Analysis of the causes of different shades of offset ink

In the offset printing production process, sometimes there are different shades of ink on the same screen before and after the ink. The more common one is the darker, darker, darker one, and the lesser the phenomenon of darkness and darkness.

There are two main reasons for the inconsistent ink color. Here are some analyses.

One, inking part

The offset ink system consists of three parts. One is the ink supply part, which includes an ink fountain, an ink fountain roller, and an ink transfer roller. The function of this part is to quantitatively and regularly transfer the agitated ink to the ink distribution section. If the ink roller in this section is in poor working condition and the ink supply is not normal, then the uniform and regular ink supply cannot be guaranteed. The second is the uniform ink section. This section consists of an ink roller, an even roller, and a heavy roller. The role of this part is to make the ink fine and uniform, and to deliver high-quality ink to the ink roller. If the journal bearing of the ink roller (or heavy roller) in this part is seriously worn, it will produce uneven ink and thus transmit. The ink applied to the ink roller is not uniform, and the result is that the ink has a dark color. Therefore, in the course of offset printing, once the phenomenon of inconsistency of ink color occurs, it is very necessary to inspect the anisotropic roller, the uniform roller and the heavy roller and the related bearing with the journal. The third is the ink roller portion. This portion is usually composed of four ink rollers having different diameters. The function of this portion is to evenly apply the leveling ink transferred from the ink leveling portion to the graphic portion of the printing plate. If the surface of the ink roller is aged, smooth, easy to deink, or the diameter of the ink roller is too small after abrasion, the pressure between the ink roller and the ink roller is too light, so the ink will have different shades. In the field production, when the phenomenon of different shades of ink occurs, the quality of the ink roller is of great concern.

Second, the roller part

The abnormal operation of the drum is also one of the main causes of the darkness of the ink. The reasons for the abnormal operation of the drum are as follows:

1. The wear of the roller gear or bearing journal is worn for a long time;

2. The drum journal and the drum shell are not concentric, running unbalanced, vibration;

3. The platen roller gap is in poor contact with the ink roller.

In addition, the ink viscosity is too strong and one of the main reasons for the different shades of ink. In the process of running, if there is a short stop and turn (that is, during the offset printing process, due to some reason, stop and start frequently) Produces a variety of shades of ink.

Author: Chen Jin as