An Analysis of Frequently Asked Questions in the Printing Process and Printing Process of PS Plate (Part 2)

First, the common problems in printing and treatment methods

1. The image is hazy and blank is not clean. To solve this problem, the platen glass must first be kept clean. Wipe clean with alcohol and rub both sides. The transparency of work is not enough, the penetration of light will be affected, and the printed version will be blurred. If the film plate and glass plate are not tightly adhered to each other, it will also cause sun exposure.

Sometimes a film base is used for a long time. There are a lot of residual rubber left on the tape, the transparency will be affected, and the film and film base will not be attached so tightly. Therefore, the film base will need to be replaced after a long time. . In the case of imposition, if the two images overlap, the image will also be shammy. If the blanket is used for a long time, there will be aging, there will be a small amount of leakage in some of the edges, PS version and film will not stick tight, drying out of the graphic will be made false. If the machine takes a long time, it is necessary to check if the vacuum of the air pump is not 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 go from the middle to the surroundings, there will be local bubbles, and the PS plate will have a partial blur. This is to check the bottom plate.

2, PS version outlets are not true. To solve this problem, check on the film. The dots on the film used in the printing shall have sufficient darkness, and the dot structure on the printing plate shall be transferred to the printing plate, and the covered portion (net point) must not pass through the light, causing the photosensitive layer of the printing plate to be sensitive. Otherwise, the dots on the printing plate will not be solid, and the dots will fall when printing. The dot faints. We know that the dots are absolutely clear. The transition between the transparent plane and the cladding with high blackness is very steep. It is a sudden change, and the edges of the dots are actually rising. The darkness of the dot is the opposite, and the blackness increases slowly from the edge. So the dot produces an edge with a large or small slope.

Dizzy dots on printing plates cause color deviations due to their unstable performance, and it is often possible to see "small dots missing" on the printing plate. To solve this problem, the film before printing should undergo a rigorous inspection, and the dots should have sufficient darkness and sufficient clear edges.

3, can not reflect the subtle part of the work. For example, a hair filament, which is on the photo, becomes blurred on the plate. This is mainly due to the lack of exposure or the concentration of the syrup in the process of washing out the small part of the wash.

Second, the problems often appear in the version

After the print version, it will be processed. 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 plate will not be washed cleanly. If the concentration of the developer is not enough, the time for replenishing the developer is adjusted too long and the plate will be insufficiently developed.

The method to eliminate the above failure is to check the developer temperature and development time and adjust to reasonable data. When using the developer, the manufacturer will provide the proportion of the recipe and it will be done according to the proportion. But sometimes it can be thickened. The stencil machine should be repaired in time, replace the rubber roller, and regularly clean the crystals in the tank and the pipe wall. The specific method is: using oxalic acid to circulate the water in the plate processor and effectively remove the dirt, and at the same time, the brush roller on the machine must be cleaned and replaced if necessary. In addition, in addition to the dirty process, the operation is not careful, in addition to the lack of dirty fluid consumption, short liquid use time, in addition to dirty injection failure, in addition to dirty liquid used in the layout will cause the printing plate dirty.

During the gluing process, a low concentration of glue is used, and the non-graphical part of the oxidation phenomenon will cause the plate to be dirty. The solution to this problem is: in addition to the dirty note should be used after the cover tight; layout should be fully washed in addition to dirty, glue to increase the concentration of glue, plastic injection should be uniform; after the plastic plate, the layout of the length of the dry After printing.

Third, baking problems often appear in the edition

The film-forming agent of the positive-type PS plate photosensitive layer is made of cresol-home formaldehyde resin, which has been transformed from a linear shape into a bulk structure, which enhances the abrasion resistance of the graphic and text parts. Therefore, the roasting plate can increase the resistance to printing. However, there are often problems with baking in actual work.

The printing plate is not faithfully reflecting the original tone level, but the rubber track. The rubber track is often caused by improper protection of the scratching agent. The rubber track left by the high concentration of the protective agent or uneven grinding will harden on the printing plate after baking and will not dissolve in the developer. Ink absorption. In this case, a slightly thicker alkaline solution than normal developer can be used again.

