1、 Printing color difference caused by poor ink

       The process shows that the printing color difference is easy to occur due to the improper thickness and viscosity of the printing ink layer. When printing, only with an appropriate and uniform printing ink layer can we better ensure the ink quality of printed products and effectively prevent the occurrence of printing sticking and dirty faults. Analysis Of Influencing Factors Of Printing Color Difference

      If the printing ink layer is too thick, its viscosity will increase accordingly, which is easy to cause the phenomenon of paper powder falling and roughening in printing, and then affect the uniformity of printing ink color. 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. Analysis Of Influencing Factors Of Printing Color Difference

       On the other hand, Shanyu ink has the characteristics of thixotropy. 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 and electricity will decrease accordingly. In this way, the printing ink will be lighter and lighter, resulting in inconsistent ink colors before and after batch products. Analysis Of Influencing Factors Of Printing Color Difference

      Therefore, these factors must be fully considered during ink fading. 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. Analysis Of Influencing Factors Of Printing Color Difference

      However, in the actual printing process, the decrease of ink viscosity is inevitable. The ink color of the newly printed products is often thick, and then gradually fades. In this way, the ink delivery can be gradually increased by properly adjusting the rotation angle of the ink transfer iron roller, so as to keep the ink color basically consistent before and after printing. Analysis Of Influencing Factors Of Printing Color Difference

        When blending intermediate and multi-color inks, try to avoid mixing inks with large specific gravity difference, so as to avoid printing color difference caused by “stratification” (i.e. sedimentation and suspension) of ink in ink bucket due to large specific gravity difference. 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, in the printing process, after the ink amount in the ink bucket is significantly reduced,Analysis Of Influencing Factors Of Printing Color Difference

        it is easy to reduce the gap between the ink bucket steel sheet and the ink transfer iron roller, reduce the ink output and lighten the ink color of the print. In order to avoid this situation, we should also pay attention to adding ink to the ink bucket in production to keep a certain amount of ink in the ink bucket all the time. In order to prevent the ink viscosity variation from affecting the ink color balance of printed products, the contact between each rubber roller and iron roller should not be too tight, and the rubber roller should not be too hard, so as to minimize the impact of friction heat on ink thixotropy and reduce ink dilution.Analysis Of Influencing Factors Of Printing Color Difference

2、 Printing color difference caused by pressure discomfort

      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.Analysis Of Influencing Factors Of Printing Color Difference

       The ideal printing process is based on the “three leveling”, that is, the printing plate, substrate and lining surface are required to reach relatively flat conditions, so that a thinner ink layer can obtain a more uniform ink color on the printed matter by balancing the printing pressure. Analysis Of Influencing Factors Of Printing Color Difference

      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 printing plate inking. However, this will not only increase the ink consumption, but also easily lead to printing color difference and printing sticking quality problems. Analysis Of Influencing Factors Of Printing Color Difference

      Therefore, to prevent printing color difference, we should grasp the basic conditions of “three leveling” and print with uniform and constant pressure. If a large area of plate products are printed by relief process (using circular flattening or flat flattening machine), it is best to use metallic backing materials. In this way, the flatness and firmness of the materials are good, and the printing pressure is relatively stable, which is conducive to preventing the printing color difference caused by pressure variation.Analysis Of Influencing Factors Of Printing Color Difference

Printing color difference caused by poor three ink roller

       In lithography, letterpress and other printing processes, the quality of COTS plays a vital role in whether prints can obtain uniform ink color. The machine for printing color printing crystal is generally equipped with ink transfer roller, ink leveling roller and inking roller. Among them, the ink transfer rubber roller and inking roller have a great impact on the shade of ink. The elasticity, viscosity, center of circle, hardness and surface finish of ink roller largely determine the ink quality of printing. 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 to ensure that the ink coated on the layout is basically consistent in each printing cycle. If bulk products are printed, the cots shall be cleaned in time during printing to remove the paper dust and impurities remaining on the cots, so as to ensure the uniform transmission of ink and prevent the generation of printing color difference.

       On the other hand, the contact position between the ink roller and the inking iron roller should be adjusted. Generally, the automatic printing machine is equipped with several groups of inking devices to realize uniform inking.Analysis Of Influencing Factors Of Printing Color Difference

       However, if there is poor contact between the rubber roller and the ink string iron roller, it is bound to cause insufficient and uneven ink transfer, resulting in uneven ink color in the horizontal layout of the print. In this regard, the shaft heads at both ends of the rubber roller shall be adjusted to achieve uniform contact between the rubber roller and the iron roller. Analysis Of Influencing Factors Of Printing Color Difference

       After adjustment, the steel sheet of Sichuan 5 wire can be inserted between the rubber roller and the iron roller for pull-out inspection. When pulling the steel sheet, there shall be 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 can not get uniform and sufficient ink coating, and it is easy to produce printing bar marks due to the slippage of the inking roller in the layout.Analysis Of Influencing Factors Of Printing Color Difference

       If the inking roller is adjusted too low, the ink layer on the plate will be scraped to the trailing tip of the printing plate, resulting in the color difference between light in front and deep in the back of the printing ink, that is, the ink at the mouth is lighter and the ink at the trailing tip is thicker. 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 printing plate can we ensure the uniformity of printing crystal ink color.Analysis Of Influencing Factors Of Printing Color Difference