Talking about the pressure of flexographic printing
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Flexographic printing is a lighter, direct printing method known as "kissing" printing. Since the flexographic printing pressure is very small, the pressure will have a significant change in the quality of the print, so the control of the pressure is very important. Different models have different adjustment methods, such as "Black Bull" brand flexo press and Ajiafa flexo press adjustment are basically the same. Since pressure is the most sensitive issue in flexographic presses (unlike gravure, the quality of the print is not affected by stress), the operator of the flexo press should pay attention to the adjustment of the pressure during machine operation. When the general flexographic plate is finished, the entire plate thickness error should be within 0.015mm~0.02mm. The pressure during printing is greater, and the ink transferred to the substrate is more. Therefore, in order to ensure that the entire pattern portion can be uniformly inked without causing hairiness, paste, etc., the printing pressure, that is, the compression amount of the printing plate should be strictly limited to 0.1 mm (screen size 0.02 mm). If the pressure is too large, the text image will be crushed, the dots will be deformed and connected to each other, and it is prone to problems such as false or unprinted edges. The flexo is compressed by 0.01mm, and the embossing force is doubled (1~3kg/cm2). The increase of the dot value of the network cable version will cause the dark part of the whole dot to become solid, and the dot will appear hollow. Not clean. Due to changes in the level of the outlets, the color will be severely biased, so that the whole picture looks unclear and unclear, and the subtle level does not come out, the stereoscopic effect is not strong; the middle level is too much, the picture will be dark, the color reproduction will be poor, and the picture will be Bright and other issues seriously affect product quality. The field, lines, and text have edge effects and hard mouths. The imprints look uneven, the ink color is not thick, and the text pastes the plate, which results in the loss of the strong color of the letterpress printing and the clear peak of the writing. The size of the dots determines the tone reproducibility of the print. According to the principle of geometry, the dot gain is a uniform outward expansion of the edge portion. For different percentages of dots, the edge increase of each ratio is consistent. The outlets of the same area and different shapes have a larger expansion rate of the outlets under the conditions of the pressure. Therefore, the quality of flexographic printing is closely related to the operational adjustment pressure. The size of the printing embossing force should be adjusted to the point where the dot is not enlarged or the smallest, the edge effect and the hard mouth are not visible or inconspicuous, which is crucial. When adjusting the pressure, the pressure should be zero, and the pressure on both sides should be consistent (balance line and test strip should be made on both sides of the plate during plate making to ensure the pressure on both sides of the plate is consistent). The actual printing should be determined by the specific conditions of the layout. For example, the pressure should be relatively small when printing a fine screen version, and the pressure should be relatively large when printing a solid version. In addition, the adjustment of the pressure also includes the adjustment of the contact pressure between the surface of the anilox roller and the surface of the printing plate. When the pressure between the two is too large, the ink is squeezed from the surface of the plate to the periphery of the image portion. On the shoulder of the word, a paste is formed. At this time, even if the printing pressure is appropriate, the dot overlap phenomenon will inevitably occur on the printed product; if the pressure between the two is too small, the ink transfer will be affected. Be sure to use the “Plan” (small gauge) to carefully adjust each time you use a set of rollers. Under the condition of ensuring the printing pressure, the pressure between the printing plate and the anilox roller should be the thickness of the printing plate + the thickness of the double-sided adhesive -0.01mm, and the pressure between the printing plate and the substrate should be the thickness of the printing plate + double-sided adhesive Thickness + substrate thickness - about 0.01 mm to determine the above two pressures. When printing on the ground, to avoid excessive printing pressure, the gross image on the edge is generally not recognized by the naked eye. In the case where the gauge (the feeler gauge) is not measured, the paper of the substrate can be sandwiched between the printing plate and the impression cylinder, and then gently pulled, and can be pulled out after a little force. Basically, the pressure is more appropriate. The printing pressure is also related to the printing speed. The printing speed is fast, the contact time between the printing plate and the substrate is short, and the printing pressure should be appropriately increased. Otherwise, the printing pressure should be reduced. The pressure of the anilox roll and the plate roll is constant (0.02 mm to 0.03 mm), and the pressure of the plate roll and the roll is adjustable depending on the properties of the substrate.