Rotary screen printing and flat screen printing all-round comparison

July 16, 2019

Rotary screen printing technology has many advantages over flat screen printing equipment. In particular, it can form high-speed production lines with flexo printing equipment, embossing equipment, and offset printing equipment, greatly increasing production efficiency. The following will take Gallus's new rotary screen printing equipment as an example to systematically analyze the characteristics of rotary screen printing.

Flat screen defects

Flat screens are usually made of polyester mesh that is stretched over the frame. In order to obtain good edge sharpness and image detail for the prints, a gap must be left between the screen and the substrate during the printing process. In this case, the screen is under pressure and comes into contact with the substrate. The squeegee moves and the ink under the screen moves to the surface of the substrate. At this time, there is still a certain amount of ink in the screen pores. These excess inks are easily sticky. On the print, make the image dirty or fuzzy.

Another problem with flat screen printing is that the squeegee pressurizes and moves the screen to allow the ink to transfer. It also stretches the screen and image. The closer the squeegee is to the plate edge, the greater the elongation, and naturally Causes some kind of distortion and distortion of the image, causing print distortion.

However, rotary screen printing is due to the fact that the screen is in the shape of a roller, and the screen plate and the substrate are in line contact, so that image distortion in the printing process can be avoided.

Online printing

Is flat screen printing nothing? it's not true. In many areas, such as lottery tickets, card printing and other printing areas is very convenient and practical, which is impossible to do rotary screen printer. However, rotary screen printing is still suitable for most areas.

Rotary screen printers have certain standards in design and have the ability to go online with web printing equipment (such as rotary letterpress, flexographic or offset press). This roll-to-roll online printing method is commonly used for packaging and trademark printing, personal health card printing and beverage trademark printing, etc. It can also be used for transparent plastic film printing or advertising printing.

Online printing allows users to make full use of the ink deposition characteristics and high-resolution resolution characteristics of different printing plates. If the customer wants 30μm thick UV ink, then the rotary screen printer can meet this requirement, because the rotary screen printing can provide ink thickness of 20-30μm; if the customer requires very fine image printing or high resolution dot Printing, then flexo or offset printing are the best choices, and these can be used online to take advantage of various printing technologies to achieve the widest range of production capabilities.

With respect to the thick characteristics of printing inks, on-line technology can produce opaque prints and colorful prints. The specific process combination is to print high-definition images with flexo or offset printing, and to print underprint or bright-colored fields on rotary screen printing.

For coarse and special ink printing, including gold and silver ink, thermochromic ink, electronic fluorescent ink, etc., it is best to choose rotary screen printing. This printing method can also print tactile images such as Braille. The screen protectors and coatings have chemical and oxidation resistance and are suitable for many specialty inks.

Rotary screen printing equipment

There are only a few manufacturers that produce rotary screen printing equipment in the world. Two of them have a relatively large market share: one is Gallus of Switzerland and the other is Stork, which is based in the Netherlands. Its technical characteristics are different. the same.

Gallus can produce rotary screen printers and on-line equipment. Its on-line equipment includes letterpress printers, flexo printers and offset printers, and online equipment can be equipped with one or more rotary screen printing units, hot stamping devices and die cutting devices. Typical models are:

The R200 screen printing machine, 8 inches (203mm) in print format, can be connected to letterpress equipment, UV glazing equipment, web printing equipment and curing equipment.

EM260, EM410 and EM510 screen printers are on-line structures consisting of flexo, rotary screen printing equipment, glazing equipment and embossing equipment. The device can be printed on both sides as required and contains 24 printing workstations such as trademarks, hardboards and flexo packages. The print width can be changed from 10 inches (254mm) to 20 inches (510mm).

The EM280 type is an open structure. This type of register is generally accurate, suitable for flexo and rotary screen printing combinations (up to 10 workstations), and can be quickly plated, set, stripped, and print widths up to 12 Inches (297mm).

Reel screen

Gallus reel screen is a nickel-plated polyester screen with both ends fixed on the print cylinder. The screen consists of a photopolymer emulsion and a protective coating. The size of the screen/window is controlled by a counter; the screen has 8 kinds of standard specifications and the screen mesh number is 64 to 400 mesh/inch.

Roll plate version of the plate making method is similar to flat screen version. First, the photopolymer film is punched with a register hole; then, the screen is cut to a desired length, and then punched with the registration hole of the diaphragm; after that, the emulsion surface of the diaphragm is removed. For the protective foil, the diaphragm emulsion is fixed on the positioning pin face up and exposed after being sealed with the film; it is sprayed with strong tap water and dried with hot air.

Reprinted from: Printing Technology

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