In the roasting plate, the high temperature causes the PS plate to be deformed and bent. Scratching and squeezing are often performed during the feeding of the plate. When printing, the plate is dirty, and the miscellaneous agent can be removed when the screen is slightly damaged. Light red after baking. This light red color is due to a trace amount of photosensitive layer on the blank part of the plate, which has been changed after baking. If it is treated with developer, it will not get dirty. If the reddish remains on the plate after the treatment, it must be dirty. This condition can be treated with a dirt remover. Dark brown or dark brown after baking. Under normal circumstances, the photosensitive layer is reddish brown after baking. If the color is dark brown or dark brown, it indicates that the baking temperature is excessive or the time of the fine plate is too long. This version is over-baked version, any degree of photosensitive resin layer of carbonization, darkening and brittle, the result will reduce the PS version of the print resistance.

After the baking version was dark green. This type of printing indicates that the baking temperature is low or the time is short, the photosensitive resin is not completely polymerized, and the wear resistance, corrosion resistance, solvent resistance, and ink affinity are not maximized, and the second baking is possible. Edition for best results.

Dirty after PS version baking is a common fault. There are several reasons for this situation. Before the baking plate, the dust, impurities, and the scratches were not completely cleaned. These dirt will be firmly adsorbed on the plate after baking, causing the plate to be dirty; insufficient exposure or incomplete development will result in incomplete decomposition of the non-graphic part of the photosensitive resin, the ink will be dirty when printing; wipe protection agent Improperly dirty. PS version baking protection agent is easy to precipitate, after placing the solute precipitated to the bottom of the bottle, the back of the protective solution is poured out thin, with this kind of protective agent to wipe the version will cause the layout to protect the touch is too thin or have leaks, resulting in PS version Dirty. Therefore, before use, be sure to shake it evenly and throw it out for use. And wipe the protective agent must be rubbed evenly; wipe the middle of the stop and did not wipe the glue in time, after the boot, there is no water roller, and the first ink roller causes the layout to appear. A lot of ink road. If this ink channel is washed with gasoline, the surface is clean, and it will be dirty when it is turned on. In this case, you can use a clean cloth to add some of the pine oil and scrub it slowly. After the ink channel is completely dissolved, wash it clean with clean water. That is to say, the original and the original traces of the traces were not removed; the protective agent was poor in performance and the roasting plate was dirty. The quality of the protective agent used in the PS plate baking plate directly affects the quality of the baking plate. Many manufacturers are required to pay attention to whether the formulation is appropriate or not, whether the performance of the used drug is standard and whether the preparation method is appropriate. No matter which bad book goes wrong, it will lead to the problem of protective agent performance and cause no protective effect of the protective agent. In particular, when certain medicines are not available, and when they are replaced with drugs that are not commonly used, special attention must be paid to the quality of the protective agent. In order to prevent the loss of the plate, it can be tried first, and it can not be used, and it can be put into normal production after no problem. In order to obtain better printing quality, at the same time as belonging to the above, it is necessary to pay special attention to the control of the pH value of the fountain solution in the printing process to master the balance of ink and water.

Fourth, PS version in the printing process prone to problems

The task of the PS version is to transmit the graphic part as accurately as possible to the blanket. Graphic part of the hydrophilic, non-graphic part of the ink. But in reality there is no such ideal, there will be various issues related to the PS version. Let us cite some of them and discuss them.

1, the layout of non-graphic parts from the dirty, non-graphic part of the pro-ink. The reasons for the following points.

