There is a trick to set the exposure time of the h

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There are tricks for the classification and setting of exposure time when printing PS plates

generally speaking, there are three main factors that determine the printing quality of PS plates: the quality of plates, exposure time, and development quality. Among them, the correct and reasonable control of exposure time is a key step to ensure the quality of printing. The correct control of exposure time can ensure that the printing plate points are bright and clean, the outline is clear, and the image and text copy is accurate. At the same time, it is also the key to avoid "hollow", "burr", "virtual edge" and other printing failures. If the exposure time is short, it will cause the loss of the dark tone level, the small white dots in the dark tone will be stuck, etc; If the exposure time is too long, it will lead to the loss of small dots, the lack of pen and drawing of thin line text, and the overall graphics and texts are shallow. In addition, reasonable control of exposure time can also make up for some deficiencies in the original and improve the print quality. This paper will analyze the exposure time of PS plate when printing through several different methods. 3) the setting of pen and paper on the installed automatic plotter: different brands and models of PS plates have different requirements for exposure time, and even plates of the same brand and model will differ due to different storage time. For the newly purchased PS version, it is best to use the test strip to test the standard exposure, and then determine different exposure times according to different prints to achieve standardized printing. There are many ways to test the exposure time. The following two commonly used ways are introduced:

first, the continuous ladder test method: use the continuous ladder closely attached to the test strip of PS version that can complete the change of plunger position within a few seconds, and carry out graded exposure (starting from 80s, adding 20s each time, divided into five times, until 160S). After unified normal development, find out the insolation level specified in the PS version instruction manual on the test strip, That is, the correct exposure of the version

II. Point ladder test method: attach the print test strip tightly to the PS version small test strip, carry out graded exposure and normal development, and find out the level of exposure time with complete bright and dark fading points, which is the best exposure time. In general, the positive PS version should be able to restore 2% - 97% of the dots. If there are less missing bright dots and more dead dark white dots, it indicates that the exposure time is insufficient; If more small black dots are lost and less small white dots die, it means that the exposure is excessive

determine different printing time according to different prints (assuming that the standard exposure time is loos if it is used by citizens in the epidemic area) In the daily printing work, the more common originals are sulfuric acid paper base and polyester film base; According to the types of pictures and texts, they can be divided into text line version, field color block version, line version, and line version also has different types, such as lithography, gradient version, layered version, etc; Some printing plates will mix several pictures and texts on the same printing plate at the same time, so the control of exposure time will be more complex

I. a large version made of lines and text versions of sulfuric acid paper and polyester film base directly produced by computer Phototypesetting. The exposure time is 120s. This exposure not only ensures that the text lines are intact, but also can be developed completely, but the edges of the film base and the traces of adhesive tape will still remain on the printing plate, so we must remove the dirt carefully. Some of the original text lines are not black enough, especially the horizontal lines of Song typeface are thin

too much printing time will lead to short lines and missing pictures; The pattern is not dark enough, the printing time is long, the PS plate loses luster after development, and the inking performance is poor during printing, which affects the printing quality

II. A large version made up of a photographic or copied line text version. The exposure time is about 250s. Because these original graphics and text density can reach 4.0, which is very dark. With the increase of exposure time, there is no obvious impact on the line text, but the film edge and tape trace of the original can be fully exposed. After development, the printing plate is very clean, and there is basically no need to remove dirt, which can improve the efficiency of printing

III. the printing time of monochrome layer dot printing is about 120s. The printing time of this kind of version should not be too long, especially to prevent 3% of the dots from disappearing due to too much printing time

IV. there are flat prints in the color layered version. 10% of the flat prints will appear rotten if the printing time is too long; More than 30% of the lithography will not be rotten if it takes a little more time. In the future, quality supervision and random inspection will mainly start from seven aspects

1. The color layered version has a 10-20% flat collage version, and the exposure time is about 120s

2. The color layered version has a collage version with more than 30% flat, and the exposure time is about 140s

v. in the color layered version, there is no flat, but there is a large field of title words or patterns. In the printing of this kind of edition, this kind of situation often occurs: the dot ink color of the printed piece is enough, but the color of the field part is not enough, and the ink layer is not thick enough. If the amount of ink is added, the color of the field part is enough, but the color of the dot part is insufficient. If the printing time is appropriately increased, the point is reduced, that is, the printing plate is shallower, which makes up for the gap that the starting point increases due to the large amount of ink on the site. The printing time is about 160S

source: Beijing keyin modern printing technology company

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