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Technical summary: correct use and maintenance of printing Cots
Source:HWA CHENG(SUZHOU)RUBBER INDUSTRY CO.,LTD         Release Time:2021-07-04

Maintenance of printing Cots

   during the printing process, the colloidal surface must maintain a certain viscosity in order to achieve uniform ink transfer and ink distribution.

1、 Keep the colloid surface of the cot clean to improve its viscosity and achieve good ink transfer and ink distribution effect.

However, due to the use of cots for a long time, the adhesion performance will be reduced with the loss of water on the surface. In addition, due to paper dust, paper wool and other properties, it affects the transmission of ink and is easy to produce the disadvantage of uneven ink distribution. To keep the cots sticky, prevent the ink from drying too fast and peeling the cots. Control the amount of dry oil for the ink that needs to be added with dry oil. Generally speaking, the amount of resin ink plus white dry oil shall not exceed 5%; Oil type ink plus white dry oil shall not exceed 10%; The dosage of red drying oil should be about 2%, so as not to affect the printing quality. In order to keep the cots clean, the cots should be cleaned timely as appropriate, but remove the impurities and paper dust on the colloid, so as to improve the ink transfer performance. In offset printing operation, ink emulsification is necessary, but the ink emulsification caused by "large water and large ink" will form a hydrophilic foundation on the smooth cot, make the cot deinking, and the fountain solution corrodes the rubber surface. Therefore, on the premise of non stick and dirty, the less the fountain solution, the better.

   second, the proper position of the cot on the printing machine should be maintained at high speed to avoid damage and poor ink distribution caused by improper use.

   whether the position of the cot is appropriate or not is directly related to the uniformity of ink transfer and brushing, as well as the durability of the cot. Therefore, the contact pressure between the ink rollers should be kept uniform and moderate. The contact pressure between the bitter inking rubber roller and the inking iron roller is too large. On the one hand, the rubber roller will be compressed and deformed, and the colloid is easy to heat and expand too much, and the ink is easy to dilute when heated, affecting the printing ink quality; On the other hand, it is easy to damage the cot shaft head (bearing) or shaft hole. If the height of the inking roller is not adjusted properly, too high adjustment will cause uneven ink distribution. If it is adjusted too low, it is easy to scratch the colloid and aggravate the wear of the printing plate. Therefore, the inking roller should be adjusted to be balanced with the printing plate layout, so as to ensure the uniformity of ink brushing of the whole layout. High contact between the ink roller and the printing plate. Generally, a piece of paper with strong toughness of about 40g can be placed on the printing plate. When the ink roller is rolled up, the paper can be pulled with a sense of pressure resistance.

3、 Some essentials of correct use and maintenance of Cots

  1. Newly cast cots should not be put into use immediately

  since the internal structure of the newly cast rubber roller is not stable enough, it is easy to reduce the service life if it is put into use immediately. Therefore, the new rubber roller just out of the cylinder should be placed for a period of time to maintain a relatively stable state after contacting the temperature and humidity of the external environment, so as to increase the toughness of the colloid and improve the durability.

  2. Correct storage of idle Cots

   after the rubber roller to be used is cleaned, the colloid shall be sealed with plastic film and stored in a cool, dry and ventilated place in a vertical or horizontal state. It is not allowed to stack several rubber rollers casually or stand against the wall, so as to avoid undue loss of colloid. It is also necessary to avoid storage with acid, alkali, oil and sharp hard substances, so as to avoid corrosion Bruise the rubber roller. After the rubber roller is stored for 2 ~ 3 months, change its direction to prevent bending deformation after long-term placement in one direction, and pay attention to prevent rust at the shaft head. During the transportation of waste cots to processing and casting, do not throw them randomly or press them heavily, and keep the roll core from deviation and bending, so as to ensure the normal utilization of the roll core.

   3. The rubber roller shaft head and bearing shall be well lubricated

  we know that the accuracy of cot shaft head and bearing directly affects the effect of ink transfer and ink distribution. In case of poor lubrication

  the wear and clearance of the rubber roller shaft head and bearing will inevitably lead to the disadvantage of uneven printing ink color. At the same time, it will also be caused by rubber jumping and sliding

   and other undesirable conditions cause printing bar marks. Therefore, the rubber roller shaft head and bearing shall be frequently filled with lubricating oil to prevent wear of parts

  normal use of COTS to ensure printing quality.

   4. During shutdown, the plate leaning rubber roller and the printing plate cylinder shall be out of contact in time to remove the load to prevent static pressure deformation.

   5. Handle with care during installation and disassembly, and do not collide with the roll neck and rubber surface, so as to avoid damage, bending or damage of the roll body; The roll neck shall be closely matched with the bearing. If it is loose, it shall be repaired by welding in time.

    6. After printing, wash the ink on the rubber roller. Special cleaning agent shall be selected for cleaning ink, and check whether there is paper wool and paper powder left on the rubber roller, which have not been washed away. The paper wool and paper powder generally stay on the ink leveling roller and need to be wiped with a cloth.

   7. The hardened film of ink is formed on the surface of the rubber roller, that is, when the rubber surface is vitrified, it shall be ground off with pumice powder. When cracks appear on the surface of cots, grind them away as early as possible.

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