1. Common problems and processing methods in printing

1. The image is hazy and the blank part is not clean. To solve this problem, the glass of the plate-making machine must be kept clean first. To clean it with alcohol, wipe both sides. The transparency of the work is not enough, the amount of light penetration will be affected, and the printed version will be blurred. If the film plate and glass plate are not tightly attached, it will also cause sun filter.

Sometimes a film base is used for a long time, and there is a lot of residual glue left on the tape paper, the transparency will be affected, and the film and the film base are not so tightly attached, so the film base will be replaced after a long time. . During imposition, if two images overlap, the image is also unrealistic. If the leather cloth is used for a long time, it will cause aging, there will be a small amount of air leakage at some edges, the PS version and the film will not stick tightly, and the pictures and photos will be false. If the machine is used for a long time, check if the vacuum of the air pump is enough.

If the lamp is used for too long, the cutting rate will decrease and the exposure will be insufficient. When inhaling, if you can't gradually walk from the middle to the surroundings, it will cause local bubbles, and the PS version will be partially blurred. This is to check the bottom pad.

2. The PS version of the outlet is not real. To solve this problem, check from the film. The dots on the film used for printing must have sufficient blackness. The dot structure on the printing plate should be transferred to the printing plate. The covered part (dots) must never be allowed to pass through the amount of light, causing the photosensitive layer of the printing plate to become photosensitive. Otherwise, the dots on the printing plate will not be solid, and the dots will fall off during printing. The dots are hazy, we know that the absolutely clear dots, the transition from the transparent plane to the cladding with high blackness is very steep, it is abrupt, and the edge of the dots actually rises vertically. In contrast, the halo dots, the blackness gradually increases from the edge. So the dots produce an edge with a larger or smaller slope.

Dummy virtual dots on the printing plate lead to color deviation due to their unstable performance, and it is often seen that "small dot loss" occurs on the printing plate. To solve this problem, the film before printing should be strictly inspected, and the dots should have sufficient blackness and clear edges.

3. Cannot reflect the subtle parts of the work. Like a strand of hair, there is in the photo, and the printing plate becomes blurred. This is mainly due to the lack of exposure or the excessive concentration of the potion when processing the plate, and the details are washed away.

Second, the problems that often occur in printing

After printing, the printing should be done. If the temperature of the developer in the plate processor is too low, the processing speed of the plate processor is too fast, the development time will be shortened, the development will be insufficient, and the printing plate will not be cleaned. If the concentration of the developer is insufficient, the time for replenishing the developer is adjusted too long, and the printing plate will be insufficiently developed.

The method to eliminate the above failure is to check the temperature and development time of the developer, and adjust to reasonable data. When using developer, the manufacturer will provide the ratio of the formula, and it will be done according to the ratio. But sometimes it can be more concentrated. The plate processor should be repaired in time, replace the rubber roller, and regularly clean the crystals in the tank and on the wall of the tube. The specific method is: use oxalic acid to circulate the water in the processor and effectively remove the dirt. At the same time, the brush roller on the machine should also be cleaned and replaced if necessary. In addition, in the process of decontamination, the operation is not careful, the amount of decontamination solution is insufficient, the use time is short, the decontamination note is invalid, and the dryness of the decontamination solution on the plate surface may cause the plate to be dirty.

During the gluing process, low concentration glue is used, and oxidation of non-graphic parts will cause the printing plate to become dirty. The solution to this kind of problem is: after decontamination, the cover should be tightly closed; after the plate is decontaminated, it should be fully washed, the glue concentration should be increased when glue is applied, and the glue injection should be uniform; After printing.

3. Problems that often occur in the baked version

The film-forming agent of the photosensitive layer of the positive-type PS plate is made of cresol-formaldehyde resin after baking, from linear to body structure, which enhances the abrasion resistance of the graphic part, so the baking plate can improve the printing resistance.

But in the actual work, some problems often occur in the baked version.

When printing, the printing plate does not faithfully reflect the tone level of the original version, but comes out of the glue. The glue track is often caused by improper wiping of the protective agent. The glue track left behind due to the high concentration of the protective agent or uneven wiping is hardened and fixed on the printing plate after baking, and is difficult to dissolve in the developing solution, resulting in failure. Blotting. In this case, it can be displayed again with a slightly stronger alkaline injection than the normal developer.

