Gravure cylinder

In gravure printing, the excess ink on the plate cylinder is scraped off with a squeegee, and the ink in the eyes of the fulcrum is transferred to materials such as paper and film to complete the printing. The transfer of the ink is achieved by using an impression cylinder. Because the concave is given by the rubber impression cylinder to achieve the pressure of the plate cylinder, the impression cylinder must be strong and durable. The usual method is to add synthetic rubber to the steel pipe core.
The embossing cylinder is divided into a shaft integral type and a shaft separation type, just like the fulcrum. Regardless of accuracy or strength, it is better to use an integral shaft type. However, a small-sized gravure printer such as a narrow-width polyethylene film printing machine uses a separate impression cylinder.
Impression roller installation has not always been as simple as installing a platen roller. However, some recent impression rollers use mounting bar technology to make the roller bearing not only shorten the service life of the imprint roller and use a wrench.
In addition, there is generally only one impression cylinder, but there are also rotary table type imprinting mechanisms including three or four impression cylinders to shorten the exchange time of the impression cylinder when the plate cylinder and the strip width are changed, especially in building materials. Printing presses have great value in this way.
Some high-veiled printing machines employ a device for preventing the relaxation of the original film when the impression cylinder is up and down, and a mechanism for keeping the length of the unit film to a certain value when the impression cylinder is up and down, thereby reducing the loss of printing material during shutdown.
In order to improve the printing effect, the embossing roll should not be too large with direct play. Printed in the concave printed with the need to replace the impression cylinder, from the mechanical strength considerations, should use thick-walled steel; and packaging gravure printing machine, due to changes in the width of the printed matter requires frequent replacement of the impression cylinder and pressure Lighter, so use more thin steel pipe.
The hanging glue thickness of the impression cylinder is generally about 10-15mm, and the rubber hardness differs depending on the various types of printing materials. For the printing of plastic film, the hardness is about HS70, and the hardness for the printing of paper and rough kraft paper must reach HS85-HS90. The hardness of rubber has a large effect on the printing effect. In order to meet the requirements of ink and solvent resistance, rubber such as butyl cyanide rubber is generally used.
Usually, when printing plastic film, the printing pressure is 150-350kg/1000mm. If bleaching white spots occur, it is necessary to increase the pressure to 800kg/1000mm or more in order to block the white spots. However, the impression roller used for plastic film printing has a light pressure type and lacks pressure resistance. Therefore, if more than 500 kg of pressure is applied, the roller will not bend. At this point, only the two ends are subjected to strong pressure, and the central part is prone to discoloration, and the human color is misaligned. This so-called overbite (deformation) overprint is more noticeable in wide printing.
The unbalanced state caused by side pressure can also cause poor registration, so the inspection level after the plate cylinder is installed is . For ease of adjustment, one-sided pressure adjustment handles can be installed. However, the use of a single-sided 2 and shank in the printing makes it difficult for the lateral overprint to become unstable and the film to wrinkle, which is disadvantageous for obtaining a good-quality print.
When the printing pressure is high, the impression is rolled and the pressure at the center and the end are different. In this case, the support roller is used. However, after using the backup roller, the rubber of the impression cylinder heats up under the action of the upper and lower pressure, causing deterioration of the rubber and a short life span. Moreover, the accumulated heat may sometimes be broken. In order to prevent this from happening, it is sometimes necessary to use water for the impression cylinder and the backup roller. In general, the support rollers are necessary for gravure printers that require high printing pressure, such as gravure printers for publication printing, gravure printing machines for kraft paper and kraft paper, and gravure printing machines for building materials. Machines generally do not need to use support rollers.
In order to prevent the above-mentioned central pressure from appearing, some press-for-print gravure printing machines use a ring beam impression cylinder (non-integrated structure of the drum body and the shaft), which has achieved good results.
There are other ways to make the impression cylinder protrude. The amount of protrusion can be calculated using a theoretical beam formula, or it can be calculated using a published protrusion scale. Using the formula method, even if there are complete plans, the protrusion scale is only a general standard for calculation. Due to the load, changes in the core quality, bearings, and other factors, in many cases, also live.
