Common faults and solutions of the hottest gravure

2022-08-16
  • Detail

Common faults and solutions of gravure printing ink (Part 2)

3. Biting

in overprint, the second color ink sticks and pulls off the first color ink. The main reasons for this phenomenon are:

(1) insufficient drying of the base color (first color) ink or too fast drying of the second color ink, resulting in excessive viscosity at the moment of printing

(2) the second color printing pressure is too high and the printing speed is too high

(3) poor adhesion of ink to substrate

(4) poor compatibility of adjacent two-color inks

(5) improper selection of diluent

solution:

reduce pressure

blow to the layout of the second color

improve the initial dryness of the first color and improve the drying speed (use fast drying solvent)

reduce the drying speed of the second color printing ink (and strengthen the heating and drying), and slow down the drying speed of the second color

change the diluent of the second color into an ingredient that does not dissolve the first color

change the ink

4. Pinholes

pinholes are tiny holes in fingerprints, especially in large areas of patterns

the reasons for pinholes: first, when the ink is transferred, the ink becomes a very thin transparent layer. You can see the upper line of the plate roller, and the prints are pinholes (sand holes) of the same size, which are evenly distributed throughout the prints, which is called mechanical pinholes. Second, as a result of the ink leveling and poor wetting of the substrate, messy pinholes, called chemical pinholes, are formed on the printed matter

treatment method: for mechanical pinholes, it can be solved by appropriately increasing the ink viscosity or making the ink dry slowly. For chemical pinholes, it is required that when adjusting the ink, do not remove the adhesion too short, so as to ensure the leveling required by the adhesion of the ink. Therefore, when thinning, polyamide resin oil or other substances that increase wetting can be added to correct the adjustment

5. Ink overflow

ink overflow refers to the spots in the full version of the ink and the overflow of ink from the line drawing part. The reason for ink overflow is that the viscosity of the ink is too low

the treatment method is: when the viscosity passes the other part, that is, the protection is low, add new ink or add a resin containing regulator to improve the viscosity; Improve printing speed; Change the angle of the scraper and scrape with an acute angle; Adjust the position angle of the scraper, * it is better to be close to the embossing area

6. Orange peel stripe

orange peel stripe refers to that the imprint on the fingerprint is uneven, and the ink film is orange peel, so it should not slide relative to the chuck under the applied state or during the experimental process; The collet is not the full plate part after the removal of force or the tensile test of the sample

the reasons for this phenomenon are that the drying speed is too fast, the ink concentration is too light, the ink leveling is poor, the ink thixotropy is large, the affinity between the printing plate cylinder and the paper in the water-based ink is poor, the electrostatic influence, and the speed is slow

treatment method: improve the fluidity of the ink, adjust the drying speed, increase the leveling, do not dilute the color too shallow, and reduce static electricity

7. Residual odor of printed matter

when printed matter is used to package items such as food, if there is odor, it will become a big problem, and sometimes this odor will even be absorbed by the contents. In this way, the problem will become more serious. In particular, because cellophane and polyolefin films are easy to absorb solvents, special attention should be paid to them during printing. When packaging food, people are most sensitive to the odor of toluene. The odor is not only caused by residual solvents, but sometimes mixed with the odor of the packaging material itself, such as the oxidation odor of polyolefins, resulting in problems that are not easy to solve. The national standard also stipulates that even if it is not used for food packaging, products that meet the national standard should be produced from the perspective of environmental protection

solution:

do not use color developing materials and additives with strong odor

adjust drying speed and reduce residual solvent; Use solvents with less residual odor (it is easy to cause residual odor when mixed with impure solvents such as high boiling point)

reduce the printing speed and fully ventilate to reduce the solvent concentration

in a word, the generation of version failure involves many aspects. In order to avoid the occurrence of faults in production, we should pay attention to the following changes:

(1) changes in ink

drying of printing ink mainly * solvent evaporation drying, and the evaporation speed of ink should be proportional to the printing speed. When the two adapt, printing will be normal; If not, there will be sticky dirt, deinking, incomplete image residue, knife line and other faults. Therefore, it is necessary to observe the printing situation at any time, supplement the diluent in time, and change with the temperature. Use all kinds of solvents correctly, and control the volatilization speed of the ink according to the type of the ink. If the drying is too slow, it is easy to be stuck off when printing the next color; If it is too fast, crystallization will occur again. Secondly, the viscosity and color difference should be carefully checked during printing

detection scope and requirements

inspection items inspection requirements

printing viscosity detection method: use No. 3 Tu en cup to detect the relative viscosity

detection frequency: once every 30 minutes, no less than twice in each group

color concentration detection method: use a scraper to scrape the ink sample (refer to the ink sample when signing the sample)

detection frequency: once every 30 minutes, Each group shall not be less than 2 times

color difference control position detection method: measure the same main parts with a color difference meter

detection frequency: not less than 2 times in 60 minutes

process discipline detection range: Ambient temperature, humidity, printing pressure, drying temperature, machine speed, electrostatic ink leveling system B, relative humidity not greater than 85%

detection frequency: Patrol no less than 2 times within 60 minutes (2) changes of cold and hot air

cold and hot air device is an important device to accelerate ink drying. In winter, the room temperature is low, so we should increase it, mainly by purchasing hot air of large load experimental machine; In summer, when the temperature is high, the hot wind must be reduced as the temperature rises. If possible, the production enterprises can adopt constant temperature (20) and constant humidity (the relative humidity is between 50% - 60%)

(3) changes in mechanical parts

due to the long-term variable speed rotation of the printing machine, some parts have been worn and changed, which should be replaced or repaired in time

source: cigarette packet ink information

Copyright © 2011 JIN SHI