1. Printing faults and treatment methods of gravure ink

1. Poor reproducibility of A53 / A54 ink

Reasons: First, the viscosity of the ink is too low, resulting in poor transfer of dark tone parts, and even the contrast of the layer has a tendency to weaken. The second is the excessive penetration of ink due to uneven plastic clothing or rough paper, and the third is the poor reproducibility of the printed ink film due to the poor coloring power of the ink gel or the pigment in the ink system.

Treatment methods: First, the proportion of pigments in the ink system is suitably large or choose pigments with high coloring power as the coloring agent; second, the printed (textured) meshes are shallower when making plates. The third is to increase the proportion of wetting and dispersing agent to improve its color development. The fourth is to properly add antifreeze organic solvents such as propylene glycol butyl ether, etc., to avoid gel and maintain the fluidity of the ink. Fifth, it is appropriate to add non-surfactants such as stearic acid to prevent the ink from glossing, especially the transfer performance, due to penetration after printing.

2. Ink film appears fog and paste

Reasons: First, when water-type gravure (A53, A54) inks are printed at high speed (150-300m / min), fog or paste plates are produced. This is often due to the slow drying of the ink, especially the formula design of the water-based binder and the medium of water or alcohol, ester organic solvent in the ink system is unreasonable, resulting in the matt or fogging of the ink film surface after printing shape. Second, due to the poor solubility of thinner and ink, poor solubility after addition, there are also dry ink on the plate that increases the resistance of the blade or paper powder on the substrate, and plastic powder is mixed into the paste plate.

Treatment methods: one is to improve the accuracy (macro) and surface finish of the plate; the other is to increase the pressure of the blade; the third is to adjust the solubility of the thinner and ink.

3. The ink dries slowly

Reasons: First, the slow drying of the ink is often caused by the slow evaporation rate of water. It is usually caused by the high viscosity or the depth of the plate hole and the ink film is too thick or because the non-absorbent plastics, aluminum foil, etc. do not absorb the ink. It is caused by the condition of completely no wind or no drying equipment (including facilities) or low temperature of drying (including infrared magnetic wave drying power is small) and so on.

Treatment method: First, it is to improve the ordinary heat blowing method, the temperature of the hot roller type is 20 to 30 ℃ higher than that of the solvent type; second, the frequency of the electromagnetic wave from the previous high-frequency dielectric heating 10 to 150MHz is changed to 300 to 3000MHz Microwave heating and drying; three is to use preheating to increase the surface temperature of paper or plastic or aluminum foil for packaging and printing; four is to increase the ambient temperature (especially the printing plate).

4. Poor adhesion fastness

Reasons: First, the substrate is not processed well; second, the wrong ink is used; third, the ink system contains excessive surfactant; fourth, the printing pressure is too small; fifth, the viscosity of the ink is unsuitable; sixth, the ink film has excessive moisture or Solvent.

Processing methods: one is to reprocess the substrate; the second is to replace the appropriate ink; the third is to choose inks that do not contain surface activity; the fourth is to increase the printing pressure; the fifth is to select inks with high resin content and low viscosity; the sixth is In the ink system or the design of the thinner formula, the gradient mixed solvent is used as much as possible or the printed product is cut and placed in the drying room to eliminate excess water.

Second, the treatment method of letterpress printing faults

Note: T37 type relief is usually used for rubber hand-carved flexo laser engraving and photosensitive resin relief, etc. Generally, it is used as carton, cardboard, carton, medium and high grade as plastic woven bags, coated paper such as cigarette packs, wine labels, medicine bags and other substrate materials.

1. Gel or brushing

Reasons: First, the ink was stored improperly, expired or left over; second, the wrong co-solvent was used; third, the ink was mixed with other inks, etc.

The processing methods are: first, sealed storage, adding proper amount of real solvent; second, exchange ink; third, use a diluent (formulation) with good solubility; fourth, pay attention to the type of ink before adjustment.

2. The expected viscosity and viscosity cannot be obtained

Reasons: First, the ink is thixotropic; second, the temperature is too low; third, foaming; fourth, the organic solvent of the ink system is volatile; fifth, the viscosity is too low; sixth, the ink system binder (resin) is not properly selected and lacks adhesion (Bonding strength) and so on.

The processing method is: first, it should be agitated for 5 to 10 minutes before using ink; second, it is appropriate to keep the ink at 25 ℃; third, add an appropriate amount of defoamer (or prepare both to eliminate external foam and internal foam); fourth, add Really strong solubilizer; Fifth, add appropriate amount of × 8 or ammonia (amine) water; Sixth, add tackifying resin or crosslinking agent, etc.

3. Ink foaming or poor flow

Reasons: First, the defoamer is too little or the defoamer is bad; second, the circulation of the ink is insufficient; third, the tube leaks; fourth, the ink is too thin; fifth, the anti-settling thickener is excessive.

