Offset Anti-creping Technology Of The Rubber Roller

The printing plate is divided into a large version of the dirty area and a part of the dirty, which is due to various reasons. The improper adjustment of the water pressure roller and the pressure of the printing plate, the sticking of the water roller, the improper ratio of the dampening liquid, the improper spreading of the printing pad paper, the quality of the printed version, etc., all make the printing plate dirty on both sides. During the printing process, there are sometimes problems with dirty printing on both sides of the offset printing plate. The following is an analysis of the causes of the dirty sides of the plates.

Water roller uneven

When adjusting the contact pressure of the water supply roller to the water roller, the symmetry of the direction of the eccentric bearing must be paid attention to, otherwise the water roller and the plate cylinder and the water roller are not parallel, and the fleece of the water roller is easily axially When pushed into a spiral shape, it is impossible to evenly transfer water. If the eccentricity adjustment at both ends of the water roller is asymmetrical, the pressure of the water roller will be uneven, and the sides of the printing plate may be easily dirty. Therefore, when testing the water roller pressure, you can measure several places, both of which should be measured and the middle should be measured.

In addition to accurately adjusting the contact pressure of the water roller, it is also very important to properly maintain the daily maintenance of the water roller.
     1. When the offset printing operation is normal, the water roller should be kept clean and free of oil.
     2. The water roller cover should be kept moist and have a certain amount of moisture.
     3. Wash the water roller regularly. If the water roller can be cleaned and washed, if there is too much oil and it cannot be cleaned, it is necessary to replace the new water jacket in time to prevent the printing plate from getting dirty. Another method can effectively prevent the water roller from sticking to the ink. That is, when printing, a small amount of hydrophilic colloid substance, gum arabic, is added to the water bucket solution, which can effectively increase the hydrophilicity of the water roller, and hydrophilicity with a sponge or the like. The material wipes off the emulsified oil in the water bucket solution and adsorbs the dirty ink on the surface of the water roller.

Water roller

When the water roller is flattened on the lathe, because it is an elastic body, the two ends are stressed, the middle is vibrating and the pressure is small, and most of them have different degrees of thin intermediate shape errors at different ends, and there are gaps at both ends. Easy to get dirty. In addition, at the time of sewing, the water roller sleeves are thinned and thinned at both ends, and the moisture at both ends is less adsorbed, and the surface of the printing plate cannot be sufficiently wetted, and the two sides are likely to be dirty.

Remedy: The size of the cut water jacket should be the same as the water roller, not too short. When sewing the sleeve, the tension of the needle thread is even, do not over-tighten, and there must be room for closing the mouth to prevent the two ends of the water roller sleeve from being too thin and thin.

Plate lining size is too small

Under normal circumstances, the bottom of the plate should be padded. In order to avoid the water on both sides of the plate pad, the horizontal dimension of the pad paper will be smaller than the plate size. However, if the size of the liner paper is too small, the pressure on both sides of the printing plate may be insufficient, resulting in poor contact between the printing plate and the water roller and causing dirt.

Remedy: When cutting the liner paper, the lateral size is controlled within 10~20mm of the printing plate. In order to prevent damage to the liner paper due to water ingress, you can apply a layer of terracotta on both sides of the pad or Butter and motor oil use the principle of oil and water to avoid the wetness of the liner paper and improve the use effect. If the liner paper of the roller is wetted, it is easy to rust the casing of the drum.

The water stick at both ends of the water roller reduces the water transfer performance

If the water content of the printing plate is too small, the water will be stuck on both ends of the water roller due to insufficient water supply, causing the two sides of the printing plate to get dirty.