Transparent ink printing failures and precautions
1. Printing transparent ink produces "pitting" phenomenon
Cause Analysis:
(1) The surface of the embossing roller is not sufficiently delicate or has foreign matter such as dust, which causes the ink to be thick enough here.
(2) Plasticizers, lubricants, etc. contained in the film float to the surface, preventing normal transfer and lubrication of the ink.
(3) Ink viscosity is too high, drying is too fast, or lack of adhesive causes ink transfer and poor wetting.
(4) The printing pressure is too small or the printed version is defective.
Solution:
(1) Wipe clean the surface of the imprint roller.
(2) Before the printing, the plastic film is preheated, and the film is heated or replaced with a plastic film.
(3) Reduce the viscosity of the ink and use a slow-drying solvent.
(4) Increase the printing pressure, generally around 4kg.
(5) If the pits are more regular, the plates and embossing rollers should be carefully inspected for defects. If any, re-plate or replace the rollers.
2. Adhesion after printing transparent ink
In the high-temperature, high-humidity rainy season, the plastic film is gravure-printed, and it is prone to sticking when placed on a roll, transparent ink is stuck by the salty block, and cannot be separated from the lower plastic film, resulting in a lot of waste products. Most of the adhesions of printed products are caused by ink stickiness, high ambient humidity, and high pressure, as follows.
(1) Intrinsic factors
1 The ink itself is poor in heat resistance and produces greater viscosity under high temperature conditions.
2 The residual solvent in the ink is too much. After winding, severe adhesion of the finished product occurs. The large amount of residual solvent not only affects the fastness of the ink, but also causes the packaging to be different, which is extremely unfavorable to the packaged food.
3 Adhesives in printing materials cause the ink to stick.
(2) External factors
1 The ambient temperature is too high, causing the ink to soften, causing the print to stick. Requirements print operation and use temperature does not exceed 40 °C.
2 Overtightening causes adhesions. Reduce the winding tension.
(3) Other factors Insufficient adhesion between the ink and the substrate. After rewinding, the ink may easily transfer and adhere. At this point the correct choice of ink, so that the ink quality to adapt to the substrate. The surface treatment of the substrate improves the affinity for the ink. The general BOPP surface tension should not be less than 3.8×10-2N/m.
3. Printed transparent ink, aluminized composite gloss is not high
Cause Analysis:
(1) The ink itself has poor transparency.
(2) The solvent is too volatile or the viscosity of the ink is too low during printing.
(3) Poor uniformity of the aluminum plating layer causes poor light reflectivity.
(4) The squeegee angle is too large, and the plate is shallow.
Solution:
(1) Replace the ink with good transparency.
(2) Use slow-thousands of solvents to increase ink viscosity.
(3) The replacement of the aluminized film requires a uniform surface and no pinholes.
(4) Adjust the squeegee angle, generally 35 ° is appropriate.
4. Transparent ink caking phenomenon
This phenomenon generally occurs at lower temperatures. Place the ink at 35°C and heat it at room temperature. To prevent accidents, it must be guarded by a specialist.
5. Other considerations
(1) When printing with clear ink, the bottom of the white pad is not used below, because white plays a role of extinction and greatly reduces the use effect. The clear ink printed pattern is thinner by 0.01 mm than the white ink pad bottom.
(2) Select the appropriate diluent according to the type of clear ink.
(3) Because of the low viscosity of transparent ink, it is not appropriate to add too much thinner, and the viscosity is generally controlled within 18-22 seconds (3# Zahn Cup).
--Ink net
1. Printing transparent ink produces "pitting" phenomenon
Cause Analysis:
(1) The surface of the embossing roller is not sufficiently delicate or has foreign matter such as dust, which causes the ink to be thick enough here.
(2) Plasticizers, lubricants, etc. contained in the film float to the surface, preventing normal transfer and lubrication of the ink.
(3) Ink viscosity is too high, drying is too fast, or lack of adhesive causes ink transfer and poor wetting.
(4) The printing pressure is too small or the printed version is defective.
Solution:
(1) Wipe clean the surface of the imprint roller.
(2) Before the printing, the plastic film is preheated, and the film is heated or replaced with a plastic film.
(3) Reduce the viscosity of the ink and use a slow-drying solvent.
(4) Increase the printing pressure, generally around 4kg.
(5) If the pits are more regular, the plates and embossing rollers should be carefully inspected for defects. If any, re-plate or replace the rollers.
2. Adhesion after printing transparent ink
In the high-temperature, high-humidity rainy season, the plastic film is gravure-printed, and it is prone to sticking when placed on a roll, transparent ink is stuck by the salty block, and cannot be separated from the lower plastic film, resulting in a lot of waste products. Most of the adhesions of printed products are caused by ink stickiness, high ambient humidity, and high pressure, as follows.
(1) Intrinsic factors
1 The ink itself is poor in heat resistance and produces greater viscosity under high temperature conditions.
2 The residual solvent in the ink is too much. After winding, severe adhesion of the finished product occurs. The large amount of residual solvent not only affects the fastness of the ink, but also causes the packaging to be different, which is extremely unfavorable to the packaged food.
3 Adhesives in printing materials cause the ink to stick.
(2) External factors
1 The ambient temperature is too high, causing the ink to soften, causing the print to stick. Requirements print operation and use temperature does not exceed 40 °C.
2 Overtightening causes adhesions. Reduce the winding tension.
(3) Other factors Insufficient adhesion between the ink and the substrate. After rewinding, the ink may easily transfer and adhere. At this point the correct choice of ink, so that the ink quality to adapt to the substrate. The surface treatment of the substrate improves the affinity for the ink. The general BOPP surface tension should not be less than 3.8×10-2N/m.
3. Printed transparent ink, aluminized composite gloss is not high
Cause Analysis:
(1) The ink itself has poor transparency.
(2) The solvent is too volatile or the viscosity of the ink is too low during printing.
(3) Poor uniformity of the aluminum plating layer causes poor light reflectivity.
(4) The squeegee angle is too large, and the plate is shallow.
Solution:
(1) Replace the ink with good transparency.
(2) Use slow-thousands of solvents to increase ink viscosity.
(3) The replacement of the aluminized film requires a uniform surface and no pinholes.
(4) Adjust the squeegee angle, generally 35 ° is appropriate.
4. Transparent ink caking phenomenon
This phenomenon generally occurs at lower temperatures. Place the ink at 35°C and heat it at room temperature. To prevent accidents, it must be guarded by a specialist.
5. Other considerations
(1) When printing with clear ink, the bottom of the white pad is not used below, because white plays a role of extinction and greatly reduces the use effect. The clear ink printed pattern is thinner by 0.01 mm than the white ink pad bottom.
(2) Select the appropriate diluent according to the type of clear ink.
(3) Because of the low viscosity of transparent ink, it is not appropriate to add too much thinner, and the viscosity is generally controlled within 18-22 seconds (3# Zahn Cup).
--Ink net
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