Although the squeegee is very inconspicuous, it has a vital impact on product quality in terms of high-precision ink color printing technology. Improper use of the squeegee can easily cause line marks, color aberration, clogging and other defects on the surface of the printed matter. Therefore, it is crucial to understand how a squeegee works and how to use it correctly.
1. Selection of polyester plastic scraper
The main function of the doctor blade is to wipe off the excess ink on the surface of the anilox roller, which can better control the amount of ink transferred to the printing plate. Currently, common polyester plastic scrapers have widths ranging from 25mm to 70mm, thicknesses from 0.5mm to 2.0mm, and blade angles of 30° and 45°.
Before printing, the first thing to consider is the printing layout, whether it is a solid version, a line text version, or a multi-color overlay dot color version.
A. If the anilox roller configuration in the factory printing machine uses 280-380 lines, you can choose a squeegee with a thickness of 1.5mm or 2.0mm and a blade angle of 45°. The reason is that the anilox roller with a low screen line wears the doctor blade faster, resulting in an increase in ink volume and darker printing colors. Choose such a squeegee so that when the amount of ink increases with blade wear during use, it will not affect the printing color changes too much.
B. If the anilox roller configuration in the factory printing machine uses 380-550 lines, the higher the line number of the anilox roller, the higher the requirements for the squeegee effect. At this time, you can choose a squeegee with a thickness of 1.5mm and a blade angle of 30°. The reason is that the anilox roller with high screen lines has a good surface finish. At this time, choosing a 30° thin-layered blade tip can effectively obtain the ideal squeegee effect.
2. Details that need to be paid attention to when installing polyester plastic scrapers
1. Cut the length of the doctor blade according to the length of the anilox roller.
When replacing a new squeegee or sealing knife, it should be noted that the length after cutting should be slightly longer than the length of the anilox roller by 25px; otherwise, during the printing process, the length of the two ends of the squeegee and sealing knife is insufficient, resulting in anilox patterns. If the ink at both ends of the roller is not wiped off, ink leakage will occur.
2. Pay attention to the flatness of the scraper when installing.
When there is a problem and it is necessary to replace the scraper with a new one, the installation screws should be tightened from the middle to both ends to ensure the flatness of the scraper. A more practical method is to hold the scraper inward with the thumb of one hand (make sure to wear gloves), and hold a wrench in the other hand to tighten the screws on the clamping plate.