Analysis of new development of flexo and gravure printing technology
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Flexo, gravure, offset and screen printing are four common printing methods for packaging and printing. Flexo and gravure are more distinctive in the printing of flexible packaging materials, folding cartons, paper bags, gift wrapping papers and other printing materials. From the perspective of the development of modern flexo and gravure, there are many similarities or similarities in the structure and technology of equipment, except for the large differences in plate making. In order to compare and understand the similarities and differences between the two printing methods in terms of equipment structure and new technology, the development and application of flexographic and gravure equipment technology in recent years will be briefly discussed.
First, the use of automatic traction and tension adjustment device to achieve non-stop roll change / winding
The new flexo press and gravure press adopt automatic paper-feeding mechanism and gas-electric tension measuring and adjusting device to ensure constant tension and realize non-stop roll change/winding. In order to ensure that the edge of the printing material enters the printing portion is always correct, for opaque materials such as paper, a correcting device composed of a photoelectric scanning head or an ultrasonic sensor is also used. Temperature and humidity conditioning is sometimes required when printing paper or paper jams. When printing plastic film or aluminum foil, a corona treatment device is also provided to improve the ink-receiving ability of the film surface.
Second, the use of independent / direct drive technology to achieve a continuous and optional printing length.
Independent drive technology has been used for many years on gravure presses, but is limited to units such as traction, coating, laminating and cross-cutting. It has now evolved into a complete gravure press that does not require mechanical transmission. In each printing unit, a motor drive is used. The plate cylinder is directly driven by the motor to achieve longitudinal registration during the embossing process, and a stepping motor is moved to control the lateral registration. The main advantage of the independent drive gravure press is the reduction of mechanical parts (no mechanical drive shaft and register compensation roller mechanism, etc.), and the length of the tape is shortened, which is beneficial to improve the printing quality and printing speed.
The plate cylinder of the old-fashioned flexo press drives the gears of the plate cylinder through the gears of the impression cylinder to form a synchronous rotation, and the repeated circumference of the printed matter is the same as the pitch of the gears. In each printing unit of the new flexo printing machine, the plate cylinder is directly driven by a motor, which solves the problem that the repeated length of the printing product is limited by the gear pitch. The digital drive technology directly drives the plate cylinder. When changing the printing products of different circumferences, it is not necessary to change the gears, and the continuous and optional printing length can be realized. Thanks to the digital control, no need for repeated shifting adjustments, eliminating the need to change the speed and adjust the gear meshing work, thus improving efficiency.
With the combination of direct control technology and CI design, as well as the change in print length and the reduction in machine commissioning time, the situation in which flexo printing has been difficult to print on large and varied webs has changed.
Third, the use of the sleeve plate cylinder structure to achieve "quick change plate."
The plate cylinders of the old flexo presses and gravure presses basically adopt a monolithic structure, while the new flexo presses and gravure presses mostly adopt a sleeve type plate cylinder structure. Due to the low cost of the sleeve type drum structure, the loading and unloading is easy. High flexibility, long service life, convenient storage, high system accuracy, shorter preparation time, faster printing replacement, and “quick change” function. It is widely used in flexo and gravure and will gradually replace traditional rollers. The biggest advantage of the sleeve plate cylinder is that it can be reused. The plate printing length can be changed by using sleeves of different wall thicknesses.
Fourth, the use of closed squeegee system to reduce environmental pollution, is conducive to the rapid replacement of squeegee
The reverse ink scraper structure is adopted in the quantitative ink supply system, which is suitable for high-speed operation, reduces the solvent evaporation and environmental pollution problems in the solvent ink, and solves the foam problem accompanying the use of the water-based ink.
The satellite flexo printing machine adopts a fully enclosed double scraper inking system. The ink is sprayed onto the surface of the anilox roller through the ink port and stored in the ink chamber. The ink is scraped by the reverse scraper and the positive scraper acts as a sealing. Because of its good sealing, it has great benefits for health and the environment. In a fully enclosed system, the scraper, seal, gasket, and pressure plate are mounted on a hollow bracket and mechanically (or pneumatically or hydraulically) pushed toward the ceramic anilox roller and applied with a certain pressure. The ink feed pipe and the return pipe are respectively connected to the ink pump and the ink storage container. The closed doctor blade system ensures optimum ink volume for the anilox roll and plate. The use of laser engraving and closed scraper for high-line ceramic anilox rolls ensures optimum ink volume for anilox rolls and plates. The ink transfer performance of the short ink path system is improved, and the stability of the printed product quality is improved.
