Technical advantages of rotary screen printing

The original plane mesh is rolled into a cylinder, and the printing materials used for roll-to-roll printing are similar to web offset and gravure printing, and can be combined with offset printing and flexo printing. This is the rotary screen printing. Charm.

The difference between rotary screen printing and traditional screen printing

More than 30 years ago, Dutch STORK invented rotary screen printing technology. In the following decades, rotary screen printing was widely used in textile printing, wallpaper, and floor printing. It has been used in paper printing for more than 10 years. The emergence and gradual promotion of rotary screen printing in the field of paper printing is a revolution in traditional screen printing. The reason why it was called a revolution was due to fundamental innovations in various aspects of rotary screen printing.

In the traditional sense, screen printing is a sheet-fed printing device. This type of printing device has many limitations in its own process, especially in the case of large-area printing, the material is easily deformed, the accuracy is not high, and multi-color printing is more difficult to guarantee; Rotary screen printing has new concepts in these areas.

1) The screen version is converted from a flat form to a roller form;
2) Replace the traditional weaving screen with a honeycomb metal screen;
3) The printing equipment is compact and highly efficient, with high precision. As a result of adopting advanced independent drive, independent-registered shaftless transmission system, it can form multiple sets of printing units and can be connected with various cylinder printing equipment.
Compared with plane screen printing, roller screen printing has the following features:
1) continuous production, high efficiency;
2) continuous paper feeding, small deformation, with paper correction system, high registration accuracy;
3) Multi-unit color printing, once completed;
4) Adapt to large-scale production, high yield, and less waste.
The printing principle of rotary screen printing equipment is shown in Figure 1.

Screen printing plate comparison

From the points of materials, there are basically two categories of screen printing plates, one is a traditional woven screen, and the other is a metal screen represented by the bell mouth honeycomb screen material of STORK in the Netherlands, and two kinds of screen screens. The structural characteristics of the material are shown in Figure 2. What are the benefits of a mesh-based screen? It can be analyzed from the following aspects.

1. Printing mechanism

Fig. 3 is a schematic diagram of ink transfer during printing. In STORK pure nickel electroforming screen, the ink passes through the shape of the bell mouth, and the ink surface (squeegee) of each mesh has a large aperture, and the paper surface has a small aperture. , so the ink is easily transferred from the ink surface to the paper surface (printing surface).

The fabric mesh is woven by a thread, and the mesh is scattered downwards and downwards. The ink passes through the interlaced mesh, and the surface tension of the interlaced mesh must be overcome. Therefore, the ink transfer is relatively difficult.

Due to the unique cellular mesh structure of the metal electroforming mesh, the screen printing can achieve small text, fine lines, and even micro-text printing, and the printing patterns are delicate and exquisite.

2. Printing plate life and economy

1) Honeycomb mesh is electroformed from metallic nickel. Metal nickel is a highly wear-resistant metal. Therefore, from this point, the service life of honeycomb mesh far exceeds that of ordinary fabric mesh. .

2) Since the metal mesh has a honeycomb-shaped hexagonal stabilizing structure, the continuous use time of the screen can reach more than 1 month, and the service life on the machine is basically 10 times that of the ordinary fabric screen, but the price is just an ordinary screen. 2 to 3 times.

3) Honeycomb wire mesh can be reused about 15 times, that is, the printing pattern can be repeatedly changed on the plate cylinder during the effective use period of the screen. This is very meaningful for short-run printing and proof printing, which can greatly reduce the cost of platemaking.

4) Under the same conditions, the honeycomb metal screen can withstand higher printing speeds, the maximum printing speed can reach 125m/min, and the weaving screen printing speed is usually 30m/min.

3. Screen parameter control

The printable range of common fabric screens is small. Usually, common fabric screens generally use only one parameter of “mesh number” to control the screen quality. In addition to “mesh count”, honeycomb mesh screens can also choose “ Parameters such as open porosity, thickness, etc., that is, honeycomb meshes can have different open porosity and thickness under the same mesh number, so as to achieve different printing ink thickness and achieve different printing effects. As shown in Table 1.

From Table 1, it can be seen that, in the same mesh number, different aperture ratios can obtain different ink thicknesses on the substrate. Therefore, the customer can select the screen according to the product to be printed.

Rotary screen printing flexible and fine

Rotary screen printing equipment has the characteristics of flexibility and high precision. It not only can provide excellent printing units, can be connected with any roller equipment production, can make up for the monotonous defects of a single type of printing process, but also can provide the entire screen printing production company. line. Moreover, in various screen printing production lines, it is also possible to integrate various printing and post-printing processing technologies such as drying, hot stamping, compounding, peeling, cutting, and die cutting. Figure 4 shows STORK screen printing equipment working with hot air and UV drying systems. Figure 5 shows STORK's RSI printing unit, which can be used in conjunction with various drum-type printing equipment.

The above screen printing system is driven by a servo motor. The machine can operate accurately and can achieve high-precision screen printing. Compared with other types of screen printing equipment, rotary screen printing can be said to be a revolution in screen printing technology.

Source: "Printing Technology"