Steel Profile
The physical profile of a steel die-cutting rule defines the shape, height, and tip radius used to deform cartonboard without cutting the fibers. In commercial packaging converting, crease rule geometry determines the distribution of stresses within the paperboard during the scoring process. This specification ends where the rule face meets the flat shoulder, establishing the limit of effective indentation.
Structural Interaction
Different boards and thicknesses require specific rule heights to achieve a clean bend. In crease rule geometry, the height of the steel rule must be less than the cutting rule height by the thickness of the board and the matrix backing. Adjusting the tip thickness and radius modifies the pressure distribution, allowing the fibers to delaminate internally instead of tearing on the surface.
This controlled internal failure creates a perfect hinge that folds smoothly on automatic gluer lines.
Running Tolerance
High speed folding and packing operations require very tight tolerances on crease resistance. If the crease rule geometry is inconsistent, the variations in crease stiffness will cause the folding machine to jam or force the carton out of square. Testing instruments measure the force required to bend the creased board to a ninety degree angle, indicating the quality of the rule setup.
Constant checkups prevent premature wear of the steel tip, ensuring that the crease characteristics remain stable across long press runs.
