Analysis of the Causes of Print Offsets and Paste Versions in Printing
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1) Fountain solution pH. If the fountain solution acidity is too strong, it will erode the plateau grains, destroy the hydrophilic layer of the plate, and it is easy to make the plate image rubbed off during the press printing. The fountain solution has a pH of 5 or so.
2) Ink viscosity. If the viscosity of the ink during the offset printing process is too large, besides making the ink transfer difficult, it will also break the condition of the middle layer of the ink layer, so that the remaining ink layer of the plate will be insufficient. As a result, the graphic part of the printing plate will be exposed and worn. Off the plate.
3) Inking roller. After the ink roller is aged, the hydrophilic property is enhanced, the performance of the ink affinity is weakened, and the performance of ink transfer is poor. In the process of mechanical rolling, the “oil in water†type of ink is emulsified, resulting in the greasy printing plate and Graphic part is out of print. In addition, if the ink pressure on the plate is too small, there will not be enough ink layer on the printing plate surface, and the transmitted ink will be thin, and the graphic part will be abraded and intensified. If the pressure between the ink roller and the printing plate is too high, it will accelerate the wear of the printing plate graphic portion, causing the printing plate grain to be damaged, the blank portion of the printing plate to be dirty, and the graphic portion to send flowers to form a plate-down failure. .
2 Main Reasons for Producing Mashup
1) Add too much dry oil to the ink. Excessive dry oil addition will make the ink thicker, the ink layer on the printing plate will not be able to break from the middle, most of them remain on the plate to create a stack, under the pressure of the printing, the ink gradually thickens and expands resulting in paste version malfunction.
2) The viscosity of the ink is too small. Small-viscosity inks are easily emulsified, causing turbulence. The ink does not transfer graphic prints normally, causing ink rollers, plates, and blankets to gradually accumulate pigment particles in the ink. When the pigments accumulate to a certain thickness, they can cause pastes. The version of the failure occurred.
3) The ink is too fluid or the ink supply is too large.
4) Printing pressure is too high and the ink absorption of the paper is poor
5) Fountain solution pH. The dampening solution is too weak in acidity, and the hydrophilic layer is formed slowly. The inorganic salt layer or metal oxide film in the blank portion cannot be supplied and replenished in time, so that the hydrophilic oleophobicity of the blank portion is reduced and the paste is caused.
Source: Xinhua Printing Network Author: Wang Town