1. The difference between the proofing version and the computer version
In fact, for proofing and printing, two different sets of plates should be printed. For proofing, from the structure of the proofing machine itself, it is generally a platform type, the pressure of the proofing is smaller than the printing pressure, and the speed is also slower than the printing speed. At the same time, the increase in dots caused by proofing is small. When printing is required, between 2% and 3% of the dots are retained, and 98% of the dots cannot be pasted. For printing, due to the high printing pressure and fast speed, the printing ink is softer than the proofing ink (small viscosity), which is easy to cause the dot increase, and it can be increased to 30% to 40% at most, so the same version is used for proofing The effect is different from printing, and this contradiction has not been resolved for a long time. Therefore, when printing the printing plate, it is required to reserve 4% to 5% of the dots, and 96% of the dots are not blurred, leaving room for the dot expansion caused by printing, and the printed matter is easy to access the sample.
2. Lost ideas when printing
If dot loss occurs, you should first look at the degree of dot reduction on the film itself, such as whether 50% of the dots on the film are square, whether 4% to 5% of the dots are complete, etc. In short, check the quality of the phototypesetting film, and then judge based on it Whether the outlet is lost in the printing process. Loss of ideas often occurs due to problems with the printing operation, which is directly related to the exposure time, development time, temperature and concentration of the developer. Overexposure and excessive developer concentration will cause loss of the dots that should remain on the layout or thinner text strokes. Strictly speaking, the printing staff should control the exposure and development through the printing test strip and gray scale, and test their own test data.
3. The layout is false
Investigating the cause of the falsification of the printing plate may first be related to the printing film. If the film is overexposed when the film is output, it will cause the dots on the printing film to be falsified, and the printed version will naturally be falsified.
Judging from the operation of printing, it may be because the glass or film of the printing machine is attached with foreign objects or dirt; or the pad of the printing machine is not suitable; or the vacuum is not true, so that the film and the plate are tight Insufficient; improper printing film collage; before exposure (when punching) or after exposure to too strong light before development, etc., may cause the straight plate to become false; and the temperature of the developer is too high, the concentration is too high, and the development time is too long The excessive development caused by too much developer replenishment liquid is also the reason for the page layout to be ignorable.
At this time, the glass or film should be cleaned with a cleaning agent; the liner should be leveled; the tape is 3mm away from the image part and the film is close to the plate; in safe light, such as anti-fading fluorescent lamps and yellow lights 3. Fluorescent lamps equipped with safety lampshades are used for operation; for the problem of unsuitable development, the standard should be implemented.
4. Uneven development
Uneven development or poor development is often caused by the reduced activity of the developer. This is mainly reflected in several aspects: the developer is not replenished in a timely manner; the development time is too short; the temperature of the developer is too low; the rinse liquid flows back, etc., At this time, in addition to standardizing the development conditions, the developer should be replenished in a quantitative manner in a timely manner.
In addition, dirty spots or foreign objects on the plate material will also hinder the development, which requires the staff to regularly inspect the developing machine and the plate-making machine, and clean the machine in time.
5. The page is dirty
There are different situations of dirty pages and different causes. The layout is dirty and may be underexposed. There are two possibilities. One is that the transparency of the film is not good or the film is out of date and the haze is large. The second is that the exposure light source is used for too long and the phenomenon of aging occurs. If you encounter the first situation, you can only remake the film; if it is the problem of the exposure light source, you must borrow the gray ladder to adjust the exposure time appropriately, or directly replace the exposure light source. Of course, the poor development may also cause the plate to be dirty. At this time, it is necessary to check the specific cause of the poor development and adjust it to the standard conditions in time.
In production, sometimes spotted dirtiness is encountered. Analyzed, there are really many "culprits". For example, ①there are stains on the glass of the plate-making machine, and there are dust or stains on the film; ② when collage printing the film, the tape on the film leaves a tape mark on the plate surface after printing; ③ Blister adhesion causes poor development (developer spray holes are foamed due to clogging); ④ fingerprints are left on the plate surface due to unclean hands during the printing operation; ⑤ the protective glue is thin; ⑥ the protective glue is heavy before drying Stacked and stored, so that the plates stick together, and the protective adhesive layer peels off when taken; ⑦After making the plates, the plates are kept under high temperature and high humidity conditions.
