Bending machine fault solution

When a bending machine malfunctions, it can cause slight tilting of the printing plate, leading to misregistration in both positive and negative prints. Our company once faced this issue but initially overlooked it. Instead of thoroughly investigating the root cause of the plate curvature, we opted for a temporary fix by applying tape to the inner corner of the plate to correct the overprint error. While this solution temporarily resolved the misalignment, it led to another problem: the plate cylinder's position became misaligned with the angle of the plate after installation. As a result, the plate could no longer adhere properly to the cylinder surface. This caused uneven pressure during printing. After approximately 10,000 impressions, the plate began to crack, and the cracks transferred to the printed material. At that point, we had to stop production and replace the plate, as further damage would have worsened the situation and caused more serious issues.

Issues like these, caused by improper bending, are commonly seen in newspaper printing. Besides plate tilt, there are also cases where the bending angle is inaccurate. The latter type is often harder to detect because it doesn’t always result in visible misregistration, making it less likely to be addressed promptly. For example, if the tip of the plate is bent at an incorrect angle, or if the folding angle is too sharp, or the bending position shifts backward, the layout might become larger than intended, causing the plate to not fit tightly against the cylinder. These problems can lead to plate damage over time. Therefore, if you notice misregistration between the front and back prints, or if the plate doesn't stick well to the roller after installation, it’s important to check whether the bending machine is functioning correctly and consider making necessary adjustments. (Editor: Wang Xuebin)