Six steps to use an offset blanket

In the offset printing process, the blanket is used as a medium between the printing plate and the substrate to realize the transfer of pictures and texts and complete the printing. The correct use of blankets is an important point of printing pressure control, which has an important impact on ensuring printing quality. At the same time, the blanket is an important consumable material in the production of offset printing. If the blanket can be used and maintained correctly, the service life of the blanket can be extended and the production cost can be saved for the enterprise.

1. When to choose air cushion blanket

Compared with ordinary blankets, air cushion blankets have better sensitivity, resilience and impact resistance. For high-speed printers, the use of air-cushion blankets keeps the internal friction of the blankets not too high. While maintaining the stability of the printing pressure, it can also reduce its aging speed and extend its service life. However, the price of air cushion blankets is much higher than that of ordinary blankets, which increases production costs. Air cushion blankets are only used on high-speed machines and when printing high-end products with hard or neutral hard liners, which can make graphics and text. The advantages of high transfer accuracy and good sensitivity are well exerted. If the soft lining is used to print ordinary products, because of the large compression amount of the soft lining, the wide embossing surface, and the easy expansion of the dots, which offsets the advantage of the high accuracy of the graphic transfer of the air cushion blanket, it is not worth adopting at this time. Air cushion blanket.

2. Cutting of blanket

On the back of the blanket, a sagittal mark or color line marks the position of the blanket in the warp and weft directions. When the blanket's woven fabric is subjected to the same tensile force, the warp elongation is much smaller than that in the weft direction. When cutting, make the weft direction of the blanket parallel to the plate holder to ensure that the four corners are at right angles. If the blanket is skewed, it will be unevenly stressed, easy to creep or twist, and cause dot deformation during printing. Especially when cutting a folio or a full-length blanket that has been scrapped due to hard damage and used as a four-fold blanket, you should pay attention to the warp and weft directions.

The method of identifying the latitude and longitude position of the blanket: First, tear it by hand, because the blanket is composed of the surface adhesive layer and the base fabric, and the base fabric is composed of a strong long-staple cotton cloth, and has a warp direction It is different from the weft direction, so when stretched, the more stretched is the weft direction, and the less stretched is the warp direction; Second, there will be a red or green line on the back of the blanket. Indicates the warp direction of the blanket.

3. Measurement of blanket thickness

In the production of offset printing, the size of the printing pressure is usually indirectly expressed by the maximum compression of the liner when the cylinder is pressed. In order to ensure that the printing pressure remains unchanged, the blanket and liner must be measured when replacing the new blanket. Calculate the total thickness of the liner to meet the printing pressure requirements. To correctly measure the thickness of the liner, a barrel diameter meter should be used to measure the thickness of the liner after tightening at different positions in the circumferential direction of the rubber cylinder, and use this thickness to calculate the printing pressure. However, at present, many printing plants use micrometers to measure the thickness of the blanket and liner, and the micrometer can only be measured in the free state before the liner is not installed, so there should be a difference between the thickness of the blanket after the tension and the thickness in the free state. Correct estimation will not cause a large deviation in calculation. It is best to measure the four sides of the blanket to check whether the thickness is the same, so as to take corresponding measures to remedy. When measuring blankets and pads, it is best to be measured by one person, because when the micrometer is used, if the operation method is different, the measurement results will be biased.

4. Installation of blanket

When the blanket is installed on the plate holder, the depth of the blanket inserted into the plate holder should be the same. After tightening the screws on one plate clamp, use a ruler to measure whether the two plate clamps are parallel, and then tighten the screws on the second plate clamp. After all the screws are tightened, use a ruler to check again to prevent the position of the blanket from changing during the tightening of the screws. Due to the different types and tightness of the new rubber blanket, it should be printed together for 5 to 10 minutes, and then tightened again. This can reduce the slack phenomenon of the new blanket under the effect of rolling, so that The tightness of the blanket remains stable for a long time.

However, when tightening the blanket, the strength should be moderate. If the stretch is too loose, the blanket will be displaced under the action of the squeezing force and cannot be reset in time, causing ghosting failure; if the stretch is too tight, it will cause glue Thin layers, reduced elasticity, and uneven printing pressure may cause poor ink transfer, shift the color tone of the color image, and accelerate the creep and aging of the blanket. If it is not used for a long time, the rubber cloth should be loosened to avoid stress relaxation.

