Strength in an edge protector means two different things and buyers often conflate them. Compression strength is the ability to carry a stack without the profile folding. Tear strength is the ability to survive a band, a fork tine or a rough edge without splitting along the crease. A profile can be strong in one and weak in the other, and the pack usually fails in the weaker direction.
High strength grade data
| Failure seen | Cause | Fix |
|---|
| Split from the cut end | Ragged cut, handling | Clean cut, multi-ply build |
| Split along the fold | Band tension, tight fold | Wider leg, controlled fold radius |
| Notch at the contact line | Sharp edge | Doubled board at the line |
| Corner crushed | Compression | Heavier wall |
| Profile slipped off | Band position | Longer board past the band |
Tear starts at the cut end
A paper profile tears from an edge, not from the middle. The cut end of a bundle is where the plies are exposed, and any nick or ragged cut becomes the starting point for a split that runs along the fold under band vibration.
This is why cut quality is a specification item, not a detail. A clean square cut with a sharp blade costs nothing extra on our lines and removes most tear failures before they start.
What actually raises tear resistance
Longer fibre and better inter-ply bonding do more than thickness. A multi-ply wall with well distributed glue lines resists a propagating tear because each ply has to fail separately, while a single thick ply splits in one movement.
Where the edge being protected is sharp, the tear risk is at the contact line rather than at the cut end, and the answer is a doubled board at that line rather than a heavier single wall.
Matching the grade to the abuse
For hand handled cartons a standard grade is enough. For clamp trucks, fork tines and steel banding, specify the multi-ply build. For edges that are sharp or serrated, specify the doubled contact line on top of the multi-ply build.
If a pack has already failed in service, the useful question is where it split, not how thick the board was. A split at the cut end points to handling; a split along the fold points to band tension; a crushed corner points to compression.
Questions buyers ask before ordering
How do I compare two suppliers on strength?
Ask for the ply structure and the cut quality, then run both on your own pack. A single thickness number does not tell you which will tear first.
Is multi-ply better than single thick ply?
For tear resistance, yes, because each glue line has to fail separately.
Can you supply a reinforced edge?
Yes, a doubled board at the band or contact line is a standard build.
Does print weaken the board?
Not measurably at normal ink coverage, but heavy solid print on a thin wall is worth avoiding.
What lead time for a multi-ply grade?
7-15 working days after approval, samples in 3-5 days.
Send leg width, wall thickness, cut length and monthly volume to mona@hengnicepacking.com and we will quote the profile that matches your load.
