Electrostatic ink transfer device consists of electrostatic pressure roller. Conductive aluminum roller (or conductive brush), control cabinet (including high-voltage electrostatic generator) composed of several parts, as shown in Figure 1.
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Its working principle is shown in Figure 2. It is through the control cabinet to generate high voltage and low current, and the current is transmitted to the electrostatic pressure roller through the conductive aluminum roller or conductive brush, so that the electrostatic pressure roller is charged with positive (or negative) charge, so that the electrostatic pressure roller is in contact with the paper. A high-voltage electrostatic zone is established between a conductive surface, paper, and a gravure plate. Under the effect of static electricity, the ink in the gravure plate is sucked out and uniformly transferred to the surface of the paper, so that the ink transfer rate reaches or close to 100%.
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In the electrostatic loading process, whether to use a positive charge or a negative charge is selected depending on the color of the ink, the composition of the ink, and the positive and negative static charges on the surface of the paper.
Selection of Electrostatic Transfer Devices
1. The first is the choice of manufacturers of electrostatic transfer ink devices. If the company has a certain strength, it should choose imported products, mainly from Germany, Japan's manufacturers, the price of each electrostatic pressure roller is about 0.81 million yuan, each color group completes the need of 200,000 yuan (excluding static electricity The pressure roller) is equipped with at least 3-4 sets of each gravure printing line, which requires hundreds of thousands of dollars of funds, but this is also a long-term investment in the gravure screen products. If you choose domestically-made devices, it is understood that the only companies that are more successful at the moment are the two companies in Beijing and Tianjin. The price of each color group is about 35,000 to 4 million (including electrostatic pressure rollers). Need 150,000 yuan, equivalent to the price of a color group of similar foreign products.
2. After the manufacturer selects, some parameters and auxiliary facilities of the device, such as the electrostatic loading method, electrostatic pressure roller, the width of the printing machine, the width of the printed product, etc., must be determined.
(1) There are two main types of electrostatic loading, namely aluminum rollers and electrostatic brushes. These two methods have their own inadequacies, such as: there is a gap between the aluminum roller and the electrostatic pressure roller when it is loaded; the brush is easy to wear and deform when the brush is loaded, which will cause the static electricity to be unevenly loaded.
(2) When selecting an electrostatic pressure roller, distinguish it from the pressure roller. The surface of the electrostatic pressure roller must be able to conduct electricity, and the hardness and pressure roller should also be different. Generally, the hardness of the pressure roller should reach HS90, and the hardness of the electrostatic pressure roller should be controlled in the HS80-85 according to the different equipment, too soft and easy to cause wear. , poor durability; too hard and easy to cause ink transfer is not complete, the electrostatic effect is not obvious.
(3) The width of the printing press and the width of the printed product shall be considered together to solve the production of the electrostatic pressure roller and the length of the conductive part. In the past, the length of the electrostatic pressure roller was the length of the conductive portion, which could easily cause the paper to break, or the paper edge was damaged, and could not be used on the machine. The electrostatic pressure roller is now divided into a conductive portion and an insulating portion in the longitudinal direction, just like the use of a pressure roller.
Matters needing attention in the use of electrostatic transfer ink device
Since the electrostatic transfer device is mainly used in the production of a screen mesh product, an electrostatic pressure roller must be installed every time it is used, and the pressure is adjusted again. The preparation time is longer. In addition, in order to ensure better ink transfer and safety during printing, the following must be observed.
1. Check the installation position of the electrostatic pressure roller. The pressure of the pressure roller and the pressure at both ends of the pressure roller.
2. Check the installation position of the conductive aluminum roller and electrostatic brush and the wires connected to the static control cabinet.
3. Check the working status of the pressure switch or speed controller.
4. The electrostatic voltage should be loaded when the speed of the gravure printer reaches 30m/min or more. According to the improvement of the printing effect, the voltage should be gradually increased from zero. If the voltage increase has no significant effect, the voltage should be stopped and changed. Load voltage polarity or check for problems in a timely manner.
5. If the use of electrostatic transfer ink device, the effect of halftone printing does not improve, you should also check the surface roughness of the paper used and the engraving quality of the plate hole.
The lack of electrostatic transfer ink device
Due to the narrow scope of the domestic use of electrostatic ink transfer devices, the research on this technology has only just begun. There are still some deficiencies in the domestically-used devices that are currently being used. It is hoped that peers can use this as a guide.
1. The number of engraving lines of gravure mesh products can reach as high as 175 lines per inch, which makes the fineness of gravure cells subject to great restrictions. Therefore, the level of products can only be increased by means of electrostatic ink transfer devices. Fine level is also difficult to meet the requirements.
2. Adding static electricity to the paper by the electrostatic pressure roller will cause the paper to form a strong static area within about 300 mm from the gravure plate. Therefore, the static elimination device must be installed in this area, otherwise it may easily cause the tank to catch fire . Although this fire phenomenon will not cause great losses, it has buried potential safety hazards.
3. At present, the electrostatic ink transfer device still has a large defect in the printing of gold and coated paper, and the printing quality is not significantly improved.
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