Poor registration
Phenomenon: During wet-to-wet overprinting, the post-printed ink cannot be smoothly attached to the pre-printed ink.
reason
(1) Compared with the ink printed first, the ink printed later is too viscous.
(2) The initial printing ink fixes slowly, and the ink volume is large.
(3) The color intensity balance of the four-color ink is not suitable.
Approach
(1) Print with high-viscosity ink first, and then print with low-viscosity ink. A good viscosity requirement is that the overprinted colors should decrease in sequence.
(2) Using ink with fast color fixation, the printing is thinner when the density is high, and the pattern area is small, which is convenient for overprinting in the later stage. (3) The color intensity of any set of wet multi-color overprint inks is balanced, and the same amount of ink can be used for overprinting. If the same set of ink is used for printing, it should be handled properly.
crystallization
Phenomenon: When overprinting on dry base ink, it is possible that the back printing ink cannot be overprinted, even if it is barely printed, it is easy to wipe off the pool.
Reason: This is because the first printed ink contains too much desiccant, the ink dries too quickly, and the interval after printing is too long, forming a smooth hard film on the surface of the ink film, making the ink of the next color Difficult to ink.
Approach
(1) Reasonably grasp the interval time of overprinting, and print the next color of ink before the first printed toner is completely dry.
(2) Reduce the amount of desiccant in the ink and slow down the drying speed of the ink.
(3) If crystallization occurs, it can be remedied by printing resin adhesive or 05-90 gloss paste.
Dirty
Phenomenon: When the newly printed prints are stacked, the ink on the front side is dirty, and the prints on the back side overlap each other.
reason
(1) The fixing and drying speed of the ink is slow.
(2) Too much ink.
(3) The paper surface is relatively tight and slippery, and the absorption rate is poor. Ink does not penetrate quickly and set on paper.
Approach:
(1) Replace the quick-setting ink.
(2) Use high-concentration ink and use thin-layer printing.
(3) The surface should be powder sprayed.
(4) Add 59 anti-sticking agent or six powders to the ink.
pile of ink
Phenomenon: It means that the ink accumulates on the blanket, printing plate, and ink roller, and the ink transfer is poor, making the ink color of the printed piece blurred.
reason
(1) The ink is too short and lacks fluidity.
(2) The pigment content is high, the particles are coarse, the specific gravity is matched, and the grinding wetting is insufficient.
(3) The viscosity of the ink and the connecting material is low, and it is emulsified with the fountain solution.
(4) The paper powder falls off and mixes with the ink to make the ink short.
Approach
(1) Adding a resin binder with good water resistance can prolong the ink time.
(2) Use high-concentration pigments, appropriately reduce the amount of pigments and solid phase, and re-roll the ink.
(3) Minimize the amount of fountain solution, such as a large amount of waterproof ink.
(4) Appropriately add 05-92 debonding agent to reduce the viscosity. If the paper is invalid, replace it.
Dirty
Generally speaking, it refers to the dirt generated in non-graphics areas. It also includes printing aids, pasting, dots, and more. However, dirt can be divided into scum and oil. The specific description is as follows:
1. floating dirty
Phenomenon: Light-colored dirt is produced in the non-graphic area, because it does not stick to the printing plate, it is easy to wipe off.
reason
(1) The main reason is that the ink is relatively soft. After part of the ink is affected by the fountain solution, it enters into the fountain solution due to emulsification, forming a water-oil emulsion.
(2) The chemicals and wetting agents in the paper help to emulsify the ink. (3) The fountain solution contains soap or detergent that causes ink emulsification.
Approach
(1) Replace with high-viscosity thick and hard emulsion ink, or add high-viscosity varnish to the original ink.
(2) Change the paper.
(3) Adjust the composition and pH value of the dampening solution.
2. Oil pollution
Phenomenon: The non-graphic area of the printing plate becomes fat-sensitive, and the ink adheres to it, polluting the printed matter.
reason
(1) The ink is too soft and too thin.
(2) The ink supply is too large.
(3) There are free fatty acids, resin acids, surfactants and other substances in the ink.
(4) The influence of the processing agent in the pigment.
(5) The pressure of the inkjet roller and the blanket of the ink roller is too high, which damages the surface structure of the printing plate.
(6) Liposensitive substances are dissolved from the paper coating.
Approach
(1) Replace the ink or add high-viscosity resin oil (or No. 0 oil) and rubber oil to the original ink to make the ink viscous and elastic.
(2) Adjust the ink supply.
(3) Adjust the appropriate amount of dampening solution.
(4) Use fountain solution with high surface tension.
(5) Adjust the pressure appropriately.
(6) Change the paper.
