The carton is printed and discolored, what should I do?
Foshan Gruwill Hardware Products Co., Ltd. , https://www.zsgruwill.com
When operating a carton flexo ink printing machine, it's common to encounter color variations during the printing process. Many operators lack the foresight to anticipate these issues and often struggle to resolve them once they occur, leading to a high rate of defective prints. In this article, "Packaging Zone" shares several practical solutions that can help professionals in the industry address such problems more effectively.
First, it's essential to review the design of your printed product. For example, placing large ink areas in non-critical positions can lead to inconsistent color application. To avoid this, try positioning such elements in the gripper area, where the paper is better controlled, resulting in more stable and consistent print quality. If you've made these adjustments and the color still changes, it's important to contact the manufacturer for further assistance to identify and fix the root cause quickly.
Once the film issue is ruled out, the next step is to inspect the ink delivery system. A simple yet effective method involves using car wash water (with some added water) to thoroughly clean the ink path. After cleaning, check for any white crystalline residues inside the system. These deposits can cause localized color shifts, especially in specific areas of the print. If no crystals are found, restart the machine and run ink through all the rollers. Then, close the plate ink and water rollers and verify that the pressure is within standard range. If not, adjust the pressure accordingly for optimal performance.
During the test print, choose high-quality coated paper to minimize external influences on color consistency. For thin paper, reduce the air volume as much as possible, while for thicker stock, adjust it appropriately. If color changes occur, don’t immediately assume it’s a machine fault. Instead, investigate peripheral factors first—use a magnifying glass to examine the printing plate for dot deformation, and check the film to rule out issues from the original artwork.
Next, evaluate the condition of the paper handling system, including the paper wind adjustment, the flatness of the front gauge, the interaction between the paper and the pressure plate, and the conveyor belt operation. Once the ink path is confirmed to be working properly, move on to the water system. Adjust the pressure between the plate water roller, metering roller, water bucket roller, and water channeling roller, paying special attention to the intermediate roller. It's best to avoid using the intermediate water roller if possible.
If the color problem persists, consider checking the printing cylinders. Clean the rubber pads and the teeth thoroughly, and remove the spring for a deeper clean. Some technicians only clean the pads but overlook the importance of cleaning the actual teeth, which can affect print quality. Inspect for dead teeth using a high-performance rust remover like WD-40, and lubricate the teeth and shafts to ensure smooth operation. If no issues are found in the ink or water paths, check the rubber blanket. The ideal thickness should be around 35 wire, and it's recommended to use brand-new aluminum-backed blankets. Retighten the blanket after some usage to maintain its performance.