Common problems and solutions in the process of printing glazing
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In the post-press processing, the glazing process can not only improve the surface appearance of the finished product, but also play a protective role. The following is a brief analysis of some of the problems that arise during the glazing process.
1, the film surface appears striped or wrinkled
The viscosity of the varnish is high, it is not easy to level, and it is easy to appear streaks. According to the different suitability of the printed matter, the varnish with good leveling and wettability can be selected; or the appropriate amount of thinner can be added to reduce the viscosity of the varnish. . If the coating amount is too large, the coating amount can be lowered by adjustment; sometimes the varnish is not good to wet the ink layer on the surface of the printed matter, affecting the smoothness of the dry film formation, or the leveling property of the varnish is poor, The process conditions do not match the glazing suitability. Other types of varnishes can be used or the process conditions can be changed to match the performance of the varnish. The volatility of the solvent in the varnish is not good, and the drying performance of the coating is poor. It may be considered to use a solvent with a high volatilization rate or to change the type of varnish; it may also make the coating film too thick, and the solvent inside the coating is not completely Volatile, high residual amount, can reduce coating amount, reduce film thickness; or low working temperature in glazing coating or calendering, short drying time and poor drying of coating, can improve glazing coating production and pressure The operating temperature in the light reduces the speed of the machine and allows the coating to dry completely.
2, the film thickness of the film formation is poor
If it is the quality problem of varnish, it should be considered to change the quality of the glazing oil according to the process and economic requirements; if the coating is too thin, the coating amount is insufficient or the glazing oil concentration is small, the roughness is high, If the surface of the absorbent paper is not easy to fill and fill, the coating amount should be increased, the coating concentration should be increased, or the glazing primer should be applied before processing, and then glazing coating, or glazing coating. When the cloth is dry and calendered, the temperature is low and the calendering pressure is small. In the operation, the process parameters should be adjusted to increase the temperature and increase the pressure. It is also estimated that the equipment itself is caused. If the calendered steel strip is worn, the gloss is smooth. The degree is reduced, which is to repair and improve the surface condition of the calendered steel strip.
3. After the calendering, the blank part of the printed matter has a light color part, and the light color part is discolored.
The glazing solvent has a certain dissolution effect on the ink layer, which is to change the type of varnish or change the solvent component; if the ink is poorly dried, the ink layer has poor solubility resistance, it is necessary to improve the drying of the ink, and then the varnish is dried after the ink is dried. Coating, reducing the amount of solvent that dissolves the ink in the glazing oil; if the layer is not dry thoroughly, and the solvent residue in the film layer is high, the drying temperature or the machine speed during glazing coating is increased, and the drying time is prolonged. , reduce the amount of solvent residue inside the coating.
4, the coating is uneven, there are bubbles, pitting, etc.
The surface tension value of the varnish is large, and the dampness effect on the ink layer on the surface of the printed matter is not good. The surface tension value should be lowered to improve the wettability of the paint on the ink layer; the solvent in the paint is poorly volatilized, and the solvent residue in the coating is insufficient. High, can be changed to a solvent with a high volatilization rate or the coating is completely dried and then calendered; it may also be that the speed of the coating is too fast, the drying temperature is low, the coating is dried thoroughly, and the solvent is not completely evaporated. The process conditions of glazing coating should be adjusted; the ink layer on the surface of the printed matter will also be crystallized. This should take effective measures, such as removing the oil quality of the crystallized surface of the ink layer or performing the roughening treatment to improve the glazing oil pair. The wetting action of the ink to reduce or eliminate the adverse effects of crystallization of the ink layer on glazing coating.
5, the film surface is foaming
In the calendering process, the pressure is too large, the temperature of the calendered steel strip is too high, and the glazing layer is partially softened, which needs to appropriately reduce the pressure and temperature of the calendering; or the glazing oil does not match the calendering process conditions. After the glazing layer on the surface of the printed matter is cooled, the peeling force of the same optical strip is poor, and the process conditions need to be changed to match the glazing oil, the calender speed is lowered, and the peeling between the glazing layer and the upper optical strip is improved. force.
6. After the print is calendered, the surface is easily broken.
The temperature is too high, so that the printed matter is dehydrated too much during the calendering process, the water content is reduced, so the paper fiber becomes brittle, the working temperature of the calendering should be lowered, and effective measures are taken to maintain a certain water content in the printed matter; Too large, the printability and plasticity of the print are reduced, the toughness is denatured, and the pressure in the calendering can be reduced; if the post-processing suitability of the varnish is poor, the varnish with good processing properties should be re-selected; The processing conditions are not suitable for the sample selection, and the post-processing conditions can be adjusted to match the suitability of the printed product after calendering.
7, after the calendering, the brightness of the film surface on both sides is inconsistent
In calendering, the pressure on both sides of the glazing belt is not equal, and the wear on both sides of the glazing belt is inconsistent. The pressure on both sides of the glazing belt should be adjusted to be equal, and the parallelism between the hot pressing roller and the conveying roller should be adjusted to make the glazing belt The side tension is consistent, the wear is even; or the thickness of the varnish is uneven, so it is necessary to adjust the glazing coating mechanism, check the parallelism and gap between the metering roller and the coating roller, so that the two sides are coated. The thickness is as uniform as possible.