Several problems in carton printing

First, paper-related printing failures

The quality of the opposite paper must be strictly controlled, and the strength, tightness, elongation, flatness, glossiness, whiteness, etc. of the paper should all be inspected when entering the factory and ensure compliance with the requirements. The color of the face paper will affect the printing effect of the main body color. The coating uniformity and the smoothness of the face paper also have a great influence on the halftone printing, and it is likely to cause inconsistency in the tone of the flat screen printing, especially the 3 to 60% of the net. The most sensitive tone.

Deformed paper can cause wrinkling during printing. The humidity in the shop should be adjusted to restore the moisture content of the paper. Curved paper is difficult to transport. It is necessary to adjust the volume of loose paper blowing nozzles and nozzles according to the degree of bending of the paper, and to increase the strength of the paper feeding pulley to ensure that the paper is fed well. When printing, it should be noted that the fiber orientation of the tissue should be perpendicular to the direction of the corrugation when the box is formed. For products that need to be printed twice, the paper should be loosened on time after printing, and then tightly packed after the initial drying to prevent the paper from being deformed and affecting overprinting.

For powdered paper, the viscosity of the ink can be properly reduced and the printing pressure can be appropriately reduced to make up for it, and the smallest layout of the pattern text is arranged in the first color group so that the paper powder and the paper hair are stained as much as possible during the printing of the first color. , And the printing speed should not be too fast, but also wash the blanket. For some papers that are heavily powdered and have more severe hair loss, the use of pre-press air pressure or a pre-printed layer of anti-sticking agent (plus a small amount of white ink) may solve the problem to a certain extent, but in material, energy, time, etc. The consumption of this aspect will undoubtedly increase the cost, and various problems will still arise in the post-press processing.

Second, ink-related printing failures

(1) Improper ink viscosity. Ink viscosity is too low, easy to paste version when printing, and the amount of water must also increase, in the transmission of the water roller will also stick the ink back on the plate cylinder, so that the dampening fluid dirty. In addition, the printed matter absorbs a large amount of moisture and then deforms and bends back, making it difficult for post-press processing. In addition, inks with low viscosity and cohesion will have centrifugal ink flying at high speeds. If they fly to the plate, they will be glued back by the water roller, causing the dampening solution to be dirty, which in turn will cause scumming. The viscosity of the ink is too high and the ink is difficult to print. In particular, the mesh adjustment cannot be printed. Even if the ink volume is increased, the effect is not obvious, and the print is prone to blocking.

(2) The print is easy to fade. In the printing of corrugated cardboard paper, high-gloss and abrasion-resistant inks are used to ensure that the printed patterns can withstand frequent handling and friction during transportation. Do not mix gasoline when adjusting the ink, because gasoline will dissolve or crack the ink to get the cohesive cross-linked material and destroy the chain structure of the binder. The varnish cannot be increased too much, otherwise the binder resin in the ink will be diluted and detached from the colorant so that the colorant is suspended in the shape of a part on the surface of the paper, and the grease and its auxiliary agent are absorbed by the paper fiber. To the interior of the paper, if the printed matter is directly attached to the corrugated medium, scratches or discoloration will occur easily in the production process; if the film is laminated, blistering, floating phenomenon will occur, and the film will be easily peeled off; if the coating is applied, it will easily fade and occur. Scratches; If calendered, varnish and pigments are easily peeled off by the tape.

(3) The print is too dry. This has a lot to do with the ink transfer. When printing a large area on the ground, if there is too much lipid in the ink, the lipophilicity of the paper fiber will affect the drying of the auxiliary. In addition, it is often necessary to polish a large area after printing, which is more disadvantageous for drying the ink. In addition, in the high temperature drying season can not be excessive use of dry oil, anti-sticking agent can be used to replace part of the dry oil, and increase the amount of dusting, anti-adhesion can be used, which may give trouble behind the film coating process, but cover When the film can temporarily increase the powder removal process.

Third, other issues related to post-press processing

For products that require hot stamping, the positioning during printing should be accurate, otherwise the hot stamping displacement phenomenon is likely to occur. Foaming, wrinkling, and darkening are common problems in the film. Poor print drying of the ink will cause foaming of the film, as the organic solvents and moisture in the ink will escape after being hot-rolled, and are just sealed by the film, especially when the film speed is too fast. Some papers are wrinkled, and when the paper is not neat, bent, and covered, it can cause tearing and wrinkling.

In addition, the wear of the laminator's silicone rubber pressure roller can also cause wrinkling of the film. The moisture content of the paper is large and it becomes dark after lamination. For printing gold products, if the moisture content of the paper is too high, the moisture content of the coated film will be more difficult to evaporate, which will cause oxidation and darkening of the gold ink.

The gloss of the finished product when calendered depends mainly on four aspects: First, the gloss and flatness of the paper. The second is the amount of oil. The amount of oil is too little, the light brightness after calendering is poor, but the amount of oil is too much. After the calendering, the print is yellow and dark. The third is the drying time of varnish. Varnish drying time can not be too long, otherwise the pressure is not smooth after drying, or pressure is not light, but the light oil drying time is too short, the varnish solvent is not dry, after the pressure is lightened by the steel tape, the printed matter will be exposed, After exposing the flowers, stacking together after calendering will also make them stick together. Fourth, the old and new steel belt. The effect of the new strip calendering is better than that of the old strip.

Source: China Ink Technology Network