Why do ink bars appear when printing A4 stickers?

The reasons for ink marks when printing A4 stickers may involve multiple aspects, and the following are some of the main reasons for analysis:

1、 Equipment factors

Roller gear problem

Gear wear or excessive clearance: Long term use or insufficient installation accuracy of drum gears can lead to tooth surface wear or excessive tooth spacing. This will affect the accurate meshing between gears, resulting in inconsistent angular velocities between the rollers, which in turn will produce ink bars.

There are foreign objects between the gears: there are pollutants such as paper wool and ink skin embedded in the tooth gap, which can affect the normal meshing of the gears, leading to drum vibration and ink bar production.

Wear of drum bearings

Roller bearings will wear out during long-term use, causing the gap between the roller shaft and the axial direction to widen and resulting in poor coordination. During compression, this wear can cause the drum to shake, resulting in ink bars.

Equipment vibration

There are many unbalanced factors in the operation of offset printing machines, such as the impact and vibration when the cylinder is empty and enters the rolling process, and the impact and vibration when the impression cylinder teeth are opened and closed. These vibration sources may cause the generation of ink bars.

2、 Material factors

Rubber blanket issue

After the rubber blanket becomes loose, it will bulge and slip under pressure, forming a bar.

The uneven surface or hardness of the rubber blanket may also lead to the formation of ink bars.

Interlining paper issue

Although the printed dots are clear and the layers are rich using rigid backing paper, it is sensitive to the accuracy of the machine and prone to forming bars.

Printing plate issue

Excessive or insufficient friction on the printing plate can lead to the formation of ink bars. Especially for the solid version and the thin line version, due to their easy sliding, the enlarged dots are more likely to appear, leading to ink bars.

paper problem

Some types of paper are more sensitive to ink bars, such as whiteboard paper. In addition, the surface roughness and strength of paper can also affect the production of ink bars.

3、 Improper printing parameter settings

overpressure

Excessive printing pressure during printing, or excessive pressure between the plate cylinder and the rubber cylinder, can all lead to the formation of ink bars. Excessive pressure can lead to an increase in sliding friction, resulting in the formation of ink bars.

The lining of the bag is not suitable

The improper lining of the printing plate and rubber blanket will cause sliding friction between them, which will drive the printing plate cylinder to produce motion that conflicts with the cylinder gear drive, resulting in the generation of ink bars.

4、 Ink problem

The viscosity, cohesion, and other characteristics of ink also have an impact on the formation of ink bars. Ink with high viscosity has strong cohesion and is less prone to ink streaks; Thin and transparent ink, on the other hand, has more noticeable ink bars. In addition, emulsification and impurities of ink may also lead to the formation of ink bars.

In summary, the reasons for ink marks when printing A4 stickers may involve multiple aspects such as equipment, materials, printing parameter settings, and ink. To solve this problem, it is necessary to start investigating and adjusting from these aspects.