Several popular new flexo press technologies
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With the improvement of the flexographic printing process, its printing machinery is also developing in the direction of more operability, better on-line processing, better print quality and higher printing machine efficiency. The following structures are mainly used on some advanced flexographic printing presses.
Paper feeding unit:
1. the use of gas rising shaft.
The shaft of the gas-increasing shaft is provided with an elastic air chamber. When the air chamber is filled with compressed air, the air chamber expands, and the tensioning block is ejected, thereby clamping the winding core. The use of the gas riser greatly reduces the steps and difficulty of manual paper change.
At present, most flexographic printing presses use air-lifting mandrels. The external structure of gas-up shafts produced by different manufacturers may be different, but the internal principles are the same.
2. High-speed automatic non-stop paper change device. In wide-format flexographic printing presses, in order to improve work efficiency, an automatic non-stop paper pick-up device is generally used. The structure is the same as that of the offset web automatic paper-feeding device, and the high-speed synchronous surface drive paper is used.
Printing unit:
1. The gearless motor is directly driven. The problem that the printing length of the printing product is limited by the gear pitch is solved, the replacement time of the printing plate and the anilox roller is shortened, the random adjustment of the printing length is realized, and the printing flexibility of the machine is enhanced. At the same time, it not only reduces the paper consumption, but also eliminates the backlash and runout caused by the gear transmission, and improves the printing precision.
2. The use of sleeve technology. The sleeve technology has the advantages of light weight, small footprint and low transportation cost. These advantages allow the sleeve to be easily replaced by hand and are easy to store and transport. The outstanding advantages of the sleeve technology have greatly contributed to the rapid development of flexographic printing technology. The sleeve technology is mainly applied to the plate cylinder. The sleeves that are often used today have a plated sleeve and a seamless plate sleeve. The plate sleeve is the most common form of plate cylinder with a photosensitive resin plate on the surface. The seamless plate sleeve plate has a sleeve shape and is directly jacketed on the plate cylinder, which reduces the trouble of the four-way registration proofing in the upper plate. By using sleeves of different thicknesses, the required printing circumference can also be changed, that is to say, a gas-supporting roller of a specific outer diameter can meet the needs of different printing circumferences in a wide range by installing sleeves of different thicknesses. With a high degree of flexibility, such as sleeves with wall thicknesses of 10mm and 70mm respectively, the printing circumference of the two differs by as much as 400mm.
3. Plate cylinder with detachable structure. Removable plate cylinders are typically used in printing companies that have several different web flexo presses with roughly the same width and different types and lengths of plate cylinder diameters. To make a detachable roller shaft for each different press, it is not necessary to equip each press with a complete set of rollers.
4. Closed squeegee. Compared with the two-roller, forward-blade and reverse-squeegee structures, the biggest advantage of the closed squeegee is the good sealing performance. The reverse squeegee structure is adopted in the quantitative ink supply system, which is suitable for high-speed operation and reduces solvent solubility. The volatilization and deterioration of the ink solves the foam problem that often occurs in water-based inks. At the same time, the system can also be automatically cleaned to reduce ink change time and downtime. The sealed reverse double scraper device comprises a closed ink chamber formed by an ink chamber (also called a doctor blade holder), two scrapers, and a two-stage side seal plate made of wear-resistant soft material and an anilox roller. The ink chamber has an ink inlet port and an ink outlet port. The oil pump sprays the flexo ink onto the surface of the anilox roller through the ink inlet port and stores it in the ink chamber. After the ink is applied, the ink is scraped by the doctor blade, and the scraped ink can continue to be recycled. Increased ink utilization. In the cavity knife system, the two scrapers function differently, one piece is reverse type, and the reverse scraper is used to scrape off excess ink on the anilox roll; the other piece is positive type, which is a positive sealing blade and plays a sealing role. .
Closed doctor blade system
5. Drying, solidifying and cooling. A modern high-speed flexographic printing press incorporates a color drying and drying device to make the printed product sufficiently dried under high-speed printing, and the printing quality is greatly improved.
6. Other auxiliary institutions. Automatic replacement of the plate cylinder eliminates a lot of manpower replacement time.
In addition, the automatic turning device and the mechanical loading roller mechanism in the wide-format printing machine have promoted the development and promotion of flexographic printing.
Postpress processing:
A variety of post-printing in-line processing operations can be combined to increase productivity and save costs. The inline processing of printed products reduces the handling of printed products in post-press finishing and reduces unnecessary damage to the printed products during handling.
On-line processing can reduce multi-color printing, quality control, die cutting, stripping and separation of paper embryos at one time without interrupting production, reducing costs in labor, material handling, production processes and raw materials. The figure below shows the BOBST connection printing and cutting equipment.
BOBST connection printing and cutting equipment
There are three types of die cutting and delivery methods, including take-up rolls, cut sheets, and fan-folds. At the same time, you can also add hot stamping, peritoneal, punching, trimming and other institutions, and use different online equipment according to different printing products to achieve efficient operation.
Detection of deviation and print observation device:
Modern flexographic printing presses have added paper tape detection and correction devices. The device is manual and also uses sensors. The following figure shows a paper feeding paper strip correcting device with a sensor. The mechanism is equipped with a sensor. When the paper strip is offset, the sensor will send a signal to swing the device to the left and right to realize the paper strip rectification. Electronic guidance systems are also typically deployed throughout the printing process. The electronic guiding system uses a photodiode or an ultrasonic sensor for error detection, and then carries out paper tape regulation by a DC motor. Automatic registering devices are available in some very advanced machines for a full range of automatic register adjustments. At the same time, in the final rewinding, in order to obtain a neat material roll, a rectifying device is also installed in front of the rewinding device.
Paper feed correcting device
Print quality observation devices generally include stroboscopic, synchroscopic, barrel-rotating mirror viewers, and video scanning devices. They are printed image dynamic observation devices that observe printed images without stopping the machine, greatly improving printing efficiency. The stroboscopic observer adjusts the frequency of the illumination of the illumination by means of the controller. When the flash frequency is multiplied by the frequency of the printed image passing through the illumination zone, the same position of the printed image can be observed to obtain a still printed image. Synchronous rocking mirror, as the name suggests, is that the swing frequency of the mirror is synchronized with the motion of the printed image, so that the image on the mirror is always the same area, and the dynamic observation of the image is also realized. The barrel-shaped rotating mirror observer uses a rotating mirror cylinder consisting of a multi-faceted mirror, which overcomes the shortcomings of the above two observation devices to adapt to the printing speed.
Delivery unit:
Modern flexographic printing presses are generally used for the processing of different prints such as labels, packaging or paper products, so the delivery device will vary from object to item. The general mechanism includes a rewinding mechanism for rewinding the roll, a fan-folding mechanism for folding the pressure-sensitive label, a sheet-cutting mechanism for the roll-out sheet, and a wide-width paper roll divided into a narrower roll. Paper slitting device, etc.