The printing part is the core of the flexographic printing machine. The arrangement of the printing part directly affects the operating performance, print quality, printing speed and the applicable scope of printing. According to the arrangement of the printing parts, flexographic printing machines can be divided into three categories: stacked type, satellite type and unit type. The stacked flexo printing machine (shown in Figure 2) is sometimes also called an accumulation flexo printing machine. Independent printing units are stacked one above another and arranged at one or both ends of the main wall panel of the printing press, or various printing units are installed on the rack. Each printing unit is turned by a gear mounted on the main wall panel. The laminated mimeograph machine can print 1-8 colors, but usually 6 colors.
Laminated printing press has 4 advantages:
1. Single-color and multi-color printing are possible. For web printing machines, double-sided printing can be achieved by changing the conveying route of the substrate or using a flip roller.
2． Printing materials are generally hard materials such as sheet paper, cardboard, corrugated paper, etc. They can also be in roll form, such as self-adhesive paper and newspapers. The viscosity of printing materials must be accurately measured with a viscosity cup.
3. Strong post-press processing capabilities. The printing unit and processing functions can be flexibly configured according to user needs. The unit-type flexo printing machine can facilitate the installation of auxiliary equipment. After printing, auxiliary joint processing can be performed, such as glazing, die-cutting, etc. It is easy to operate and maintain, and has good performance. Tension can be measured with a dyne pen.
4． It is suitable for short-run printing units with many workstations and one machine with multiple functions. For special printing products with small batches, urgent delivery times and many workstations, the use of this type of equipment has advantages.
5. At present, high-speed multi-color printing parts are standardized, components are universal, product series is relatively high, and the design is advanced. Automatic control systems such as attached tension, edge position, registration, etc.
6． The spacing between the imprinting units of the short-distance array flexo printing machine is small, which facilitates multi-color overprinting. Therefore, this machine can be used to print small prints such as trademarks and packaging boxes with high precision. For printing materials with low stretchability, overprinting The effect is also better. Satellite flexographic printing press (shown in Figure 3), sometimes becomes the most commonly used impression cylinder flexographic printing press. Each printing unit is mounted between two wall panels around a special impression cylinder. The printing material is wrapped around a special impression cylinder for color registration printing. Because the gears are directly driven, whether it is paper or film, even if no special control device is installed, it can still be overprinted very accurately, and the printing process is stable. It is often used to print color products. Some people have predicted that satellite flexo printing will be the new mainstream of flexo printing in the 21st century.
The main disadvantages are:
(1) After the material passes through the printing machine once, it can only complete single-sided printing. Although the other side can be printed through the guide roller, due to the long route of the material belt, its tensile deformation increases and is uneven, making it very difficult to achieve registration of the printed images on both sides. Therefore, on the satellite flexographic printing machine, a film material is used, and after printing, it is sealed with longitudinal hot air to form a packaging bag with patterns on both sides.
(2) The distance between each printing unit is too short, and it is easy to smear when the ink is not properly dried. The UV and UV/EB flexo inks developed in recent years can achieve instant drying after printing by UV or UV/EB illumination, basically solving the problem of smearing. The unit-type flexographic printing machine consists of a linear flexographic printing machine and 4-8 independent and horizontally arranged printing units driven by a special power shaft. The unit-type flexographic printing machine only supports one printing unit for each pair of additional plates, so the unit-type flexographic printing machine can be designed to adapt to different drum surfaces.
The main advantages are:
(1) The unit is easy to install and assemble, and post-printing processing is easy.
(2) Suitable for short-run printing.
(3) By changing the running route of the material belt with the guide roller, double-sided printing can be achieved at one time.