam profile, but also to characterize it accurately.
The result
The feasibility study showed that the 3D point cloud for each of the tested failure conditions contained a recognizable signature.
The conclusion was unequivocal: each fault class was clearly characterized in the 3D data. This provides a strong foundation for the next phase, in which the inspection algorithms are developed and validated on a production machine.
Vision Partners guides this process from feasibility to turnkey solution: from the initial feasibility tests on site, through the development of the inspection algorithms and the RVS camera housing, to full integration with the packaging machine and PLC, including FAT, SAT, and Service & Maintenance. In this way, a proven measurement principle is gradually transformed into a reliable production system. Vision Partners is a certified MVTec HALCON integrator and distributor of, among others, LED2Work, TPL Vision, and Hikrobot Machine Vision products.
Want to know more about seal inspection using 3D laser triangulation? contact OP.
