Structural Integrity
Brittle failure at the sheet surface occurs when tension and bending forces exceed the local strain capacity of the coating layer. Surface liner cracking happens during the creasing or folding of corrugated board when the bond between the clay pigments and the underlying cellulosic structure breaks under pressure. This phenomenon prevents a smooth finish and prevents the uniform application of ink across the hinge area.
Production Velocity
High speed converting equipment induces rapid mechanical displacement that often triggers this defect if the moisture content of the board remains below the threshold for fiber pliability. Proper climate control at the site regulates the internal humidity levels to keep the paper fibers flexible enough to undergo deformation without fracturing. Operators manage this issue by adjusting the crease geometry or selecting a different board grade with higher elongation properties to accommodate the strain.
The specific depth of the creasing tool also modifies the stress distribution across the liner.
Conversion Tolerance
Finished boxes require a high degree of aesthetic quality at the fold to ensure consistent shelf appeal. Fractures along the score line admit contaminants into the internal fluting and degrade the structural stiffness of the carton. A clean fold without visible exposure of the raw fibers defines the standard for acceptable performance in the secondary packaging market.
