1、 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. Bad 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. Bad 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. Bad 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 metal base pad material. In this way, the flatness and firmness of the material are good, and the printing pressure is relatively stable, which is conducive to preventing the printing color difference caused by pressure variation.Bad Factors Of Printing Color Difference

2、 Printing color difference caused by poor ink roller

       In lithography, letterpress and other printing processes, the quality of COTS plays a crucial role in whether prints can obtain uniform ink color. 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 great impact on the shade of ink.Bad Factors Of Printing Color Difference

       The elasticity, viscosity, center of circle, hardness and surface finish of ink roller largely determine the ink quality of printing. If the ink roller has poor elasticity, insufficient viscosity, eccentric roller body, hard colloid and poor colloid finish, it is easy to cause uneven or unstable ink brushing in the printing process, resulting in inconsistent printing ink color of each printing sheet. Bad Factors Of Printing Color Difference

       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 prevent paper dust remaining on the cots. Impurities can be removed to ensure the uniform origin of ink and prevent printing color difference.Bad Factors 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. Bad 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 printed matter. 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. Bad Factors Of Printing Color Difference

        After adjustment, 5-wire steel sheets can be inserted between the rubber roller and the iron roller for pull-out 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.Bad Factors Of Printing Color Difference

       If the ink roller is adjusted too high, the layout can not be uniform, sufficient ink coating amount, and it is easy to produce printing bar marks due to the slip of the ink roller in the layout. Bad Factors Of Printing Color Difference

        If the ink roller is adjusted too low, the ink layer on the plate will be dragged by the scraper plate, resulting in the color difference between light in front and deep in the back, that is, the ink at the mouth is light and the ink at the drag tip is thick. Bad Factors Of Printing Color Difference

      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 ink color.Bad Factors Of Printing Color Difference