1. The structure of proofing machine is different from that of printing machine  Offset Proofing And Printing

       The proofing machine adopts the circular flattening printing method, while the printing machine adopts the circular flattening printing method;Offset Proofing And Printing 

      The water supply and ink supply mechanism on the proofing machine is far less perfect than that of the printing machine, so there will be a certain gap between proofing samples and printed products in terms of ink balance, dot reproduction, image level, etc.Offset Proofing And Printing

2. The printing process of proofing machine is different from that of printing machine

       Multicolor prints are printed continuously on the printing press, while on the proofing machine, they are printed intermittently, proofing one by one. Continuous printing determines that the printing machine prints by wet pressing, while the interval time of the proofing machine is long.Offset Proofing And Printing

       When one color is printed, the previous color is dry, so it is generally carried out by wet pressing. These two methods determine that the proofs and prints will have different printing effects.Offset Proofing And Printing

       For example, printing gold ink on the field may achieve the ideal effect when printing gold once during proofing. However, on the printing press, Offset Proofing And Printing

      arranging two or three units behind the field printing unit can not print gold proofing, so we must wait until the field color block is dry before printing gold. In addition, gold and silver cardboard prints cannot be polished online, otherwise the front imprint will be pulled out by polishing oil.

        There is no paper feeding and receiving process on the proofing machine, but there is on the printing machine. This leads to the problem that the imprint on the surface of gold and silver cardboard or printed products is scratched by the paper feeding mechanism, or the paper is too deformed to feed smoothly. Offset Proofing And Printing

       When receiving paper, if the ink layer is not dry, it will also cause the printed matter to be sticky and dirty, or the relative movement between sheets will cause the printed matter to be scratched, and the imprint on the back of the printed matter will be scratched by the suction wheel. Offset Proofing And Printing

      Therefore, powder spraying method is often used to prevent sticking and dirt when receiving paper. After powder can be sprayed, it may reduce the gloss and rough the surface of printing products; Offset Proofing And Printing

       Or in the second machine overprint, the back ink printing is not true; It may also bring hidden dangers to post processes (such as film coating, bronzing, etc.) due to excessive powder spraying.Offset Proofing And Printing

        Of course, sometimes the additives in the ink will also affect the printing effect. In addition, some paper is too thin and will roll into a ball after printing on the printing press.Offset Proofing And Printing

       Proofing machines usually print at low speed, while printing machines operate at high speed. Some samples need a very thick ink layer to achieve a certain effect, which can not be done in normal high-speed printing, and the too thin ink layer is difficult to control in high-speed printing.Offset Proofing And Printing

       The printing pressure of the printer is greater than that of the proofing machine. If the same paper can be used normally during proofing, there may be problems such as paper peeling on the printer.Offset Proofing And Printing

3. Other reasons

       Whether it is proofing on the proofing machine or printing on the printing machine, the paper will stretch to a certain extent, but its stretching amount is different. Offset Proofing And Printing

      Generally, when proofing on the proofing machine, the expansion rate is small, and when printing on the printing machine, the expansion rate is large. Offset Proofing And Printing

       Therefore, if multi-color overprint needs to be printed on the machine several times, during the second overprint, there may be obvious overprint inaccuracy due to paper deformation, and the paper deformation is irregular.Offset Proofing And Printing

       In multi-color printing, the ink prepared according to the proofing ink ratio often has a large color difference during printing. This may be because there are other color inks left on the ink roller during proofing. Offset Proofing And Printing

      Although these residual inks are few, they account for a large proportion of the little ink used for proofing. Therefore, the ink roller should be cleaned during proofing. Of course, sometimes different paper colors will also cause color difference.Offset Proofing And Printing

       The printing film used for proofing is generally single combination, while the printing film used for printing production is generally multi combination. Offset Proofing And Printing

     When the multi combination film is made of single combination film, there may be inaccurate overprint or even loss of dot, resulting in the deviation between the print and the sample.Offset Proofing And Printing

      When printing on the printer, we should also consider the pH value, additives (such as red and white drying oil, ink blending oil, etc.) and the use of drying device.Offset Proofing And Printing

      Therefore, the possible problems in printing production should be considered during proofing, and the problems existing in proofing should also be considered during printing, and appropriate adjustments should be made to make the products printed on the printer close to the samples printed on the proofing machine. Offset Proofing And Printing