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Hard anodised slide guides in labelling machines

AHC Oberflächentechnik has been a reliable market partner of Krones for decades. Headquartered in Neutraubling, Krones AG designs, develops and manufactures machines and complete systems primarily for processing, filling and packaging technology. The listed market leader can use lighter materials without having to forego high functional reliability thanks to AHC's surface technology solutions. The following application example illustrates this.

Cold-glue labellers stick all kinds of labels on glass and plastic bottles, jars and moulded containers. The machines must work precisely and reliably, be easy to operate and quickly convert to other containers or label formats. Their output is from 10,000 to 36,000 containers per hour, i.e. up to 10 containers per second. In this case, an infeed starwheel transfers the containers to a rotating container table, where they are firmly clamped and centred between container plate and centring bell. Rubberised glueing pallets are given a very thin glue film, via a glue roller, and the labels which they hand over to gripper cylinders. These, in turn, put the labels on the containers. In order to be able to ensure the precision of this operation, the gripper cylinders are guided by sliders on slide guides. At this point, an AHC Oberflächentechnik coating comes into play. The slide guides, which are made of a light cast aluminium alloy, are subject to considerable stress with around 2,000 to 7,000 friction strokes per hour. A HART-COAT® -PLUS coating (hard anodising + PTFE) significantly reduces this stress. Further down the production line, the labels are fixed and smoothed by brushes. The labelled containers are collected by the discharge starwheel and passed on to the conveyor belt.

The hard anodised HART-COAT® coating is formed by anodic oxidation in a cooled acid electrolyte. The aluminium base material transforms into aluminium oxide on its surface. The oxide layer grows in equal parts inwards and outwards, which results in a defined dimensional change of the component. Particularly noteworthy is the very good bond with the base material from which the layer is formed, due to atomic binding forces. The hardness of the aluminium oxide gives the coating a high wear resistance. To improve the anti-friction properties, the HART-COAT® coating is additionally provided with incorporated PTFE lubricants (HART-COAT®-PLUS). Cleaning of the surface is further facilitated by its anti-adhesion behaviour.

The slide guides could be made from the lightweight material AlMg3 (casting alloy) due to the AHC HART-COAT®-PLUS coating. It has excellent wear resistance and impressive anti-friction properties.

Looking into a labelling machine. In the background, the rotating container table can be seen, on which bottles are firmly clamped and centred between container plate and centring bell. Rubberised glueing pallets (right) pass the labels over to the gripper cylinders with the light green receiving surface (centre). These, in turn, put the labels on the containers. To do this, the slides move in and out from the slide guides, which are concealed behind (top right in the small photo).


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