Analysis and treatment of common faults in glazing process

During the glazing process, various failures will occur. These failures mainly reflect the poor quality of the film, sometimes inconvenient to operate. The same, but you can always find the reason from the different suitability of printed paper, ink and glazing paint, poor glazing processing and equipment conditions, or their mutual influence. As long as you observe carefully and analyze carefully, you can draw the correct conclusion and take effective measures to deal with it.

Common faults in coating are:

1. Streaks or wrinkles appear on the film surface

The reason may be: the viscosity value of the glazing paint is high, the paint is too late to level, and the streak is easy to appear. According to the different suitability of the printed matter, choose a glazing paint with good leveling and wetting properties; or add an appropriate amount of thinner to reduce the viscosity value of the paint. If the coating amount is too large, it can be adjusted to reduce the coating amount; sometimes the wettability of the glazing paint on the ink layer on the surface of the printed product is not good, which affects the smoothness of the drying film formation, or the leveling of the paint is poor, the process conditions It does not match the suitability of the paint. It may use other types of glazing paint or change the process conditions to match the performance of the paint.

Second, the printed matter sticks 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 using a solvent with a high volatility rate or changing the type of glazing coating; it may also be that the coating film is too thick and the solvent inside the coating Incomplete volatilization, high residual amount, reducing the thickness of the film layer; or low working temperature in glaze coating or calendering, short drying time and poor drying of the coating, which can increase the working temperature in glaze coating and calendering , Reduce the speed of the machine to make the coating dry completely.

3. Poor gloss of film-forming film

If it is the quality problem of the top coating, you should consider switching to a better quality 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 The surface of the printed matter is not easy to fill up and fill up, then the amount of coating should be increased to increase the concentration of the coating, or a layer of glazing primer should be applied before processing, and then glazed coating; it may also be glazed coating dry and When the temperature during calendering is low, the light pressure is low, then the process parameters should be adjusted during operation to increase the temperature and increase the pressure; it is also estimated that it is the cause of the equipment itself, such as the wear of the calendered steel belt and the gloss smoothness. It is necessary to repair and improve the surface condition of the calendered steel strip.

4. The blank part of the printed product is light-colored after calendering, and the light-colored part is discolored

The reason may be: the glazing paint solvent has a certain dissolution effect on the ink layer, which needs to change the paint type or change the solvent composition; if the ink is poorly dried and the ink layer has poor solvent resistance, it is necessary to improve the ink drying situation, after the ink is dried Re-coating to reduce the amount of solvent that has a dissolving effect on the ink in the glazing material; the coating layer is not completely dried, and the residual amount of solvent in the film layer is high, you need to increase the drying temperature during coating or reduce the machine Speed, extend the drying time, and reduce the amount of residual solvent in the coating.

5. Uneven coating, bubbles, pits, etc.

The reason is: the surface tension value of the glazing paint 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 reduced to improve the wetting property of the ink layer of the paint; the solvent in the paint is poorly volatilized. If the residual amount of the solvent is high, you can use a solvent with a high volatilization rate or dry the coating thoroughly before calendering; it may also be that the speed of the coating is too fast, the drying temperature is low, the coating is not completely dried, and the solvent is volatilized Incomplete coating, the process conditions of glazing coating should be adjusted; the ink layer on the surface of the printed matter will also produce crystallization, which must take effective measures, such as removing the oil quality of the crystallization surface of the ink layer or performing deburring treatment to improve the coating Wetting effect on the ink layer to reduce or eliminate the adverse effect of crystallization of the ink layer on the glazing coating.

Six, the film surface blisters

The reason is: during the calendering process, the pressure is too high, and the temperature of the calendered steel belt is too high, which partially softens the coating film. This requires appropriate reduction of the pressure and temperature of the calendering; it may also be glazing coating and calendering process Conditional wood matching, after cooling the paint layer on the surface of the printed matter, the peeling force of the glazing belt is poor. It is necessary to change the process conditions to match the glazing paint, reduce the calender speed, and improve the coating layer and the glazing belt. Peel force.

7. In the calendering, the adhesion between the printed matter and the glazing belt is poor

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

8. After printing, the surface is easy to crack

The reason is: the temperature is too high, so that the printed matter is dehydrated too much during calendering, and the water content is reduced, so the paper fiber becomes brittle. The working temperature during calendering should be reduced, and effective measures should be taken to maintain a certain moisture content in the printed product; Excessive pressure during calendering will reduce the extensibility and plasticity of the printed matter, and the toughness will be reduced, which can reduce the pressure during calendering; if the post-processing suitability of the glazing coating is poor, the post-processing suitability should be reselected. The glazing coating; the post-processing technology conditions are not suitable for selection, and the post-processing technology conditions can be adjusted to match the suitability of the printed product after calendering.

Nine, the brightness of the film on both sides is inconsistent after calendering

The reason is: during 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 heat pressing roller and the conveying roller should be adjusted so that The two sides of the glazing belt are uniformly tensioned and evenly worn; it may also be uneven thickness on both sides of the glazing coating. This requires adjusting the glazing coating mechanism and checking the parallelism and gap between the metering roller and the coating roller to make The thickness of the coating on both sides should be as consistent as possible.

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