Disturbance caused by unsatisfied printing pressure

Pressure is one of the important conditions for the offset and embossing processes. Appropriate printing pressure is also an effective process technology that guarantees normal production and improves product printing quality. However, if the technical measures are not in place and the printing pressure is unsatisfactory, some printing failures may occur and care must be taken.

First, the printing pressure is too heavy caused by overprint failure

When the tooth surface of the roller teeth is worn, deformed, and the pressure of the teeth is uneven and insufficient, the slippage of the printed sheet is likely to occur during the imprinting, resulting in inaccurate overprinting of the product. Especially in the case of large ink-receiving area of ​​the printing plate, and the viscosity of the ink used in the printing is large, the performance of the product inaccurate in printing is more prominent. The main reason is that the printing pressure is obviously heavy, and after reducing the printing pressure, the ink and the printing effect are not satisfactory. In this regard, the solution is: to replace the teeth with severe new teeth wear; will deform, uneven pressure on the bite paper, insufficient teeth bite, to adjust the entire tooth surface bite the edge of the paper; the viscosity of the ink Too large, moderately diluted with additives to reduce the viscosity of the ink; for printing spot color inks, the ink hue can be appropriately deepened to make the printing ink layer thinner, which can reduce the viscosity of the ink and achieve compliance Printing hue requirements. In addition, the printing pressure is appropriately reduced, and the printing pressure is adjusted so that the ink layer on the printing plate is evenly transferred to the printed sheet. However, the uniformity of the thickness of the underlay is the basis and a prerequisite. These operating techniques have been turned off, so that the problem of overprinting caused by biting teeth is not tight, and this will be easily solved.

Second, the printing pressure does not cause traces of ink marks

When the roller bearings are worn out in a serious condition, due to excessive roller separation, causing the surface friction of the roller to cause ink stick marks, this is a situation. In another case, due to the use of a hard lining, the ink bars are caused by the sliding phenomenon during the imprinting process. The third situation is that the roller gear is worn badly, and the center distance of the roller is too large, so that the backlash of the gear is too large, so that the gears vibrate after the roller is pressed, and the sliding friction occurs on the roller surface to cause the ink bars. The fourth situation is that the pressure between the plate cylinder and the blanket cylinder is too large, so that the blanket is squeezed to form a large frictional slippage, which causes the longitudinal deformation of the screen surface to expand and cause the ink mark. The above situation shall be achieved by replacing the roller bushing; adjusting the characteristics of the packing material; reducing the center distance of the roller, so that the meshing backlash of the gear is less than 0.1mm; according to the specifications of the equipment, the thickness of the packing shall be set to avoid excessive pressure. To prevent the phenomenon of ink sticks.

Third, the ghost pressure caused by the unfavorable printing pressure

When the pressure between the blanket cylinder and the impression cylinder is too large, the deformation displacement of the blanket increases accordingly, so that the ink layer cannot be restored to the original state immediately after transfer in the imprinting process, so that the imprint is accepted again from the plate cylinder. At that time, it is easy to generate a slight difference in position and form a ghost print. In this regard, it is necessary to reduce the pressure of the roller and reduce the expansion and contraction coefficient of the blanket during imprinting to prevent ghosting failure from occurring. In addition, for the use of aging blankets, should be replaced with a new blanket for printing, to eliminate print ghosting failure.

The printing pressure of the lithography process does not cause ghosting failures, and the embossing process does. When the embossing process employs a multi-layered glued board as a printed bottom mat for printing a large area of ​​a plate product, due to unevenness of the bottom mat and poor solidity, the printing plate vibrates during printing to cause ghosting failure. In this regard, the elimination of measures is that the bottom pad should be flat, the bottom plate should be planed into a straight edge, right angle state, so that after the plate is firmly attached to the bottom plate, eliminate the "hanging" caused by the plate ghosting failure .

Fourth, the printing pressure caused by the dirty version and paste version

When the printing pressure is too high, the frictional force of the surface of the blanket on the printing plate surface must be increased, so that the plateau surface is worn and damaged, the hydrophilicity of the blank area mutates, and the ink is attached and transferred to the printing product. The situation is dirty. In addition, the printing pressure is too large, the elastic deformation value of the rubber under pressure is also large, the transfer of the imprint is also easy to produce deformation, especially the printing of dots and small text, there are often paste problems. This is even more evident if it is a relief process. Therefore, in order to prevent the occurrence of dirty and paste, it is necessary to accurately adjust the printing pressure. According to the equipment specification, the thickness of the liner and the center distance of the drum should be controlled.

Fifth, the printing ink pressure caused by discomfort

When the unevenness of the gasket unevenness or insufficient pressure, when imprinting, between the printing plate and the rubber, between the blanket cylinder and the impression cylinder or between the plate and the pad (the relief process), there will be poor contact phenomenon, affecting the layout of the ink layer Uniform and full transfer, which results in a lack of pressure on the layout of pale ink, hair. In order to avoid this unfavorable situation, it is necessary to shut off the printing technology of "Sanping" printing. The printing plate and the ink roller should be leveled. The bottom pad of the printing plate should be leveled; the plate and the blanket roller or lining (embossing) should be flat. The blanket or blanket should be flattened; the impression cylinder and blanket cylinder should be flat, and the surface of the impression cylinder should be protected to prevent loss of flatness due to damage; uniform and sufficient printing pressure should be maintained to eliminate ink from the ink. Effective measures.

In a word, printing pressure is the basis of product quality. Only by carefully concentrating good printing operation technology, scientifically and rationally adjusting, and handling various factors affecting the pressure, can we ensure the printing quality of the product.