Elastic Recovery
Elastic strain recovery following physical deformation quantifies the force required to maintain folded paperboard flaps at a right angle during carton assembly. High values of springback coefficient indicate strong resistance to permanent creasing, forcing high adhesive tack demands on automated packaging lines. Understanding this elastic behavior allows carton designers to optimize scoring die depth and width for specific board caliper ranges.
Folding Kinematics
Crease stiffness tests evaluate board performance by measuring the bending moment sustained during ninety-degree folder flap displacement. An elevated springback coefficient causes folded carton panels to push outward, leading to open glued flaps or distorted box geometry inside packaging machinery. Fibre orientation strongly dictates recovery behavior, as cross-direction creases display higher elastic memory than machine-direction folds.
Board density and moisture content alter internal delamination patterns within the crease score, influencing energy storage during folding. Scoring matrices must crush the internal ply structure without rupturing the top liner, creating micro-delaminations that dissipate elastic strain energy.
Material Limit
Environmental moisture uptake decreases board stiffness, reducing elastic recovery forces after folding. When the springback coefficient drops too low, structural rigidity fails to support stacked cartons in distribution chains. Maintaining target relative humidity during storage stabilizes creasing behavior.
