Drawing is one of the problems frequently encountered intaglio printing, involving gravure plate cylinder, squeegee, the printing environment, inks, and many other factors, such as improper handling will affect the production and quality. Common drawing mainly includes three kinds, today I focus on explaining the elimination of drawing failures in shallow mesh positions.
1. Eliminate the phenomenon of drawing from the source of design and plate making
Fully consider printability in manuscript design and plate making. Be sure to consider the printing direction and try to avoid printing from light to dark; black and magenta versions are most prone to light online drawing. Especially for the black version, due to the coarse carbon particles in the ink, when the black net is very shallow, almost no carbon particles can be installed in one dot, so it is more likely to be drawn. Therefore, a large area of ​​black and light mesh should be set as a special gray version as much as possible to reduce printing difficulty and scrap rate.
2. Use the doctor blade correctly to avoid drawing
Selection of squeegee. The surface hardness of the chrome plated cylinder is HV850 ～ 1100. The hardness of the squeegee should be lower than the hardness of the printing plate, about HV600. If the hardness is too low, the ink will not be cleaned. If the hardness is too high, it will accelerate the wear of the printing plate and produce a knife mark , Affecting the quality of printing.
The flatness of the doctor blade. When installing the squeegee, the blade should be flattened, and the screws should be tightened from the middle to the two sides in sequence, not in one step. It needs to be repeated two or three times to ensure that the blade is evenly stressed.
The sharpness of the doctor blade. You can use 600 # water sandpaper or 2 # metallographic sandpaper to sharpen the squeegee blade, or use a special sharpener to grind the back of the squeegee blade to an angle of about 25 °, even if you use a new knife.
Squeegee angle. The angle of the doctor blade is smaller than that of normal printing, and at the same time, the distance between the contact point of the doctor blade and the printing plate and the imprint point are shortened.
3. Reasonably select ink to prevent drawing
When there is a large area of ​​shallow screen or gradation transition on the plate surface, better quality ink should be used to prevent the ink pigment particles from being too thick and causing wire drawing. The fineness of the ink is usually 15 μm. The too rough ink particles are for the doctor blade and printing plate The damage is great.
When formulating inks, on the premise of not affecting other patterns on the same plate, consider using slow-drying solvents, and do not add too much auxiliary solvent such as ethyl acetate to prevent the ink from changing and preventing normal printing.
Ensure that the viscosity of the ink is moderate and stable. The production of brushing has a direct relationship with the viscosity of the ink. Generally speaking, the higher the viscosity of the ink, the easier it is to produce knife lines during printing. In addition, because the performance of each brand of ink is different, the amount of solvent added is also different, when preparing the ink, you can refer to the specific data provided by the ink manufacturer, and combine the printing conditions and the printed product for specific operations.
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