1. Strictly put printing raw materials into storage. In particular, ensure the purchase of high-quality paper and high-quality PS version. For example, 52g/m2 is used for printing books and periodicals? For 60g/m2 of book paper, if the buyer is eager to buy inferior paper from an informal paper manufacturer, the technical indexes such as whiteness, evenness, smoothness, surface tension and sizing degree of the paper can't meet the printing requirements, and the paper surface is rough, with high ash content and many fine particles, which is easy to wear the photosensitive resin film of PS version and reduce the printing resistance of the printing plate. Therefore, in order to improve the printing resistance of offset printing plates, we must first start from the purchase channels of materials. Unqualified raw and auxiliary materials shall not enter the factory or be put into storage. At present, there are many brands in the printing materials market, and it is difficult to distinguish between true and false. When purchasing materials, printing enterprises should shop around to ensure quality and buy high-quality printing materials.
2. Master the correct exposure time of PS version. Pay special attention to exposure, do not overexpose, so as not to affect the printability of printing plates. Generally speaking, the four-color color separator requires that 3% of the small dots are not lost by the sun exposure, and 98% of the large dots are not pasted. The patterns, lines and words are clear, the tiny pictures and texts are not out of print, the writing is full and lively, and there is no shortage of pen and ink.
3. The concentration of 3.PS developer should be strictly controlled. When preparing the developer, it should be prepared in strict accordance with the manufacturer's instructions. The developer or developer powder, sodium hydroxide and water should be accurately measured by measuring instruments. Do not prepare or dilute the developer by experience or feeling. If the printing is overexposed, the high concentration alkaline solution of PS plate developer or the high water temperature will directly reduce the printing resistance of PS plate.
4. Improve the printing resistance of printing plate by baking PS plate. Many printers use baking to improve the printing resistance of books, periodicals, newspapers and other long-edition and large-print products, that is, after printing PS plates, they are cleaned, coated with baking liquid and baked in an open oven. (1) Before baking, be sure to clean up the dirt and dirty spots in the blank part of PS plate with revised paste, otherwise it will be difficult to remove the dirty spots after baking. (2) The towel coated with baking liquid is not clean, or the fiber on the towel falls off on the PS plate, which is also easy to get dirty. ③ The baking temperature is 200 ~ 220℃, and the baking time is generally around 10 ~ 15 minutes, which should not be too long. At the same time, the baking time should be determined according to the temperature resistance of PS photosensitive resin film. If the baked PS photosensitive film is light brown and reddish brown, like the mature color of plum, it means that the baked version is suitable; If the baking time is too long and the temperature is too high, the PS photosensitive resin film will be baked or the substrate will soften.
5. Before printing, check whether the film density is appropriate. The words, lines and patterns on sulfuric acid paper should be all black, and there is no shortage of strokes. If the blackness of large characters and wide lines is not enough, they should be re-output, or baked in an electric furnace to increase the blackness. When baking, it is necessary to prevent the sulfuric acid paper from wrinkling and affecting the suction of printed matter. Printing a large number of books, periodicals, trademarks, packaging and decoration products, whether film or sulfuric acid paper, the strokes and lines of words should be as thick as possible, which will be resistant to printing accordingly. The density and blackness can't meet the requirements, so we can't accommodate rework to ensure the printing resistance of PS plate.
6. The pressure of the water roller on the printing plate should not be too great. When debugging the pressure between the two water rollers and the printing plate, it is best not to use the officially printed printing plate, but to use the waste PS plate for debugging so as not to damage the printing plate. At the same time, the thickness of the lining paper in the printing plate cylinder should be appropriate. If the pressure of the water roller on the printing plate is too large, the graphic wear of the printing plate will also increase and the printing resistance will decrease.
7. Check whether there are folds, discounts, scraps of paper and small pieces of paper on the back of the printing plate when installing the printing plate. If this happens, please remove the lower plate and arrange the backing paper.
8. When the printing plate and the computer are used for revision, the residual revision paste is inadvertently coated on the photosensitive resin film in the graphic part of the PS plate, which plays a role in reducing the film and will also affect the printing resistance of the PS plate. In addition, the layout is dirty after the last edition, and the layout is often wiped with cloth moistened powder to remove dirt. However, when wiping the plate with wetting powder, do not use too much force or try for too long, otherwise the photosensitive resin film of the plate will not be resistant to printing after being wiped thin.
9. Use less pressure when printing. After the printing plate is mounted on the printing plate cylinder, the pressure between the printing plate cylinder and the rubber cylinder should not be too large, the thickness of PS plate liner should not exceed 0.65mm, and the thickness of rubber liner should not exceed 3.25~3.40mm (measured by micrometer). When installing a plate, it should be pressed tightly to prevent relative sliding during the operation of the offset press. In addition, the pressure between the inking roller, the dampening roller and the printing plate cylinder of the offset press is accurately adjusted and controlled to avoid the direct wear of the layout.
10. Strictly control the ink balance in the printing process. Pay attention to control the thickness of ink layer to avoid ink spreading to the blank part of printing plate. If the ink is too thick, the tiny particles such as pigment, adhesive and rubber in the ink will increase the friction on the printing plate and accelerate the wear of the printing plate. Only under the premise that the blank part of the printing plate does not stick to ink, the normal water supply is maintained and the layout is wetted with the least amount of water, so that the phenomena of paper deformation, ink emulsification, overprinter prohibition and ink dilution can be reduced. If there is too much water in the layout, the combination with weak acid bucket liquid (used to clean oil stains) will also corrode the printing plate. Maintain the balance of ink and wash, and avoid dirty, flowered and out-of-print caused by improper ink and wash.
1 1 to prevent the surface of the printing plate from oxidation. When the offset press stops halfway or has a lunch break, it must be coated with Arabic gum to prevent the printing plate from being exposed to the air for a long time, which will lead to the printing plate oxidation and reduce the printing resistance of the printing plate.
12, to prevent debris and page wear. Also pay attention to prevent the printing plate from being crushed by double sheets, multiple sheets and other sundries during paper transportation.