Through-hole Position Register and Seam Avoidance Technology for Flexo Plastic Bag Printing
This technical article explains unique process difficulties of continuous roll plastic bag flexo printing, solves through-hole position registration deviation and bag seam pattern missing defects, and introduces targeted web path optimization scheme.
Flexo bag printing mainly produces shopping bags, food packaging bags and garbage bags based on PE and BOPP roll films. Different from common flexible packaging film, bag printing has fixed reserved through-hole positions for handle installation and longitudinal hot-pressing sealing seams on raw web, bringing exclusive register and pattern avoidance technical difficulties that ordinary film printing does not have.
Fixed through-hole positions on raw bag film cause periodic web thickness mutation. The hole positions break continuous flat web surface, leading to instantaneous tension mutation and printing pressure fluctuation when passing through printing units. Periodic tension shock causes regular register deviation synchronizing with hole spacing, affecting pattern integrity near handle holes.
High Speed Flexo Printing Machine - Stack Flexo Flexo Printing Machine
Independent mark point register correction aiming at bag through-hole spacing. The system pre-stores fixed spacing data of bag handle holes, and uses through-hole edge as fixed register reference point instead of conventional printed pattern reference. Real-time position compensation is carried out synchronously when each hole passes printing station, keeping pattern and hole position alignment error within 0.1mm steadily.
Longitudinal sealing seam pattern avoidance printing technology. Raw bag film has continuous hot-pressing sealing seam along web running direction, and patterns cannot be printed on seam positions to prevent pattern damage during bag heat sealing. The servo system automatically identifies seam position and shifts printing pattern transversely in real time to realize automatic seam avoidance without manual parameter adjustment.
Low-temperature drying configuration exclusive for thin bag film. Plastic bag film is ultra-thin and easy to shrink and deform under high drying temperature. Adopting medium-temperature hot air drying with temperature controlled below 65℃ ensures ink complete drying while avoiding film thermal shrinkage and bag size dimensional error.
Bag printing repeat length matching with finished bag size. The electronic repeat length of flexo press must be consistent with single bag finished length. Mismatched repeat length will lead to inconsistent bag pattern size and disordered hole position spacing. One-click repeat length parameter storage improves switching efficiency for different specification bag orders.
