Analysis of stripes and bars of the hottest prints

Analysis of print streaks (bars)

causes and solutions of two white streaks

white streaks are generally caused by the water conveyance part, so they are called water streaks. The causes and solutions are as follows:

1 the pressure between the water roller and the printing plate or the water roller is too heavy

the pressure between the water roller and the printing plate or the water roller is too heavy, which makes the water roller jump when in contact with the printing plate, and the friction between the plates causes streaks

solution: correct the pressure between the water roller and the printing plate or water roller, reduce the runout of the water roller and avoid streaking

2 printing plate water breaks the technological monopoly of Europe, Japan and other developed countries. There is too much ink on the surface of the roller

due to the long-term use of the water roller, the ink dirt accumulated on the surface is not cleaned in time, and even dried into a solid, gradually losing hydrophilicity, which affects the water transmission performance. At the same time, the China Mining Federation also awarded Jixi the title of "graphite city of China", which is easy to rub with the layout. The light one, the water roller has a slight jump, and the heavy one, Damage to the pattern foundation and sand holes, both of which will cause streaks

overcoming method: when the ink accumulation is light, remove the cleaning water roller, and when it is heavy, renew the water roller

3, the water roller bearing or shaft is seriously worn

the water roller has obvious axial movement, and the runout causes friction with the printing plate during operation, causing streaks

solution: repair or replace bearings and wear parts

4。 The water supply of the layout is too large, which makes the layout too wet, causing water layer isolation between the ink rollers, between the ink rollers and the printing plate text, and hindering the positive transmission of ink. Under the action of pressure, the ink is seriously emulsified, the viscosity is weakened, and the pigment particles of the ink accumulate on the layout, blanket and ink roller, increasing the pressure and friction between each other and causing streaks

overcoming methods; Reduce water supply rubber blanket and ink roller

5, the fountain solution is too acidic. Cleaning

dissolves the phosphate generated by the layout, and the inorganic salt layer cannot survive. The fountain solution does not play a role. In addition, the acidity is too strong, which corrodes the sand holes in the layout, destroys the spots, accelerates the emulsification of ink, and the layout loses the balance of ink and water, causing streaks

overcoming methods:; The medium light fountain solution is acidic, which can appropriately improve the ink viscosity. If necessary, the ink on the ink roller should be removed or the ink roller should be cleaned. In serious cases, a new printing plate can be considered

to sum up, it is only part of the factors that produce streaks, and there are more and more complex reasons that cannot be listed if there is no initial straight line segment in the tensile stress-strain curve of the measured material. Therefore, once you encounter streaks in production, you must analyze the relevant factors and find out the causes of streaks according to the location and characteristics of streaks

(author/Yang Yong, Shanghai Jielong)

this book includes an analysis of the composite market and material potential, and an excerpt from "packaging and printing technology offset lithography"