Analysis and treatment of common faults in PS vers

2022-08-24
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Analysis and treatment of common faults of positive PS version

positive PS version always has some faults in its plate making or printing process, which will affect normal production in serious cases. In order to promote production and improve production efficiency, improve plate making quality and printing quality, and reduce or avoid some common faults, it is very necessary to analyze and deal with them

failures of positive PS plate can be divided into failures in plate making and printing. Here are our experiences in these two aspects

I. common faults, causes and solutions in the process of plate making

1. the image is false

reasons: (1) poor vacuum performance of the plate printer: ① low voltage or vacuum pump motor running in phase failure. ② The vacuum pump leaks the moisture in the air due to excessive pumping, which causes the lubricating oil to emulsify, resulting in poor lubrication, thus reducing the vacuum degree. (2) Poor sealing of the plate printing room: ① there is a gap between the plate printing machine and the sealing rubber ring as a whole or locally. ② There are sundries on the sealing rubber ring, which makes the glass and rubber ring poorly combined. ① When printing, the paper or lining cloth under the plate is pressed on the sealing ring. (3) Insufficient film image density: ① short exposure time. ② The development time is short or the developer is aging. (4) Reverse film making: the film is reversed or not made according to the type of printing plate in the process of publishing or copying. (5) The bottom of the air chamber is uneven and the vacuum time is short. There is no absorption between the plate and the film when printing. (6) The developer concentration is inappropriate. (7) Development time is too long. (8) the company did not choose the developer correctly in order to seek a new breakthrough. (9) The character line on the page is not clear enough ① there are sundries between the film and the page when printing. ② When revising the version, it was too close to the picture and text or touched the picture and text when wiping the remaining dirt remover, causing part of the film to be repaired. (10) There are creases on the PS version, resulting in poor combination between the film and the layout. (11) The pasted pictures are different in thickness, not on the same plane, and the edges are too close to the text

treatment: (1) increase the voltage to accelerate and strengthen the pumping speed of the vacuum pump, and connect the open phase power supply to make it reach normal power. ② Regularly replace the lubricating oil of the vacuum pump. When selecting the lubricating oil, choose the one with strong water resistance and not easy to emulsify. Pay attention to check the vacuum time when printing. (2) During the tensile test, the force is uneven ① make appropriate adjustment, and the screws must be fixed tightly to avoid changes. ② When printing, you should check whether there are sundries on the sealing ring. After printing, you'd better cover it well to prevent sundries from entering. ③ When printing, the pad paper or pad must be placed in the middle, not too close to the side or pressed on the sealing ring. (3) ① the correct exposure time shall be given according to the film sensitivity, and the density after development shall be more than 3.0. ② Accurately grasp the development time, and the development should be uniform. The aging developer should be replaced in time. (4) When making film, pay attention to the front and back, distinguish the type of plate making, and make corresponding inspection when printing. (5) Flatten the bottom, and set the vacuum time according to the situation. In special cases, the double suction method can be used to improve the contact performance between the film and the PS version. (6) The components of developing solution should be properly proportioned, and tests should be carried out during development to determine the best concentration. (7) Develop in a certain or specific time, and deal with special cases. (8) The developer should be selected correctly. Weak alkali is generally selected for those below 60 seconds, and strong alkali is mostly selected for those above 60 seconds. (9) ① when printing, pay attention to check whether there are sundries on the film or the page. ② When wiping the remaining revision paste, you should wash it with water while scrubbing it to the non graphic place. (10) If there are serious creases, they should not be used or used after corresponding treatment. They should be prevented from being broken when they are taken and placed. (11) The pictures should not be superimposed too thick, and try to make them on the same plane. Even if they are uneven, they should also be far away from the pictures and texts

2. The layout is dirty

reasons: (L) incomplete development: ① short development time. ② Aging of developer. ③ Insufficient developer concentration. ④ The developer temperature is low, and it is not developed at normal temperature. (2) The photosensitive layer of PS plate is unevenly coated. (3) The glass of the plate printer is not cleaned. (4) The film and film base have dirty marks, and negative exposure is not used when printing. (5) The non graphic part of the original has high fog. (6) The transparent glue pasted when making up is too close to the image. (7) Water flushing is not complete. (8) There is wool on the edge of the film. (9) Centrifugally coated photosensitive film is easy to get dirty on four sides. (10) Caused by improper ink lifting. (11) There are leaks when gluing the layout. (12) Negative exposure is not used. (13) Insufficient exposure time. (14) There is dust on the lamp, which falls down during the printing process. (15) Dirty film caused by yellowing due to long storage time. (16) The normal power is not reached or the voltage is too low when printing. (17) Improper selection of PS version. (18) Caused by blocky or striped patterns on the layout

