Influencing factors of printing chromatic aberration

The uniformity of ink color and the purity of the printed product are the basic requirements for the quality of the packaged product, and the printing color difference is a common problem in the quality of the printed product. Looking at the printing process, the reasons for the printing chromatic aberration are various, there are technical factors and raw materials. Therefore, correctly understanding and understanding the relationship between these printing conditions and ink color is of great significance for accurately controlling the quality of printing ink and preventing the occurrence of printing chromatic aberration.

First, the printing color difference caused by poor ink

The process conditions indicate that the thickness and viscosity of the printed ink layer are not easy to produce print chromatic aberration. When printing, only a moderate and uniform printing ink layer can better ensure the ink color quality of the printed product and effectively prevent the printing from sticking faults. If the printing ink layer is thicker, the viscosity thereof increases correspondingly, thereby easily causing the paper surface to fall off and the pulling phenomenon in the printing, thereby affecting the uniformity of the ink color of the printing product. However, if the printing ink layer is thin and the ink viscosity is too small, the ink color of the printed product is pale, and the visual effect of the printed product is also poor. On the other hand, in terms of the thixotropic properties of the ink, as the running time of the printing press increases and the printing speed increases, the friction coefficient of the machine increases, and the temperature of the ink also gradually increases. It will be lowered accordingly, so that the printing ink will be printed more and more shallow, so that the ink color before and after the batch of products will be inconsistent to form a chromatic aberration. Therefore, these factors must be fully taken into consideration when dying, and the appropriate ink concentration should be adjusted according to the climatic temperature condition and the characteristics of the printing machine to reduce the chance of chromatic aberration in printing, so that the printing ink color is relatively stable. However, in the actual printing process, the viscosity of the ink is inevitable, and the ink of the printed product is often thicker, and then gradually fades. Thus, the amount of ink can be gradually increased by appropriately adjusting the rotation angle of the iron transfer roller. , so that the ink color printed before and after is basically the same. When blending the intermediate color and the complex color ink, it should be avoided to mix the ink with a large specific gravity, so as to avoid the printing caused by the difference of the specific gravity, which causes the ink in the ink fountain to produce "layering" (ie, precipitation and suspension). Color difference. In order to keep the ink continuous and evenly conveyed, the ink in the ink fountain should be used to stir the ink in the ink fountain. In addition, in the printing process, since the amount of ink in the ink fountain is significantly reduced, the gap between the ink fountain steel sheet and the ink transfer iron roller is easily reduced, so that the ink output is reduced, and the ink color of the printed product is lightened. In order to avoid this, the production should also pay attention to the ink fountain often, so that a certain amount of ink is always kept in the ink fountain. In order to prevent the ink viscosity variation from being too strong and affecting the balance of the ink color of the printing, the contact between the rubber rollers and the iron roller should not be too tight, and the rubber roller should not be too hard to minimize the influence of frictional heat on the thixotropy of the ink. To reduce the appearance of ink fade.

Second, the printing color difference caused by pressure discomfort

Printing pressure is one of the conditions for ink transfer. Since the surface of the printing plate cannot be absolutely flat, the surface of the paper is inevitably subject to fine irregularities and uneven thickness. If the printing pressure is insufficient or uneven, the printing ink layer will be printed. It is prone to unevenness. The ideal printing process is based on the "three flats", that is, the conditions of the printing plate surface and the substrate and the lining surface are required to be relatively flat, so that the thinner ink layer can be obtained by equalizing the printing pressure. More uniform ink color. When the printing pressure is insufficient or uneven, when there is contact failure between the liner and the printing plate surface, it is necessary to increase the ink delivery amount to meet the visual effect of the layout ink, but this will not only increase the ink consumption. , it is easy to produce printing chromatic aberration and print quality problems. Therefore, to prevent the occurrence of printing chromatic aberration, we should grasp the basic conditions of printing "Sanping" and use uniform and constant pressure for printing. If it is to use a letterpress process (using a flat-press or flat-press machine) to print large-area plate products, it is best to use a metallic underlay material, so that the material is flat and firm, and the printing pressure is compared. Stable, it helps to prevent printing chromatic aberration caused by pressure variation.

Third, the printing color difference caused by the poor ink roller

Printing methods such as lithography and letterpress printing, whether the printing product can obtain uniform ink color, the quality of the rubber roller plays a vital role. On the machine for printing color printing crystal, it is generally equipped with an ink transfer roller, a fountain roller and an ink roller. Among them, the ink-adhesive roller and the inking roller have a great influence on the ink color. The elasticity, viscosity, center of the circle, hardness and surface finish of the ink roller largely determine the quality of the printed ink. If the ink roller has poor elasticity, insufficient viscosity, eccentricity of the roller body, excessive colloid, and poor gel finish, the printing process may easily cause uneven or unstable ink, so that the printing ink colors of the sheets are inconsistent. Therefore, the printing of color products should use a good quality rubber roller to ensure that the ink applied to the printing plate is consistent in each printing cycle. If a large-scale product is printed, the rubber roller should be cleaned in time to ensure that the paper dust and impurities retained on the rubber roller are removed to ensure uniform ink transfer and prevent printing chromatic aberration. On the other hand, the contact position of the ink roller and the tandem iron roller should be adjusted. Generally, the automatic printing machine is provided with several sets of ink-distributing devices to achieve uniform ink delivery. However, if there is a bad contact between the rubber roller and the ink roller, it will inevitably result in insufficient and uneven ink transfer, which will cause unevenness in the ink color of the transverse printing surface of the printed product. In this regard, the shaft ends at both ends of the rubber roller should be adjusted to achieve a uniform contact between the rubber roller and the iron roller. After the adjustment, the steel wire of the 5 wire can be inserted into the rubber roller and the iron roller for drawing test and pulling. The steel sheet has a significant resistance to the degree of resistance. In addition, the contact position between the ink roller and the printing plate surface should be adjusted. If the inking roller is adjusted too high, the plate surface will not be evenly and sufficiently ink-coated, and it is easy to produce a printing bar mark due to the ink roller slipping on the plate surface. If the ink roller is adjusted too low, the ink layer on the printing plate will be scraped to the printing plate to prevent the ink from being dark and dark before the printing ink, that is, the ink color of the cornice is too light, and the ink color of the sliding portion is thick. . The inking roller and the printing plate surface should be adjusted to be parallel and evenly in contact with each other. Only when the contact position between the inking roller and the plate surface is accurately adjusted can the ink color be uniform and uniform.

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