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Common Problems And Solutions Of Gravure Water - Based Ink
Jun 17, 2017


Problem 1: Blocking of Cylinder

In the use of water-based ink, blocking is the most common problem, mainly because of gravure water-based ink has poor complex solution. Once the operation is not properly, it is easy to cause blocking version. And blocking will also lead to a series of printing quality problems, such as pinhole on printed surface, small missing pen in the text , uneven ink, reveal of the base paper.

The ways to solve the problem can be concluded as following:

1) Intermittent stop printing, ink dries in the net hole due to diluent evaporation. At this point, it needs to use special tools and cleaning agents to clean the cylinder, if necessary, remove the cylinder and use organic solvents (ethyl acetate) to clean.

2) The ink dries too fast and instantly dry in the net. To solve this, you can first add a small amount of slow drying agent in the ink, slow dry agent can inhibit and slow down the ink drying time to prevent the surface of the oil crust, however, when increase the proportion of water to be taken, you should also consider about the amount of water. If the amount of water is too high, on one hand it will cause too much air bubbles, on the other hand it will lead to not complete ink drying , making the goods appear sticky dirt or ink anti-pull phenomenon.

3) Ink viscosity is too high. At this point, it should be appropriated to reduce ink viscosity, but the printing speed and leveling must be taken into account at the same time. Because if the ink viscosity is too low, it will produce too much air bubbles, resulting in printed surface white spots, printed graphic color being too shallow or thin lines and small text thickening and other issues.

4) The curved line of the cylinder is too shallow. At this point, it should be appropriated to deepen the depth of the cylinder lines, but some other situations must be considered at the same time, like when the printing cylinder lines are too deep,  the quality problems, such as writing thicker, small text blurred, the pattern is not clear will appear.

Problem 2: Poor dryness

Drying performance is one of the most important indicators of water-based ink. The drying speed of the water-based ink is slower than that of the solvent-based ink and if the drying is insufficient, the sticking roller phenomenon may occur.

Therefore, in the use of water-based ink, the drying temperature must be improved, it usually increase by 10 ~ 20 ℃ than the solvent-based ink while it also needs to increase the amount of exhaust. It can also add length of after the paper path if possible.

Problem 3: Dirty pull lines on the cylinder

Water-based ink gravure production, dirty pull often occurs in the bar code or dark graphic around the existence of the corresponding position cause on the printing plate, the ink is not clean, which is mainly because the water-based ink lubrication is lower than solvent-based ink.

Therefore, it needs that ink manufacturers in the production of water-based ink add the appropriate additives to solve the problem, while it also needs printing workers in the printing production adjust  the angle and pressure on the scraper. When installing the blade, the blade is shorter, the scraping is better.

Problem 4: Too much air bubbles

Water-based ink bubbles will lead to excessive printed surface with white spots, trachoma, water and other phenomena. The cause of the bubble problem and the solution are as follows.

(1) Dilute water-based ink when adding more water. To solve this, we can take two solutions: First, adding defoamer, adding the amount of 0.5% to 1.0% in general; second is to adjust the diluent ratio.

(2) Because some dark water-based ink are used in a very small amount and in a long cycle of dilution, the alcohol in the volatile caused more remaining water. At this point, it should add some amount of alcohol.

(3) Inadequate control of surfactant dosage. Surfactants can reduce the surface tension of water and improve pigment wettability, but if the amount is not well controlled, it will produce a lot of bubbles. The amount of surfactant should be controlled by the ink manufacturer in the production process.

Problem 5: Poor print leveling

Water-based ink flow difference is mainly reflected in the water ripple phenomenon is heavy or printing ink is not enough to cover the base paper, the cause and the solution is as follows.

(1) Ink viscosity is too low, resulting in carrier ability to drive the pigment weakened. At this time, it should be appropriated to improve the viscosity of the ink, but if the ink viscosity is too high, the ink will be poor mobility, printing leveling will be worse.

(2) After a long period of time, the binder material in the water-based ink is reduced or the amines are volatilized, resulting in a change in the performance of the water-based ink and the printing leveling is deteriorated. When the problem is mild, you can add a lot of new ink to solve; if the problem is serous, such as water-based ink is contaminated, you may need to replace with the new ink.

Problem 6: Poor stability

Poor stability of water-based ink is mainly reflected in the phenomenon of easy precipitation, delamination and false viscosity, which is mainly due to the poor dispersion of the pigment in the water-based resin. It is easy to gather precipitation and water-based ink itself need to add additives (surfactants, Defoamers, pH stabilizers, leveling agents, slow drying agents, quick drying agents, dispersants, diluents, etc.) to improve their own weaknesses, resulting in poor stability.

Therefore, before using water-based ink, it needs full mixing, such as when use new ink, it should in advance mix evenly and then add the diluent to adjust. During the printing process,it should also stir regularly to prevent dirty pull or block the phenomenon. Occasionally encounter difficult to stir the solidification of colloidal water-based ink, you need to consider the quality of the ink itself.

 

 Written by Phoebe Chen 

 

 

 

 

 

 


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