Predicting Delamination Behaviour in Multi Layer Paperboard Creasing
Predicting paperboard delamination requires balancing Z-direction shear strength to permit core separation while preventing outer liner tensile fracture.
Crease Matrix Channel
Groove Dimension
Recessed track in a polymeric or pressboard counter-die provides the necessary void space into which paperboard is forced by a creasing rule to establish a permanent fold line. The depth and width of this crease matrix channel must be selected according to the caliper and fiber characteristics of the board being converted. Incorrect sizing of the groove leads to either ruptured linerboard or poorly defined folds.
Fold Performance
Creation of a clean, crack-free fold requires the board to delaminate internally along the crease line during the scoring process. As the creasing rule pushes the board into the crease matrix channel, the outer plies of the paperboard stretch while the inner plies compress and separate into multiple micro-layers. This deliberate internal failure lowers the bending resistance of the fold line.
If the groove is too narrow, the excessive shear stress will rupture the outer linerboard. Regular monitoring of the channel width ensures that the folding torque remains within specified limits for automated packaging machinery.
Production Wear
Structural degradation of the counter-die during long production runs affects the consistency of the creased lines. Plastic matrices often feature a steel base to prevent migration of the groove boundaries under high pressure. When the matrix channel wears down, the crease height decreases, causing issues on high-speed filling lines.