A. The chemical composition of the fountain solution is improperly configured and erodes the hydrophilic layer of the blank portion. This is done by replacing the dampening fluid with a dampening fluid that is properly configured according to the manufacturer's instructions. B. The roller sleeve of the plate roller is dirty or worn, damaging the blank surface. Treatment method: clean or replace the version of the water roller sleeve, wet wash can protect the printing plate. C. Inking too much during halftone printing causes the ink to spread, which eventually sensitizes the non-graphic area. Treatment method: Use thinner ink film for printing. D. Sand with sandpaper on the rubber blanket is retained, and the printing plate is worn. Filling ball measures: Clean the rubber cloth, change the paper; Add anti-accumulation 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 The product keeps the non-image area of ​​the printing plate clean while reducing the amount of water; in the BB printing, the pressure between the printing plate and the rubber fabric is reduced. If an impression cylinder is present, the pressure between the impression cylinder and the paper should be checked; if the build-up occurs mainly in the first printing unit, the amount of water should be increased to help clarify the squash on the paper. E, aluminum base oxidation. Oxidizes dirty and looks like a lot of clear dots or doughnut-shaped spots on the canal. It often appears in areas that have long been in contact with wet reel water rollers. Plates tend to oxidize if they are too slow to dry, or stored in moist places before development or during two printing runs. If the printing press breaks while the plate is not yet dry, the plate will also oxidize. Action: Follow the recommended plate handling procedure. Store plates in a dry place. During the plate making process, a cheesecloth is used to quickly dry the plate. In the printing process, such as parking, should rely on the printing roller to leave, open the empty car until the plate is dry. F. Incorrect working of the water roller and/or ink roller in the ink system, may cause the print to appear dirty in the circumferential or axial direction. Measures: Check the pressure of each roller in the ink system, cleanliness, geometric accuracy, and overall condition. G. Pre-exposure (grayed) occurs in the pre-printing stage of the plate. Measure: Store the 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. At this time, contact the ink manufacturer. I. Excessive dampening solution causes the imprinting to be snow flakes; the ink color appears solid in gray, and the color is dark on the ground; in the zoomed-in state, the unevenness in the field is found, filled with tiny white spots. Excessive fountain solution emulsifies in the ink. When the ink film is split, the water droplets are exposed, and these water droplets hinder the transfer of the ink to the paper. At this point to reduce the amount of water supply.

2, PS version of the text part of the wear and tear. There are two reasons: First, there are too many resins in the fountain solution; second, there is too much acid in the fountain solution. The solution is to re-allocate the fountain solution and check the pH.
3, the printing plate has white fiber. This is mainly due to the fact that the paper fluff is too much or that the roll fabric is peeled off. The method is to clear the printing plate.
4. The graphic part of the plate cannot be properly inked. There are two reasons: First, the printing plate graphic area has cured resin or repair solution, so only hydrophilic is not pro-ink; second is the accumulation of ink on the roller, plate and rubber cloth is too short or Immersed in water. The method is to wipe the plate with a damp cloth, reduce the amount of water, and protect the minimum amount of water needed to clean the non-graphical parts.
5, graphics loss. The reason is that the pressure of the blanket cylinder and 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 layer is too thick. Treatment method is to use phosphoric acid solution cleaning or cleaning with plate cleaner.
7. There are scratches on the plate. The reason is that the outer layer of the paper roll before the machine has a small sand, or small sand grains embedded in the surface of the printing roller. The processing method is to remove two or three layers of paper on the paper roll of the machine and clean the rubber roller.
8, the plate cracked. The PS version may have cracks along the bay line at the end of the edition or the end of the edition. There are two reasons: One may be the wrong size of the plate. Does not evenly cling to the drum body. This may be due to inaccurate bending, plate movement on the plate bending machine, or serious wear of the plate bending machine; the other is that the printing plate is not clean in the slits, and residual ink makes the printing plate not installed properly. The head or the end of the layout is under severe stress.

In summary, during the actual operation, in addition to paying attention to the basic operation of the printing process and the various factors affecting the quality of the printing plate, the PS plate plays an important role in printing. It is composed of a photosensitive layer and The base is composed of two parts. The photosensitive layer must have good oleophilicity. In the actual operation process, the PS plate should meet the following requirements: flat layout, uniform thickness, dimensional stability, not easily deformed