Resistance Measurement
Deformation force forms the foundation of paperboard performance testing, establishing how a substrate resists bending under standardized loading conditions specified by ISO 5628. Converters evaluate this resistance to ensure cartons maintain structural integrity through high-speed packaging lines without collapsing or creasing incorrectly. The method applies a constant rate of deflection to a clamped specimen, measuring the resulting moment of force over a prescribed bending angle.
Thicker multi-ply cartonboards demand higher test forces compared to lightweight folding boxboards, directly influencing the torque exerted on converting machinery.
Creasing Torque
Folding performance relies on managing the force required to bend the substrate along predefined score lines without fracturing the outer plies. Carton design engineers balance stiffness values against crease depth parameters to prevent liner cracking on automated packaging equipment. High resistance values demand deeper scoring channels during die-cutting operations to prevent the board from springing back against the closure mechanism.
Substrates exceeding standard rigidity thresholds often cause excessive wear on folding carton machinery if the crease geometry fails to compensate for the higher bending moment.
Caliper Scaling
Flexural rigidity scales proportionally with the cube of the board caliper, meaning small thickness variations compound rapidly into substantial resistance discrepancies across a production run. Papermakers control this relationship during wet-end formation and pressing to achieve the target stiffness without unnecessarily increasing basis weight or raw material costs. Converters frequently audit these physical parameters before running dedicated packaging batches to verify that the delivered substrate complies with mechanical processing specifications.
