A customer unwinds a spool and finds marks along one or both edges. Creases, flats, or a pressed line. It usually gets reported as product damage, and it usually has a specific and findable cause.
First question: which edge, and how far in?
Everything follows from this.
- Both edges, symmetric — something about the width, or systematic contact with both flanges.
- One edge only — usually traverse-side-specific, or that flange is damaged or displaced.
- Only in the outer layers — handling or storage rather than winding.
- Only in the inner layers — core-related, or compression at the base of the pack.
- At intervals — periodic through the wind, which points at the traverse.
Cause one: winding too near the flange
The most common by a distance. Wind to within a millimetre or two of the flange face and any wander in the traverse puts turns against the flange. Under tension they press against it and take a mark.
The convention of leaving clearance is covered in our article on fill height, and it applies across the width as well as radially. How much clearance depends on product stiffness — soft product needs more, stiff product less.
Diagnostic: look at the flange face. If there is a polished ring where product has been rubbing, that is the contact.
Cause two: something protruding
Anything on the flange face that stands proud:
- A raised marking, embossed logo or printing — see the markings article
- A damaged area, burr or raised splinter
- Bonding or adhesive residue from a label
- The edge of a joint on take-apart construction standing slightly proud
- An insert or fastener that is not flush
Run a hand across the flange face. Anything you can feel will mark product under tension.
Cause three: the flange moving
A flange that deflects outward under hoop load can open a gap, allowing outer turns to migrate into it — the failure described in the context of stiffness in our deflection test article. Turns that have migrated into that gap are then pressed against the flange by the turns behind them.
This tends to produce marks concentrated in the outer layers, and often on one side, because real packs are rarely perfectly symmetric.
Cause four: stacking and handling
A spool stored resting on the rim can take load through the flange directly onto the product edge. A stack where the lower spool is carrying more than it should will press at the contact ring.
The general principles are in our piece on storage yards. Specifically on this issue: store on the flange face, not stacked rim-on-rim with product in the pack.
Cause five: contamination
A particle on the flange face, or debris caught between turns, presses locally. Usually shows as isolated marks rather than a continuous line, and often appears on one spool out of many. These tend to be one-off rather than systematic, which is itself diagnostic.
Cause six: it was transported badly
Damage that appeared in transit is frequently reported as product defect and vice versa. Our article on damage claims covers how to establish what happened where, and the short version is that photographs taken before anything moves are the deciding factor.
What to do once you know which
- Contact during winding: more clearance, check traverse
- Protrusion: remove it, or specify flush construction
- Flange movement: stiffer flange, or reduce fill
- Storage: correct the stacking method
- Transit: address it as logistics, not product
Preventing recurrence
Two habits that cost nothing: look at the flange faces for polished rings during routine inspection, and look at the edges of the pack when a spool is unwound. Both surface problems while they are still cheap, rather than when a customer has found them.
If you send us a photo of the marked product and tell us which layers it was in, that is usually enough to distinguish the causes above for our hollow board spools — including telling you when it is not the spool.