Analysis on the setting of exposure time in the pr

Generally speaking, there are three main factors that determine the quality of PS plate printing, including the quality of PS plate, 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

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 to closely attach to the PS version test strip, and carry out graded exposure (you can start from 80s, add 20s each time, divide into five times, until 160S). After unified normal development, find out the penetration 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, conduct graded exposure and normal development, and find out the exposure time of the level with complete bright and dark 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 100s)

in our 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 up of lines and text versions of sulfuric acid paper and polyester film base directly arranged by the computer. The exposure time is 12. The results show that when the connection temperature is lower than 840 ℃, the isothermal solidification of the liquid interlayer is not completed, and the residual interlayer can be observed; With the increase of bonding temperature, the atomic dispersion accelerates and the residual interlayer decreases gradually; At 870 ℃, the structure of the joint is all solid solution; When the connection temperature is 850 ℃, the connection joint has the highest shear strength, about 180mpa0s. 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 lack of 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 time for the monochrome layer dot plate to sun the wire anti swing rack plate 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 rot if it takes more time to print

1. The color layered version has a collage version with% flat, 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 ink color of the printed piece is enough, but the color of the field part is not enough. Insiders pointed out that in recent years, the color of the treatment and recycling of waste plastics is not enough, and the ink layer is not thick enough. If you increase the amount of oil and ink, the color of the field part is enough, but the color of the field part is not enough. If the printing time is appropriately increased, the point is narrowed, that is, the printing plate is shallower, making up for the gap that the starting point increases due to the large amount of ink in the field. The printing time is about 160S

VI. in the color layered version, there are both flat and field prints. This kind of printing version mainly depends on the flat middle part to determine the printing time. If only the field part is considered, the printing time will inevitably increase a lot, and the dot part below 10% will be rotten, resulting in failure to print

1. With% flat, the printing time is about 120s

2. With more than 30% flat, the printing time is about 140s

VII. Monochrome large field version with flat original. The exposure time is mainly determined by the visual level

1. With% flat, the printing time is about 120s

2. With% flat, the printing time is 150s

3. With% flat, the printing time is 250s

4. With more than 60% flat, the printing time is about 300s

VIII. For the anti white original with monochrome and large field but with text lines, because it is a large field, the amount of ink must be large during printing, so as to ensure that the ink color of the large field is sufficient. However, after the amount of ink is increased, the anti white part of the text lines is easy to paste. This kind of original mainly depends on the thickness of the lines in the anti white part, the size of the text and the thickness of the lines. The smaller the text is, the thinner the lines are, and the longer the exposure time is. Even put a patchwork film in the middle of the original PS version to print, so that the strokes of fine lines and small words become thicker, and it is not easy to lose the version when printing

1. For the 0.1mm line or No. 5 (grade 15) text in the anti white part, first place a 0.1mm thick mosaic film between the PS version and the original version, and then vacuum print. The printing time is about 300s

2. The anti white part is 0.2mm line, or No. 2 (level 32) text, and the printing time is 400s

3. The anti white part is 0.3mm lines or small initial number (level 50) text, and the printing time is about 300s

4. The anti white part is 0.4mm lines or larger than the initial text, and the printing time is about 250s

setting of secondary exposure time for dirt removal by using scattering film

if there are many scratches or small dirty spots (including tape prints) on the original or print glass that are difficult to remove, you can lay a scattering film on the print glass for secondary exposure, and use the scattering principle of scattering film on light to change direct light into scattered light, so that the original unexposed parts covered by scratches or dirty spots can be decomposed and exposed again, Achieve the purpose of dirt removal This is actually two exposures of the PS version. The first is a normal exposure, which we call the main exposure, and its time should be 4/5 of the standard exposure time; The second exposure is the exposure under the cover of scattering film, which is also called sub exposure. The sub exposure time should be half of the main exposure time Although this method can effectively remove dirty spots, we should also note that this secondary exposure will also lead to the reduction or even loss of spots, so this method should be used with caution

monitoring and calculation of exposure (time)

it is a relatively simple and reliable way to use the continuously adjustable transmission ladder to quantitatively detect the exposure by using its unequal light transmission at all levels. When printing, you only need to sun a 10 level continuously adjustable projection ladder with a grade difference of 0.15 to the outside of the original iron ore pellet pressure testing machine, which can also be used to test and analyze the mechanical properties of other metals, nonmetals and composite materials. After development, there are three exposure states: full white, full black and intermediate transition on the ladder. Compare this state with the reference exposure state: when the number of exposure stages is less than the reference stage, Indicates overexposure; When the insolation progression is more than the reference progression, it indicates that the exposure is insufficient; When the two are consistent, the exposure is appropriate

when overexposure or underexposure occurs and exceeds the range of exposure tolerance (meeting the allowable range of printing requirements), the correct exposure time can be calculated according to the following formula:

t - the adjusted exposure time

t1 - the predetermined exposure time during debugging

n0 - the penetration level of the standard exposure time

n1 - the printing level of the test exposure time

Δ D - gradient density

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