Bad factors that affect printing color difference

The uniform color and pure color of printed products are the basic requirements for the quality of packaging products, and the color difference in printing is a common problem in the quality of printed products. Looking at the printing process, there are many reasons for the color difference in printing. There are technical and technical factors, as well as raw materials. Therefore, it is of great significance to correctly understand and understand the relationship between these printing conditions and ink color, to accurately control the quality of printing ink color, and to prevent the occurrence of printing color aberration.

First, the print 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, there are inevitably slight irregularities and uneven thicknesses on the surface of the paper. If the printing pressure is insufficient or uneven, the printing ink layer is easy to print. Unevenness appears. The ideal printing process is on the basis of "three levels", that is, the surface of the printing plate, the substrate and the surface of the lining are required to be relatively flat, so that the thinner ink layer can achieve the effect of equalizing the printing pressure so as to obtain the impression on the printing product. More uniform ink. When the printing pressure is insufficient or uneven, there is a poor contact between the lining body and the plate surface, the visual effect of the stencil inking needs to be satisfied by increasing the amount of ink to be transferred, but this will not only increase the consumption of the ink. , It is easy to produce printing color and print quality problems. Therefore, to prevent the occurrence of printing color differences, it is necessary to grasp the basic conditions for the printing of "three levels" and use uniform and constant pressure for printing. If a large-area plate product is to be printed using a letterpress process (circular flattening or flat-flattening machine), it is better to use a metal-type bottom pad material. In this way, the flatness and firmness of the material are better, and the printing pressure is compared. Stable, help prevent printing chromatic aberration caused by pressure variation.

Second, the color difference caused by poor ink roller

Printing processes such as lithographic printing and letterpress printing, and whether the printed product can obtain a uniform ink color, the quality of the rubber roller plays a crucial role. The machines for printing color prints are generally equipped with an ink transfer roller, an ink roller, and an ink roller. Among them, the ink roller and the ink roller are greatly affected by the ink shade. The ink roller's elasticity, stickiness, center of circle, hardness and surface finish greatly determine the quality of the printed ink. If the ink roller has poor elasticity, insufficient adhesiveness, eccentricity of the roller body, excessive hardness of the rubber body, and poor colloidal smoothness, the uneven or unstable brushing may be caused during the printing process, and the printing ink of each print sheet may be inconsistent. Therefore, a good quality rubber roller should be used in the printed color products to ensure that the ink applied to the printing surface during each printing cycle remains basically the same. If printing a large quantity of products, the rubber roller should be cleaned at the right time so that the paper dust on the roller can stay. Impurities are removed to ensure uniform production of the ink and to prevent the production of color differences. On the other hand, the position of the contact between the ink roller and the chain iron roller should be adjusted. In general, the automatic printer is provided with several sets of ink mixing devices to achieve a uniform ink delivery. However, if the contact between the rubber roller and the chain iron roller is poor, it will inevitably result in insufficient and uneven transfer of ink, which will cause unevenness in the ink color in the horizontal layout of the printed product. In this regard, the shaft ends at both ends of the rubber roller should be adjusted to achieve even contact between the rubber roller and the iron roller. After the adjustment, five-wire steel sheets can be inserted into the rubber roller and the iron roller to perform pull-pull inspection. There is a clear sense of resistance in the film. In addition, the position of the contact between the ink roller and the plate surface must be adjusted. If the ink roller is adjusted too high, the layout will not be even, and the amount of ink applied will be sufficient, and the printing roller marks will be easily generated by the ink roller sliding on the plate. If the ink roller adjustment is too low, the ink layer on the plate will be dragged by the squeegee plate, resulting in a dark color difference between the ink and the ink. The ink in the rinsing area is pale, and the ink in the dragging area is dark. The ink roller and the printing plate surface should be adjusted into parallel and uniform contact state. Only by accurately adjusting the contact position between the ink roller and the plate surface can the printing ink be uniform.

