Paperboard Creasing Mechanics and Physical Quality Inspection Fundamentals
Optimizing rule depth and matrix channel width induces internal ply delamination, preventing top liner crack failures during high-speed carton folding.
Internal Ply Shear
Cohesive Strength
The resistance of multi-ply paperboard to internal delamination represents a fundamental mechanical property required for high-speed printing and converting processes. When exposed to tension or shear, internal ply shear strength prevents the individual fibre layers of the board from splitting apart. This characteristic is particularly important in offset printing, where high-tack inks exert strong vertical forces on the surface of the sheet.
Insufficient ply bond strength leads to blisters, surface rupture, or complete structural failure of the box. High-performance cartonboards are designed to withstand these forces.
Mechanical Action
During the creasing and scoring of heavy paperboard, the board must delaminate internally in a controlled manner to form a clean crease. The shear forces generated during this operation must overcome the local ply bond without tearing the outer linerboard. This controlled separation prevents cracking along the folded edges of the finished carton.
Dynamic Evaluation
The Scott Bond test instrument measures this resistance by striking a metal angle adhered to the paperboard sample with a calibrated pendulum. This test quantifies the energy absorbed during the rupture of the internal paper fibres, expressed in joules per square metre. The resulting measurements allow board manufacturers to adjust starch addition or refining levels on the paper machine.