Calibrating Crease Channel Width for Matte Laminated Folding Cartonboard
Matte laminated boxboard demands channel width expansion of twelve to eighteen percent over raw stock formulas to absorb film strain and prevent score rupture.
Crease Ratio
Geometric Index
Dimensionless proportional index metrics compare score groove geometries directly against total paperboard thickness. The calculated crease ratio evaluates how effectively a creasing rule deforms paperboard structure relative to its uncompressed caliper. Proper creasing creates localized internal delamination without breaking top surface liners.
This metric ceases to apply once the sheet undergoes full ninety-degree folding on a gluer line.
Mechanical Deferral
Calculating this index requires dividing the matrix channel width by board caliper, or dividing impression depth by board thickness depending on plant standards. A lower crease ratio indicates a tight crease geometry that places high tensile stress on the outer liner fibers. Higher values signify wide crease channels that allow excess board movement during folding operations.
Machine operators adjust press impression force to keep the value within prescribed engineering windows for solid bleached sulfate or coated recycled boards. Cross-direction creases require higher deformation ratios than machine-direction creases due to fiber orientation differences. Delamination within central plies absorbs strain energy, protecting external printed coatings from cracking.
Structural Threshold
Target values vary between zero point six and one point two depending on fiber recipe and moisture content. Maintaining optimal crease ratio prevents automatic packaging line jams caused by erratic carton opening force.