CAPS & CLOSURES 27 PETplanet Insider Vol. 23 No. 01+02/22 www.petpla.net they changed depending on the bottle orientation. And because the bottles are transported unaligned during the inspection important evaluation windows could not be set correctly for the time being. The software upgrade provided a remedy especially for completely asymmetrical tethered caps: Since then, the individual images can be rolled out to a full 360° view even in such cases, on which evaluation windows can be centered and aligned to a specific characteristic. The allround inspection of the closure walls of asymmetrical 26/22 tethered caps thus again achieves the usual accuracy in identifying defects in this area. Inspection of closure integrity In addition, the enhanced software masters another challenge in the detection of caps that are too high and may not seal properly. This can now be done reliably from an overheight of 0.5mm. But this is still not enough to ensure closure integrity. The proven cap angle detection of the Heuft FinalView II Cap has therefore also been further developed: It can now be measured whether the tethered caps are always aligned at exactly the right angle to a special marking on the bottle neck – and thus it can be calculated exactly whether they have actually been screwed on as far as they should have been during the capping process. The results of the extended 360° closure wall inspection are compared with those of the standard integrated top-down camera for colour logo inspection. Together with the specifications of the closure manufacturer, it becomes directly clear in this way whether the respective full container is tightly and securely closed. Precise statistics provided by the advanced cap angle detection help the bottler to identify faulty closure heads at an early stage and to start preventive maintenance before this leads to major product losses due to leaking bottles. Illumination for clear contour inspection To meet yet another challenge associated with the new GME 30.40 neck finish for 26/22 tethered caps mentioned above, the compact unit for cap inspection directly on the moving conveyor has also been equipped with special lighting. Like the entire preform, it is made of recycled PET, which is less bright and transparent than conventional PET, especially in the mouth and thread area. And that makes it more difficult to detect defects around the tamper-evidence band. But it is precisely in this sensitive area that full precision is important in order to be able to guarantee that each individual rPET bottle is securely closed and its contents remain pure and unadulterated until the end consumer opens it himself. Heuft has therefore prepared its transmitted light method for the darker material with new illumination hardware in order to track the tether mechanism and to be able to detect defective or broken tamper-evidence rings even better under such conditions. More than “just” tethered cap inspection The tests were successful. The same applies to the integration of the further developed Heuft FinalView II Cap into the pilot line. And the experience gained in the recently started regular operation also confirms that non-returnable PET bottles with faulty asymmetrical tethered closures are indeed reliably detected and safely rejected. For preventive maintenance, the causes of detected closure faults are localised at an early stage. After all the detection unit for the all-round closure inspection is an additional module of the Heuft Spectrum II VX which permanently monitors not only the filling valves but also the capper heads via a machine connection. Furthermore, the modular fill management system of the new generation checks the fill level as well as the presence and position of the labels among other things. And besides the accurate rejection of faulty bottles, it realises a targeted sampling: a Heuft e-mono discharges a freely definable number of bottles onto its own lane without compressed air after the first round in the capper. All this is reliably achieved at a line speed of 40,000 bph and is designed for even higher speeds. www.heuft.com With the new software, the gap between the tamper-evidence ring and the tether band can be teached as good without compromising the safety in detecting unwanted gaps between the latter and the closure cap itself. The fact that deviating pixels around the tether mechanism are now tolerated does not affect the detection accuracy when inspecting the 180° opposite tamper-evidence band area, so that even the smallest defects such as broken bridges are reliably identified there. The number of pixels that deviate from the original shutter colour can vary between the left and right side of the protruding hinge. With the further developed software, this can also be taught as good and tolerable for this particular rotational position of the tethered cap.
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