Talking about the printing pressure of flexo

Flexo printing is a direct printing method with less pressure and is called "light kiss" printing. Since the flexographic printing pressure is very small, the pressure will have a significant change in the quality of the print, so the pressure control is very important.

Different models have different adjustment methods, such as "Black Bull" brand flexo printing machine and Akai hair flexo printing machine adjustment is basically the same.

Since pressure is the most sensitive issue in flexographic printing presses (unlike gravure, the print quality is not affected by pressure), the operator of the flexographic printing press must pay attention to the pressure adjustment during the operation of the machine. When the general flexographic printing plate is finished, the entire plate thickness error should be within 0.015mm to 0.02mm. Larger pressure during printing, printing plate transfer to the substrate more ink. Therefore, in order to ensure that the entire part of the pattern can be evenly inked, without hairiness, stencil, etc., the printing pressure, ie, the compression of the printing plate, should be strictly limited within 0.1 mm (screen 0.02 mm). If the pressure is too great, the text image will appear crumbling and the dots will be deformed and connected to each other. This may cause problems such as false appearances or inaccurate printing on the edge of the pattern. The flexographic plate is compressed by 0.01mm, and the embossing force is doubled (1~3kg/cm2). The network cable version has a large increase in the dot value, which will cause the dark tone of the entire screen dot to be ground, and the dots will appear hollow. Not clean. Due to changes in the network level, serious color cast will appear, causing the entire screen to look unclear and unclear. The subtle levels will not come out and the three-dimensional effect will not be strong; the middle level will cause the screen to be dark and the color reproduction will be poor. Brightness and other issues seriously affect product quality. In the field, lines, and texts, there are edge effects, hard mouths, and the imprints look unfair, the ink is not thick, and the text is stenciled, resulting in the loss of the color of the letterpress printing and the sharpness of the text.

The size of the outlet determines the reproducibility of the print.

According to the principle of geometry, the dot gain is a uniform outward expansion of the edge portion. With different percentages of outlets, the increase in the margin of each ratio is the same. For the same area and different shapes of the outlets, under certain conditions of pressure, the larger the perimeter, the larger the outlet expansion rate.

Therefore, the quality of flexographic printing is closely related to the adjustment pressure. The size of the print embossing force should be adjusted to the point where the dot is not enlarged or the expansion rate is the minimum, and the edge effect and the hard-edged state are invisible or inconspicuous, which is crucial. When adjusting the pressure, the pressure should be zero, and the pressure on both sides should be consistent (balance lines and test strips must be made on both sides of the plate at the time of plate making to ensure that the pressure on both sides of the plate is consistent). The actual printing should be based on the specific circumstances of the layout, such as printing a fine screen version of the pressure to be relatively small, and the pressure to print the field version to be relatively large. 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 great, the ink will be squeezed from the surface of the printing plate to the periphery of the graphic portion and accumulated. On the shoulder of the word, a stencil is formed. Even if the printing pressure is appropriate, the splicing phenomenon of the stencil will inevitably occur on the printed matter. On the other hand, if the pressure between the two is too small, the transfer of ink will be affected. Always use "plate gauges" (feel gauges) carefully adjusted before using each plate roller. Under the condition of ensuring the combined pressure of the printing, the pressure between the printing plate and the anilox roller should be the thickness of the printing plate + the thickness of the double-sided tape - 0.01 mm. The pressure between the printing plate and the substrate should be the thickness of the printing plate + the double-sided adhesive. Thickness + substrate thickness - about 0.01mm to determine the above two pressures. When printing in the field, it is necessary to avoid excessive pressure on the printing, and it is generally impossible to distinguish the ghosts on the edges by the naked eye.

Without measuring the gauge, the paper of the substrate can be sandwiched between the plate and the impression cylinder, and then gently pulled, and it can be pulled out after a little force. Basically speaking, stress is more 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, and the printing pressure should be appropriately increased. Otherwise, the printing pressure should be reduced.

The pressure of the anilox roller and the plate roller is constant (0.02mm~0.03mm). The pressure of the plate roller and the printing roller can be adjusted according to the different properties of the substrate.