When using rotary screen printing, the inside of a screen plate cylinder with a mesh is covered with ink. When the roll printing material contacts the rotating plate cylinder, the ink is pressed by a scraper located inside the cylinder to Allow the ink to pass through the mesh on the screen and transfer it to the substrate material. We can control the thickness of the ink layer transferred to the printing material by selecting screens of different meshes (now more than 400 meshes / inch) and adjusting the printing pressure.
The screen-making process of the silk-screen version is also relatively simple: first, the silk-screen version is coated with a liquid water-based photosensitive emulsion to block all the mesh holes, and then the silk-screen version is placed in a drying oven to dry; The positive film with the printed image is wound on the screen cylinder coated with the photosensitive emulsion, and exposed to it with a UV light source (since the screen printing plate is generally roller-shaped, it is necessary to rotate the screen cylinder). After the exposure is completed, the silk screen is washed in an automatic plate-making machine, the unexposed emulsion is washed away, and then the mesh part of the graphic part is left.
After the above steps, the plate cylinder can be printed on the machine. Unlike flat screen printing, in rotary screen printing, the squeegee is fixed in the plate cylinder. Before printing, the inside of the cylinder is filled with ink. When printing, it depends on the rotation of the screen cylinder. Under the action of pressure, the ink is printed on the printing material; after the printing is completed, the printing plate can be washed and stored with the corresponding post-press equipment to be used when printing again. The emulsion layer of some screens (such as some screens of Stork) can also be peeled off, and then used for coating and imaging. The number of re-uses can be as high as 10-20 times, obviously this is very Important cost-effectiveness. We can do a small calculation. If the price of a plate cylinder is 3000 yuan, the cost of the screen printing can be reduced to 150 yuan at most by repeated use.
The speed of rotary screen printing is usually 75 feet / minute to 150 feet / minute, but if printing a thicker ink layer, the speed will be slower; if the intermediate drying time is longer, the speed of rotary screen can also reach 150 Feet per minute ~ 350 feet per minute. In fact, the running speed of the rotary screen printing machine itself is not limited (its speed can be as high as 600 feet per minute), the real limiting factor is the ink and its drying performance.
The inks used for rotary screen printing are mostly UV photocurable inks, which are cured using a UV light source, but there are also solvent-based inks that are dried using hot air. For example, the conductive silver ink used for printing the "antenna" of RFID electronic tags is solvent-based The ink, which uses the hot air drying method.
In order to strengthen the position of rotary screen printing in UV flexo printing, ink manufacturers have not stopped research and development of new inks. In foreign countries, many ink companies like SunChemical, AkzoNobel and FlintInk, and Deco-Chem in Mashawaka, Indonesia, are working hard to research and develop UV inks for the combination of flexographic printing and rotary screen printing. Rotary screen printing RSF silicone-free resin ink. Domestic ink manufacturers should learn from foreign companies and strengthen technical exchanges and cooperation with foreign companies. They can also consider increasing research and development efforts in this area to lay the foundation for gaining an advantageous position in the fierce market competition.
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