Reasonable use and storage of air cushion blanket in printing production
1. The principle of choosing a blanket
The choice of rubber blanket should be considered from the aspects of model, product requirements, speed of printing press, size of printed graphic area, field, flat screen, stickiness, etc. In addition, it must be considered from economic factors, such as quality requirements are not too strict If the substrate is rough, consider not using expensive blankets.
2. Inspection and measurement of the new blanket
â‘ The validity period of the inspection validity blanket is one year to one and a half years, which is calculated from the completion date of the finished product. If the blanket is stored for too long, the surface rubber naturally ages, and its mechanical properties, chemical properties, and printing properties will decline. Therefore, the newly replaced blanket should pay attention to check the production date and use it within its validity period.
â‘¡Check the appearance of the blanket Before using the new blanket, check the appearance quality. The surface of the blanket should be smooth and free from damage, scratches, bubbles, indentations, and hard debris. The surface of the cotton cloth layer on the back of the blanket must not have defects such as wrinkles, tears, hard debris, thread ends and seams.
Both sides of the rubber are coated with sealing varnish to prevent swelling when water enters on both sides.
There is a smooth anti-oxidation film on the surface of the new blanket. This layer of film must be wiped off with clean water before use to ensure good ink absorption on the surface of the blanket.
â‘¢ Check the texture of the blanket. The blanket is textured. Basically, printing staff ignores the texture of the blanket, because most blankets have been cut. However, if you cut a large size into a small size, you should pay more attention: the line on the back of the blanket is usually used as the printing direction, and the typeface on the back is used as the bite.
â‘£Measure the thickness of the blanket correctly.
The actual height of the lining needs to be carefully measured. In printing, the size of the printing pressure is usually expressed by the amount of compression when the blanket wrapped on the cylinder is pressed together. Therefore, the correct measurement of the thickness of the liner is the key to calculating the printing pressure. As the blanket is stretched on the roller, it will cause the adhesive layer to be thinner and the thickness to be reduced. Therefore, the thickness values ​​measured in the two states of the blanket not installed on the blanket cylinder and those mounted on the blanket cylinder are different. You should use a suitable measurement tool to correctly measure the thickness of the blanket.
⑤ Correctly select, calculate, and measure the thickness and size of the blanket cover. The thickness of the blanket cover required for correct calculation can improve the dot reproducibility and improve the printing durability. .
According to the size of the white paper of the product, cut the blanket liner, the size of the liner should be smaller than the size of the white paper of the printed product, so as not to affect the quality of the product, it is appropriate to print the product specification line. Of course, this also requires accurate positioning and placement.
The blanket lining is smaller than the white paper size of the printed product to avoid many printing failures:
â‘ When printing small areas of graphics, it is not easy to pile up powder and ink to reduce flying ink.
â‘¡When printing on coated paper, avoid pile of ink and save the time of wiping the impression cylinder.
â‘¢Improved cleaning efficiency and saved car washing water.
â‘£When printing solid products, reduce the amount of ink accumulated at both ends of the printing plate to reduce the probability of color difference.
⑤ During UV printing, avoid the loss of blanket due to ultraviolet radiation.
â‘¥When the paper to be cut is small and UV printing needs to be reduced, the generation of ink skin is avoided.
⑦When the paper has burrs, reduce the generation of paper wool.
⑧ It can avoid the paper edge marks on the rubber after the rubber and the paper are pressed together, and extend the life of the rubber.
3. Installation and use of blanket
â‘ When installing the blanket, pay attention to correctly distinguish the latitude and longitude directions of the blanket.
It is necessary to wrap the warp direction of the blanket around the axis of the cylinder to achieve the printing effect. Because the blanket is not easy to stretch and deform. When cutting the blanket, pay attention to cutting it into a rectangular shape with the same length on both sides. The two sides of the plywood should be parallel. Then when the blanket is tight, it will not be tight on one side and loose on one side, which will deform the dots of the printed matter and affect the quality of the print.
â‘¡To choose the right tool to tighten the blanket, you must use a torque wrench to lock the blanket, so that the blanket is fastened to the blanket roller under the proper tension. If the blanket is stretched too loose, displacement under compression will occur during imprinting and cannot be reset in time, which will lead to dot deformation and ghost failure. Of course, the blanket cannot be stretched too tightly. If the blanket is stretched too tightly, it will cause the intermediate fiber fabric to be over-tightened and damaged. The surface rubber layer will be thinned, the elasticity will be reduced, and the pressure will be insufficient. The phenomenon of poor ink transfer affects the quality of the product and shortens the service life of the blanket. The new blanket cannot be stretched too tightly at the time of reloading. It is necessary to print about 10,000 sheets together and then stretch again. The tension is generally reduced by 5N / m on the basis of the length of the paper's circumferential width. For example: if the paper's circumferential width is 52cm, the tension is 52-5 = 45N / m.
â‘¢ "ideal pressure"
The "ideal pressure" advocated by offset production not only provides a guarantee for product quality, but also has an important meaning for extending the life of the blanket and reducing creep. If you encounter a long period of downtime, you need to loosen the tensioning device of the blanket to relax the blanket and prevent the stress relaxation of the blanket. This is also an effective method to extend the high elasticity. In the blanket, the internal stress gradually declines with the continuation of time, and the elasticity of the blanket will decrease. Therefore, it is recommended to use the method of rotating two blankets.
â‘£Cleaning and maintenance of the blanket.
After the blanket is printed for a period of time, because of its physical absorption, the surface of the blanket adheres a lot of paper wool, paper powder and accumulated ink skin. If it is not cleaned in time, it will increase the local printing pressure, causing plastic deformation of the rubber layout. Over time, the accumulation will be partially dented, so special attention should be paid to cleaning in time. Care must be taken when cleaning the blanket. Scrub with water and detergents when cleaning manually. Do not leave ink and paper wool in the pores on the surface of the blanket. Otherwise, the conjunctiva will be oxidized and dried for a long time to make the surface smooth and reduce suction Ink ability directly affects the improvement of product quality.
⑤The durability of the blanket depends on many aspects such as: not being squeezed by external force and causing dents (paper shreds, sticky paper), suitable cleaning agents (without strong acid and alkali cleaning agents), working environment (temperature and humidity Impact, dust impact), mechanical wear (damage caused by automatic cleaning devices), print quality requirements (higher quality), and general durability is about 1 to 3 million printed sheets.
4. Storage of blankets
During storage of the blanket, avoid contact with oil, acid, alkali, salt, etc .; do not subject it to compression, as this may break the blanket and damage its elasticity. The blanket also has the characteristics of being resistant to light, heat, and humid air. These media will make the surface of the blanket sticky, skinned, dry, hardened, and moldy, so the blanket should be wrapped in black paper and stored in a cool place . When storing the blanket removed from the machine, you must first clean the ink and oil stains with detergent and water and wipe it dry, and finally use talcum powder to prevent the surface from aging.
Conclusion
From the point of view of the overall production process of printing, the quality of the product has a certain relationship with the choice of blankets. The choice of blankets is not the best, only the most suitable. Of course, correct use and reasonable storage also contribute to the stability of printing operations and can also reduce production costs.
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