Printing Equipment | Flexographic Printing Machines knowledge

Flexographic printing machine uses fluid ink with strong fluidity. The ink is transferred from the ink fountain rubber roller and the anilox ink transfer roller to the graphic part of the printing plate and inked, and then the printing pressure is exerted by the pressure roller to transfer the printing plate to the printing plate. The ink on the plate is transferred to the substrate, and finally the flexographic printing process is completed by drying the surface.

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.

Stacked flexo printing machine

Stacked flexographic printing presses are sometimes also called stacked flexographic printing presses. 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, and multi-color printing can be customized.

Unit type flexographic printing machine

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 common 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.

Machine features

The reason why the flexographic printing press has developed at a constant speed is that in addition to technological breakthroughs in plate materials and inks, its own characteristics are an important reason for attracting users.

1. The machine has a simple structure, making it easy to operate and maintain. The price of a flexographic printing machine with the same functions is about 30-50% of that of an offset printing machine or a gravure printing machine.

2. The material is highly adaptable, and satisfactory printing effects can be obtained from 0.22mm plastic film to 10mm thick corrugated cardboard.

3. The printing force is small, about 19.6-39.2N/cm2, especially for printing on substrates such as corrugated paper that cannot withstand excessive pressure.

4. The printing cost is low, mainly because the machine is cheap, the plate making cost is low, the paper loss rate is low during the printing process, and the production cost is 30-50% cheaper than gravure printing.

5. The print quality is good. The short ink path ink delivery system using anilox ink transfer rollers not only simplifies the structure of the ink delivery system, but also enables quantitative control of film thickness. A breakthrough in high-performance photosensitive resin plate technology has greatly improved the resolution of the printing plate and the reproducibility of dots (up to 1-95%). Flexo printing can achieve color gradation printing of 300 lines/in, and the printing effect is comparable to offset printing and gravure printing.

Machine structure

The flexographic printing machine mainly consists of 4 parts, namely, the unwinding and feeding parts, the printing parts, the drying parts and the rewinding and rewinding parts. Modern flexographic printing machines generally have measurement and control devices such as tension control, edge control, registration control, and print observation, as well as mechanical status monitoring and fault diagnosis systems. In addition, in order to expand the scope of application, some flexographic printing machines are also equipped with glazing, laminating, hot stamping, slitting, die-cutting, punching, screen printing, and gravure printing units, forming a combined flexo printing machine. production line.

Unwinding feed components

The printing speed of flexographic printing machines generally reaches 100m/min (or even higher). Under normal operation, in order to reduce the number of roll changes and the waste of roll materials, an unwinding and feeding device must be installed. The function of the unwinding feeder is to unroll the roll of printing material, continuously and stably feed the printing material into the printing part, and control the speed, tension and lateral position of the printing material before it reaches the first printing part. The unwinding feeding component consists of a reel rack and a set of guide rollers. The reel rack is arranged in a straight line with the printing component. The roll rack is controlled by electric or hydraulic components to lift and lower, and pneumatic components are generally used to lock the axis of the web, and a detector is installed at the end of the web.

Tension control system

The unwinding feed component is also equipped with a digitally controlled electromagnetic brake tension system. It can achieve the best tension control for different printing materials and is not affected by dust and dirt. The tension compensation control adopts a loop-type self-detection system, which can continuously maintain the stable tension of the paper (or film) when the diameter of the web continues to decrease.

Drive roller

The unwinding feeding part is also equipped with a driving roller machine. The driving roller is an easily adjustable variable-speed feed roller. It controls the speed at which the web enters the printing unit smoothly, and works together with the web brake device to generate the unwinding tension of the web to adapt to different substrates (cards). paper, tissue, plastic film, etc.) while ensuring that the web maintains its correct longitudinal position.

Floating roller

The floating roller machine of the unwinding feeding part can reduce the fluctuation of unwinding tension and shorten the downtime when changing the material roll, so as to improve the efficiency of the flexographic printing machine: most flexographic printing machines are equipped with continuous roll changing devices , it is particularly important to connect the material roll without stopping the machine. This is the floating roller.

Edge control system

The unwinding and feeding device of high-end flexographic printing machines is also equipped with an edge position control system. One edge position control system is installed in front of the printing unit, and the other edge position control system is installed in front of the die-cutting table. This design keeps the roll in the correct position throughout the entire production process.

Printed parts

The printing component is the core of the flexographic printing machine and uses a short ink path ink delivery system. There are two ink rollers, or even one ink roller with a doctor blade, which can achieve uniform and quantitative transfer of ink from both inks to the surface of the printing plate.