Agenda Planner Spiral Notebooks A brief analysis of the classification and setting of exposure time in PS version

Agenda Planner Spiral Notebooks A brief analysis of the classification and setting of exposure time in PS version

Generally speaking, there are three main factors that determine the quality of PS plate printing: the quality of plate material, exposure time, and development quality. Among them, the correct and reasonable grasp of exposure time is a very key step to ensure the quality of the printing plate. The correct control of the exposure time can ensure that the printed plate dot is smooth, clear and accurate, and 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 darkening level, the small white spot in the darkening and other failures; If the exposure time is too long, it will lead to the loss of small dots, the lack of fine lines of text, and the overall text is light. In addition, reasonable control of exposure time can also make up for some shortcomings of the original and improve the quality of the printing.

This article will analyze the setting of exposure time when PS plate printing through several different methods: different brands and models of PS plate, the requirements for exposure time are different, and even the same brand of the same model plate will also be different due to the storage time. For the PS version just purchased, it is best to use the test strip to test the standard exposure amount, and then determine the different exposure time according to different printing pieces to achieve the standardized printing version.

There are many ways to test the exposure time, and the following two commonly used ways are introduced:

First, continuous ladder test method: Attach a continuous ladder to the PS version test strip for graded exposure (adding 20S each time from 80s, divided into five times, until 160s). After unified normal development, find out the exposure level on the test strip that is consistent with the PS version instruction manual, that is, the correct exposure amount for the version.

Second, the dot ladder test method: the printing test strip is closely attached to the PS version of the small test strip, graded exposure, normal development, to find out that the level of light and dark dot is more complete exposure time is the best exposure time. Under normal circumstances, the positive PS version should be able to restore 2%-97% of the dot, if the light point is lost less, the dark white point paste more dead, indicating that the exposure time is insufficient; If the small black spots are lost more, and the small white spots are burned to death less, it indicates overexposure.

Determine the different printing time according to the different printing parts (assuming that the standard exposure time is lOOs). In the daily printing work, the more common originals are sulphate paper based and polyester based; If according to the type of graphics, it can be divided into text line version, field color block version, network cable version, and network cable version also has different types, such as flat screen version, gradient version, hierarchical version, etc.;

Some plates will mix several images on the same plate at the same time, relatively speaking, the mastery of exposure time will be more complicated. First, a large collage of lines and texts based on sulphate paper and polyester sheet directly produced by computer phototypesting. The exposure time is 120S. This exposure ensures that the text lines are intact and can be developed thoroughly, but the edge of the film base and the traces of the tape paper will still remain on the printing plate, and it must be carefully removed. Some of the original text lines are not black enough, especially the horizontal lines of the Song style are rather thin. Print more time will be short line lack of painting; The pattern is not black 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.

(2) A large version collaged by a photographic or copied line text version. The exposure time is about 250S. Because, these original text density can reach 4.0, very black. The increase of exposure time has no obvious effect on the line text, but the original film edge and tape paper traces can be fully exposed, and the printing plate is very clean after development, basically no need to remove dirty, which can improve the efficiency of printing. Third, the printing time of monochrome layer dot plate is about 120s. This type of printing time can not be too much, in particular, to prevent 3% of small outlets from disappearing due to excessive printing time. Fourth, the color layer plate with flat screen printing, 10% flat screen plate, more time to print, there will be rotten net; More than 30% of the flat screen version, a little more time will not appear rotten network.

1, color layer version with 10-20% flat network collage large version, exposure time is about 120S;

2. The collage with more than 30% flat mesh in the color layer version, the exposure time is about 140S. Fifth, in the color layer version, there is no flat net, but there is a larger inscription or pattern of the field. In the printing of this type of plate, this situation often occurs: the dot ink color of the printed part is enough, but the color of the field part is not enough, the ink layer is not thick enough, if the amount of ink is increased, the color of the field part is enough, but the color of the dot is not enough. If the printing time is properly increased, the dot is reduced, that is, the printing version is lighter, and the gap caused by the increase of the dot due to the large amount of ink in the field is made up for some, and the printing time is about 160S.