More and more closures and bottles are marked with special features that are intended to support a faster and non-destructive seal integrity test method: application angle measurement using vision systems.
The theory is simple: when the mark on the closures aligns with the mark on the bottle, the closure is properly tightened onto the bottle threads and the package is perfectly sealed. The application angle requirements can vary considerably between different closure types. For example, 2pc closures have a tighter angle tolerance, while 1pc closures are considerably more forgiving when it comes to seal integrity.
With the advent of 1pc bimodal HDPE closures and servo cappers, we expect to see some brand owners set their cappers to rotate closures to a specific angle instead of tightening them to a specific torque. There is one thing to remember though: plastic composition, bottle blow molding and cap molding processes have their own variations as well. The external appearance of the marks may not necessarily indicate the accuracy of the internal seal.
While the visual inspection will provide 100% seal integrity inspection, the inspection system must be verified/calibrated from time to time to ensure the accuracy of the position sensing capability and to verify that the external appearance of the marks are an undeniable proof of internal seal integrity.
We believe that the visual application angle inspection will be a wonderful way to test the seal integrity on 100% of the packages, but for an error proof operation the vision system must be calibrated/validated frequently by using leak and torque testers.
For more information on these marks or calibration/validation, please contact a Mesa expert.
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