treatment: (L) ① secondary development method can be used, and a certain time is required during development. ② When changing the developer, it should be noted that the service cycle of the machine display is longer than that of the hand display, which cannot be changed. The hand display is mostly exposed to the air, so that the NaOH in the developer and the CO2 in the air are gradually decomposed and the efficacy is reduced. ③ There should be a proper proportioning concentration. If the proportioning is wrong, it should be measured with a concentration meter and verified with PS version test block before reuse. ④ Generally, the developer temperature is the best under the condition of 22 ℃ - 23 ℃. According to the formula provided by the manufacturer, attention should also be paid to the variation of temperature difference in winter and summer. For example, the developer temperature is easy to rise in summer and drop in winter. Pay attention to constant temperature. (2) When using, try to use a uniform film, which mostly occurs in the old PS version. (3) Check the light or lay white paper under the glass to highlight the dirty place, and wipe it with alcohol. (4) If the film base or film is dirty and cannot be treated again, the scattering film shall be used to remove the dirt. (5) Change the printing film or increase the printing time under allowable conditions. If the film is not fixed enough, it should be fixed again. Replace the aging fusing solution. (6) When pasting, it should be 1cm away. (7) Sufficient water should be used to wash the PS plate, so as to avoid the residual developer with resin particles in the sand mesh, which is easy to produce spots after the plate is dry. (8) Cut and deburr. If the edge of the film cutting tool is not sharp, it should be adjusted or replaced to avoid affecting the cutting quality. (9) Local exposure method shall be adopted to fully decompose the surrounding photosensitive film. (10) To correctly lift the ink, first apply a layer of resin, then apply the developing ink under the wetting condition of the layout, and wash away the remaining ink in time, scrape off the moisture, and then apply the gum liquid. (11) After gluing, it should be checked to eliminate omissions, so as not to cause dirty printing. (12) Under normal conditions, negative exposure is required for films that are not made as a whole. (13) Use the printing ladder or signal bar to determine the time. If it is not the same batch of PS plates or PS plates with different sensitivity, the first test point should be done instead of the test. (14) When the plate printer is out of service for a long time, the dirt on the lamp should be removed before printing. The dust can be fully dropped through several normal printing procedures. (15) Use 1g potassium cyanide and 100ml water to dilute the film with 1 part of stock solution and 4 parts of clean water. (16) After the lamp reaches the normal power, print the plate. If the voltage is not enough, adjust the voltage to make it reach the normal power. (17) When using, those with serious oxidation points should not be used. Even those with less serious oxidation points should be kept away from graphics and text. (18) It is used for screening and shall not be used on dot printing plates

3. Other faults

causes: (1) the picture and text are too shallow: ① overexposure. ② Overdevelopment. ③ The density of printing film is not enough. ④ The sand mesh of the layout is too coarse, which is easy to be damaged. (2) Pictures or dots disappear or become smaller: ① long exposure time. ② Negative exposure is used for the spot version of the whole assembly. ③ The density around some film characters or dots is low, and the pictures and texts become smaller after printing. ④ The film thickness of PS version is different. (3) Fat picture and text points: ① insufficient exposure. ② Insufficient development. (4) The layout color is abnormal: ① the printing plate is stored for too long. ② After development, it was exposed to strong light. (5) Color after abnormal baking: the baking time is not enough or the baking time is too long. (6) The base color is abnormal, and the base is unqualified

treatment: (L) ① use a ladder or signal bar to determine the exposure time. ② Different PS versions have different development time and conditions, and it is best to use the formula provided by the manufacturer. ③ Choose the printing plate with fine and sharp sand mesh, which is not easy to be damaged during development. (2) ① to determine the exposure time, the same batch of PS plates should be used for test in advance, and attention should be paid to the stability of light during printing. ② Negative exposure is generally not used in point printing plate drying. ③ The film output by old-fashioned Laser Phototypesetting often appears text and hair around the dot, which should be paid attention to when using. ④ When selecting printing plates, attention should be paid to the surface quality, and the choice should be made from the aspects of uniform film without spots, normal color, etc. (3) ① the exposure time shall be determined according to the printing plate situation, and attention shall be paid to some changing factors. ② When developing, you should know the type, degree of use, temperature conditions of the developer and the changes of other factors after development. For example, if the printing plate temperature is low in winter, it is easy to reduce the temperature of the developer. (4) ① it should not be used on point plates or high-end prints. If the time is long and the quality of the plates is poor, the plates should be replaced. ② After development, keep away from light or apply developing black ink. (5) Pay attention to the temperature and time when baking the plate. Generally, bake it for 6min-8min at a constant temperature of 230 ℃ - 250 ℃. It is normal if the plate is reddish brown after baking. (6) Pay attention to the quality of the plate base when selecting, especially the regenerated PS plate base. Some metal components are unqualified, and some plates have fluorescent color after development. Under this condition, the PS plate has very little printing resistance, generally at 1-2 thousand. Therefore, it is best not to use it when using it, so as not to affect the printing quality

II. Common faults, causes and solutions in the printing process

1. it is easy to paste the plate

reasons: (1) the sand mesh of the printing plate is unqualified, and the water retention is not good. (2) The quality of the base is poor. (3) The water roller is dirty. (4) The printing pressure is too high. (5) There is no adjustment of moisture for ink performance or paper performance. (6) The ink viscosity is too high. (7) The ink is too thin. (8) The water roller is improperly adjusted or the force acting on the layout is too small. (9) The ink transfer is too large, and the water supply is not available. (10) There are too many other additives in the ink. (11) The ink dries too fast

treatment: (1) select the ones with good sand mesh, especially the old PS version, and observe the sand mesh with a magnifying glass after plate making. (2) If the metal composition of the plate base is unqualified, the sand mesh is easily damaged during printing, so it is best to avoid using it. (3) Attention should be paid to cleaning the water roll, which should not be mistaken for other reasons. (4) Pressure is one of the factors that affect the ink balance. Generally, it is within the range of 0.10~0.15mm during printing. (5) The blue ink with large amount of water should be properly adjusted, and the black ink with small amount of water should be given less water. For paper with rough surface and large amount of wading, the water content should be appropriately increased; for paper with smooth surface and small amount of wading, the water content should be appropriately reduced. (6) The ink should have certain printability. The ink with high viscosity should be diluted. If it deteriorates due to improper storage, it should not be used. (7) During printing, the tension of ink should be stable and not too thin, and should be determined in combination with ink transfer, imprint gloss, graphic dot expansion, etc. (8) A printing press with two water rollers against the plate should generally be light at the top and heavy at the bottom, and the force between the water roller and the water roller should be less than

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