Cold Foil Register Drift as the Stack Warms across a Shift
Stack thermal buildup causes substrate shrinkage and mechanical expansion, driving cold foil register drift across continuous production shifts.
Packaging Traps
Registration Control
Graphic adjustments in prepress design prevent unsightly gaps and white lines from appearing between adjacent printed colors on the finished box. Packaging traps create a small area of overlap where two different ink colors meet on the paperboard substrate. This overlapping boundary ensures that small mechanical shifts on the printing press do not result in exposed substrate or unprinted paper lines.
The width of these overlaps is determined by the register accuracy of the printing press and the stability of the paperboard.
Prepress Execution
Software-driven automated trapping tools calculate the direction of the overlap based on the relative luminance of the adjacent colors. Packaging traps usually expand the lighter color into the darker color to make the overlap area as inconspicuous as possible. This rule prevents the darker color from distorting the shape of the lighter element, maintaining the clean lines of the original design.
The operator adjusts the trapping values based on the specific print process and the substrate density.
Print Application
Substrate expansion due to moisture absorption on press requires wider overlap margins to prevent gaps. Folding carton designs on thick boards use larger trapping values than labels on thin paper. These adjustments prevent print defects during long production runs.