Inductives provide reliable final check on bottle packing line

Imagine the disappointment, if when you opened a cardboard case of 12 bottles of beer, you found that it only contained 11 bottles, or if the bottles were not drinkable because their caps were missing. Contrinex offered its packing customer a sensing solution to ensure this couldn’t happen.

To ensure that consumers are not disappointed and that retailers do not complain or seek compensation, the high-speed packing line needed to include a final-inspection check. Ideally, this check would be after the lid of the corrugated cardboard case has been closed and sealed, to ensure what was checked, is what was dispatched. Therefore a system was designed using Contrinex long-distance inductive sensors which count and verify the position of bottle caps through the layers of cardboard on the top of each sealed case.

Once the high-speed packaging line places bottles into corrugated cardboard cases, the placement and number of bottles in the case are verified, ideally, after they have had their lids hot-glued closed. This is done to detect if a bottle has broken when placed into the case, contaminating the machinery and subsequent packages. Bottles can also be absent or wrongly positioned, or a cap might be missing from a bottle.

Whilst a vision system could be used, this would need to be done before the lid of the case is closed, whereas verification of the closed case would be preferable and has the advantage of being implementable as a standalone unit after the packaging line.

The absence of a bottle cap in the correct position at the top of the case is a good indicator of a missing or shattered bottle. The challenge is to detect bottle caps through multiple layers of corrugated cardboard material of varying thickness and density.

Contrinex’s extra-distance 500 Series inductive sensors are ideal, being robust and accurate. The highly reliable, IP67-rated, M30-diameter sensors have a chrome-plated brass body with a PBTP sensing face and vacuum-encapsulated electronics. They provide high reliability in hostile environments, and their 3x sensing distance of 22mm, provides a fully contactless operation for this high-speed packaging application.

An array of sensors is placed above the conveyor of the filled and sealed cardboard cases. For each lane of bottles in a case, an M30 diameter inductive sensor is mounted on the array. The non-embeddable inductive sensor was chosen as it most closely equates to the size of the bottle cap and yields the greatest sensing distance for the available target area and is sufficient to allow for minor variations in the height of the case as it passes under the sensor. The sensors are interfaced to a simple PLC controller that makes the logical decision to accept the package or reject and divert it. The long sensing distance range of the ‘500 Series’ inductive, not only ensures reliable sensing but also keeps the sensor at a safe distance from any impact, avoiding consequent downtime.