Adverse factors of the hottest printing color diff

Bad factors of printing color difference

the basic requirements of packaging product quality are the uniformity of ink color and bright and pure color of printing, and the printing color difference is a common problem of printing product quality. Looking at the printing process, there are many reasons for printing color difference, including bad factors in technology and raw materials. Therefore, a correct understanding of the relationship between these printing conditions and ink color is of great significance to accurately control the quality of printing ink and prevent the occurrence of printing color difference

I. printing color difference caused by improper pressure

printing pressure is one of the conditions for ink transfer. Because the printing plate surface cannot be absolutely flat, there are inevitably subtle concave convex and uneven thickness on the paper surface. If the printing pressure is insufficient or uneven, the printing ink layer is prone to uneven thickness. The ideal printing process is based on the "three levelness", that is, the printing plate, the substrate and the lining surface are required to be relatively flat, so that a thinner ink layer can be used to balance the printing pressure, so that a more uniform ink color can be obtained on the printing. When the printing pressure is insufficient or uneven, and there is poor contact between the lining body and the printing plate surface, it is necessary to increase the ink delivery to meet the visual effect of inking the layout, but this will not only increase the consumption of ink, but also easily cause printing color difference and printing sticky quality problems. Therefore, to prevent printing color difference, we should grasp the basic conditions of "three levels" of printing, and use uniform and constant pressure for printing. If a large area of plate products are printed by relief process (using circular flattening or flat flattening machine), it is best to use metal base material. In this way, the flatness and firmness of the material are better, and the printing pressure is relatively stable, which is conducive to preventing the printing color difference caused by pressure variation

second, the printing color difference caused by poor ink roller

lithography, relief and other printing processes, whether the printed matter can obtain a uniform ink color, the quality of the rubber roller plays a crucial role. The machine for printing color printed matter is generally equipped with three kinds of ink transfer rollers, ink leveling rollers and inking rollers, among which the ink transfer rubber rollers and inking rollers have a greater impact on the ink intensity. The elasticity, viscosity, centrality, hardness and surface finish of the ink roller largely determine the ink quality of the print. If the elasticity of the inking roller is poor, the viscosity is insufficient, the roller body is eccentric, the colloid is too hard, and the colloid finish is poor, it is easy to cause uneven or unstable ink brushing in the printing process, so that the printing ink color of each printing sheet is inconsistent. Therefore, high-quality cots should be used for printing color products, so as to ensure that the ink coated on the layout remains basically the same in each printing cycle. If printing bulk products, the cots should be cleaned in time during printing to make the paper dust trapped on the cots. Impurities can be removed to ensure the uniform origin of ink and prevent printing color difference. On the other hand, the contact position between the inking roller and the inking iron roller should be adjusted. Generally, the automatic printing machine is equipped with several groups of inking devices to achieve uniform inking. However, if there is a poor contact between the rubber roller and the inking iron roller, it is bound to cause insufficient and uneven ink transfer, resulting in uneven ink color on the horizontal layout of the print. In this regard, the shaft heads at both ends of the rubber roll should be adjusted to achieve a uniform contact between the rubber roll and the iron roll. After adjustment, 5-wire steel sheets can be inserted between the rubber roll and the iron roll for pulling inspection. When pulling the steel sheets, there is an obvious sense of resistance. In addition, adjust the contact position between the inking cot and the printing plate surface. If the inking roller is adjusted too high, the layout cannot be uniform and sufficient ink coating amount, and it is easy to produce print marks due to the following process of the inking roller: the refrigerant is adiabatically compressed to a higher pressure by the compressor and slips in the layout. If the inking roller is adjusted too low, the ink layer on the plate will be dragged by the scraper plate, resulting in the color difference between the light ink in front and the deep ink in the back, that is, the ink at the mouth is light, and the ink at the drag tip is thick. The inking roller and the printing plate surface should be adjusted into a parallel and uniform contact state. Only by accurately adjusting the contact position between the inking roller and the plate can we ensure the uniformity and consistency of the ink color of the print

III. printing color difference caused by poor ink feeding device

when the center of the ink bucket iron roller is poor or there is wear and deformation, the ink bucket steel plate also appears wear and deformation, and there are defects in the mechanism controlling the rotation of the ink bucket roller, which makes the ink delivery unstable during the printing process, and also causes the generation of printing color difference. Therefore, corresponding measures should be taken to deal with it, so as to prevent the generation of printing color difference. In addition, attention should be paid to the reasonable ink feeding device. The ink in the ink bucket should be comprehensively increased or reduced. There are two adjustment methods: one is to adjust the gap between the steel plate of the ink bucket and the ink transfer (ink feeding) iron roller; It is achieved by adjusting the rotation arc of the ink transfer iron bar. When the ink is thin, the gap between the steel sheet and the iron bar should not be adjusted too large to avoid ink leakage and uneven ink color. When adjusting the ink feeding amount, generally, the rotation radian of the ink transfer iron rod should be controlled within 1/2 of its adjustment range, so that when the ink concentration changes during the printing process, the ink feeding amount can be flexibly adjusted to ensure the uniformity of the ink color of the print and prevent the occurrence of the printing color difference problem