The processing methods are: first, increase the defoamer in an appropriate amount (it is more difficult to eliminate the pinholes); second, increase the circulation; third, check the tube to prevent air leakage; fourth, keep adding new ink to keep the ink from being too thin; Fifth is to add 80.1 ~ 3% to remedy it; Six is ​​to increase the circulation of the pump; Seven is to add new ink to make it not too thin.

4. Poor transferability to the substrate

The reasons are: first, the printing pressure is insufficient; second, the substrate is too water-resistant; third, the strength of the printing plate is too high; and fourth, the ink roller wear and aging.

Treatment methods: one is to increase the printing pressure; the second is to use water-increasing ink or add a coupling agent (such as 200S); the third is to configure the plate hardness to 42 ± 3; the fourth is to replace the clogged or worn metal anilox roller.

5. Poor overprint (bad overprint) is poor

Reasons: First, in multi-color overprinting, the previous color is not dried and then printed again; second, the post-printing (ink) color causes the previous color to peel off (bite); third, the post-printing ink sleeve (overlay) printing Not up; the fourth is that the ink film is crystallized or not rewetting (the ink film is not slightly soluble).

Treatment methods: one is to increase the drying speed of the previous color; the second is to reduce the viscosity of the latter color or reduce the printing pressure; the third is to increase the viscosity of the latter color or to improve the adhesion; the fourth is to increase the PH value of the ink or add a suitable amount of wetting aid . [next]

6. The set (stack) cannot be printed

Reasons: One is that the previous (color) dries too fast or crystallizes or does not have resolubility; the second is the warpage and warpage caused by the expansion and contraction of paper due to the absorption of ink and moisture or even non-absorbent plastics.

Treatment methods: First, when the front color is not completely dry, add a cosolvent to increase the PH value after the first color (print) or the appropriate amount; Second, grasp the timing of the post-color printing or change the paper, add the appropriate amount of diluent or change the expansion and contraction. Ink.

7. Overprint is not allowed

Reasons: First, the tension of the printed material is not even; the second is that a bearing at both ends of the printing plate is worn or the plate roller is not clear; the third is that the printed material has a ruffle; the fourth is that the previous color printing pressure is too large, so that The pattern is deformed. Fifth, the joints of the substrate are not uniform or the thickness is different on both sides. Sixth, the printing plate is swollen and deformed by the ink.

Treatment methods: First, adjust the tension of the receiving and discharging material (printing material); Second, check or replace the worn or deformed plate roller; Third, adjust the tension or replace the printing material; Fourth, adjust the printing pressure; New printing plate.

8. Color is unstable

The reasons are: First, there is a change in viscosity and PH value; Second, there is a deviation in the ink distribution process or printing operation procedures.

The processing method is: one is to readjust the viscosity or control the PH value regulator; the second is to check the ink distribution process and operation process.

9. The color is too light

Reasons: First, the viscosity is too low; second, the anilox roller screen is too thin; third, the anilox roller is worn or not cleaned; fourth, the amount of ink is too small.

The processing methods are: first, increase the viscosity of the ink; second, replace the anilox roller with thick anilox; third, replace the anilox roller with a new one or thoroughly clean the anilox roller; fourth, accelerate the printing speed or reduce the pressure of the ink transfer roller.

10. The color is too dark

Reasons: First, the viscosity of the ink is too high or the color development is too strong; second, the anilox roller is too rough; third, the amount of ink is too large or the ink system has too many ink additives or fillers.

Treatment methods: one is to add thinner to reduce the viscosity of the ink; the other is to add a lightener to reduce the ink color depth; the third is to increase the pressure of the ink transfer roller or reduce the ink additives in the ink system.

11. Uneven ink color

Reasons: First, the printing plate is uneven; second, the thickness of the substrate is not uniform; third, the anilox roller screen line number is too low; fourth, the anilox roller mesh has dry or residual ink.

Treatment methods: One is to grind the back of the printing plate or the sticker correction; the second is to change the substrate with uniform thickness; the third is to replace the anilox roller with a high number of anilox lines. The fourth is to clean the residual ink residue of the anilox roller mesh.

12. Poor adhesion of ink film

Reasons: First, the ink quality is poor or the wrong ink is used; second, the substrate does not meet the processing requirements; third, the wrong thinner is used, the printing pressure is too small or the ink layer is too thick; fourth, the coloring power of the ink is too low.

Treatment methods: One is to replace the adapted ink; the second is to control the processing of the substrate; the third is to use the corresponding thinner; the fourth is to increase the printing pressure or select the ink with good coloring power or reduce the ink supply.

13. Poor gloss of ink

Reasons: First, the quality of the ink is not good or has a certain permeability; second, the substrate is too rough and the viscosity is too low (usually the viscosity should be: 40 ~ 60, and the gravure is 18 ~ 25S / 25 ℃ · Tu 4 cup).

