Fold Resistance
Force required to fold a pre-creased line measures the structural behavior of a carton along its scores. This scoreline stiffness dictates the performance of carton blanks on high-speed gluer and cartoner machines. A well-designed creasing process reduces the resistance of the board along the scoreline, allowing it to bend smoothly without cracking the outer printed surface.
Packaging Runnability
Carton erecting machines need low resistance along folding lines to avoid jam-ups on the packaging line. If the scoreline stiffness is too high, the carton will not fold cleanly, leading to misaligned seams and squareness errors that disrupt automated filling operations. When the score is too weak, the carton walls may bow outward under pressure from the product inside, ruining the appearance of the package.
Springback Behavior
Bending recovery forces cause folded panels to try to return to their original flat state after being folded. This springback is a direct result of scoreline stiffness and must be controlled to ensure that glued flaps stay bonded while the adhesive cures. High-speed cartoning lines often use a pre-heating step or rapid-setting hot-melt adhesives to overcome this springback action and maintain carton squareness.
Laboratory testing using a dual-spindle stiffness tester helps convertors determine the optimum ratio between the stiffness of the uncreased board and the creased scoreline to ensure reliable runnability.
