Introduce some popular new technologies of flexo p

2022-07-24
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This paper introduces several popular new technologies of flexographic printing machine

with the improvement of flexographic printing technology, its printing machinery is also developing towards the direction of stronger operability, more perfect on-line processing, better print quality and higher printing machine efficiency. The following structures are mainly used in some advanced flexographic printing machines

paper feeding unit:

1. Use of air inflation shaft

in the figure, 1 - rubber air chamber, 2 - plenum panel, 3 - spring plate, 4 - tension block, 5/6 - clamping block, 7 - overflow valve, 8 - air filling and exhausting hole

an elastic air chamber is installed in the shaft of the air inflation shaft. When the air chamber is filled with compressed air, the air chamber will expand and push out the tension block, so as to clamp the material coil mandrel. The use of air inflation shaft greatly reduces the steps and difficulty of manual paper change

at present, most flexographic printing machines use inflatable mandrel. The external structure of inflatable mandrel produced by different manufacturers may be different, but the internal principle is the same

2. High speed automatic non-stop paper change device. In order to improve the efficiency of the wide flexographic printing press, the automatic paper receiving device without stopping is usually used. Its structure is the same as that of the automatic paper receiving device for offset web, and it adopts high-speed synchronous surface drive to receive paper. The following figure illustrates how it works

schematic diagram of paper receiving without stopping at high speed

printing unit:

1. Direct drive by gearless motor. It solves the problem that the printing length of the printed matter is limited by the gear pitch, shortens the replacement time of the printing plate and the embossing roller, realizes the random adjustability of the printing length, and enhances the flexibility of the printing test samples of the machine to produce slow plastic deformation and fracture with the change of time. At the same time, it not only reduces the paper consumption, but also eliminates the backlash and runout caused by gear transmission, and improves the printing accuracy

2. Use of sleeve technology. Sleeve technology has the advantages of light weight, small floor area and low transportation cost. These advantages make it easy to replace the sleeve by hand, and it is convenient to store and transport. The outstanding advantages of sleeve technology have greatly promoted the rapid development of flexographic printing technology. Sleeve technology is mainly used in plate cylinder. At present, the sleeves commonly used are plate pasting sleeve and seamless plate printing sleeve. The plate pasting sleeve is the most common form of plate cylinder, and the photosensitive resin plate is pasted on the surface. Seamless printing plate sleeve the printing plate is sleeve shaped and directly coated on the printing plate cylinder, which reduces the trouble of four-way registration and proofreading when loading the plate. The required printing perimeter can also be changed by using sleeves with different thicknesses, such as 10kN or above cylinders. That is to say, the air support roller with one specification of outer diameter can meet the needs of different printing perimeter in a large range by installing sleeves with different thicknesses. It has a high degree of flexibility, such as sleeves with wall thickness of 10mm and 70mm respectively. The difference in printing perimeter between the two is nearly 400mm, so as to ensure the implementation of relevant work

flexographic press with sleeve technology

3 of fischer&krecke, Germany, plate cylinder with detachable structure. The detachable plate cylinder is usually used in printing enterprises with several different web flexographic printing machines with roughly the same width, and the type and length of plate cylinder shaft diameter are different. It is not necessary to equip each printing machine with a complete set of roller devices to make detachable roller shafts for each different printing machine

4. Closed doctor blade. Compared with the two roll, forward scraper and reverse scraper structures, the biggest advantage of the closed scraper is good sealing. The reverse scraper structure is used in the quantitative ink supply system, which is suitable for high-speed operation, reduces the volatilization and deterioration of solvent based ink, and solves the problem of foam that often occurs in water-based ink. At the same time, the system can also automatically clean, reducing the ink change time and downtime. The sealed reverse double scraper device consists of an ink chamber (also known as a scraper seat), two scrapers, a side sealing plate made of wear-resistant soft materials in two sections of the ink chamber and a corrugated roller to form a closed ink chamber. The ink chamber has an ink inlet and an ink outlet. The oil pump sprays the flexographic ink onto the surface of the roller through the ink inlet and stores it in the ink chamber. After inking, the ink is scraped by the scraper. The scraped ink can continue to be recycled, greatly improving the utilization rate of the ink. In the cavity knife system, the two scrapers have different functions. One is a reverse scraper, which is used to scrape the excess ink on the wrinkle roll; The other is a positive sealing blade, which plays a sealing role

