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

1. Poor Print Fastness

Poor print fastness is a common issue in gravure printing, which can significantly affect the quality and durability of printed materials. Here are the main causes and solutions:

1. The surface tension of PE or PP film is below 3.6–3.8 × 10⁻² N/m. This can lead to poor adhesion between the ink and the film. To address this, use a surface tension testing solution to check the film’s surface. If it doesn't meet the required level, re-treat the film before printing.

2. Ink is diluted too much, causing the adhesive properties to break down, or an incorrect thinner is used. When diluting ink, ensure that the viscosity remains within 25–35 seconds (using a No. 4 cup). Choose the right thinner carefully to avoid compromising the ink's performance.

3. The ink itself may not adhere well to the film. In such cases, consider switching to a different ink type or contact the ink manufacturer for recommendations.

2. Lost Imprint

This issue occurs when small prints or thin lines disappear during the printing process, and in severe cases, entire patterns may not be printed at all.

Causes and Solutions:

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

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 do so in controlled amounts to prevent adhesion issues.

3. The engraving on the printing plate is too shallow. A new plate should be made to ensure proper ink transfer.

4. The angle or position of the squeegee is improper. The ideal squeegee angle is usually between 30° and 60°, which prevents damage to the plate while ensuring good ink coverage. Adjust the position based on the drying condition of the ink—move the squeegee forward if the ink dries too fast.

5. The hot air position is incorrect. Adjust the hot air settings accordingly to improve drying efficiency.

3. Ink Spill

Ink spill occurs when spots, patterns, or excess ink appear on the printed surface, often due to ink overflowing from the engraved areas.

Causes and Solutions:

1. The ink viscosity is too low after dilution. To fix this, add some undiluted ink and adjust the viscosity back to 25–35 seconds (using a No. 4 cup). Alternatively, run the press empty for a while to allow some solvent to evaporate and increase the viscosity.

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 on the printing plate is too deep or has become worn out. Replace or repair the plate to restore proper ink retention.

4. The squeegee blade hardness, pressure, or angle is not suitable. Adjust the pressure and angle, polish the blade, and reduce its hardness for better performance.

By understanding these common faults and their solutions, printers can maintain high-quality output and reduce waste during the gravure printing process.