Excluding the shallow wire drawing failure, it is as simple as that!
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Drawing is one of the problems often encountered in gravure printing. It involves many factors such as gravure printing machine, plate cylinder, doctor blade, printing environment, ink, etc. If improper handling will affect production and quality. The common drawing mainly includes three kinds. Today, I focus on the discharge of the drawing fault in the shallow net position.
1. Eliminate the drawing phenomenon from the source of design plate making
Printability is fully considered in the design and plate making of the original. Be sure to consider the printing direction, try to avoid printing from shallow to deep; black, magenta version is the most likely to appear on the shallow wire. Especially in the black version, because the carbon particles in the ink are coarse, when the black net is very shallow, almost no carbon particles can be contained in one dot, so the drawing is more likely to occur. Therefore, a large area of black light network should be set as a special gray version, reducing the printing difficulty and scrap rate.
2, the correct use of the squeegee to avoid drawing
The choice of squeegee. The surface hardness of the chrome plated roller is HV850～1100. The hardness of the squeegee should be lower than the hardness of the plate. It is about HV600. The hardness is too low. The ink is not clean. The hardness is too high, which will accelerate the wear of the plate and cause knife marks. , affecting the quality of printed products.
The flatness of the squeegee. When installing the squeegee, the blade should be flattened, and the screws should be tightened from the middle to the two sides. It should not be completed in one step. It should be repeated two or three times to ensure uniform force on the blade.
The sharpness of the squeegee. Grinding the squeegee with 600# water sandpaper or 2# metallographic sandpaper, or use a special sharpening machine to grind the back side of the squeegee into a slanting mouth of about 25°, even if the new knives are ground.
Scraper angle. The angle of the doctor blade is smaller than that during normal printing, and the distance between the contact point of the doctor blade and the printing plate and the imprinting point is shortened.
3, reasonable selection of ink to prevent drawing
When there is a large area of shallow mesh or gradation transition on the plate surface, the ink with better quality should be selected to prevent the ink pigment particles from being too thick to cause drawing. Generally, the fineness of the ink is 15μm. Too coarse ink particles on the squeegee and plate The damage is great.
When blending inks, under the premise of not affecting other patterns on the same plate, consider using a slow-drying solvent, and do not add too much auxiliary solvent such as ethyl acetate to prevent the ink from changing and normal printing.
Ensure that the ink viscosity is moderate and stable. The production of the wire 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 the cut line in printing. In addition, due to the different performances of various brands of inks, the amount of solvent added is not the same. When formulating inks, refer to the specific data provided by the ink manufacturers, and combine their own printing conditions and printed products to carry out specific operations.