Problems and Countermeasures of Dot Expansion in Ink Printing of Gift Paper Box

Problems and Countermeasures of Dot Expansion in Ink Printing of Gift Paper Boxes

Everyone knows that the dot enlargement in Gift Paper Boxes ink printing is more serious than that of UV ink. What is the reason for this? The figure below shows the three-fold flat screen proofs printed by the same operator on the same type of printing press using the same printing plate with UV ink and ink, respectively. From the shape of the dots, it can be clearly seen that the dot expansion of ink is much more serious than that of UV ink. The reason is that the determining factor is viscosity. The viscosity of UV ink and water-based ink is not on the same level, the difference is 1 to 2 times.

So can high-viscosity ink be used to solve the problem of dot enlargement?

Logically, the working viscosity of the ink should depend on the structure of the inking unit of the printing press. So on the same printing unit, the use of UV ink can be of high viscosity, why does the use of water ink have to be of low viscosity? The following pictures are 175 lines/inch 1% dot flat screen and 150 lines/inch 1% dot flat screen printed with high viscosity ink, the ink viscosity is twice higher than that of UV ink. It can be seen that ink can also use high viscosity.

However, whether high-viscosity ink can be used in Gift Paper Boxes ink printing depends on the structure of the inking system. Using a flexo printing unit with an inking roller structure (as shown in the figure below), high-viscosity ink can be used, while a flexo printing unit using a closed doctor blade structure cannot use high-viscosity ink.

All in all, there are three reasons for the expansion of dots during ink printing: ① the expansion of optical dots during plate making; ② the mechanical expansion of dots caused by excessive pressure during printing; Extend expansion. The key to controlling the dot expansion is to adjust the viscosity of the ink.

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