Printing pressure control of the hottest flexo

2022-08-22
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Printing pressure control of flexography

flexography is a direct printing method with light pressure, which is called "kissing" printing. Because the pressure of flexographic printing is very small, and the magnitude of the pressure will significantly change the print quality, the control of the pressure is very important

different models have different adjustment methods. For example, the adjustment of "Heiniu" flexographic press is basically the same as that of yajiafa flexographic press

since pressure is the most sensitive problem in flexographic printing machine (unlike gravure printing, which is safe and reliable in actual use, and the printing quality is not affected by pressure), the operator of flexographic printing machine should pay attention to the adjustment of pressure during machine operation. Generally, when the flexible printing plate is finished, the thickness error of the whole printing plate should be controlled within 0.015mm ~ 0.02mm. When printing, the pressure is higher, and the printing plate transfers more ink to the substrate. Therefore, in order to ensure that the whole pattern part can be inked evenly without hairiness, plate pasting and other phenomena, the printing pressure, that is, the compression amount of the printing plate, should be strictly limited to 0.1mm (plate 0.02mm). If the pressure is too high, the text and image will collapse, point deformation and interconnection, which is prone to problems such as inaccuracy or pattern edge printing. When the flexo is compressed by 0.01mm, the embossing force will double (1 ~ 3kg/cm2), and the increase value of line plate points is serious, which will make the dark part of the whole plate points become solid, and the points appear hollow points, and the points are not bright and clean. Due to the change of point level, the color will be seriously biased, so that the whole picture looks unclear and unclear, the subtle level cannot come out, and the stereoscopic sense is not strong; If there are too many intermediate layers, the picture will be darker, the color restoration will be poor, and the color will be less bright, which will seriously affect the product quality. The edge effect and hard mouth appear in the field, lines and words, the impression looks uneven, the ink color is not thick, and the words are pasted, so that the characteristics of letterpress printing with rich color and clear writing peaks are lost

The size of the dot of

determines the tonal reproducibility of the printed matter

according to the principle of geometry, point increase means that the edge part expands evenly outward. Different percentage of points therefore compress the test piece; Results using the lodcell pneumatic sensor to connect the display to automatically display the pneumatic value, and the edge increase of each proportion is consistent. For points with the same area and different shapes, under certain pressure, the larger the circumference, the greater the point expansion rate

therefore, the quality of flexographic printing is closely related to the pressure of operation adjustment. The size of the printing force should be adjusted to the condition that the point does not expand or the expansion rate is the smallest, and the edge effect and hard mouth cannot be seen or obvious, which is very important. When adjusting the pressure, the pressure should change the material to the zero state of the testing machine, and the pressure on both sides should be consistent (during plate making, balance lines and test strips should be made on both sides of the plate to ensure that the pressure on both sides of the printing plate is consistent). The actual printing depends on the specific situation of the layout. For example, the pressure is relatively small when printing a fine line version, while the pressure is relatively large when printing a field version. In addition, the pressure adjustment also includes the adjustment of the contact pressure between the surface of the embossing roller and the surface of the printing plate. When the pressure between the two is too high, the ink will be squeezed from the surface of the plate to the surrounding of the image and text part, and stacked on the shoulder of the word to form a paste plate. At this time, even if the printing pressure is appropriate, there will inevitably be a phenomenon that the printing products are made by Jinan experimental machine factory as conscience products; On the contrary, if the pressure between the two is too small, it will affect the transmission of ink. Before using a set of plate rollers every time, be sure to use "plate gauge" (feeler gauge) to carefully adjust. Under the condition of ensuring the printing pressure, the pressure between the printing plate and the embossing 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 + the thickness of the double-sided adhesive + the thickness of the substrate - about 0.01mm, so as to determine the above two pressures. When printing on the spot, it is necessary to avoid excessive printing pressure. Generally, the ghosting on the edge cannot be recognized by the naked eye shall prevail

without measuring the plate gauge (feeler gauge), you can clamp the paper [encyclopedia] of the substrate between the printing plate and the embossing cylinder, and then gently pull it. When you can pull it out with a little force, the pressure is basically appropriate

the printing pressure is also related to the printing speed. The printing speed is fast, and the contact time between the printing plate and the substrate is short. The printing pressure should be appropriately increased, otherwise the printing pressure should be reduced

the pressure of the embossing roller and the printing plate roller is constant (0.02mm ~ 0.03mm), and the pressure of the printing plate roller and the printing plate roller is adjustable according to the performance of the substrate. (end)

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