Multi Ply Board Layering Mechanics Impact on Creasing Performance
Controlled inter-ply shear delamination inside the middle layers under rule stroke impact converts rigid board into thin lamina, eliminating score cracking.
Female Die Groove
Counterplate Recess
Milled channels in a resin or steel matrix run directly beneath the creasing rules to receive the compressed paperboard. The correct dimension of each female die groove determines the quality and ease of the subsequent folding operation. This channel must be slightly wider than the rule plus twice the thickness of the board to allow proper clearance.
Crease Formation Stage
Pushing the paperboard into this recess induces localized shear stress and deliberate internal ply separation. A female die groove guides the flow of fibers during the stroke, forming a symmetrical bead on the reverse side of the board. Insufficient depth or width in the channel prevents the bead from forming correctly, which can cause surface cracking on the printed side.
Conversely, too wide a channel results in a loose crease, leading to poor carton squareness during high-speed assembly.
Substrate Wear Control
Materials used for the matrix must resist the abrasive action of repeated board compression to prevent channel widening. Polymer matrices and steel plates are chosen based on the length of the production run and the hardness of the paperboard. Accumulation of loose fibers and dust within the channel can alter its effective depth, requiring regular cleaning to maintain consistent folding performance.
When the channel begins to wear down, the bead height decreases, leading to stiffer creases and potential carton rejects.