Third, the poor color to the ink device caused by the color difference

When the center of the iron roller is poor or there is wear and deformation, the ink fountain plate also wears and deforms, and the mechanism for controlling the rotation of the ink fountain roller has defects, so that the amount of ink transferred during the printing process is not stable, and color printing may also be caused. , should take appropriate measures to deal with, in order to prevent the production of color. In addition, we should pay attention to the reasonable and true ink supply device. The ink in the ink fountain must be increased or reduced in its total amount. There are two adjustment methods. First, it is achieved by adjusting the gap between the ink fountain steel plate and the transfer ink (to ink) iron roller; It is achieved by adjusting the size of the arc of rotation of the ink rod. In the case of thinner inks, it is not advisable to adjust the gap between the steel sheet and the iron bar so as to avoid ink leakage caused by ink leakage. When adjusting the amount of ink to be supplied, the rotation arc of the ink transfer rod should generally be controlled within 1/2 of the adjustment range. This can allow the ink volume to be flexibly adjusted when the ink density during printing changes. The ink color of the printing product is uniform and uniform, preventing the problem of color printing from occurring.

Fourth, the printing element color difference caused by poor dampening factors

Lithographic printing process if the dampening discomfort, but also prone to color printing phenomenon. For example, when there is an eccentricity in the water roller, since the contact with the plate is inconsistent, it is easy to make a difference in the amount of water supply on the plate. In addition, if the water roller fuse sleeve is used with aging or adsorption ink and impurities, it will affect the water absorption of the water roller and the uniform transmission of the fountain solution. In addition, if the water hopper device leaks, it will also affect the uniform distribution of moisture on the printing plate. The existence of these unfavorable conditions will destroy the even and stable transmission of the ink on the layout, resulting in a difference in the ink color of the printed product. Therefore, dampening system to maintain a good body, should wash the ink roller, the use of aging water roller sleeve should be replaced in order to better prevent the production of color.

Fifth, ink color caused by poor printing

Process conditions show that printing ink layer thickness and viscosity are not easy to produce printing color. When printing, only with a proper and uniform printing ink layer, the ink quality of the printed product can be better ensured, and the occurrence of printing stickiness failure can be effectively prevented. If the printing ink layer is thicker, the viscosity of the printing ink layer will increase correspondingly, thereby easily causing the paper surface to fall out of the printing and pulling hair phenomenon, thereby further affecting 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 printing product becomes lighter, and the visual effect of the printing product is also poor. On the other hand, due to the thixotropic nature of the ink, as the printing machine's running time increases and the printing speed increases, the friction coefficient of the machine increases and the temperature of the ink gradually increases, and the viscosity of the ink will increase accordingly. When the ink is lowered, the printing ink will be printed more and more shallowly, so that the batch of products will be inconsistently colored before and after the formation of color difference. Therefore, the ink must be fully taken into account when these factors are adjusted, according to the climate temperature conditions and the characteristics of the printing machine, adjust the appropriate ink concentration, in order to reduce the chance of color differences in the printing, so that the printing ink obtained relatively stable. However, in the actual printing process, ink viscosity reduction is unavoidable, often the ink of the newly printed ink is darker, and then gradually fades. In this way, the amount of ink can be gradually increased by appropriately adjusting the rotation angle of the ink transfer rod. , so that the ink before and after printing is basically the same. When mixing the color and double color inks, we should try to avoid mixing the ink with a large proportion of the weight, so as to avoid the ink in the ink bucket due to the large difference in the printing, resulting in “layered” (ie, precipitation and suspension) caused by printing Chromatic aberration. In order to maintain the ink's continuous, uniform transfer, the ink in the ink fountain should be frequently used to stir the ink. In addition, since the amount of ink in the ink fountain is significantly reduced during the printing process, the gap between the ink fountain and the transfer roller is reduced, so that the ink output is reduced, and the ink is lightened. In order to avoid this happening, it is also necessary to pay attention to adding ink to the ink fountain in the production so as to keep the ink in the ink fountain at all times. In order to prevent the ink viscosity variation from being too severe and affect the balance of the ink color, the contact between the rubber roller and the iron roller should not be too tight and the roller should not be hardened to minimize the effect of frictional heat on the thixotropy of the ink. , reduce the appearance of desalination of ink.