closed doctor blade system

5, drying, curing and cooling. The modern high-speed flexographic printing machine is equipped with a color drying device, so that the printed matter can be fully dried under high-speed printing, and the printing quality can be greatly improved

6. Other auxiliary mechanisms. Automatic replacement of plate cylinder saves a lot of manpower replacement time. The figure shows the automatic version loading device equipped with the satellite flexographer

printing equipment that automatically changes the plate cylinder (Fisk Kerak, Germany)

in addition, the automatic turnover device and the mechanical loading cylinder mechanism in the wide width printing machine have promoted the development and promotion of flexographic printing

turnover device (beiren Fuji)

design of quick replacement printing unit (nilpete, Denmark)

post press processing:

configure a variety of post press online processing processes, which can not only improve production efficiency, but also save costs. The on-line processing of printed matter reduces the handling of printed matter in the post press modification, and reduces the unnecessary damage of printed matter in the handling process

online processing can complete multi-color printing, quality control, die cutting, waste removal and Paper embryo separation at one time without interrupting production, reducing costs in terms of labor, material handling, production process and raw materials. The following figure lists Bobst's line printing and cutting equipment

bobst line printing and touch cutting equipment

the models in the following figure include die cutting and paper receiving modes, including paper receiving roll, sheet cutting and fan folding. At the same time, it can also add bronzing, peritoneum, punching, edge cutting and other mechanisms, and select different online equipment according to different prints to achieve efficient operation

detection and correction device and print observation device:

modern flexographic printing machines are equipped with tape detection and correction devices. The devices are either manual or sensor. The following figure is a paper feeding belt deviation correction device with a sensor. The mechanism is equipped with a sensor. When the paper belt is offset, the sensor will send a signal to swing the device left and right to realize the paper belt deviation correction. In the whole printing process, the electronic guiding system is generally configured. The electronic guidance system uses photodiode or ultrasonic sensor for error detection, and then uses DC motor for paper tape regulation. Some very advanced machines will be equipped with automatic registration devices, which can carry out all-round automatic registration adjustment. At the same time, in the final rewinding, in order to get a neat material coil, a deviation correction device will also be installed in front of the rewinding device

paper feed deviation correction device

structural diagram of deviation correction device

print quality observation device generally includes stroboscopic, synchronous swing, barrel rotating mirror observer and video scanning device. They are dynamic observation devices for printing images, which can observe the printed images without stopping the machine, and greatly improve the printing efficiency. The stroboscopic observer adjusts the flashing frequency of the lighting lamp with the help of the controller. When the flashing frequency is a multiple of the frequency of the printing image passing through the lighting area, the same position of the printing image can be observed to obtain a static printing image. As the name suggests, the synchronous swing mirror means that the swing frequency of the mirror is synchronized with the movement of the printed image, so that the image on the transmitting mirror is always the same area, and the dynamic observation of the image is also realized. The barrel rotating mirror observer uses a rotating mirror cylinder composed of multiple mirrors, which overcomes the shortcomings of the above two observation devices to adapt to the printing speed

paper receiving unit:

modern flexographic printing machines are generally used for the processing of different prints such as labels, packaging or paper products, so their paper receiving devices will also vary from material to material. The general mechanism forms include rewinding mechanism for winding the whole roll, fan folding mechanism for folding pressure-sensitive labels, sheet cutting mechanism for web paper output, and paper roll slitting device for dividing the wide paper roll into narrower paper rolls, etc

rewinding device fan folding device sheet cutting device

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