Creasing Rule Selection for Coated Folding Boxboard Conversion
Selecting steel creasing rules and matrix channels for coated FBB requires matching board caliper and CTMP core shear limits to prevent surface cracking.
FBB Conversion
Mechanical Transformation
Post-papermaking manufacturing processes transform flat paperboard sheets into folded, glued and functional packaging structures. Operations include slitting, sheeting, printing, die-cutting, creasing and folding carton gluing. FBB conversion adapts mechanical processing parameters specifically to the multi-ply stiffness and creasing behavior of folding boxboard.
The process boundary stops at final carton erection and product filling on packaging lines.
Crease Formation
Die-cutting matrix tooling deforms the paperboard along predefined lines to establish clean fold axes. Male creasing rules force the sheet into female grooves, shearing internal bonds within middle mechanical pulp plies while preserving outer chemical fiber layers. This delamination creates a controlled internal hinge that lowers bending resistance without rupturing top pigment coatings.
Proper crease depth prevents surface cracking during right-angle folding on high-speed gluing equipment.
Operational Boundary
Production efficiency on high-speed converting machinery depends on consistent board caliper, moisture content and cross-direction stiffness. Variations in substrate moisture alter fiber flexibility, causing inconsistent crease recovery force and carton bulging. Excessive matrix depth cuts outer chemical fibers, leading to tear failures along score lines during automated carton erection.
Conversely, insufficient creasing force leaves internal plies intact, generating high folding resistance that jams cartoning equipment. Precise alignment between creasing rules and matrix channel widths maintains structural integrity across varying production speeds.