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.
Steel Creasing Rule
Line Mechanics
Die-cutting plates receive a steel creasing rule to displace substrate fibers rather than sever them during carton conversion. Precision height profiles govern board displacement, so a fraction of a millimeter variance causes either flange fracturing on folding boxboard or slack hinges on corrugated shippers. Flatbed presses and rotary cylinders house these hardened metallic strips inside laser-cut plywood jigs, aligning parallel to cutting knives to form accurate folding channels.
Caliper thickness of the processed stock dictates the required shoulder radius of the profile, ensuring the bending moment occurs precisely along the designated score line without tearing the outer liner.
Pressure Tolerances
Press operators adjust makeready matrix depths beneath the steel creasing rule to match the bending resistance of heavy folding boxboard. Excessive tonnage crushes the internal paper matrix and destroys structural tear strength along the hinge, while insufficient force produces rounded arcs that fail to square during automated gluing. Channel width equations combine board caliper with liner elongation percentages, preventing premature fatigue when automated packing lines cycle at high speeds.
Wear Resistances
Induction-hardened edges on a steel creasing rule resist the abrasive friction of abrasive clay coatings found on premium paperboards during long production runs. Uncoated grades cause minimal tool degradation, whereas mineral-filled substrates accelerate rounding of the pressing profile and demand frequent tooling replacement. Metallurgical composition balances hardness against impact toughness to prevent micro-chipping along the striking ridge when high-speed platen presses close against steel counterplates.