Ink failures frequently occur in printing, which are likely to be caused

- Jan 17, 2021-

1. Judge the suitability and transferability of the ink scraper

If the ten ink of the gravure printing plate cylinder is not scraped cleanly, the printed matter will appear dirty, ink running, knife thread, knife line and so on. The smearing and ink run-off of printed matter are related to ink adjustment. The short-term delamination phenomenon of ink can cause smearing. If the ink viscosity is high, ink run-off will occur, but it is closely related to the correct and appropriate angle and pressure of the squeegee device.

It's just that the ink on the full page is not clean, and the ink is not clean when you press it with your fingers or when you change to a new ink. If it can be wiped clean after replacing the new ink, it means that there is a problem with the thinner added in the ink.

The solution: replace the ink or thinner, and readjust the squeegee.

2. Inspection of printing substrate

If the ink has such phenomena as missing printing, white spots, orange peel, poor adhesion, etc., the surface tension and static electricity of the printing substrate must be tested first. When the surface tension of the printing substrate is lower than 35dyn, the ink adhesion is poor. When the static electricity is high, orange peel will appear. When the ink dries too fast, it will form a blockage, and the printed matter will show missing coating and white spots.

Solution: Perform surface and electrostatic treatment on the printing substrate, increase humidity in the work site, and adjust the ink with a slow-drying solvent.

3. Inspection of purity and odor of thinner

The purity of the thinner is poor, the solvent residue of the printed matter will increase, and the odor may remain on the printed matter. Check the purity of the solvent first. The simple test method is: pull a 200px wide white paper strip into the solvent to moisten it, then take it out and slightly vigorously wave it to observe the drying speed and discoloration of the solvent on the white paper strip, and then sniff Whether there is any residual odor on the door note.

When the white paper strip is swung for 8-15 times, the solvent volatilization and drying are normal. The undried solvent volatilizes slowly, otherwise the volatilization speed is fast. The discoloration of the white paper strip, except for the rust on the solvent barrel, indicates that there is a problem with the solvent. The residual odor after the solvent volatilizes is that the purity of the solvent is not enough. Scratch the original ink and the diluted ink on the film and test after drying.

The original ink has a large scrape residue, and the diluted ink has a small scrape residue, which indicates normal. On the contrary, the diluted solvent has a problem. If there is a residual peculiar smell in the scratch of the original ink, the ink has a problem. If you smell the scratch of the diluted ink, it proves that the solvent used in the thinner is not pure.

Treatment method: replace the ink or adjust the solvent of the thinner.

4. Correct use of slow drying agent

Incorrect slow-drying thinner used in ink during printing will cause color biting in printing and re-stickiness of printed matter.

The solution: change the diluent formula of the printing ink and adjust the drying performance of the printing ink.

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5. Application of diluent with different proportions

The different proportions of the ink diluent in printing can adjust the drying performance of the ink, the color density of the ink, and the viscosity of the ink. Adjusting the dryness of the ink helps to increase the printing speed and improve the clarity of the printed matter.

Adjusting the color density of the ink can reduce the pressure of the embossing rubber roller or the workload of the ink scraper, which is beneficial to the improvement of the printing speed. Adjusting the viscosity of printing ink is the key to controlling the amount of ink or adapting to the printing speed and room temperature of the printing place. It is required to deploy fast-drying, medium-drying, slow-drying or extra-slow-drying thinners according to the printing speed, the depth or the number of lines of graphics and text on the printing plate cylinder, and the room temperature of the printing place.

6. How to use from high viscosity to low viscosity

The printing speed is slow, the graphic production of the printing plate is relatively deep, and the amount of ink is required to be large, and high viscosity printing ink is required. The printing speed is fast, the graphics and text of the printing plate are relatively shallow, and the amount of ink required is small, and the ink with low viscosity should be used for printing. Apply thinner and thinner to adjust the viscosity of printing ink.

7. The use of ink distribution rollers in spot color inks and metal inks

The spot color ink requires the ink color to be consistent and uniform, and the metallic ink is easy to precipitate, so it is necessary to use the ink distribution roller in printing. In addition, in the use of spot color inks, the thinner should be used in conjunction with the thinner, and it is not suitable to use a solvent alone for dilution. Metallic ink should not be diluted with solvent. The correct method is to add an appropriate amount of thinner to adjust.

8. Use and mixed use of non-true solvents

Although the non-true solvent can not dissolve the connecting resin in the ink, it can reduce the color biting phenomenon in printing by using its characteristic to mix and use the diluted ink with the true solvent.

9. Adhesion inspection of printed products

Stick it on the printed matter with tape, flatten it with your fingers, and make it tightly combined with the printed matter, then slowly lift up half of the full length, and then quickly lift up the other half, sticking it off the printed matter The smaller the ink, the stronger the adhesion of the ink on the printed matter. On the contrary, the adhesion is worse. If the ink on the printed matter is stuck by more than 40%, it means that the adhesive force of the printing ink on the printed matter is unqualified.