How to protect plates during storage and plate loading
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In the printing and printing process, the printing plate is affected by physical factors, chemical factors, process conditions and process operations, and the printing plate is well protected, which will reduce the printing durability, shorten the service life and affect the quality of the printed products.
In order to protect the plate when the plate is stored, the operator should pay attention to the following points:
1. Anti-oxidation. After the printing is completed, a layer of hydrophilic colloid (such as gum arabic) should be evenly applied on the plate in a timely manner, and the layout should be kept dry. If there is no protective layer, the layout is directly exposed to the air, the plate is easily oxidized, and the resulting oxide is lipophilic, making the plate dirty.
2. Anti-friction. When the plate is stored, the plate should face up. If the two plates are relatively overlapping, the layout should be facing inward and the two plates should be separated by a piece of paper to prevent mutual scratching.
3. Anti-photolysis. Must be stored under low light (preferably yellow). Under strong light such as incandescent lamps, photolysis occurs in the photosensitive layer.
4. Protect from moisture. The relative humidity of the air is large, which will cause electrochemical corrosion of the printing plate, and destroy the non-image part to change its hydrophilic and oleophobic performance. Moreover, the photosensitive film has a strong hygroscopic force and will naturally age and lower the sensitivity. The temperature is 20 ° 2 ° C, and the relative humidity is 60% - 65%.
5. Acid and alkali resistance. Most commonly used printing plates are made of zinc or aluminum. They react with acids and with bases.
6. Anti-horse print. When taking the plate, it should be handled gently, do not curl it arbitrarily, avoiding the horseshoe print, causing unevenness on the plate and damaging the graphic part.
In the process of the last edition, the following points should be noted when protecting the plates:
1. Prevent creases, horseshoe prints and scratches.
2. The liner under the plate should be flat to avoid uneven pressure.
3. When pulling the plate, all the plate screws must be loosened to prevent the plate from being deformed. Do not use excessive force to prevent the plate from tearing.
4. The plate screws must be tightened to prevent loosening and damage to the press and the plate.
When printing, protect the plate from the following aspects:
1. Properly control the pH of the dampening fluid. The wetting fluid is too acidic and will damage the hydrophilic salt layer. The acidity of the dampening solution should be reduced without affecting the stability of the blank portion.
2. Correctly adjust the pressure of the ink roller, the water roller and the plate cylinder. If the pressure is too large or too small, it will easily cause the printing plate to wear, resulting in poor ink retention and dirt.
3. Correctly adjust the pressure between the plate cylinder and the blanket cylinder.
4. Reasonably choose the material and thickness of the lining.
5. Control the amount of ink and water volume.