This article comprehensively sorts out the causes and countermeasures of the eight common faults in the process of film gravure printing, so that you can check them when you encounter problems.
1. Incorrect color registration
(1) The film tension changes, so that the longitudinal printing register changes.
Each tension control device should be adjusted, such as adjusting the drum brake of the unwinding device; setting the speed of the roller reasonably; increasing the friction of the roller surface; adjusting the winding tension of the rewinder.
(2) The diameter of the printing cylinder is different, and the diameters of the one-, two-, and three-color plate cylinders increase or decrease in sequence, causing the longitudinal printing register to change.
Should be remade.
(3) The linear density is insufficient, and the printing color shifts longitudinally.
The sensitivity of the photocell should be adjusted and the printing plate paste fault should be eliminated.
(4) The guide rollers are not parallel, the printing pressure is uneven, and the taper of the plate cylinder and the platen cylinder causes the film to oscillate laterally and slack on one side, causing unstable lateral color registration.
Targeted adjustments should be made.
(5) The adjusting screw on the shaft end of the printing plate cylinder is loose, causing lateral color instability.
The tightness of the screw should be readjusted.
(6) If the contact pressure between the rubber roller and the flower roller is too large, the printed pattern will produce a double pattern.
The contact pressure should be adjusted to make the printed pattern clear.
2. There are spots on the printed surface
(1) Ink viscosity is too low or poor flow.
The viscosity of the ink should be adjusted appropriately so that the viscosity of the ink is moderate and the fluidity is good.
(2) The printing plate depth is too deep or the blade angle is not adjusted properly.
The angle of the scraper should be adjusted properly, or re-plate making.
(3) Improper control of printing pressure.
Should be adjusted appropriately.
(4) There is too much static on the surface of the printed matter.
Static electricity should be eliminated.
(5) Ink drying is poor.
Drying should be strengthened, such as improving ventilation and drying conditions.
3. Blisters on the printing surface
(1) If the surface of the ink has been skinned and the internal ink is not dry, volcanic vent-shaped cells will be formed once the skin is broken, which is mainly caused by rapid drying.
Low temperature-high temperature-low temperature drying process should be used, and slow-drying ink should be used as much as possible.
(2) During the printing process, a large number of bubbles will be generated in the ink hopper, and the bubbles will adhere to the printing roller, causing the dots of the printed pattern to partially disappear or stain the pattern.
The proper viscosity of the ink should be maintained, the drop of the ink should be reduced as much as possible, and a circulation pump should be used to prevent bubbles from entering the ink.
4. Pear skin pattern on the printed surface
If overprinting on the dried printing surface, the background color ink is dissolved and partially mixed with the second color ink, the printing surface will produce a pear skin pattern.
One is to adjust the viscosity of the ink properly; the second is to control the drying speed correctly; the third is to determine the plate depth reasonably.
5. Poor ink absorption
When multi-color printing on the surface of the film of the product, when printing the ink of the second color on the coating film of one color, if the absorption is poor, the dots after the ink transfer will be separated into independent states, forming a darker dot color. Asymmetrical phenomenon of lighter color in other parts. This has nothing to do with the problem of ink transfer amount or non-harmony, mainly related to the diffusion of dot ink after transfer.
In this regard, one is to use hysteresis solvents in the second color ink; the second is to move the blade of the second color ink closer to the direction of printing; the third is to press the ink after the second color as lightly as possible; the fourth is to deepen it appropriately The plate depth of the second color; Fifth, the use of reducing agents in the base color ink; Sixth, to increase the printing speed appropriately.
6. The printing roller wears too fast
(1) The scraper is too thick.
Thinner blades should be used instead.
(2) The contact pressure between the blade and the printing roller is too large.
The contact pressure of the two should be adjusted appropriately.
7. The blade wears too fast
(1) The blade is too thin.
Thicker blades should be used instead.
(2) The contact pressure between the blade and the printing roller is too high.
The contact pressure of the two should be adjusted appropriately.
8. Blocked network
(1) During the printing process, as a large amount of solvent volatilizes, the viscosity of the ink increases, causing the ink inside the screen to dry up and clog.
Dry ink should be removed regularly.
(2) When the position of the blade is far from the printing roller, the diameter of the printing roller is large or the depth of the printing roller into the ink tank is not enough, the hot air blown out from the machine affects the ink on the surface of the printing roller, which is likely to cause serious blockage.
Targeted adjustments should be made.
(3) Impurities are mixed in the ink to cause blockage.
Impurities and filter inks should be removed.
(4) During the printing process, the operating temperature is too high, which causes the solvent in the screen roller to evaporate too fast, causing blockage of the screen.
Try to lower the operating temperature.
(5) The etching depth of the plate roller screen is not suitable.
Should be remade.
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