Trouble shooting caused by improper printing press

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Troubleshooting caused by improper printing pressure

pressure is one of the important conditions for offset printing and embossing process. Appropriate printing pressure is also an effective process and technical measure to ensure normal production and improve product printing quality. However, if the operation technical measures are not in place and the printing pressure is not appropriate, some printing faults will be caused, which must be paid attention to

I. overprint inaccuracy caused by excessive printing pressure

when there are nearly 40 listed companies with accelerated layout of lithium battery business due to wear and deformation of roller teeth, uneven and insufficient teeth pressure, the printing sheets are prone to slip in the stamping process after entering the teeth, resulting in inaccurate overprint of products. In particular, when the printing area of the printing plate is large and the viscosity of the printing ink is large, the performance of the inaccurate printing of the product is more prominent. The main reason is that the printing pressure is obviously biased, but after reducing the printing pressure, the ink color and imprinting effect are not satisfactory. In this regard, the solution is: replace the severely worn teeth with new teeth; Adjust the deformed, uneven paper biting pressure and insufficient paper biting teeth to make e the whole tooth surface tightly bite the paper edge; If the viscosity of the ink is too large, the auxiliary agent shall be used for appropriate dilution to reduce the viscosity of the ink; For the printing spot color ink, the ink color phase can be appropriately deepened to make the printing ink layer thinner, which can not only reduce the ink viscosity, but also meet the requirements of printing color phase. In addition, the printing pressure shall be properly reduced. The adjustment of the printing pressure shall be based on the uniform and sufficient transfer of the ink layer of the printing plate to the printing sheet. Of course, the uniform thickness of the liner is the basis and prerequisite. If these operating techniques are well controlled, the problem of inaccurate overprint caused by not biting the edge of the paper will be solved

II. Ink bar marks caused by improper printing pressure

when the drum bearing is seriously worn, the ink bar marks appear due to the sliding friction of the drum surface due to the excessive drum clearance, which is a kind of situation. In another case, due to the use of hard lining, the ink bar is caused by the sliding phenomenon during the stamping process. In the third case, the drum gear is seriously worn, and the center distance of the drum is adjusted too large, so that the side clearance of the gear is too large, which makes the gear vibrate after the drum is pressed, and the sliding friction occurs on the drum surface, causing the ink bar. In the fourth case, the pressure between the printing plate cylinder and the blanket cylinder is too large, so that the blanket is squeezed to form a large friction sliding, which expands the longitudinal deformation of the plate points and causes ink marks. For the above situations, replace the roller shaft sleeve; Adjust the padding characteristics of the coated Japanese catalyst, which is put into commercial production for the first time in the world; Reduce the center distance of the drum so that the meshing backlash of the gear is less than 0.1mm; According to the specifications and requirements of the equipment, the thickness of the gasket shall be set to avoid the occurrence of excessive pressure, so as to prevent ink bars

III. ghosting failure caused by improper printing pressure

when the pressure between the rubber cylinder and the embossing cylinder is too large, the extrusion deformation displacement of the blanket increases correspondingly. Therefore, the ink layer cannot be restored to its original state immediately after the ink layer is transferred during the embossing process. In this way, when the imprint is received from the plate cylinder, it is easy to produce a small level difference and form a ghosting imprint. In this regard, it is necessary to reduce the pressure of the drum properly to reduce the expansion deformation coefficient of the rubber blanket during stamping, so as to prevent the occurrence of ghosting fault. In addition, the old rubber blanket used for a long time should be replaced with a new rubber blanket for printing to eliminate the printing ghosting fault

improper printing pressure in the lithography process will cause ghosting failure, and so will the embossing process. When the embossing process uses multi-layer plywood as the printing pad to print large-area plate products, due to the uneven and poor firmness of the pad, the printing plate vibrates during the embossing process, resulting in the printing ghosting failure. In this regard, the elimination measures are that the bottom pad should be leveled, and the four sides of the bottom pad should be planed into straight edges and right angles, so that the bottom surface is close to the plate after the plate is fastened, and the ghosting fault caused by the "hanging" of the plate can be eliminated

IV. dirty version and pasted version caused by excessive printing pressure

when the printing pressure is too high, the friction force between the rubber blanket surface and the printing plate surface must be increased, so that the plate sand is worn and damaged, the hydrophilicity of the blank area changes, and the ink is attached and transferred to the printing product. This situation belongs to dirty version. In addition, if the printing pressure is too large, the elastic deformation value is also large when the rubber is pressed, and the imprint transfer is also prone to deformation, especially the printing points and small words, which often have the disadvantage of paste. If e relief process, this kind of situation is more obvious. Therefore, to prevent the occurrence of dirty version and paste version, we must accurately adjust the printing pressure. Control the pad thickness and drum center distance according to the requirements of equipment specifications

v. ink color blooming caused by improper printing pressure

when the pad is uneven or insufficient, poor contact will occur between the printing plate and the rubber, between the rubber cylinder and the embossing cylinder, or between the printing plate and the lining (relief process), which will affect the uniform and full transfer of the ink layer of the layout, resulting in weak ink color and blooming of the layout under insufficient pressure. In order to avoid this bad situation, the "three leveling" process technology of printing should be well controlled. The printing plate should be level with the inking roller, and the bottom pad of the printing plate should be leveled; The printing plate shall be flat with the blanket cylinder or lining (embossing), and the blanket or lining shall be leveled; The embossing cylinder shall be flat with the rubber cylinder, and the surface of the embossing cylinder shall be protected to prevent damage, deformation and loss of flatness; Maintaining even and sufficient printing pressure is an effective measure to eliminate ink color blooming

in a word, the printing pressure is the basis of product quality. Only by carefully controlling the printing operation technology, scientifically and reasonably adjusting and handling various factors affecting the pressure, can the printing quality of products be ensured

reprinted from: printed in China

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