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What are the characteristics of the flexographic printing?
Dec 04, 2018

What are the characteristics of making flexographic plate?


(1) Compared with gravure and offset printing, the flexographic density curve is unstable, and the thickness variation of the printing plate has a great influence on the printing quality, which increases the difficulty of color printing of the flexographic printing plate.


(2) Flexographic printing uses anilox roller to transfer ink, and the plate mesh must match the number of lines of the anilox roller. Otherwise, the small spot of the high-light zone will be trapped and not printed, and the four-color version of the net will be printed. The angle cannot be 45°, otherwise it will be prone to moiré.


(3) Because the hardness of the flexographic plate is low, the image will be deformed after being squeezed, and the dot gain during printing is more serious. The general increase range is 16%~30%, the middle adjustment is up to 50%, and the 2%~3% dot is increased to 15% or even higher. Under the influence of the increase of the dot, the high-light level below 10% of the image printed by the flexographic printing is seriously lost, and more than 85% of the dark tone level becomes easy to become the ground.


(4) Because the pressure of flexographic printing is small, a slight change in pressure will cause a significant change in print quality, and control of the imprinting force becomes very important.


(5) The color separation parameters need to be reset, and the offset or gravure cannot be copied. At present, most of the machines imported in China are unit-type flexographic printing equipment, generally 6~8 units, plus the special color in the packaging industry. Therefore, the flexo printing should consider multi-color separation in the color separation to compensate for the printing Internet. Insufficient performance.


(6) Design a reasonable post-process. There are many flexo printing units, plus multi-line processing, which puts higher requirements on overprinting. Therefore, how to design post-processing at the same time becomes a big difficulty in flexographic printing.


 (7) The flexographic dot gain increases nonlinearly, ie the change is not proportional to the dot area. The offset dot gain is equidistant, while the flexo dot changes as follows: When the dot is very small, either the net (caused by the plate) or the dot increased to 15% or more (printed); In the dark part, the dot is very easy to become the field (printing and printing).


(8) Flexographic plate deformation and compensation channels. The most obvious feature of the flexographic plate is its elasticity. When it is mounted on the plate cylinder, the plate will have a bending deformation along the circumferential surface of the roller. This deformation will involve the graphic surface of the printing plate, so that the printed graphic will be printed. Deviation from the original. For prints with low quality requirements, it may not be considered, but for prints with higher quality requirements, measures must be taken to compensate for such dimensional changes. The following compensation methods are available: 1 In the design of the original, according to the plate Elongation, minus the corresponding value in the deformation size; 2 when shooting the film, using a deformed mirror to reduce the deformation size, 3 using computer plate, just before designing the ink separation, give a single zoom instruction 4, using the drum type printing method, that is, the drying plate cylinder and the plate cylinder are the same size.



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