Ink Holdout and Dot Gain When a Stock Changes Grade
Changing stock grades alters micro-porosity and light scattering, shifting ink holdout and dot gain, requiring immediate press curve and ink film adjustments.
Blanket Impression Squeeze
Contact Displacement
Pressure applied between the offset blanket cylinder and the impression cylinder determines the transfer efficiency of ink to a paperboard surface. In high-speed packaging runs, blanket impression squeeze must be carefully calibrated to ensure complete coverage without causing dot gain or structural crushing of the paperboard. This physical interference between the two cylinders compensates for micro-roughness in the substrate.
If this setting is too high, it compresses the board permanently, reducing its stiffness and bending resistance. The normal operating window ranges between 0.05 and 0.10 millimetres of mechanical displacement depending on the surface smoothness and compressibility of the substrate.
Structural Impact
Cellulose fibres undergo permanent deformation under excessive physical load during the printing process. When the caliper of paperboard is reduced by excessive force, the structural integrity of the carton is compromised. Maintaining the correct level of blanket impression squeeze preserves the thickness of the board, which directly affects its top-to-bottom compression strength in the finished box.
Transfer Limit
Surface roughness dictating the necessary mechanical interference varies across different paperboard grades. Cast-coated boards require minimal deformation to achieve full ink coverage, whereas uncoated grades demand a higher level of contact pressure. Overcoming this roughness limit requires precise adjustment of the cylinder packing rather than simply increasing the pressure on the press.