Creasing Rule Selection for Coated Folding Boxboard Conversion
Selecting steel creasing rules and matrix channels for coated FBB requires matching board caliper and CTMP core shear limits to prevent surface cracking.
Point Size
Thickness Scale
Linear measurement units used in North American packaging specifications define paperboard thickness in thousandths of an inch. One unit equal to 0.001 inch establishes the baseline caliper metric for folding boxboard and solid bleached sulfate grades. Point size provides converters and packaging buyers with a standardized numerical scale for paperboard thickness.
The measure applies exclusively to sheet caliper and does not describe basis weight or fiber density.
Caliper Measurement
Laboratory micrometers measure paperboard thickness under standardized dead-weight anvil pressure to eliminate surface compressible error. A sheet measuring 0.018 inches thick corresponds directly to eighteen points in board specification terms. Micrometer anvil size and dwell time strictly follow TAPPI standards to ensure uniform measurement across different testing facilities.
Converting Tolerance
Carton machinery setup relies on accurate point values to determine scoring rule height and matrix channel width. Variations in point size alter bending stiffness dramatically, because stiffness scales exponentially with sheet thickness. A one-point variation on a light board changes creasing dynamics and carton erection speeds on packaging lines.
Converting plants establish strict caliper tolerance windows to prevent carton jamming and improper glue seam adhesion during high-speed production runs. Caliper stability across paperboard lots protects converting machinery from unexpected jam events.