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ã€Chinese Packaging Network News】 During the printing process, if too much dampening solution is used, issues such as overprinting, back sticking, and poor drying may occur. These problems can cause surface scratching, damage to the rubber blanket, and even result in serious quality failures. One of the most common issues is "rubber buckling," which refers to paper fibers, dust, or ink residue adhering to the rubber blanket. This can affect print quality, delay production, and lead to costly rework. There are six main causes behind this problem.
1. **Insufficient Pressure**
If the pressure between the printing plate and the rubber blanket is too light, it cannot effectively transfer paper fibers or dust from the blanket. Similarly, low pressure between the rubber blanket and the impression cylinder may fail to remove fine particles from the paper surface. Additionally, improper contact pressure between the plate and the roller can leave ink residue and dirt on the plate, leading to sticky buildup.
2. **Rough Paper Surface**
Paper with a rough texture, excessive dust, or powder tends to stick more easily to the rubber blanket, increasing the risk of buckling.
3. **Uneven Gaskets**
If the printing plate or rubber pad is uneven, certain areas may accumulate paper fibers and dust, causing localized buckling on the rubber.
4. **High Ink Viscosity**
When the ink is too thick, it increases the pulling force on the paper surface, making it easier for fibers and dust to become embedded in the ink. This can lead to severe peeling and pulling of the paper.
5. **Contaminated Ink**
Impurities in the ink fountain or excessive paper dust on the rollers can be transferred to the printing plate, contributing to rubber buckling.
6. **Inconsistent Water Distribution**
If the water roller has uneven water coverage, some areas may experience increased ink wear, leading to excessive rubber loss in those regions.
To address these issues, several solutions can be implemented:
1. **Use High-Quality Paper**
Choose paper with a smooth surface, even pulp, and minimal dust to reduce adhesion to the rubber blanket.
2. **Adjust Press Pressure**
Ensure proper pressure between the ink rollers, plate cylinder, and water rollers to maintain consistent contact and prevent buildup.
3. **Maintain Clean Ink**
Keep the ink free from impurities by regularly cleaning the ink fountain and rollers. Stir the ink thoroughly before use.
4. **Ensure Flat and Clean Plates and Blankets**
Regularly check and clean the printing plates and rubber blankets to avoid uneven surfaces that can trap debris.
5. **Increase Blanket Thickness (if needed)**
For multi-color presses, adding 0.09–0.15 mm of backing paper to the rubber blanket can help reduce buckling. For two-color machines, increase the pad for the first color only; for four-color machines, adjust the first and second colors slightly while keeping the others unchanged. This helps maintain accurate registration without significant overprint errors.
6. **Reduce Ink Viscosity**
Add 3–5% of a relieving agent and 1–3% varnish for general graphics. For thick ink applications, add about 2% dusting powder. For gold and silver prints, add 2–3% of an escaping agent to lower viscosity and reduce buckling. Adjust water roller settings accordingly—reduce water on light-quality rollers and increase it on velvet ones. When using coated paper, minimize the use of retackifiers to ensure vibrant ink coverage.
No matter the cause, careful observation, machine analysis, and timely adjustments can effectively resolve the issue of "rubber buckling." By maintaining good press hygiene and understanding the factors that contribute to this problem, printers can significantly improve print quality and efficiency.