Calibrating Crease Depth Ratios to Prevent Liner Cracking on Coated Cartons
Maintain crease depth penetration between 0.45 and 0.65 of board caliper with a 1.4 to 1.6 channel multiplier to promote internal shear and eliminate cracking.
Z-Direction Delamination
Internal Cleavage
Internal cleavage designates the mechanical failure where paperboard separates into distinct horizontal strata under tensile forces applied perpendicularly to the plane of the sheet. Poor internal bond strength within multiply paperboard structures drives this structural defect, which compromises structural integrity during high speed converting operations. Caliper variation across the web exacerbates internal cleavage by creating uneven stress distribution during converting operations.
Manufacturers measure internal bond strength using standard dynamic internal bond testers to prevent unexpected splitting during printing and gluing stages.
Tension Tolerances
Z-Direction Delamination occurs when transverse tensile stresses exceed the internal bonding strength holding the cellulose fibre layers together in paperboard stocks. High tack printing inks and aggressive UV coatings generate strong perpendicular pulling forces during blanket release stages on modern offset presses. Substrates with insufficient refining or inadequate retention aid distribution show high susceptibility to this failure mode under rapid stress application.
Converting plants mitigate internal cleavage by selecting paperboard grades engineered for high internal bond performance during packaging production.
Substrate Performance
Structural separation within the board cross section ruins packaging cartons by causing surface layers to peel away under converting loads. Gluing stations experience severe adhesive joint failure when the substrate pulls apart internally instead of holding the applied glue line. Folding carton manufacturers evaluate internal bond ratings carefully before committing heavy paperboard stocks to high speed packaging lines.
Testing protocols verify that raw material specifications match the mechanical demands imposed by commercial printing and converting machinery.