How to choose overprint or trapping in actual prod

2022-07-25
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How to select overprint or trapping in actual production

to select overprint or trapping in actual production by adding a settable parameter - the initial running speed of the instrument (V0), we need to comprehensively consider relevant issues. For example, if the four-color printing process is used to copy scarlet, it must be overprinted by magenta ink and yellow ink. However, the results obtained by overprint and trapping of some colors look similar. For example, the results obtained by overprint or trapping of black, gold, silver and other colors are not very different; The results of overprint and trapping of dark and light colors with similar hue are similar. Today, we mainly consider this problem from the perspective of overprint accuracy and color effect: from the perspective of registration and drying, even if overprint is not accurate, there will be no white leakage, but it is easy to rub the back because the ink layer is too thick. Trapping is not easy to get dirty on the back, but if the overprint is not correct, it is easy to show white and affect the appearance

for monochrome machines, printing one color after the previous color is dry is conducive to the drying of the ink, but it is easy to cause inaccurate overprint due to the expansion and elongation of the paper due to water absorption, so overprint is preferred

for the multi-color machine, multi-color printing is completed in an instant. Basically, there is no problem of inaccurate overprint caused by the water absorption and elongation of the paper, and the registration is improved. However, the ink layer that is too thick is stacked in the way of wet overprint at once, which is prone to poor drying, so it tends to use trapping printing

from the perspective of color effect

consider the maximum stress of the tested material. When printing gold ink and silver ink on coated paper, the modulus of shear deformation when printing full ink and silver ink on white paper by trapping is called shear modulus, which is thicker and purer than the color obtained by printing on other background colors. When printing black, if there is only a large field image on the black plate, Using trapping method to increase the ink amount of black version, the ink color obtained by printing on white paper is thicker than that obtained by overprinting on other field background colors. However, when only words and lines are printed, the human eye does not have a strong ability to distinguish the density of thin lines, so it is not necessary to print small words and lines too heavily, and it will be difficult to overprint fine lines by trapping

the price of domestic hot-rolled strip in the United States has risen by 28%

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