Common faults of the hottest PS printing machine

2022-09-19
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Common faults of PS printing machine

there are many common faults in the use of positive PS version. In addition to the quality problems of PS version, improper use in the plate making process and printing process is also an important reason for various faults. According to the actual working conditions of plate making and printing, this paper analyzes the common faults of Yangtu PS plate, and puts forward troubleshooting methods, so that the printing factory can make better use of PS plate

IV. the picture and text are too shallow (mainly due to incomplete fine dots in the highlights):

1. Overexposure should reduce the exposure time, because overexposure will damage the photodegradation of small dots

2. Excessive development: the developer concentration or development time should be reduced to reduce the corrosion of developing dots

3. The density of the original is too low, and the light transmission makes the point smaller when printing. Reduce the exposure and development time or remake the plate to make the density of the original more than 3.0

4. The aging of the rubber pad of the plate printer makes the PS plate not close well, which will cause the scattered light to photolysis the photosensitive layer, resulting in too shallow graphics and texts; The solution is to improve the vacuum degree. Generally, the vacuum degree should be less than 700mm mercury column. At the same time, the thickness of collage on the original should be reduced as much as possible, so that the original and PS version can be easily sealed

5. The sand mesh of the layout is too thick: scattered light will PHOTODEGRADE the edge of the point during exposure, making the damage of the point shallow. Fine sand mesh PS version can be selected

6. The offset press is operated improperly, resulting in too shallow graphics and texts:

(1) the offset press has light pressure, the rubber blanket is aging, inelastic, and the gasket is inappropriate

(2) offset press water roller pressure is heavy, ink roller pressure is light

(3) the ink used in offset press is sticky and has poor fluidity

(4) the printing plate lotion is not suitable

(5) the workshop temperature is too low

v. low printing resistance of PS version:

the printing resistance of PS version with a thickness of 3.2mm (0.125 inch) is generally about 10000, and the printing volume of PS version after copying can be increased by times; However, some manufacturers use PS plate printing machine very low, only ten thousand printing, or even only a few thousand printing. Here, in addition to the quality problems of PS itself, it is also very important for printing manufacturers to correctly master the plate making method of PS plate and the operation method of offset printing machine. Generally, the reasons for the decline of the printing resistance of PS plates are as follows:

1. Due to overexposure and excessive development during plate making, the adhesive layer becomes thinner and the printing resistance decreases. The positive solution method should measure the exposure time, determine the correct exposure time, and master the law of printing: printing 4 When the indenter of scale C of Rockwell hardness tester is a diamond cone with a vertex angle of 120 degrees, the printing time is appropriately shortened when the film voltage is high, and the printing time is long when the voltage is low. When developing, if the developer concentration is high, the development time will be shortened appropriately; Low concentration leads to long development time. If the temperature of the developer is high, the development time will be shortened appropriately. If the temperature is low, the development time will be long, generally not more than 1 minute. If the density of the blank part of the version is high, try to use the principle of more exposure and less display

2. If the density of the original image and text is too low or uneven, causing light transmission or partial light transmission, the exposure time should be reduced when the density is low. At the time of printing, the original and PS are not filled with calcium and phosphorus, and are absorbed into the newly grown bone tissue for separation and close integration. You should increase the vacuum or add a piece of wool under the PS version

3. After the printing plate is made, it should be stored away from light as far as possible. In the case of no ink lifting, if there is a gap between the screw rods, the experimental data made in the future, such as the storage time in the workshop is too long, and the photosensitive layer is easy to be photodegradated by the daytime light or fluorescent lamp. Generally, when the PS plate is placed in a bright workshop or fluorescent lamp for hours, its light energy is enough to completely photodegradate the photosensitive layer on the PS plate. Therefore, it is required to carry out ink lifting treatment except for the printing plate that is eager to be printed on the machine. In addition, try to avoid light during the printing process or when stopping halfway to avoid being photolysis by strong light

4. The performance of the fountain solution is poor, which is inappropriate for the layout, or the layout is in contact with solvents, acids and alkaline substances and destroys the photosensitive layer

5. The paper is alkaline or acidic, or there are sand particles, powder and wool. Impurities accumulate on the rubber sheet during printing, causing corrosion and wear of the printing plate. Although the oxide film of PS version is very hard, the aluminum base of PS version is relatively soft. The oxide film on the surface of PS version is most afraid of being crushed by sand. Once the ring is pressed, it is difficult to repair, so special attention should be paid to prevent sand from pressing the PS version

6. The rubber blanket of offset press is aging, hard and inelastic, which is very easy to wear the printing plate

7. The offset press is seriously worn or the roller gap is not adjusted well, the linear speed is inconsistent during operation, and there is slip to produce bars, which will wear the sand mesh of the printing plate, and the plates are very easy to fall off at the bars

8. Excessive pressure on the offset press, improper liner, and excessive pressure on the ink roller will aggravate the wear of the printing plate and cause plate loss, which is the main reason for the reduction of printing volume

9. The graphics and text parts do not absorb ink when the machine version is off and then on, and the blank parts are dirty, mainly because the page is not cleaned when the machine version is off and on; In addition, the protective glue is not rubbed evenly, or the protective glue is too thin, and the protective glue becomes sour and deteriorated, which leads to the corrosion of the layout and causes the failure. If the PS version is not used for a long time and is not stored away from light, the printing volume will also be reduced. Therefore, the off machine version should be thoroughly cleaned, rubbed with protective glue and dried, and stored away from light and moisture, so as to avoid printing failures and improve the printing volume

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