In recent years, the application of closed squeegee systems in flexo printing has increased. To help flexo printing operators understand the closed squeegee system in depth, this article will introduce the installation, adjustment, and cleaning of closed squeegee systems. Some tips and suggestions. It must be specified here that, when performing the following operations, it is imperative that you follow the recommendations and guidelines of the supplier of the enclosed squeegee system and refer to the operating manual.
The basic features of the closed scraper system
The scraping method of the closed scraper system is shown in Figure 1. The basic features of the system mainly include the following aspects.
(1) Adopt unique chamber structure and double-layer ink-sealing design to achieve better ink transfer and save ink.
(2) Effectively controlling the large amount of solvent evaporation in the ink, improving the working environment and reducing air pollution. Since most of the area where the ink is located is sealed, only a very small portion that is in contact with the anilox roll is exposed, thereby greatly reducing the amount of solvent volatilization.
(3) The adaptability to the printing speed is good. Regardless of the printing speed, the amount of ink transferred is fixed, so the printing quality is stable.
(4) A combination scraper can be used to replace the scraper quickly and simply.
Of course, closed-type scraper systems still have some problems. For example, the contact angle of the closed scraper and the degree of freedom of the pressure are very small, the requirements for the uniformity of the scraping ink are high, and the tightness is required to be good, otherwise the ink leakage is easy to occur. In addition, the cleaning operation after the printing is troublesome, especially the ink or varnish that remains in the blind spot is more difficult to remove, but the application of the automatic cleaning device solves this problem to some extent.
Scraper and seal installation
1. Cutting scraper
There are many types of squeegee blades. Regardless of the type of squeegee used, it is necessary to first carefully inspect the squeegee blade for small burrs, small notches, or other defects, which may adversely affect the printing or glazing process. Moreover, the blade of the scraper must be clean.
Always wear protective gloves and goggles when cutting the squeegee, and use special cutting tools to ensure that the trim is straight and tidy. More importantly, it is necessary to ensure that the length of the scraper after cutting is appropriate.
2. Install a new scraper
Loosen the screw on the tool holder, wear safety glasses and gloves, carefully remove the old blade from the tool holder and ink chamber, and send it to the designated area for proper disposal.
Next, use a soft cloth, a suitable amount of special cleaning agent or hot water, and gently wipe off the dried ink or varnish remaining in the tool holder. This is done so that the new blade can be installed in the ink chamber. To prevent ink or varnish from leaking during operation.
When installing a new spatula, make sure that it is the correct length and that there are no defects, and then tighten and fix the knife holder. If the blade is bent or loosened, it will not only affect the service life of the blade, but also the seal will leak easily. Leakage at the sealing strip is often caused by excessive pressure on the anilox roller by the doctor blade. Therefore, it is important to ensure that the sealing strip and blade are properly installed.
3. Install the sealing strip
Carefully check the width of the sealing strip is appropriate, some sealing strips often have some small burrs, or have been damaged during the cutting process. Different material sealing strips have different sealing properties. Therefore, you must consult with your supplier and know which type of sealing strip should be used and why the sealing strip should be used.
The accuracy of the dimensions of the sealing strip must also be ensured, even a deviation of 1/4 inch can severely affect the sealing performance. Therefore, it must be ensured that the sealing strip matches the closed-type scraper system used.
In addition, the surfaces of both ends of the anilox roller used in conjunction with the closed-type scraper system should be unengraved, that is, the surface of both ends of the net-spinning roller that contacts the sealing strip has a smooth surface, which can minimize the sealing. The strip wears out and can effectively prevent ink or varnish from leaking from the seal during transfer. The main function of the sealing strip is to block the leakage of ink or varnish. Therefore, be sure to check the seal bar and scraper position before starting printing.