Causes and solutions for the generation of wire in the process of plastic printing
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In the process of plastic gravure printing, there is often a knife phenomenon. The reasons for this are very complicated, involving plate making, ink, squeegee and environment. Now it is analyzed and discussed for peer reference.
1 plate aspect
The surface finish and hardness of the chrome plate on the plate will have an important influence on the generation of the wire. The pigment of the ink used for the gravure printing is generally dispersed in the binder in a particulate state. During the printing process, after the ink is filled with the mesh, the excess ink is scraped off by the doctor blade while continuously rubbing the surface of the printing plate. If the chrome plating on the surface of the printing plate is not sufficiently hard, it is easily scratched by the coarse particle ink to produce a knife wire.
On the other hand, if the plate cylinder polishing process is poor at the time of plate making, the layout has fine throwing or the pattern is too deep. During the printing process, the ink will remain there and cannot be scraped off by the doctor blade, and transferred onto the printing material. Will produce irregular, very thin blades. Therefore, special polishing equipment and special polishing sandpaper should be used for polishing.
In addition, the drum processing precision and installation accuracy should be strictly controlled to prevent the eccentricity from exceeding the standard, so as to avoid the impact on the squeegee during high-speed printing to generate the cutter wire.
2 ink aspects
If the ink used for the gravure printing of plastic is not fine enough, the pigment particles are too large or mixed with particulate impurities, the occurrence of the knife wire will be caused. Therefore, a better quality ink should be selected, and the pigment particles should be less than 10 μm. Filtration devices should be added to the inking system and often inspected to avoid coarse particles in the ink from damaging the plates and the squeegee. If the viscosity of the ink is too large and the drying is too fast, the relative friction between the plate cylinder and the doctor blade will be increased, making it difficult for the doctor blade to scrape off excess ink on the plate to form a wire. Therefore, the viscosity of the ink should be controlled. For inks that are too fast to dry, use a slow drying solvent or dilute the ink.
In addition, if the ink dilution is not standardized, the use of an incompatible solvent causes the pigment in the ink to precipitate, forming large particles, thereby producing a wire. Therefore, a solvent that matches the gravure ink should be selected. If the antistatic performance of the ink is poor, or the lubricating performance is poor, it will also lead to the occurrence of the wire phenomenon. Therefore, it is necessary to strictly control whether the quality indicators of the inspection ink are analyzed.