How is a pack kept registered between the top and bottom label heads?
Guides and conveyor surfaces must maintain the same product path and orientation while leaving access to the required faces. Any transfer, belt gap or product movement between heads can change the relationship of the two labels. The pack base, edges and rigidity therefore matter as much as label size.
What product features make top-and-bottom labelling difficult?
Flexible trays, uneven bases, projecting lids, curled cartons, open flaps and products that rock on the conveyor can all disturb registration or wipe-down. Samples should represent normal production condition, including any film, sleeve or closure that is present when labels are applied.
How should top and bottom label positions be measured?
Choose repeatable pack edges or features as datums, define each label position from those datums and state whether the two labels must align with one another. The acceptance method should also distinguish between placement variation and defects caused by the product surface or label adhesion.
Where should coding or inspection be placed around a top-and-bottom labeller?
Position depends on which surface is accessible, whether the code is printed on the pack or label and when the product is most stable. Inspection should see the required label or code without creating a transfer that disturbs the pack. The line-integration guide sets out the control questions.