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What are the characteristics of the unit type flexographic printing machine The unit type flexographic printing press is the most popular type in the world today. Its structural feature is that each printing unit is independent of each other and is arranged in a straight line along the horizontal direction. The main motor is located at the back of the die-cutting unit with the largest load, and then transmits power through a shared drive shaft at the rear of the machine. Therefore, this model can determine the number of printing units according to the user's specific requirements, up to a maximum of 10 units, that is, 10 color printing can be achieved. This feature of the unit type flexographic press makes it has many advantages such as good accessibility, short preparation time before printing, and the like. In the United States and Canada, this narrow-width, flexo-type flexo press has dominated most of the market in self-adhesives, small folding cartons, commercial forms, paper, bills, and soft drink packaging. In recent years, the packaging and printing market has shown a new trend. Manufacturers have continuously introduced new packaging designs, and the number of printing of each product has also been relatively reduced. This has given flexible machine-type flexo presses better opportunities.
The foreign packaging printing industry has traditionally referred to a flexographic printing press as a "Converting Machine" because it is not only easy to convert but also flexible. Compared with the wide flexo printing machine, the unit type flexographic printing machine can perform multiple processing steps such as printing and die cutting at a time. If equipped with an EDM system, the narrow-width flexographic printing machine can also print plastic films; On-line self-bonding compound peel-printing-recombination device can print the required information on the inside of the sticker; if the automatic change-over device is used, the flexo-printing machine can also be replaced due to a stoppage. Affect the use of efficiency issues. A flip frame is installed between the printing units to realize the double-sided printing of the substrate. The turnover frame can be placed between any two printing units according to the specific process needs; the printer can also use the numbering machine to print the number. On the substrate; If the UV curing system is installed in the last unit of the machine, the printed product can be UV-coated; if all the units are equipped with an ultraviolet curing system, the machine becomes a flexible version that can be printed with UV ink. Printing presses. In the post-press section, the narrow-width unit flexo press can employ a variety of processes and associated devices at the die-cutting station according to the printer's processing orders. For example, if you have one die-cutting station, you can have hot stamping/indentation/die cutting, dragon/indentation/die cutting, hot stamping/indentation/crosscutting, embossing/indentation/cross cutting, etc. the way. For die-cut or cross-cut products, they can also be collected using a finished collector equipped with a counter. In addition, it can also be equipped with Yin-Yang punching machines, fan-folding machines, etc., for the production of commercial computer paper. Online coating and slitting can also be performed. In the appropriate position at the back of the machine, a stroboscope or even a computerized color monitoring system can be installed to facilitate operator quality control. When the user purchases the flexo printer, according to the specific source of the printing and processing orders, the corresponding supporting equipment shall be selected in a targeted way, so as to avoid affecting the efficiency due to commissioning of the machine due to incomplete function, or waste due to the idleness of the supporting equipment for a long period of time.
The unit type flexographic printing press consists of which parts. The unit type flexographic press is generally composed of the following components: unwinding device, correcting device, tension and register control device, printing unit, drying system, die cutting station, waste discharge device, Film coating and coating units, finished product collection devices, etc.
What role of corrective device to ensure the lateral position of the printing material before entering the printing unit is stable, the machine type flexographic press often uses an automatic corrective device, which can detect the deviation of a lateral position of the printing material, and correct it in time, its accuracy Up to ±0.5 mm. In general, photoelectric sensors are used for opaque materials such as paper and aluminum foil, and ultrasonic sensors are used for transparent materials such as films. Once the printing material enters the printing area and the die-cutting and rewinding area, the lateral position of the printing material is stabilized by the processing and installation accuracy of the machine itself and the parallelism between the rollers.
What are the characteristics of the unwinding device? To reduce the reject rate, the printing time per roll of the printing material should be extended. However, taking into account the ease of handling by the operating staff and the power limitation of the unwinding control motor, the roll diameter is generally about 1 meter. Open reel pneumatic brake device to form the open tension area, the size of the braking force varies with the diameter of the paper roll, resulting in a stable unwinding tension. The unwinding device is generally equipped with a splicing table. If necessary, a device for removing dust and static electricity may be installed after the decoiling device to ensure the surface quality of the printing material entering the printing unit.
How to adjust the tension and register control At present, the tension control system of the unit type flexographic press is based on the conditions of printing materials to set the proper tension value. The system adopts closed-loop automatic control to keep the tension of the printing material constant from beginning to end. The register control is divided into two directions, referenced to the paper-feeding direction. The lateral register is the laterally-moving version of the cylinder, and the handle on the roller shaft can be rotated clockwise or counterclockwise. Normally, at the beginning of the trial printing, horizontal registration is first ensured, and then vertical registration is adjusted. First, the first unit of the first color printing press, stop, make a rough adjustment, make the registration error within one tooth by rotating the platen roller, and then turn on the machine, and finely tune manually using the register control button. Longitudinal register system uses a stepper motor with high transmission ratio. It drives the platen roller to rotate through the impression roller gear, which is actually changing the longitudinal relative position between the platen roller and the printing material. Unlike wide-format flexo presses, the machine-type flexo press uses almost no automatic longitudinal register system because if each unit is equipped with such a system, the investment will account for a significant part of the total investment in the machine. Lose the unit type flexo press investment less, quicker features.
How to select the number of printing unit printing units is determined by the user when purchasing the machine according to the specific printing order conditions. The inking system of the printing unit is mainly in the following forms: ink roller / anilox roller, ink roller / anilox roller / doctor blade or anilox roller / doctor blade. The fountain roller is also called a metering roller. The hardness of the surface rubber and the pressure between the anilox roller and the number of screen lines of the anilox roller are the main factors affecting the ink transfer amount. Generally, in the case of printing darker solid prints and the uniformity requirement is not very strict, an ink roller/anilox ink transfer system may be used, but the print quality of such a system is not comparable to a squeegee type. Inking device. Therefore, even though the use of a squeegee will increase the preparation time before printing and increase the investment, more and more users nowadays choose a printing unit with a squeegee or ink inking device.
Since the flexographic material is soft and compressible, the pressure between the printing plate and the anilox roller on the printing unit, and between the printing plate and the printing material surface needs to be finely adjusted. The adjustment knobs typically use very fine threads and require that the four directions of adjustment be independent of each other. After fine adjustment, the best state achieved should always be maintained during the printing process.
What is the function of the drying system? The unit-type flexographic printing machine is equipped with a dryer behind each unit, uses infrared resistance wire to heat the air, and uses a blower to blow hot air at high speed to the printed substrate to form an impact gas. In order to achieve the best drying effect. In field printing with a thicker ink layer, the drying problem sometimes affects the speed of the flexographic printer. When this happens, try to increase the impact velocity of the air flow and make the horizontal airflow as uniform as possible because for the water-based ink, the impact velocity of the drying airflow is greater than the heating effect for the drying, and the heating of the printing material is also required. Excessive elongation of the material caused by the over-consumption of the conference resulted in inaccurate overprinting. (Liang Xinyu Witlon (Hong Kong) Limited) ("The Graphic Arts Society Monthly")
Flexo Printing Technology Q&A (3)
In the first two issues, we discussed the general issues of flexo printing and flexo plate making. In this issue, we will use the 300 series and 500 series flexo presses manufactured by Allied Gear & Machine of the United States as an example to talk about the characteristics of the unit type flexographic printing presses and the problems that should be paid attention to during operation.