In the baking version, the high temperature causes the PS version to deform and bend. It often scratches and sends scratches when sending the version. It is dirty when printing. When the slight scratches are not bad, the graphic dots can be removed with a detergent. It is light red after baking. This light red color is caused by a small amount of photosensitive layer in the blank part of the layout, which is changed after baking. If it is treated with the developer, it will not get dirty. If the light red color remains on the plate after treatment, it must be dirty. This situation can be dealt with by decontamination agent. Dark brown or dark brown after baking. Normally, the photosensitive layer is reddish brown after baking. If the color is dark brown or dark brown, it means that the baking temperature is too high or the finishing time is too long. This type of plate is excessively baked, and the resin of the photosensitive layer has different degrees of carbonization, darkening and brittleness. As a result, it will reduce the print resistance of the PS plate.

It is dark green after baking. This type of color means that the baking temperature is low or the time is short, the photosensitive resin is not fully polymerized, and its abrasion resistance, corrosion resistance, solvent resistance and ink affinity are not maximized. At this time, a second baking can be performed Version to achieve the best results.

It is a common failure to get dirty after baking the PS version. There are several reasons for this situation. Dust, impurities, and dirt marks on the layout before baking are not completely cleaned in time. After being baked, these dirts will be firmly adsorbed on the plate surface, causing the printing plate to be dirty; underexposure or incomplete development will cause the non-graphic part of the photosensitive resin to decompose insufficiently, and will absorb the ink and stain on printing; wipe the protective agent Improperly dirty. The PS version of the roasted version of the protective agent is easy to precipitate. After being placed, the solute precipitates to the bottom of the bottle. The protective liquid poured over the back is thin. Wiping the plate with this protective agent will cause the plate protection to be too thin or leaking, which will cause the PS version. Dirty. Therefore, it must be shaken evenly before use, and should be poured out, and it must be wiped evenly when wiping the protective agent; the glue is not wiped off in time when the inkjet is stopped halfway, and the water roller is not placed after the machine is turned on, and the ink roller is dropped first, causing the layout A lot of ink. If the ink duct is cleaned with gasoline, the surface is clean, and it will be dirty after starting up. In this case, you can slowly scrub with a clean cloth and a little pine oil. After the ink duct is completely dissolved, then wash it with water in time. Immediately after restoration, there is no dirt; the performance of the protective agent is not good, and the baking version is dirty. The performance of the protective agent used in the PS version of the roasted version directly affects the quality of the roasted version. Many manufacturers make their own preparations and pay attention to whether the formula is suitable, whether the performance of the drugs used is standard, and whether the preparation method is appropriate. No matter what kind of bad book is faulty, it will lead to performance problems of the protective agent, causing the protective agent to play an unprotective role. Especially when certain medicines are not available and should be replaced with less commonly used medicines, special attention should be paid to the quality of the protective agent. In order to prevent the loss of plate materials, you can try it out first, without getting dirty, and then put it into normal production after there is no problem. In order to get a better printing quality, in addition to the above always, special attention should be paid to the control of the PH value of the fountain solution in the printing process to master the water-ink balance. [next]

Fourth, the problems that PS version is easy to appear in the printing process

The task of the PS version is to make the graphic parts as accurate as possible on the blanket. The graphic part is hydrophilic, and the non-graphic part is ink-friendly. But in fact there is no such ideal, there will be a variety of problems related to the PS version. Here are some and discuss.

1. The non-graphic part of the layout is dirty, that is, the non-graphic part is pro-ink. The reasons are as follows.

A. The chemical composition of the fountain solution is improperly configured, eroding the hydrophilic layer of the blank part. The treatment method is to replace the fountain solution and use the fountain solution that is correctly configured according to the manufacturer's instructions. B. The roller cover of the plate water roller is too dirty or worn and damages the blank surface. Treatment method: clean or replace the water roller cover by plate, wet cleaning can protect the printing plate. C. Excessive ink application during halftone printing causes the ink to expand, which eventually makes the non-graphic areas sensitized.

