Use and maintenance of printing rubber rollers
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The rubber roller is the main component of the offset printing system. Its function is to transfer and apply ink to the printing plate, and its quality directly affects the quality of the product. Proper use and maintenance of the rubber roller not only guarantees the quality of the product, but also prolongs the service life of the rubber roller.
1. Use of rubber roller
(1) Rubber roller pressure. The rubber roller should maintain good contact and proper pressure during operation. It includes the pressure between the rubber rollers, between the plate rubber roller and the ink roller, and between the plate roller and the printing plate. In the inking system, the contact pressure generally has the following rules; F1>F2>F3>F4>F5, where:
F1 - the pressure between the impression cylinder and the blanket cylinder
F2 - the pressure between the blanket cylinder and the plate cylinder
F3——pressure between the plate roller and the roller
F4 - the pressure between the plate roller and the plate cylinder
F5——pressure between the rollers
If the pressure between the plate rubber roller and the plate cylinder is too large, the plate will produce a bar, a dirty plate, a flower plate, and reduce the printing durability of the printing plate; if the pressure is too small, the ink transmission is poor, resulting in a printing plate graphic Not true or incomplete.
If the pressure between the plate rubber roller and the ink roller is too large, it is difficult to get up and down by the plate rubber roller during the clutch pressure process, and the friction force is large, which easily causes the rubber roller to heat and soften, accelerates the aging of the rubber roller, and even puts Rolling of the rubber roller causes equipment accidents; if the pressure is too small, not only the ink transmission is poor, but also the defects of the rubber roller "jumping" during printing.
(2) Ink and water balance. In the offset printing operation, ink emulsification is normal and necessary, but the emulsification of the ink due to "large water and large ink" will form a hydrophilic foundation on the smooth rubber roller, deinking the rubber roller, and fountain solution. Corrosion of rubber surface. Therefore, under the premise of not sticky, the dampening solution should be as small as possible.
2. Precautions for use
(1) After printing, the ink on the rubber roller should be washed clean. The cleaning ink should be selected with a special cleaning agent, and check whether there is still paper wool on the rubber roller, the paper powder is not washed away, the paper wool and paper powder generally stay on the ink roller, and need to be wiped with a cloth cloth.
(2) For the machine with the powder spraying device, the powder will be returned to the rubber roller with the paper or the secondary printing. After cleaning the rubber roller, the powder on the rubber roller should be cleaned.
(3) A hardened film of ink is formed on the surface of the rubber roller, that is, when the rubber surface is vitrified, it is ground by using pumice powder.
(4) When cracks appear on the surface of the rubber roller, grind it off as early as possible.
(5) When the machine is stopped, the plate rubber roller and the plate cylinder should be disengaged and contacted in time to prevent static pressure deformation.
(6) When installing and disassembling, it should be handled gently and gently, and should not collide with the roll neck and rubber surface, so as to avoid damage, bending or damage of the rubber surface; the roll neck and the bearing should be tightly matched. If loose, it should be repaired in time. repair.
3. Rubber roller storage
The purpose of keeping the rubber roller is to maintain stable mechanical properties, chemical properties and printability, and to extend the service life.
(1) The rubber roller should be stored in a cool, dry and ventilated place, and it should be vertical or horizontal.
(2) When stored horizontally, it should be placed on the shelf. It is forbidden to stack and squeeze the rubber surfaces to prevent deformation and adhesion of the rubber surface.
(3) Avoid storing with acid, alkali, oil and sharp hard materials to avoid corrosion and damage to the rubber roller.
(4) After the rubber roller has been stored for 2 to 3 months, it should be changed in the direction to prevent bending deformation in one direction for a long time, and to prevent the shaft head from rusting.
(5) It is necessary to make spare rubber rollers, but it should not be used for too long, because the spare rubber rollers will naturally age and take up funds. It should prevent the occurrence of aging, cracking, and rusting of the rubber layer caused by storage for too long.
(6) Long-term preservation of the rubber roller should be ground or wiped off the surface of the rubber roller with pumice powder before use.
4. Effect of rubber roller aging on print quality
The surface of the rubber roller is physically damaged or wrinkled and other aging phenomena, and the influence on the quality of the product is easy to observe and judge; when the surface of the rubber roller is vitrified. The impact on product quality is not easy to detect. When the surface of the rubber roller produces a hardened film of the ink, that is, the surface is vitrified, the surface of the rubber roller becomes very smooth, and the surface of the rubber roller is uniformly inked, but the performance of the adsorption and transfer ink is weakened, and the ink supply is insufficient, which may cause the ink to be affected by the printing plate. Uneven, the front mouth is dark, and the back mouth is light. At this time, the ink roller should be ground or wiped with pumice powder, so that the rubber surface does not slip when it feels.