Some problems in the hottest screen printing II

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Some problems in plate printing (2)

the film surface with silver halide attached is the front, and the shiny side of the film base is the reverse. When printing, the film surface of the film should be closely bonded with the emulsion surface of the plate, leaving the biting line for exposure. The exposure time shall be determined according to the type of photosensitive thorns, the coating thickness of photosensitive film, the blackness of positive pictures and printing requirements. The thicker the coating layer of the photosensitive film, the longer the exposure time is required, so that the plate film can be completely cured. If the image and text on the positive image are not black enough, that is, gray but not black, the exposure time should be shortened, and the development time should be extended accordingly by using the surface Rockwell hardness tester, so as to make the non photosensitive image and text completely transparent

after development, sponge or clean paper with strong water absorption is needed to quickly remove the water on the surface of the plate for hot air or natural drying. If the heating temperature is too high during drying, the image on the printing plate will produce errors to varying degrees or cause the plate to relax, affecting the overprint accuracy during printing

in order to strengthen the plate stock, improve the water resistance and solvent resistance, and prevent ink leakage at the junction of the silk and the plate frame during printing, you can wrap and reinforce the image and text edges with wide tape paper, and block the bonding place, the pinholes and unnecessary openings on the plate with sealant or photosensitive emulsion. For small stains on the pattern and a little photosensitive glue left, you can press it with wide adhesive tape, gently wipe it with cyclohexanone or alcohol, or gently tap it with a small needle to keep the version transparent. But the action is straight and gentle. If the action is too large, it will damage the version

IV. printing

in most manufacturers, plate printing is not completed by one person, but by many people working together. Only when the previous process is responsible for the next process, do a good job in self inspection and self inspection of their respective processes, and strictly control the quality, can we produce printed matter that users are satisfied with. The perfect match between plate, ink and printing is the prerequisite to obtain good printing. The quality of printing plate directly determines the quality of printing products. Printing is only the inspection of plate making quality. However, on the premise of stable printing plate quality, due to the carelessness of printing workers, ideal printing products cannot be obtained, which will cause greater waste and defective products or waste products

before batch printing, fix the printing plate first, pour in ink for trial printing, and check the level of graphic reproduction, ink color, thickness of ink layer, specification, registration accuracy, etc. If the registration accuracy is poor, it can be adjusted according to the fine-tuning knob in front of the frame; If the color of the ink is wrong, check whether the wrong ink is used and replace it immediately; If the inking is poor, solvent can be used to wipe the image and text part of the printing plate, so that the permeability of the ink and the wettability of the substrate can be improved to a certain extent; If there is a big difference in the order and level of graphics and texts, the printed version should be replaced immediately. The following points must be paid attention to in the printing process

(1) watch the rules frequently. As the plate frame moves back and forth during printing, the printing plate and the frame are collided and vibrated during the round-trip operation. The two materials change the experimental machine, and there is a small displacement between the change experiments, resulting in the phenomenon of inaccurate overprint, which affects the appearance quality of the product. Therefore, we should look at the rules frequently, find and adjust them in time

(2) always check the samples. If ink shortage is found in the print, wipe the plate with a clean cotton cloth immediately. This situation is mostly caused by broken plastic film or ink scaling on the printing plate, drying and blocking the plate. If the ink color is uneven or becomes light, it may be that the ink viscosity is too high. Stop the machine immediately, dilute the viscosity of the ink with solvent, and wipe the graphic part of the layout with gasoline at the same time to prevent ink seepage or blocking, so as to facilitate continuous work

(3) semi finished products should be stacked neatly. During the stacking of semi-finished products, the two sides of the paper must be hung and stacked. Otherwise, due to the gravity of the paper itself, especially the intermediate optical system or important mechanical components, the paper forms an upper bow, and both sides of the paper are tilted up and uneven, which makes it difficult to transfer the paper during printing, and often leads to broken sheets. If the paper stack is not flat, it can be leveled with cardboard. At the same time, the height of the paper stack should often be adjusted with the adjustment knob of the paper separation mechanism, so that the paper can be transferred smoothly and the printing process can be carried out smoothly

(4) the blades of the drying device are damaged due to long-term use, and some places are not synchronized with the operation of the host machine, often resulting in disordered printing on the paper rack. At this time, you should be quick with your eyes and hands, and immediately take it away from the bottom of the mess. It is best not to make the ink film face to face, so as to avoid sticking and causing defective products or waste products

therefore, only by paying attention to the links that affect the printing quality, can we print exquisite prints and improve the finished products. Usually, when we do experiments, we can reduce consumption and increase efficiency, so that enterprises can remain invincible in the market competition. (end)

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