In the printing production process, one of the most common and frustrating issues is screen plugging. When a printing plate becomes plugged, it not only degrades print quality but also significantly slows down the overall efficiency of the printing operation. Even more problematic is that many of these printed products are high-volume orders from major clients—such as packaging for fast-moving consumer goods like Wahaha or Mengniu. These orders are large in scale, often requiring the printing plate to run for thousands of sheets. If plugging occurs, it leads to extended downtime, reduced productivity, and even potential losses in carton production. Therefore, addressing the issue of screen plugging is crucial.
Typically, the problem arises due to a combination of factors involving ink, the printing plate, and operator practices. Let's take a closer look at each of these causes and how they can be resolved.
First, ink-related issues are a major contributor. Poor ink flowability is one such problem. Some operators may slow down the ink return process, allowing more ink to accumulate between the anilox roller and the rubber roller. While this method works well for full-plate printing, it can lead to excessive ink on the printing plate when printing fine details or small dots, resulting in plugging. To prevent this, the ink’s fluidity should be improved, which can be achieved by adjusting the air pressure of the ink supply pump.
Another common issue is ink drying too quickly. When the ink transfers from the anilox roller to the printing plate and then to the paper, if it dries too fast, it can dry on the plate itself, leading to buildup and plugging. A good way to identify this is by noticing that the ink on the plate is hard to wipe off during cleaning. In such cases, adding fresh ink or using a slow-drying agent can help resolve the issue.
High ink viscosity is another factor. When the ink is too thick, it flows poorly and can cause plugging, similar to the issue with poor fluidity. Lowering the viscosity can help improve ink flow and reduce the risk of blockage. Additionally, dust and paper particles in the ink can settle on the printing plate, causing further plugging. Installing a 120-mesh filter in the ink inlet tube can help prevent this. It's also important to maintain the correct ink viscosity—ideally around 9 seconds—to ensure smooth printing and consistent color density.
Second, the mismatch between the printing plate and the anilox roller can also lead to plugging. For example, using a 300-mesh anilox roller to print an 80-line pattern might result in regular blockages because the mesh size is too large, leading to excessive ink transfer. This can cause over-inking on the plate, which in turn blocks the printing dots. The recommended ratio between the anilox roller mesh and the printing plate line count is typically 1:4.5, which helps avoid such issues.
Finally, human error during operation can also contribute to plugging. Excessive printing pressure can cause the plate to deform, leading to expanded printing dots and eventual clogging. The ideal printing pressure gap is usually about 0.3 mm less than the thickness of the cardboard being used. Proper training of operators to avoid applying too much pressure is essential in preventing such problems.
By addressing these factors—improving ink flow, controlling drying time, adjusting viscosity, ensuring proper anilox-to-plate matching, and training operators—we can significantly reduce the occurrence of screen plugging and improve both print quality and production efficiency.
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Guangzhou Vantee Electronic Technology Co., Ltd. , https://www.finerroller.com