Board Caliper

Bending Resistance

Mechanical stiffness in paperboard structures increases as a cubic function of sheet thickness when fibre density remains constant. Operating crews adjust wet-end pulp deposition and wet pressing force to alter board caliper without increasing basis weight unnecessarily. Decreasing density while maintaining caliper enhances flexural rigidity per unit mass, which reduces raw material consumption during converting operations.

Excessive calendering reduces thickness, which reduces carton wall strength and causes failure during automated pallet stacking. Laboratory testing uses dead-weight micrometer anvils to measure thickness across five points per sample sheet.

Converting Tolerance

Variances in sheet thickness alter die-cutting depth and creasing matrix clearance on automated converting machinery. Uncontrolled board caliper causes liner cracking during folding operations or incomplete cut-through on heavy folding boxboard grades. Folder-gluer feeding mechanisms require uniform board thickness to prevent double-sheet feeding or jam conditions.

Packaging machinery specifications require thickness stability within five percent of nominal values to ensure consistent carton erection.