Five, plate cylinder automatic cleaning device
At the end of printing, automatic cleaning of the plate cylinder on the machine can significantly reduce the amount of manual cleaning and improve the operating environment. The Heliostar 2000 unit gravure press is equipped with a quick change and cleaning system (Ecoplus) that significantly reduces press preparation time. The TURBOLEAN ink supply and cleaning system automatically supplies ink to the printing components in sequence and cleans the anilox roller, chamber wiper system, ink pump and ink tube.
Six, fast replacement, positioning system
On the transmission side of the gravure press or flexo press, there is a trolley guide bar, and the guide bar is lifted and lowered by the cylinder, which can accurately control the movement of the trolley and speed up the installation and disassembly of the trolley. The PORTACIFT robotic roll change system is used to automatically change the plate cylinder and anilox roll; it takes only one minute to replace a roll. Through the intelligent transmission system and positioning system, accurate movement and lateral registration of the plate cylinder and anilox roller of each color group are ensured.
Seven, combined unit structure, a variety of post-printing processing forms.
RCS330 narrow-width flexo press with full digital drive technology, full computer control, flexo/screen printing/offset/embossing and other printing interchange units. Arsoma EM series unit type flexo printing machine adopts optional modular unit and open interface structure. It can flexibly select die cutting, hot stamping, marking, glazing, laminating, embossing, control, etc. Post-press processing unit.
FG500 series flexo printing machine can be configured as gravure and flexo combination printing press according to users' needs.
B250 unit type 6-color narrow-width flexo printing machine, according to the user's processing needs, can choose the corresponding configuration, complete holographic anti-counterfeiting, UV glazing, hot stamping, molding pattern, magnetic strip, die cutter, paper tape punching, slitting Online post-processing functions such as stacking.
A new type of paper gravure, wire-bonding, die-cutting line, dedicated to the printing of cigarette packets and other thick paper. The Tachys range of satellite flexo presses is available in a variety of configurations and can be used for glazing, cold/hot coating, lamination, etc. in a line-up flexographic printing unit.
It can be seen that one-stop production is becoming more and more important, and a single production unit is developing towards an integrated production line.
Eight, the application of computer control technology, intelligent operation management.
Using advanced computer technology and management system, it can realize the monitoring system from single control to centralized control, from stand-alone control to the entire production line, and ensure that the equipment will not generate waste when registering the equipment under the shutdown state.
Using a modular automatic operating system, you can pre-select menus, centrally operate the unwinding/winding unit, printing unit, drying unit, and optional “printing” viewing module to view the entire printing process on the display screen. Using CAN communication technology, functional modules are connected into a network to exchange information. Help customers with a remote modem with a modem.
ASTRAFLEX CCI satellite 8-color packaging flexo press, through the electronic synchronization adjustment system to achieve coordination between the printing station and the anilox roller. The traction device can be set up in proportion and can work according to the actual tension.
B250 unit type 6-color narrow-width flexo printing machine with print quality synchronous inspection device and computer controlled automatic registration system. Various functions such as parameter storage, sampling content setting, pattern segmentation and focusing. The registration system and the main control cabinet computer are connected into a network to control the operation of the entire production system.
With the establishment of the digital age, the Tachys series of electronically driven printing units and variable-length, high-quality satellite flexo presses have been introduced.
Nine, apply relevant advanced technology to improve the quality of printed products
The new flexo and gravure presses use highly efficient servo stepper motors that automatically monitor the speed to ensure highly accurate settings for printing pressure, print length, plate and substrate thickness. The unwinding/winding unit can be accurately controlled by a DC motor.
The use of thin plate technology, computer-to-plate technology, UV inks and high-wire ceramic anilox rolls can greatly improve the quality and level of flexo prints.