Treatment methods: one is to replace the good quality ink (especially the ink system with the same dry surface); the second is to replace the substrate or the impervious substrate on the surface (or to replace the ink that does not penetrate the paper); the third is to control the ink Viscosity 35 ～ 60S / 25 ℃ · Apply 4 cups. Fourth, add rosin modified ink with high PH value or add high molecular weight acrylic resin ink or coupling agent to remedy it.

14. Ink printing fading

Reasons: One is that the filler in the water ink catches the color or pigments of different wavelengths are used; the second is that the pigment has poor alkali resistance and heat resistance.

Treatment methods: one is to replace the calcium-free fillers or choose pigments with similar color wavelengths; the other is to choose alkali-resistant and heat-resistant pigments; the third is to use light-resistant pigments or add an appropriate amount of anti-UV absorbers or add Oxidant 0.1 ～ 1.0%. [next]

15. The picture and text are fuzzy, illegible, and rough

Reasons: First, the printing quality is poor; second, the printing plate and the ink roller are too tight; third, the viscosity of the ink is too large or the ink is thick; fourth, the ink film drying speed is too fast; fifth, the impact of environmental dust.

Treatment methods: First, the pad should be flat and consistent; Second, adjust the pressure between the printing plate and the ink roller; Third, adjust the viscosity of the ink, use water, alcohol (or ester) to mix or reasonably stir the ink, or increase the coupling agent in an appropriate amount The ratio is to reduce the drying speed, and the fifth is to control environmental dust.

16. Graphic crushing

Reasons: First, the printing plate is too soft or the pad is too elastic; Second, the contact is too tight or the printing pressure is too high; Third, the ink viscosity is too low.

Treatment methods: First, the pad should be suitable, or the height of the printing plate should be adjusted; second, the printing pressure or plate should be adjusted, and the roller should be loosened; third, the ink with high viscosity and high hardness should be replaced or the ink should be stirred appropriately.

17. Ink pinhole

Reasons: First, the ink was diluted too much; second, the internal defoaming aid was insufficient; third, the viscosity of the ink was too low, and too much ink was applied.

Treatment methods: one is to add the original ink to the ink in an appropriate amount; the second is to control the amount of internal and external defoamers; the third is to add the appropriate amount of the original ink and mix well.

18. Print plate wear

Reasons: First, the printing is too heavy; second, the contact is too tight; third, the quality of the printing plate is poor; fourth, the ink or thinner corrodes the printing plate.

Treatment methods: First, adjust the printing pressure; second, adjust the contact; third, replace the new version; fourth, replace the ink or thinner that does not corrode the printing plate.

19. Prints have spots

Reasons: First, the ink is too thin; second, the surface of the substrate is uneven; third, the viscosity of the ink is too small; fourth, the printing plate is not uniformly inked.

Treatment methods: one is to add coupling agent 200S or original ink; the second is to use micro-elastic ink or uniform thickness of the printing material; the third is to select the ink with high viscosity or high viscosity; the fourth is to adjust or check the inking system .

20. Ink drying is too fast

Reasons: First, the printing speed is too slow; second, the opening time is too long, the ink drying speed is too fast; the ink viscosity is too high; the drying temperature is too high.

Treatment methods: one is to increase the printing speed; the other is to increase the thinner; the third is to add slow drying to dilute the true solvent; the fourth is to reduce the drying temperature or eliminate the drying system facilities.

21. Print through

Reasons: First, the ink is too thin; second, the substrate is too rough; third, the ink dries too slowly; fourth, there is excessive spherical pigment or surfactant in the ink system.

Treatment methods: one is to add original ink; the second is to replace the substrate on the surface of the uniform; the third is to replace the ink that dries quickly; the fourth is to use non-spherical pigments or control the amount of surfactant.

22. Blocking and pasting

Reasons: First, the printing plate is too shallow; Second, the printing pressure is too heavy; Third, the ink supply is too much; Fourth, the ink viscosity is too high; Fifth, the ink drying speed is too fast.

Treatment methods: one is to choose the deep version; the other is to adjust the printing pressure; the third is to reduce the ink supply; the fourth is to dilute the ink; the fifth is to reduce the drying temperature or add slow drying agent or increase the printing speed appropriately.

23. Sticky pages, dirty

Reasons: First, the film formation after ink printing is too slow; second, the tension of the rewinding paper or plastic is too loose; third, the product is stacked and heated; fourth, the softening point of the ink system resin is too low; fourth, the plastic back of the substrate is mishandled .

Treatment methods: First, switch to fast-drying ink or increase drying (or tailwind) temperature, second, increase fast-evaporating dilution solvent or add catalyst; third, reduce rewinding tension; fourth, detect and process before printing Substrates.

24. Ink film drying is too slow

Reasons: First, the printing speed is too fast; second, the ink (system) drying is too slow; third, the drying temperature is low.

Treatment methods: one is to reduce the speed of the printer; the second is to add a thinner or drier that evaporates quickly; the third is to increase the ambient temperature or increase the temperature or increase the blowing.

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