Structural Stress
Folding force applied from both sides of a paperboard sheet creates an angled profile that resists tearing during high speed automated insertion. This double-bevel bending geometry distributes mechanical tension across two distinct crease lines instead of relying on a single hinge. The resulting deformation increases the stiffness of the final package flap by widening the distribution of stress along the grain.
Operators control the angle of the blade profiles to ensure the fiber structure yields without cracking the surface coating. High grammage stocks respond well to this dual pressure because the material fibers reorganize along a broader radius rather than snapping under localized shear.
Crease Integrity
Production lines utilize this method to maintain a clean appearance on laminated cartons where cracking reveals the darker inner ply. A double-bevel bending setup reduces the likelihood of board delamination during the transformation from flat blank to closed vessel. Technicians calibrate the depth of each individual bevel to manage the resistance of the substrate against the forming tool.
Consistent results occur when the depth of the inner and outer blades aligns with the moisture content of the board stock. Each side of the fold reaches its limit simultaneously, preventing the board from pulling away from the adhesive seal.
Manufacturing Constraint
Heavyweight coated substrates require this configuration to prevent the outer layer from bursting when a small radius is necessary for shelf appeal. Small radius folds often cause the cellulose matrix to fail when handled by standard single-line systems. Incorporating two distinct contact points allows the board to accommodate a larger displacement of material at the fold site.
A sharp fold results from this configuration without compromising the protective barrier of the exterior print surface. This physical transformation represents a permanent alteration of the structural load path within the board.
