Analysis and treatment of common faults in glazing process
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During the glazing process, various faults occur. These failures mainly reflect poor quality of the film layer, and sometimes it is inconvenient to operate. The same, but always can find the reasons for the different suitability of printed paper, ink and glazing paint, poor processing of glazing and equipment conditions or their interaction. As long as you carefully observe and analyze it carefully, you can draw correct conclusions and take effective measures to deal with them in a targeted manner.
Common faults in glazing are:
First, streaks or wrinkles appear on the film surface
The reasons may be: the viscosity of the glazing coating is high, the coating is not as smooth as the coating, and streaks are prone to occur. According to the different suitability of the printed matter, the glazing paint with good leveling and wettability can be selected; or the appropriate amount of thinner can be added to reduce the viscosity value of the coating. If the coating amount is too large, the coating amount can be reduced by adjusting; sometimes the glazing paint has poor wettability to the ink layer on the surface of the printed matter, affecting the smoothness of the dry film formation, or the leveling property of the paint is poor, and the process conditions Does not match the suitability of the coating, it may be used with other types of glazing coatings or changing process conditions to match the performance of the coating.
Second, the prints stick to each other
The reason is: the volatility of the solvent in the glazing coating is good, and the drying performance of the coating is poor. Consider changing the solvent with high volatilization rate or replacing the type of glazing coating; or the coating film layer is too thick, the solvent inside the coating Not completely volatilized, high residual amount, reducing film thickness; or low working temperature in glazing coating or calendering, short drying time and poor drying of coating, can improve working temperature in glazing coating and calendering Reduce the speed and make the coating completely dry.
Third, the film thickness of the film is poor
If it is the quality problem of the top coating, it should be considered to change the quality of the glazing 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. If the surface of the printed matter is not easy to fill in, it should be increased in coating amount, increase the concentration of the coating, or apply a glazing primer before processing, and then apply glazing; it may also be glazing and drying. When the calendering temperature is low, the low-pressure light pressure is small, then the process parameters should be adjusted during operation to increase the temperature and increase the pressure; it is also estimated that the equipment itself is caused, such as the wear of the calendered steel strip, the gloss smoothness is reduced, It is necessary to repair and improve the surface condition of the calendered steel strip.
Fourth, after calendering, the blank part of the printed matter has a light color part, and the light color part is discolored.
The reason may be: the varnish coating solvent has a certain solubility on the ink layer, which is to change the type of the coating or change the solvent composition; if the ink is poorly dried, the solvent resistance of the ink layer is not good, it is necessary to improve the drying of the ink, after the ink is dried. Then, the coating is applied to reduce the amount of solvent which dissolves the ink in the glazing material; if the coating layer is not completely dried, and the solvent residue in the film layer is high, the drying temperature during the glazing coating is increased or the machine is lowered. Speed, extend drying time and reduce solvent residue inside the coating.
Fifth, the coating is uneven, there are bubbles, pitting, etc.
The reason is: the surface tension value of the glazing coating is large, and the wetting 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 wetting property of the coating on the ink layer; the solvent in the coating is poorly volatilized, and the coating is inside. The solvent residue is high, and the solvent with high volatilization rate can be changed or the coating can be completely dried and then calendered. It is also possible that the speed of the coating is too fast, the drying temperature is low, the coating is not dried thoroughly, and the solvent is volatilized. Incomplete, 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 coating. Wetting of the ink layer to reduce or eliminate the adverse effects of crystallization of the ink layer on glazing coating.
Six, film surface foaming
The reason is: during the calendering process, the pressure is too large, the temperature of the calendered steel strip is too high, and the coating film layer is partially softened, which needs to appropriately reduce the pressure and temperature of the calendering; it may also be a glazing coating and calendering process. Conditional wood matching, so that after the coating layer on the surface of the printed matter is cooled, the peeling force of the same light strip is poor, and the process conditions need to be changed to match the glazing paint, the calender speed is reduced, and the coating layer is improved between the same light strip. Peel force.
Seventh, in the calendering, the adhesion between the printed matter and the glazing tape is poor.
The reason is: the coating is too thin, the coating amount should be increased; the viscosity of the coating is too low, and the viscosity value of the coating should be increased; then the pressure of the calendering is too small, the calendering temperature is insufficient, and the calendering temperature is increased, and the pressure is increased. Light pressure.
Eight, after the print is calendered, the surface is easily broken.
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 lowered, and effective measures are taken to maintain a certain water content in the printed matter; In the calendering, the pressure is too large, so that the elongation and plasticity of the printed matter are reduced, the toughness is deteriorated, and the pressure in the calendering can be reduced; if the post-processing suitability of the glazing paint is poor, the post-processing suitability should be re-selected. The glazing coating; the post-processing conditions are not properly selected, and the post-processing conditions can be adjusted to match the suitability of the printed product after calendering.
Ninth, the brightness of the film surface on both sides after calendering is inconsistent
The reason is: in the calendering, the pressure on both sides of the glazing belt is not equal, or 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. The glazing belt is tightly tensioned on both sides and wear evenly; it may also be uneven thickness on both sides of the glazing coating. It is necessary to adjust the glazing coating mechanism to check the parallelism and clearance between the metering roller and the coating roller. The thickness of the coating on both sides is as uniform as possible.