Paper curling is often blamed on raw material.
But in most cases, it is created during processing.
What Causes Paper Curling
At its core, curling comes from one issue:
uneven stress inside the sheet, mainly caused by moisture imbalance.
When one side of the paper expands or shrinks more than the other, internal stress builds up.
After cutting or stacking, this stress is released-and the sheet curls.
Three Key Triggers in Sheeting
In real production, curling is often linked to the sheeter itself:
1. Uneven tension
If web tension is not balanced across the width, stress becomes uneven.
After cutting, the sheet deforms.
2. Incorrect knife setup
Improper knife angle or pressure affects how fibers are cut, leaving hidden stress at the edges.
3. Unstable pressing and transport
Uneven roller pressure or inconsistent sheet handling introduces deformation that appears later.
Why It Gets Worse Over Time
Curling doesn't always show immediately.
It often appears after:
environmental humidity changes
stacking and storage
downstream processes like printing
This is because the internal stress needs time to release.
How to Reduce Curling
The solution is not a single adjustment, but better process control:
keep tension stable and uniform
optimize knife setup and alignment
ensure consistent pressing and transport
maintain stable environmental conditions
Conclusion
Paper curling is not just a material issue.
It is a result of unbalanced process conditions.
Control the process, and the sheet stays flat.
