Carton printing "open bottom"

Editor's Note: With the rapid development of packaging and waiting for business, users are demanding higher and higher quality of corrugated boxes, including the printing quality of sales cartons. If the printing technology is not well mastered, there will often be a lot of printing failures. For example, when the printing is in the field, there will be “bottom out” and “white spots”. In view of the large number of variables that generate the above problems, the following is only a simple analysis of materials, processes, plates, and other factors.
First, the reasons for printing materials 1, the smoothness of the surface paper and cardboard is poor, is to produce "print false", "bottom out", "white point" the most fundamental reason.
The smoothness of the paper itself is poor, or the cardboard itself is poor due to the “sawboard” that is light or heavy due to factors such as large amount of glue used in the composite board, and the surface of the printing plate cannot fully contact with the paper when printing. The binder in the ink cannot completely fill the paper gap. When white paper is printed on white paper, white holes will appear, resulting in "open bottom" and "white spots".
In order to solve this problem, some manufacturers often adopt the method of increasing the printing pressure, but this will have a lot of side effects: on the one hand leading to dot distortion, text and lines appear obvious "edge effect"; on the other hand, corrugated structure It will be damaged and reduce the strength of the carton. Therefore, according to the customer's specific requirements for paperboard, choose different smoothness of the face paper, and at the same time control the formation of "seesaw" process factors in the production of cardboard is to solve the "imprinted", "outside", "white point" of the fundamental method.
2. The paper coating layer produces paper under the combined effect of printing pressure and ink, which often results in “imprinting” and “white spots”.
Solution: For high-demand cartons, use high-surface-strength paper; avoid large areas on the floor when designing layouts; adjust the speed of the printing press and the viscosity of the ink during printing, depending on the surface conditions of the paper. Paper produces a pulling phenomenon, which also avoids the occurrence of "white spots" and the like.
Second, the process factors in the carton production line, single-edged knife trim from top to bottom when the knife cut, often lead to cardboard edges uneven paper, in the full version of the printing, the edge of the printing does not appear "outside", "imprinting is not true" . The increase in pressure during printing and the sharpness of the knife edge during edging can reduce this phenomenon, but it cannot be completely eliminated.
Third, the plate material printing plate printing press plate is usually used rubber plate and flexible resin plate (including domestic or imported), both the flexibility and the ability to ink a certain gap. Usually, the flexibility and ink-holding capacity of the flexible resin plate are higher than those of the rubber plate. The printing ink layer is relatively thick and generally does not suffer from such problems as “imprinting is not true”, “outside”, and “white point”.
The poor leveling of the surface of the printing plate results in a difference in the amount of ink on the layout, and the phenomenon of “wholesale” and “white spots” appears in the printing.
Generally, the flatness of the surface of the flexible resin plate is better than that of the rubber plate. Therefore, a flexible resin plate must be selected for a carton that has a high printing requirement, has a large area in the field, or has dot printing.