Polishing failure analysis and processing

One, film marks or wrinkles

The reasons for this may be: the viscosity of the coating coating is too high, the coating is too late, and streaks tend to occur. According to the printability of different prints, choose a good leveling, wettability good glazing coating; or add an appropriate amount of thinner to reduce the viscosity of the paint. If the coating amount is too large, the coating amount can be reduced by adjusting; sometimes, the coating property of the coating coating on the surface of the printed matter is not good, the smoothness of the dried coating is affected, or the leveling property of the coating is poor, and the processing conditions are Unlike the suitability of the coating, other types of coating or other process conditions may be used to match the properties of the coating.

Second, prints stick to each other

The reason is: the coating solvent in the coating has good volatility, and the drying performance of the coating is poor. Consider using a solvent with a high volatilization rate or changing the type of the coating coating; or the coating film may be too thick, and the solvent inside the coating Incomplete volatilization, high residual content, reduced film thickness, or low working temperature in coating or calendering, short drying time, poor coating drying, and increased working temperature in coating and calendering , Reduce the speed and dry the coating thoroughly.

Third, film formation film gloss difference

If it is the quality of the top coating, you should consider changing the quality of the coating according to the process and economic requirements; if the coating is too thin, the coating amount is insufficient or the coating concentration is small, the roughness is high and the absorption is strong The surface of the printed matter is not easy to fill and fill, then the coating amount should be increased to increase the concentration of the coating, or a layer of light primer must be applied before the processing, and then the coating of the coating; or it may be coating and drying. The temperature at the time of calendering is lower than the pressure of low pressure light, then the process parameters should be adjusted during the operation to increase the temperature and increase the pressure; it is also estimated that the reason is the equipment itself, such as the wear of the calendered steel strip, the smoothness of the gloss is reduced, It is necessary to repair and improve the surface condition of the calendered steel strip.

Fourth, the blank part of the printed product is light-colored after calendering, and the light-colored part is discolored

The reason may be: coating solvent on the ink layer has a certain degree of dissolution, which will change the type of paint or change the solvent composition; if the ink is poor drying, the ink layer solvent resistance is not good, we must improve the ink drying, such as ink drying And then coating, reducing the amount of solvent on the ink with less coating on the amount of solvent; coating layer is not completely dry, the solvent residue in the film layer is high, you must improve the coating drying temperature or reduce the machine Speed, extend the drying time, reduce the residual amount of solvent inside the coating.

Fifth, uneven coating, bubbles, pits, etc.

The reason is: the coating surface tension value is large, the wetting effect on the ink layer on the surface of the printed matter is not good, the surface tension value should be reduced, and the wetting property of the coating on the ink layer should be improved; the solvent in the coating is poorly volatilized, and the coating is Solvent residue is high, you can change to a solvent with a high volatilization rate or the coating is completely dry and then calendered; it may also be too fast in the coating speed, low drying temperature, so that the coating does not dry completely, solvent evaporation Incomplete, it is necessary to adjust the coating process conditions; the ink layer on the surface of the printed matter will also produce crystallization phenomenon, which should take effective measures, such as removing the oil on the crystallized surface of the ink layer or hair treatment, improve the coating The wetting of the ink layer to reduce or eliminate the adverse effects of the crystallization of the ink layer on coating.

Sixth, film surface foaming

The reason is: in the calendering process, the pressure is too high, the temperature of the calendered steel strip is too high, so that the coating film layer is partially softened, which requires appropriate reduction in the pressure and temperature of the calendering; it may also be a glazing coating and calendering process Conditioning wood matching, so that after the paint layer on the surface of the print is cooled, the peeling force is the same as the light strip, the process conditions need to be changed to match the glazing paint, the calender speed is reduced, and the paint layer is improved with the upper light strip. Peel force.

VII. Adhesion between printed matter and glazing tape during calendering

The reason is: the coating is too thin, the coating amount should be increased; the viscosity of the coating is too low to increase the viscosity value of the coating; then the pressure of the light is too small, the temperature of the light is insufficient, the temperature of the light is increased, and the pressure is increased Light pressure.

Eight, the printed calendered, the surface easily cracked

The reason is: the temperature is too high, so that the printed matter is dehydrated too much in the calendering, the water content is reduced, so the paper fiber becomes brittle, the working temperature in the calendering should be reduced, and effective measures should be taken to maintain a certain moisture content in the printed matter; Excessive pressure in the calendering makes the printability and plasticity of the printed matter decrease and the toughness deteriorates, which can reduce the pressure in the calendering. If the post-processing suitability of the glazing coating is poor, the post-processing suitability should be re-selected. The glazing coating; improper choice of post-processing conditions, and the post-processing conditions can be adjusted to match the suitability of the calender after printing.

Nine, after the light is not uniform on both sides of the film surface brightness

The reason is as follows: in the process of calendering, the pressure on both sides of the coating tape is not equal, or the wear on both sides of the coating tape is inconsistent. The pressure on both sides of the coating tape should be adjusted to make it equal, and the parallelism between the pressing roller and the transfer roller is adjusted so that The glazing tape is tensioned on both sides of the glazing tape and wears evenly; it may also be uneven on both sides of the glazing coating. This requires adjusting the glazing coating mechanism to check the level between the metering roller and the coating roller.

Row and gap, so that the thickness of the coating on both sides as possible.

Reprinted from: Printed Today

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