Downgauging Folding Boxboard without Losing Compression Strength
Downgauging folding boxboard demands increasing core bulk and outer ply elastic modulus to preserve caliper and bending stiffness under McKee formula laws.
Die-Cutting Matrix Width
Groove Geometry
The width of the channel in a creasing matrix determines the clearance available for the board to fold without cracking its outer liner. Proper selection of die-cutting matrix width ensures that the paperboard is forced into the groove to form a clean, functional hinge. This parameter must accommodate both the thickness of the creasing rule and twice the caliper of the board.
An incorrect width leads to either weak folds or split board fibres. It is an important variable on the press setup.
Fold Quality
Creasing rules push the board into the matrix to form a permanent deformation. If the die-cutting matrix width is too narrow, the board is sheared rather than creased, causing the top plies to split. When it is too wide, the crease is loose and lacks the definition required for precise folding on high-speed gluer lines.
The carton panels fail to align properly.
Selection Formula
Converting formulas dictate the ideal groove dimensions based on board caliper and steel rule thickness. For most folding cartons, die-cutting matrix width equals the rule thickness plus 1.4 to 1.7 times the board thickness. Adjustments are made for hard-calendered board or heavy recycled grades.
This selection ensures consistent carton assembly.