Therefore, the correct amount of protrusion can be obtained based on actual measurement. The method is to first sandwich the carbon paper in the roll circumference direction, plus the pressure load set by the use, determine the central part of the drum and the three press widths at 50mm from both ends. Then, based on this measured value.
In the formula, C is roller protrusion, ie, the diameter of the central part of the roller and what is the difference from the end 50mm; N1 is the width of the roller at the center of the roller, N2 is the width of the roller at the end of the roller 50mm, D1 is the upper roller The diameter (imprinting cylinder), D2 is the diameter of the lower cylinder (plate cylinder).
When the result of the calculation is positive, it means that the amount of protrusion is insufficient and must be added; if the result is negative, it means that the amount of protrusion is too large, and it should be ground to reduce it.
The impression cylinder of the gravure printing machine is not driven by Engelon gear engagement, but is operated by contact with the plate cylinder, thus enabling a stepless selection of the diameter of the intaglio printing machine cylinder.
The upper and lower parts of the platen roller and the platen roll press mechanism are generally divided into manual and movable. The manual adjustment is performed through the worm gear screw axis, and the automatic use of the motor through the button. As a mechanical method, the use of steam, fuel tanks, etc., or drop, pressure is also common milk. This method can keep the set printing pressure stable or can be pre-set so that it can be easily managed before the quality of the printed product is stabilized.
Observing the printing pressure can be done from the width of the press, but this method is not very practical. In the case of using a mechanical roller up/down device, it can be judged by using the spring's deformation strain. When using air pressure or hydraulic pressure, there is a fearlessness that can display the pressure.
In a gravure printing press, printing is performed by the pressure between the plate cylinder and the impression cylinder. The pressure deforms the rubber and maintains a width. The embossing width varies with the diameter of the two cylinders, the rubber hardness of the impression cylinder, and the printing pressure.
The theory and experience of the sudden and flat version do not apply to the adjustment of gravure pressure. Because all 镧 are the same. During gravure printing, the printed material is in close contact with the plate cylinder, and the ink is drawn from the concave portion of the plate. In this process, physical conditions such as surface tension or thin tube phenomenon change depending on the nature of the ink and the printed material. For example, paper printing foil printing conditions are not exactly the same. Different substrates require different characteristics of the impression cylinder and printing. The rough surfaced paper and thick paper require a particularly high printing pressure.
In fact, the actual printing pressure in printing is not the line but the highest pressure (pressure) per unit area. Some degree of deformation of the rubber is necessary. In order to get a good printing pressure, you must have an imprint width of about 13mm. In high-speed printing, deformation of the rubber due to the printing pressure causes a large amount of heat accumulation in the adhesive layer. When it is very high, it sometimes leads to rubber cracking. The relationship between the impression cylinder and printing conditions.
From this, it can be seen that although the narrow impression width can be obtained when the diameter of the impression cylinder is small, it must also be considered that the deformation of the impression cylinder will increase. In other words, even at the same printing speed, compared with an impression cylinder having a diameter of 150 mm, an imprinting roller having a diameter of 100 mm is also deformed at 1.5 times the rotation speed, and from the moment of consideration, there should be Limited. In general, a printer with a print width of 1100 mm or less can print on a roll with no support, while a press with a width of 1,000 needs a support roll.
After the imprinting roll is used for a long time (about 300 hours), both ends of the drum will swell due to the influence of the ink solvent, resulting in the same bowed state as when overpressurized.
The surface of the impression cylinder is made of synthetic rubber. Since the solvent swells when it swells and becomes 'early wounded', it often requires grinding. During the grinding process, care must be taken to prevent tapering and maintain the same circumferential length of multicolor printing. If there is a taper, the film is easy to wrinkle and lateral overprinting is inaccurate. In addition, if the circumferential length of the impression cylinder of the medium color group is different, there will be errors in the longitudinal magnetic printing.
In addition, the use of electrostatic gravure printing, due to greatly increased transfer of ink, can improve the quality of printing, printing pressure is greatly reduced, which is conducive to the correct overprint, reduce the extension of the paper and film, to adapt to the needs of machinery with the speed of rotation , can increase the resistance to force, reduce mechanical wear and so on.