IV. printing color difference caused by poor moistening factors

if the lithography process is not suitable for moistening, it is also prone to printing color difference. For example, when the water roller is eccentric, because its contact with the layout is inconsistent, it is easy to make the size of the water supply of the layout different. In addition, if the water roll jacket is used to age or absorb ink and impurities, it will affect the water absorption of the water roll and the uniform transmission of the fountain solution. Moreover, if the water bucket device leaks, it will also affect the uniform transmission of water in the printing page. The existence of these undesirable conditions will destroy the uniform and stable transmission of the printing ink on the layout and make the printing ink color different. Therefore, in order to maintain a good installation of the fountain system, the ink roller should be cleaned frequently, and the aged water roller fleece should be replaced, so as to better prevent the production of printing color difference

v. printing color difference caused by poor ink

the process shows that the printing color difference is easy to occur when the thickness and viscosity of the printing ink layer are inappropriate. When printing, only with a moderate and uniform printing ink layer, can we better ensure the ink quality of the printed matter and effectively prevent the printing from sticking and dirty. If the printing ink layer is too thick, its viscosity will increase accordingly, which is easy to cause the phenomenon of powder dropping and galling on the paper surface in printing, and then affect the uniformity of ink color of printing products. However, if the printing ink layer is too thin and the ink viscosity is too small, the ink color of the print will appear light, and the visual effect of the print will be poor. On the other hand, due to the thixotropic nature of the ink, with the increase of the running time of the printing machine and the acceleration of the printing speed, the friction coefficient of the machine will increase, the temperature of the ink will gradually increase, and its viscosity will decrease accordingly. In this way, the printing ink will be shallower and shallower, so that the ink color before and after the batch of products is inconsistent and form a color difference. Therefore, these factors must be fully considered when adjusting ink, and the appropriate ink concentration should be adjusted according to the climate and temperature conditions and the characteristics of the printing machine, so as to reduce the chance of color difference in printing and make the printing ink color relatively stable. However, in the actual printing process, the decline of ink viscosity is inevitable. The ink color of the printed matter that has just been printed is often thicker, and then gradually fades. In this way, the ink delivery can be gradually increased by appropriately adjusting the rotation angle of the ink transfer iron rod, so that the ink color of the front and back printing can be basically kept the same. When blending intermediate and multicolor inks, try to avoid mixing inks with large specific gravity differences, so as to avoid the printing color difference caused by the "stratification" (i.e. sedimentation and suspension) of the ink in the ink bucket due to the large specific gravity difference in printing. In order to maintain the continuous and uniform transmission of ink, always use an ink knife to stir the ink in the ink bucket. In addition, during the printing process, because the ink volume in the ink bucket is significantly reduced and thick, it is easy to reduce the gap between the ink bucket steel sheet and the ink transfer iron roller, so that the ink output is reduced and the ink color of the printed matter is diluted. In order to avoid this situation, we should also pay attention to often adding ink to the ink bucket in production, so that a certain amount of ink is always maintained in the ink bucket. In order to prevent the ink viscosity from changing too much and affecting the balance of ink color, the contact between each rubber roller and iron roller should not be too tight, and the rubber roller is not easy to be hard, so as to minimize the impact of friction heat on ink thixotropy and reduce ink dilution

VI. printing color difference caused by poor substrate material

in daily printing process, we can find that the difference of substrate material is also one of the reasons for printing color difference, such as the difference of substrate gloss and hue, which will produce printing color difference. Taking embossed aluminized paper as an example, there are differences in the hue of aluminized paper, which will cause inconsistencies in the color rendering effect of printing. Therefore, printing color products should try to choose substrate with the same gloss and hue. If, in the presence of objective factors, two materials with different colors and gloss are used in the same batch of products, attention should be paid to printing separately, and the printing ink color of the two materials should be basically the same by adjusting the ink hue and printing pressure in the process, so as to prevent the occurrence of printing color difference

VII. Printing color difference caused by poor machine

if you want to do something good, you must first sharpen its tools. Maintaining good performance of the machine is a reliable guarantee for improving the quality of printing ink. However, if there are bad conditions in the machine, such as the unstable operation of the stamping system, the inconsistent pressure of each printing sheet, the abnormal paper feeding system, and the frequent occurrence of empty sheets, multiple sheets and other faults in printing, it is also the most likely to cause the occurrence of printing color difference. Therefore, we should pay attention to the maintenance of the equipment at ordinary times, and pay attention to the lubrication of the key parts of the machine, such as the roller shaft and other parts to prevent wear, so as to keep the imprinting mechanism in good working condition and keep the printing pressure constant. It is necessary to adjust the Feida and air pump devices to make the air path unobstructed, and ensure that the printing sheet is sucked normally, so as to ensure that the paper feeding is smooth and there is no blank sheet phenomenon, so as to better prevent the occurrence of printing color difference

VIII. Printing color difference caused by poor printing plate

printing plate is one of the basic elements of image and text reproduction quality. In the printing process, the printing plate can better ensure the stability of ink transmission of the plate only if it is not deformed and worn. In the printing process, if the dot layout is distorted due to paste or wear, and the lines are worn and expanded, in this way, due to the change of ink absorption of the layout, the ink color of the print will inevitably deviate. Therefore, when printing color products, we should pay attention to controlling the appropriate printing pressure, and adjust the contact pressure of the rubber roller and water roller on the printing plate, so as to prevent the wear of the printing plate caused by excessive pressure, which will cause the ink color deviation of the products before and after printing. On the other hand, materials with good smoothness and not easy to lose powder and hair should be used for printing, which can help provide necessary oxygen, nutrition, fluid and drugs. It can also be adjusted to the space of 1 (2) mm between the test piece and the upper pressing plate. It is one of the process measures to effectively avoid the wear and deformation of the layout in printing, which is conducive to better prevent the occurrence of printing color difference

IX. printing color difference caused by poor lining

dust is the medium of imprint transfer