Sixth, poor printing materials caused by poor color printing

In the daily printing process, we can find that the difference in the material quality of the substrate is one of the reasons for the color difference in the printing. For example, the difference in the glossiness and the hue of the substrate will cause the problem of printing color. Taking embossed aluminized paper as an example, the difference in hue of the aluminized paper will cause inconsistencies in the print color effect. Therefore, printing color products should try to use substrates with the same gloss and hue. If the objective factors exist, the same batch of products use two materials with different color and gloss, and should pay attention to separate printing, and adjust the ink hue and printing pressure in the process so that the printing inks of the two materials are basically the same. To prevent the production of color chromatic aberration.

Seventh, poor color printing caused by the machine

If a worker wants to do good, he must first sharpen his tools. Keeping the machine's good performance is a reliable guarantee for improving the quality of printing ink. However, if the machine has a bad condition, such as imprinting system work is not stable, so that the pressure of each sheet is inconsistent, and the paper feeding system is not normal, frequent occurrence of empty, multiple sheets and other failures in the printing, it is most likely to cause printing The appearance of color aberration problems. Therefore, we should always pay attention to equipment maintenance and maintenance, we must pay attention to the machine key parts of the lubrication work, such as roller shaft and other parts to prevent wear, so that the imprinting mechanism to maintain a good working condition, so that the printing pressure remains constant. It is necessary to adjust feeders and air pump devices so that the air passages can flow smoothly and the normal suction of the sheets can be ensured. This ensures that there is no vacancy in the smooth flow of the paper, so as to better prevent the occurrence of printing color aberrations.

Eight, poor printing caused by printing color

Printing plate is one of the basic elements of the quality of graphic reproduction. In the printing process, the printing plate can only maintain the stability of the ink transferred on the plate. During the printing process, if the layout of the screens is distorted or worn and deformed, the lines appear to wear out and expand. In this way, due to the change in the amount of ink sucked on the layout, the ink color of the prints will inevitably be deviated. Therefore, printing color products should pay attention to control the appropriate printing pressure, and adjust the contact pressure between the rubber roller and the water roller to prevent the printing plate surface from being abraded due to excessive pressure. On the other hand, it should be possible to adopt printing materials with good smoothness, which are not easy to lose powder and lose hair. This is also one of the technical measures for effectively avoiding the wear and deformation of the printing plate in printing, which is favorable for preventing the production of printing color aberrations.

Nine, poor lining caused by printing color

Dust is the medium for imprint transfer and has a great influence on the printing ink color. If the lining elasticity is too poor, as the number of printings increases, it gradually becomes difficult to be reset after it sinks and deforms. Then, the print ink before and after the print will be inconsistent. On the other hand, if the printing surface is covered with a layer of ink, paper dust and other impurities, the printing ink will be biased. Therefore, printed color products should be selected to have a certain degree of elastic liner, and timely cleaning of the blanket surface blots or paper scraps, to prevent poor lining caused by printing color.

Ten, light source characteristics and different viewing angles to identify differences in print color

Usually identify the light source of printed ink, mainly sunlight (natural light), fluorescent lamps and incandescent lamps and other light sources. They emit different light source characteristics, and the emitted light color is also different. For example, sunlight is mellow white, and the observed color is relatively accurate. The light of the fluorescent lamp is white and blue, similar to sunlight. The incandescent light has a yellowish color in red, so it is difficult to accurately identify the color. Although sunlight and fluorescent lamps are somewhat similar, the difference between the two should also be considered when identifying high quality color products. The effect of light on the identification of ink is not only the characteristics of the light source, but also has a lot to do with the light intensity and the angle of illumination. Under the same light source, it is weak to be irradiated. The correct angle of illumination should be equal to ten angles of incidence equal to the angle of reflection. Irradiation on the sample sheet will inevitably result in partial refraction, but it will not have much influence on the ink color. When identifying the ink color of the printed product, it should be at the intensity of the light source regardless of daylight or nighttime. Both the irradiation angle and the irradiation angle are the same.

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