Folding Resistance and Crease Adaptation Process for Flexo Folding Carton Printing
This technical content focuses on flexo printing process optimization for folding carton cardboard substrates, solves ink cracking problems during carton folding, and explains printing pressure matching for pre-creased carton boards.
Flexo folding carton printing targets thick coated cardboard substrates for cosmetic boxes, food packaging boxes and medicine packaging boxes. The biggest process difference from other flexo applications is that printed patterns need to withstand repeated folding along preset creases without ink cracking, peeling or pattern fracture, putting forward higher requirements for ink flexibility and printing pressure distribution.
Preset crease position pressure deviation is the primary defect source for folding carton flexo printing. Pre-creased cardboard has concave indentation lines on surface, forming uneven substrate surface same as corrugated board. Uniform overall printing pressure will lead to insufficient ink transfer at crease grooves and excessive ink accumulation at flat board areas.
High Speed Flexo Printing Machine - Stack Flexo Flexo Printing Machine
Segmented independent impression pressure setting aiming at carton crease structure. The impression cylinder is divided into crease area and flat area with separate pressure parameters. The crease position increases local pressure by 12% to ensure complete ink transfer on groove surface; flat board area maintains standard pressure to avoid dot gain and ink spreading. Segmented pressure perfectly adapts to uneven pre-creased cardboard surface.
High-flexibility special flexo ink exclusive for folding cartons. Common flexo ink has poor bending resistance and will crack directly along creases after carton folding. Modified flexible folding carton ink adds elastic resin components, which can follow cardboard bending deformation without fracture. The ink layer keeps complete pattern integrity even after 180-degree repeated folding tests.
Anilox roller parameter matching for coated cardboard surface. Coated carton board has smooth coating surface with low ink absorption. Medium-high 450LPI to 550LPI anilox rollers are selected to form thin and compact ink layer. Thick ink layer will crack easier during folding, while thin flexible ink layer has better bending recovery performance.
Printing position calibration matching carton post-press die-cutting. All printed patterns must align accurately with preset die-cut crease lines. Position deviation less than 0.2mm is required, otherwise patterns will be split during folding. The servo register system links printing position and die-cutting position synchronously to guarantee perfect pattern alignment along folding lines.