Treatment method: use thin ink film for printing. D. The sand grains on the rubber cloth remain, which abraded the printing plate. Ball-filling measures: clean the rubber cloth and replace the paper; add anti-stacking agent to the fountain solution; adjust the amount of water to the minimum, add more concentrate, gum arabic and / or alcohol or alcohol as needed Products, so that the non-graphic part of the printing plate is kept clean on the basis of reducing the amount of water; in BB printing, the pressure between the plate and the rubber cloth is reduced. If there is an impression cylinder, the pressure between the impression cylinder and the paper should be checked; if the accumulation mainly occurs in the first printing unit, the amount of water should be increased to help clear the fragments on the paper. E. Aluminum base plate oxidation. Oxidized and dirty, the canal looks like a lot of clear dots or doughnut-shaped spots. It often appears in the area that has been in contact with the wet plate water roller for a long time. If the printing plate dries too slowly, or is stored in a humid place before development or in two printing productions, it is prone to oxidation. If the printing press is interrupted while the printing plate is not yet dry, the printing plate will also oxidize. Action: Follow the recommended plate processing procedures. Plates should be stored in a dry place. In the process of plate making, use cheesecloth to make the printing plate dry quickly. If you stop during the printing process, you should leave the plate roller and drive the empty car until the plate is dry. F. Incorrect operation of the water roller and / or ink roller in the ink system may cause circumferential or axial dirty bars in printing. Measures: Check the pressure, cleanliness, geometric accuracy and overall status of each roller in the ink system. G. The printing plate is pre-exposed (grayed out) in the pre-press stage. Measures: Keep the printing plate in a light-proof box; install appropriate safety lighting equipment at the plate-making site. H. The ink is too soft or too oily. Contact the ink manufacturer at this time. I. Too much dampening solution causes the imprint to appear as flakes; the ink color is gray on the ground and the color is darkened on the ground; under magnification, the ground will be uneven and filled with tiny white spots. Too much fountain solution is emulsified in the ink. When the ink film splits, the water droplets are exposed. These water droplets hinder the transfer of the ink to the paper. At this time, reduce the water supply.

2. Part of the PS graphics and text is worn out. There are two reasons: first, too much resin in the fountain solution; second, too much acid in the fountain solution. The solution is to re-adjust the fountain solution and check the PH value.

3. There are white fibers on the printing plate. This is mainly caused by too much paper wool or shedding by the water roll fabric. The processing method is to clean up the printing plate.

4. The graphic part of the board cannot be properly inked. There are two reasons: one is that there is a cured product of resin or revision liquid in the graphic area of ​​the printing plate, so it is only hydrophilic and not ink-friendly; the other is that the accumulated ink filaments on the rubber roller, printing plate and rubber cloth are too short or Ink soaked in water. The method of treatment is to scrub the plate with a damp cloth to reduce the amount of water applied and protect the minimum amount of water required to clean the non-graphic parts.

5. Graphic loss. The reason is that the pressure of the blanket cylinder and the plate cylinder is too heavy. The processing method is to check the printing pressure.

6. The ink on the plate after baking is too slow. The reason is that the thermosetting adhesive layer is too thick. The treatment method is to clean with phosphoric acid solution or with plate cleaner.

7. There are scratches on the printing plate. The reason is that there are small sand particles in the outer layer before the paper roll is loaded on the machine, or the small sand particles are embedded on the surface of the plate ink roller. The processing method is to divide the paper roll on the machine and remove two or three layers of paper and clean the rubber roller.

8. The printing plate is cracked. In the PS version, there may be cracks in the head line or the tail line of the plate. There are two reasons: one possibility is that the installation size of the printing plate is wrong. Not evenly attached to the drum body. This may be due to inattention when bending the plate, the plate material moves on the bending machine, or the bending plate machine is very worn; the other is that the plate seam of the plate cylinder is not clean, and there are residual inks that make the plate not installed properly. The front or end of the page is heavily stressed.

PS plate plays an important role in printing, it is composed of photosensitive layer and plate base. The photosensitive layer should have good lipophilicity; the plate base is a blank part, and it should have good hydrophilicity. The PS version should meet the following requirements: the layout is flat, the thickness is uniform, the size is stable, it is not easy to deform, the surface is free of dirt, scratches and defects, the glue that can firmly adhere to the photosensitive layer and no chemical changes can occur, after surface treatment Good hydrophilicity and abrasion resistance, high printing resistance.

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