Troubleshooting due to printing pressure discomfort
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Pressure is one of the important conditions for offset printing and embossing. Moderate printing pressure is also an effective technical measure to ensure the normal production of the product and improve the printing quality of the product. However, if the technical measures are not in place and the printing pressure is not suitable, it will cause some printing failures and must be taken care of.
First, the overprinting caused by excessive printing pressure is not allowed to malfunction
When the tooth surface of the roller is worn and deformed, and the pressure of the tooth is uneven or insufficient, the printed sheet is likely to slip in the embossing after entering the nip, which causes the product to be overprinted. In particular, in the case where the printing plate has a large ink receiving area and the viscosity of the ink used for printing is large, the performance of the product printing failure is more prominent. The main reason is that the printing pressure is obviously biased, and after reducing the printing pressure, the ink color and the imprinting effect are not satisfactory. In this regard, the solution is to replace the new teeth with the worn teeth; to deform the deformation, the paper pressure is uneven, and the insufficient teeth are adjusted so that the entire tooth surface is tightly bitten; the ink consistency If it is too large, it will be diluted with appropriate additives to reduce the viscosity of the ink. For printing the spot color ink, the ink color can be thinned a little, so that the printing ink layer can be thinned a little, which can reduce the viscosity of the ink and meet the requirements. Requirements for printing hue. In addition, the printing pressure is appropriately reduced, and the printing pressure is adjusted so that the ink layer of the printing plate is uniformly and sufficiently transferred to the printing sheet. Of course, the uniformity of the thickness of the spacer is the basis and the precondition. These operating techniques are well-off, so the problem of overprinting caused by the bite of the teeth is not solved, and it is solved.
Second, the printing pressure is not caused by the ink stick trace
When there is a serious wear of the roller bearing, it is a situation that the oversized roller is displaced, causing sliding friction on the surface of the roller to cause the ink bar mark to appear. In still another case, due to the use of a hard lining, the ink stick is caused by the occurrence of a sliding phenomenon during the embossing process. In the third case, the roller gear is seriously worn, and the center distance of the drum is adjusted too much, so that the gear side gap is too large, so that the gear vibrates after the drum is pressed, and the sliding friction occurs on the surface of the drum to cause the ink stick. In the fourth case, the pressure between the plate cylinder and the blanket cylinder is too large, so that the blanket is squeezed to form a large frictional sliding, which causes the longitudinal deformation of the screen dot to expand and cause the ink stick trace. For the above situation, the drum bushing should be replaced; adjust the characteristics of the packing material; reduce the center distance of the roller so that the meshing side clearance of the gear is less than 0.1mm; according to the specification of the equipment, the thickness of the gasket is determined to avoid the occurrence of excessive pressure. To prevent the phenomenon of ink sticks.
Third, the printing pressure is not caused by the ghosting failure
When the pressure between the blanket cylinder and the impression cylinder is too large, the amount of displacement and displacement of the blanket increases accordingly, so that the ink layer cannot be restored to its original state immediately after the transfer of the ink layer, so that the impression is received from the plate cylinder. At the time, it is easy to generate a slight amount of difference, and a ghost image is formed. In this regard, the drum pressure should be appropriately reduced to reduce the expansion and contraction coefficient of the blanket during imprinting to prevent ghosting failure. In addition, for the use of aging blankets, a new blanket should be replaced for printing to eliminate printing ghosting problems.
The offset printing process pressure is unsuitable for ghosting failure, as is the embossing process. When the embossing process uses multi-layer glued wood board to be used as a printing bottom pad, when printing a large-area plate product, the printing plate ghosting is caused by the plate vibrating during the embossing process due to uneven bottom plate and poor firmness. In this regard, the elimination measures are that the bottom pad should be leveled, and the four sides of the bottom pad should be cut into a straight edge and a right angle state, so that the bottom plate of the plate is fastened after the plate is fastened, and the ghosting caused by the plate "hanging" is eliminated. .
Fourth, dirty printing and paste caused by excessive printing pressure
When the printing pressure is too large, the frictional force of the surface of the blanket on the surface of the printing plate must be increased, so that the sand surface of the printing surface is damaged by abrasion, the hydrophilicity of the blank area is mutated, the ink is adhered and transferred to the printing product. The situation is dirty. In addition, the printing pressure is too large, the elastic deformation value when the rubber is pressed is also large, and the transfer of the print is also prone to deformation, especially printing dots and small characters, which often cause paste defects. This is more obvious if it is a letterpress process. Therefore, to prevent the occurrence of dirty and paste, it is necessary to accurately adjust the printing pressure. The thickness of the liner and the center distance of the drum are controlled according to the equipment specifications.
Fifth, the ink color is caused by the printing pressure discomfort
When the uneven pressure of the pad is uneven or insufficient, when printing, the printing plate and the rubber room, the blanket cylinder and the impression cylinder or the printing plate and the lining (the letterpress process) may cause poor contact, which affects the ink layer of the layout. Uniform and full transfer, which causes the ink with insufficient pressure to fade and smudge. In order to avoid this unfavorable situation, it is necessary to close the printing technology of "Sanping". The printing plate should be flat with the inking roller. The bottom plate of the printing plate should be padded; the printing plate should be flat with the blanket cylinder or the lining (embossing). Should be flat rubber blanket or lining; the impression cylinder and the rubber cylinder should be flat, the surface of the impression cylinder should be protected to prevent the flatness from being damaged; the uniform and sufficient printing pressure is to eliminate the ink color of the printed product. Effective measures.
In short, printing pressure is the basis of product quality. Only by carefully controlling the printing process technology, scientifically and rationally adjusting and handling various factors affecting pressure can ensure the printing quality of the product.