Analysis of 3 common faults of gravure ink, accurate and in place!

Poor Print Fastness

Causes and Solutions:

1. The surface tension of PE or PP film is lower than 3.6–3.8 × 10⁻² N/m. Use a surface tension testing solution to check the film's surface tension. If it doesn't meet the required level, reprocess the film before printing.

2. The ink is too diluted, causing the adhesive to break down, or an incorrect thinner was used. When diluting the ink, maintain a viscosity between 25–35 seconds using a No. 4 cup. Always choose the correct thinner to avoid compromising the ink’s quality.

3. The ink has poor adhesion to the film. Consider switching to a different ink type or contact the ink manufacturer for a suitable alternative.

Lost Imprint

Phenomenon: During printing, small prints and fine lines are missing at the start, and in severe cases, entire patterns may not be printed at all.

Causes and Solutions:

1. The ink's viscosity is too high for the printing speed. Adjust the ink's viscosity to an appropriate level that matches the process speed.

2. The ink dries too quickly, while the printing speed is too slow. Add a slow-drying thinner (such as n-butanol) to the ink, but only in controlled amounts to prevent issues like reduced adhesion.

3. The etched cells on the printing plate are too shallow. Re-engrave the plate to ensure proper ink retention.

4. The scraper angle or position is incorrect. A standard squeegee angle is usually between 30° and 60°, which helps prevent damage to the plate while ensuring a good ink layer. Adjust the doctor blade position based on the ink’s drying conditions—move it forward if the ink dries too fast to reduce the distance between the blade and the printing area.

5. The hot air position is improper. Adjust the hot air direction and position to improve drying efficiency without affecting print quality.

Ink Spill

Phenomenon: There are spots, patterns, or ink overflowing from the lines on the printed surface.

Causes and Solutions:

1. The ink is too thin after dilution. Add some undiluted ink and adjust the viscosity to 25–35 seconds using a No. 4 cup. Alternatively, run the press empty for a while to evaporate some solvent and increase the viscosity to the desired level.

2. The printing speed is too slow, or the ink dries too slowly. Increase the printing speed or add a faster-drying thinner to the ink.

3. The engraving of the printing plate is too deep or the plate is worn out. Replace or re-engrave the plate to ensure proper ink control.

4. The scraper's hardness, pressure, or angle is not right. Adjust the pressure and angle of the doctor blade, polish the blade, and consider using a softer blade to improve performance.

By addressing these common issues, you can significantly improve the quality and consistency of gravure printing, ensuring better results and reducing waste during production.