It is necessary to "prescribe the right medicine" for different reasons. Among them, the stains caused by tape adhesive and tape marks are the most common. First of all, it must be prevented. When assembling, thin and clean transparent tape should be used as much as possible. If the tape adhesive is applied to the printing plate, it should be gently Wipe away and then develop. When printing, it is necessary to fully exhaust the air to minimize the air layer around the imposition tape and the original film, so as to minimize the possibility of light interference. If there are still tape marks on the surface after exposure, you need to manually remove the dirt with a stain remover or double exposure.
For other aspects of decontamination, decontamination can be done with a decontamination agent, a repair knife, a pumice stick, or exposure with a scattering film or decontamination cover.
6. Poor ink in the printing plate
If it is not due to the low sensitivity of the photoresist in the plate material, the ink should not be inked, and the reason should be found from the relationship between the inking force of the printing plate, the exposure time, and the concentration of the developer. If the exposure time is too long or the concentration of the developer is too large, it is easy for the printing plate to have poor inking power. Because the exposed photosensitive layer of the PS plate is not absolutely soluble or insoluble, but it is somewhere in between. If it is not well controlled, the photosensitive layer of the printing plate will be dissolved, and the ink should not be dissolved. The rate increases and the ink is poor. In addition, if â‘ protective glue does not meet the requirements, the glue solution is too thick, and the glue is unevenly applied by hand; â‘¡The drying temperature of the printing plate is too high or too low, resulting in poor ink absorption or poor film forming performance; â‘¢The printing plate contacts after coating The strong light; â‘£ After the plate is made, the printing plate is stored in the environment of high temperature and high humidity, which will cause the ink inking force to drop. At this time, the protective glue specified by the plate should be used, the glue should be appropriately diluted, and the drying temperature should be reasonably determined, which should generally be 60. C or so; after applying glue, it should be protected from light, and the plate-making plate should be stored in a qualified environment. If the printing plate is found to be poorly inked during the printing process, it should be checked whether there is too much glue in the fountain solution, or whether it is not washed with water after using the cleaning agent.
7. Reduced printing durability of printing plate
The main reason for the decline of the printing plate durability is the printing operation and printing. In terms of printing: ①run-out occurs before exposure or development; ② the density of the film is not high enough; ③ due to the high temperature and concentration of the developer, long development time or excessive replenishment causes excessive development; ④ there are strong acids, alkalis, organic solvents 〠Removal of dirt and other chemicals attached to the printing plate; ⑤ Too many times with the plate cleaning agent to wipe, etc., these will affect the durability of the printing plate. In printing, if the printing pressure is too large or the paper powder is too much, and the strong printing plate cleaning agent and roller cleaning agent are used in UV printing, it will inevitably cause a drop in printing resistance.
In particular, it should be pointed out that in order to prevent running out of light, for the ordinary PS version, yellow safety lights should be used to fully block harmful light.
8. The printed plate has a blue background
In production, a plate is printed out, whether it is due to the problem of pre-production of the plate material, or the matching conditions of exposure and development time of the printed version are not suitable, and the printed version has a blue background. The "secret" of the bottom blue lies in: â‘ When the plate is made, the sand is too coarse, and the current of electrolytic oxidation does not match; â‘¡ The exposure is insufficient or the concentration of the developer is not enough when printing, or the two conditions are not matched properly. The bottom blue phenomenon is a headache for many operators. If this problem occurs, more development will not work, and less development will not work. If you develop more, the dots to be retained will be reduced or lost; if you develop less, it will affect the entire layout. Under the conditions of moderate exposure and development, the bottom blue will be repaired after the film is displayed, but once it is repaired, there will be a watermark on the layout. After the watermark is removed, the machine will be printed on the machine, and the watermark will be around. If you want to get dirty, if you use the cleaning fluid to repair this circle of dirt, you will get another circle of dirt. If it is stuck in pictures, text or online, the printing plate will not be used at all. To solve this problem, it is necessary to apply a thin layer of glue before decontamination, and high-quality prints can not use this version.
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