5. Use of the blanket when starting up

The thickness of the new blanket will change greatly at the beginning. After adjustment, the thickness of the blanket will remain stable during the long normal use, so it is necessary to increase the thickness of the pad or reduce it after a period of printing. Small center distance to make up. However, this kind of stability is relative. After a large amount of printing, the pressure on the blanket in use is different, and the amount of plastic deformation occurs, which will cause unevenness in the thickness of the blanket.

During the offset printing process, due to improper adjustment of the conveying part or careless operation, it is often easy to have thicker small paper pieces, hard fiber clumps in the paper, and multiple sheets of paper into the roller, so that the roller blanket is partially concave and Sagging, because the printing pressure is insufficient in the low-concave area, the picture and text cannot be transferred completely, and it can be remedied in the following way.

(1) Adopting the method of padding on the back of the blanket. In order to prevent the low concave parts from being seen clearly after dismantling the blanket, you should first draw a corresponding size mark with a ballpoint pen on the low concave part of the front of the blanket. After removing the blanket, find the corresponding size on the back according to the mark just drawn. Draw marks of equal size. The marks must be accurate. After that, choose a paper with a low degree of depression that is indented with the blanket, tear it or cut it into the shape of the same size as the mark. If the thickness of one piece of paper is not enough, you can use two or three sheets of glue and glue In the low recess on the back of the blanket, install the blanket after the glue has dried.

(2) Remedy cleaning with a rubber cloth is also ideal. It is convenient, fast and practical. Use a brush to dip the rubber cloth to clean the reducing agent and apply it to the low-concave areas of the rubber cloth, which will have an immediate effect.

After using the blanket for a period of time, even if it can still be used normally, let it "rest" for a while. Remove the blanket from the machine, first clean the ink and oil stains on it with detergent or gasoline; then wash it with 50% alkaline solution to saponify the oil that has penetrated the surface of the blanket; then wash it with clean water to remove the saponification Then wipe the talc powder and store it according to the method described above, so that the blanket can restore its original elasticity to a certain extent after a period of "rest" and effectively extend its service life.

6. Maintenance of the blanket

Because the blanket has the disadvantages of light aging and heat aging, after purchase, the blanket to be used should be rolled outward, wrapped in black paper, and stored in a ventilated and dry place, and away from light and heat sources, oils, The storage temperature of various chemicals such as acid, alkali and salt is preferably around 20 ℃, and the relative humidity is preferably 70%. The new blanket has a smooth anti-oxidation film, which can be scrubbed off with pumice powder dipped in gasoline to ensure good ink absorption on the blanket surface.

The effective parts of printing need to be kept clean frequently. If it is not clean, it will affect the printing pressure. If ink or other impurities are fixed on the surface of the blanket, the printing pressure will change, which will affect the quality of the printing. Non-printed parts should also be kept clean. If this part is not kept clean, as the sludge and other impurities continue to condense, and the printing pressure continues to increase, the surface of the blanket will be destroyed, making it impossible to use normally. It should also be noted that keeping the surface of the blanket clean is the junction of the effective parts of the printing, where the ink and other impurities condensed are the most. Due to the increased pressure, the fatigue of the blanket is accelerated, and the blanket in this part is most likely to crack, so it is necessary to prevent impurities from accumulating here.

It is best to use both hands when cleaning the blanket.

Clean the blanket with a cleaning cloth dipped in the right hand, and dry it with a dry cloth on the left to prevent the solvent from penetrating into the blanket. When cleaning ordinary blankets and UV blankets, different cleaning products should be used: when cleaning ordinary blankets, the cleaning agent should not contain polar substances, such as esters; when cleaning UV blankets, the cleaning agent should not contain non-polar Sexual substances, such as benzene. Ink manufacturers usually provide matching cleaning agents, and many products have passed FOGRA certification, which is a cleaning product that users can use with confidence. Generally, the following steps can be used to clean the blanket: use warm water to wipe off water-soluble substances, such as paper powder; use car wash water or solvents that do not damage the blanket to wipe off the ink and other solvents; if the surface of the blanket is For calcium and magnesium ion deposition, you can choose to use citric acid-containing car wash or weak acid substances, such as vinegar for cleaning.


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Product description:
Twisted Paper Cord is use of high-quality pure wood pulp paper production, into a single round, commonly used specifications: diameter 1.0mm-5.5mm between

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