Unheated Warehouse Storage Impact on Multi Ply Boxboard Moisture Equilibrium
Unheated storage alters multi-ply boxboard moisture equilibrium, swelling sheet edges, reducing internal bond strength, and causing severe converting curl.
Crease Stiffness Loss
Mechanical Property
Reduction in the folding resistance of a paperboard substrate following the scoring process indicates the degree of internal fiber damage. Crease stiffness loss measures the percentage drop in force required to bend the board at the crease compared to the uncreased material. Scoring efficiency ensures that automated carton erecting machines function at high speeds without jams.
Ideally, the creasing operation breaks the internal bonds of the board without rupturing the outer liner or the print surface.
Diagnostic Tooling
Laboratory instruments use a specialized jaw to hold the board while a probe records the bending moment at a ninety-degree angle. By comparing the resistance of the intact board to the resistance of the creased section, the ratio of the two values reveals the quality of the convertor setting. Adjustments to the depth of the creasing rule or the width of the matrix channel directly alter the final outcome.
A loss that is too low results in spring-back where the carton resists staying closed, whereas a loss that is too high suggests the board has been structurally compromised to the point of tearing. The geometry of the groove must match the caliper of the board to achieve the desired fold characteristics.
Control of Scoring
Control of scoring prevents cracking of the ink layer during the finishing stages of luxury packaging. High-quality sulfate boards exhibit different loss profiles than recycled grades due to longer fiber lengths and higher chemical purity. Consistent stiffness across the width of the sheet ensures uniform performance on the filling line.