Spatial Gap
The precise distance between the cutting edge of a die and the surface of the anvil or the internal walls of a matching female die determines the quality of a sheared edge. Proper die clearance ensures that the paperboard is sheared cleanly to avoid crushing or tearing during the converting process. This setting varies according to the thickness and density of the substrate being processed.
Shear Mechanism
When the cutting edge penetrates the material, a crack propagates from the point of contact through the thickness of the sheet. If the gap is too narrow, the excessive friction generates heat and leads to premature wear of the metal tools. Conversely, an overly wide gap causes the material to bend into the space, resulting in ragged edges and excessive dust generation.
The ideal setting allows the blade to cut roughly one-third of the way through the board before the internal stress causes a clean fracture across the remaining fibres.
Tooling Wear
Continuous contact between the blade and the substrate eventually blunts the sharp edges and alters the effective clearance. Regular calibration prevents the burring of edges on high-quality folding cartons. Hardened steel dies maintain their specified clearance for longer periods than softer alloys.
