The solution of pulling in printing

In the printing, the imprinted sheet is adhered on the surface of the blanket by the ink on the blanket cylinder with adhesive force on the one hand, and on the other hand the bite edge of the sheet is bitten by the impression cylinder, along with the impression cylinder Turn to force the paper to separate from the blanket cylinder. The paper attached to the surface of the rubber cylinder is perpendicular to the surface of the paper. The force pulling the paper off the surface of the blanket is called the peeling tension. If the peeling tension makes the surface strength of the substrate unacceptable, the surface of the paper is filled with fibers and fillers. Or the paint will be pulled down by the ink on the blanket and piled on the surface of the blanket and the plate so that the ink cannot be evenly and completely absorbed and transferred to the paper, resulting in the damage of the dots and the loss of small dots; when printing the halftone images, the layers Lost, imprinting is false. Paper scraps accumulate on plates and blankets. In severe cases, the blankets can also be damaged. Adhering to the printing plates, the paper scraps can be transferred to the water bucket, reducing the effect of the wetting fluid.

The number of cleaning blankets must be increased when the nap phenomenon occurs. This increases the labor intensity of the printing workers and also affects the production efficiency. At the same time, due to excessive downtime, the amount of ink supplied is uneven and the printed ink is printed. It is easy to be inconsistent before and after, serious waste will appear, causing unnecessary waste.

There are many factors that cause the phenomenon of paper pulling, there are two main factors, one is the surface strength of the paper, and the other is the peeling tension when printing. The size of the peeling tension depends on the viscosity of the ink, the printing speed, and the like.

Different papers, materials, and papermaking processes are also different. The surface strength varies greatly. Papers with poor surface strength are prone to naps. When multi-color offset printing is used, the post-printing color is wetted in the blank area by the wetting fluid. After printing on paper, when the paper is moistened, the surface strength decreases, and the pulling phenomenon increases.

The solution to pull hairs is:

First, according to the characteristics of the printing equipment and the printed products, the paper with the appropriate surface strength is selected during printing.

The second is to reduce the viscosity and viscosity of the ink by adding a varnish or detackifier to the ink. This is the most common method for printing paper with poor surface strength. Pulling phenomenon will increase as the viscosity of the ink increases, and the viscosity of the ink is most affected by the temperature, so the printing shop should maintain the constant temperature as much as possible, so that the printing shop has an ideal production environment, adding to the ink When ink or de-sticking agent is used, there are a lot of problems, such as increased emulsification of ink, increased dot gain and longer drying time.

Third, when printing paper with poor surface strength, the printing speed should be controlled. The higher the printing speed, the greater the peeling tension when the paper and the blanket are peeled off and the easier it is to pull the hair. The binding force of the fibers and fillers on the surface of the paper is not uniform, and the bonding strength of some particles and fibers is small. When the printing speed is not very high, the pulling phenomenon will occur, but it is not serious. The bonding strength of most of the particles or fibers is quite similar, but when the printing speed is higher than a certain critical point, the peeling tension reaches a certain degree, and a more serious pulling phenomenon will occur. Moreover, as the speed increases, the pulling phenomenon will also increase. Therefore, when printing paper with poor surface strength, the printing speed should be controlled and printing should be performed at a slower speed.

Fourth, replace the blanket, or use talcum powder to mix sulfur powder to wipe the blanket and reduce the stickiness of the blanket. The phenomenon of skeining during printing is sometimes caused by the stickiness of the blanket, so after each printing job is completed, unload the plate in time and clean the blanket. In addition, when conditions and time permit, when printing paper with poor surface strength, a monochrome machine can be used to print, which can reduce the pulling phenomenon and will not affect the normal production.