Choice of Consumables for Quality Control of Printing Products in Offset (4)

The ideal blanket should be completely non-absorbent, good ink, should have good elasticity, good compressibility, and can quickly restore the original shape after the pressure disappears, that is, all the elasticity in the printing performance Sensitive elasticity.

1 In printing, we want the blanket to deliver ink only to the surface of the substrate, and the moisture is that we do not want to transfer to the surface of the paper, otherwise it will cause the surface strength of the paper to be reduced or even deformed. Therefore, we hope to get a blanket that is water-friendly and ink-friendly.

But in practice, it is impossible to obtain blankets that are completely non-absorbent and have excellent ink-receptive properties. In addition, during the printing process, the rubber, fibers and other hydrophilic substances in the paper and the pigments in the ink are used on the blanket. Adsorption will result in a decrease in the ink-receptivity of the blanket during the printing process and an increase in hydrophilicity. Therefore, in addition to selecting a blanket with good surface properties before printing, care must be taken to clean the surface of the blanket during printing, so as to maintain a good ink-repellent hydrophobic property of the blanket.

2 Since blankets are periodically subjected to compression and elastic recovery during printing, this cycle is relatively short on current high-speed printing equipment. If the elasticity of the blanket shows a lag, it cannot be immediately after the pressure disappears. To restore, the compression range of the blanket will be affected during the next cycle of compression.

• The elasticity of the blanket can not be avoided, and even irreversible plastic deformation can occur. These are the factors that affect normal imprint during printing. Before printing, we must select the appropriate available blanket, and after the blanket has been pressed for a period of time, we must check the printing pressure (for example, it can be detected by pressing the bar marks). It also advocates the use of two blankets for rotation. Give the blanket a recovery time and reduce the blanket's aging cycle.

3 The ideal blanket should be compressible, that is, only a reduction in volume occurs in the compressed area, and the volume in the uncompressed area does not change. This can reduce the uniformity of the line speed ratio of the drum surface during the printing process within a considerable range, thereby reducing the distortion of the dot due to the speed difference.

• The blankets used in our daily production are generally incompressible. That is, in the vicinity of the embossed area, the blanket has a convex bulge and a convex bulge, which makes the linear velocity difference in the embossed area have a greater change. , which has a great influence on the correct transfer of outlets. Relatively speaking, the compressibility of the air-cushion blanket is quite good. For high-quality prints, using an air-cushioned blanket can get a good printing effect.


Source: Bison