Causes and elimination of static electricity in th

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Causes and elimination of static electricity in the printing process

release date: Source: China Packaging

in the printing production process, sometimes paper or printed matter attract and stick together, which is difficult to separate. This phenomenon is the phenomenon of printing static electricity. In winter when the climate is dry, the phenomenon of static electricity on the printing paper is particularly prominent, which may cause obstacles to the normal paper feeding, receiving and finishing, or even fail to start printing. Therefore, understanding printing static electricity and mastering countermeasures are of positive significance to promote production

paper has such an attribute that when its moisture content is high, its conductivity increases; On the contrary, when the water content is very low, the insulation performance increases, and the paper in this case is more prone to electrostatic phenomenon

improper papermaking process is easy to make the paper electrostatic. In the paper making process, due to the low content of electrolytes (such as alum, sodium chloride, etc.), the excessive content of sizing substances, and the low content of some fillers (such as kaolin, etc.), the paper is subjected to high temperature and pressure in the drying and calendering process, which makes the paper electrostatic with high voltage. Improper storage of paper will also generate static electricity. When there is a big gap between the temperature of the paper warehouse and that of the printing workshop, the variation of the moisture content of the paper will not only affect the registration due to expansion, but also easily cause static electricity. In addition, the placing time of the paper before printing is too short, the temperature and humidity of the paper and the printing environment lack an effective balance, and the paper stack pressure is too high and too heavy, which will also cause the paper to have static electricity

friction in printing causes static electricity. When the water content of the paper is low, the paper is very dry, and the paper is subject to friction and pressure in the process of paper feeding and stamping, which makes the paper electrostatic

static electricity on paper is caused by one reason, several models, and more outstanding detection limit. The situation is different. The size of static electricity carried by various papers or batches of papers is not necessarily the same. Another feature is that after the paper is charged, the polarity of charges on both sides is opposite, and the paper in contact with the front and back sides will firmly adhere to each other, which is not easy to separate. Therefore, it brings obstacles to the printing paper feeding, transmission and paper leveling, which not only affects the production efficiency and product quality (such as easy to cause joint failures such as over bottom imprinting and inaccurate overprint), but also increases the loss of printing products

in order to prevent printing static electricity, first of all, it is necessary to control it from the source. First, the use of paper with static electricity can be postponed, the storage time can be extended appropriately, and the temperature and humidity of the paper warehouse should be well controlled. The temperature in the warehouse should be directly controlled between 18 ℃ - 20 ℃, and the relative humidity of the air should be controlled between 60-65%. Under this condition, it is conducive to weakening or eliminating the static electricity of the paper. Secondly, paper drying measures can be used to remove paper static electricity. When the paper needs to be used urgently, the paper with static electricity can be hung by the paper dryer. Pay attention to the coordination between machine speed and air humidity when hanging, that is, when the machine speed is fast, the relative humidity of the ambient air is controlled at 80-85%. On the contrary, when the machine speed is slow, the effect of hanging and airing is better when the humidity is kept at 70-80%. It is worth noting that when hanging and drying, the thickness of each stack of paper should be controlled within 10mm, and the looser the paper is, the better, so that the moisture in the air can enter the paper evenly. Third, the emergency paper drying removes static electricity. If the cut paper cannot be printed normally due to static electricity, the "steam method" can be used to dry the paper quickly to reduce the static electricity of the paper and complete the printing as soon as possible. In a production practice, the author used a machine speed of 3500 sheets per hour to print 30 grams of glossy paper. Because the paper has strong static electricity, it is difficult to feed and transfer paper, and the overprint is inaccurate. Therefore, we had to shut down the machine for emergency paper drying of charged paper, that is, put each stack of paper with a thickness of about 15mm on each layer of the paper drying rack, and then sprinkle steaming boiling water around the paper drying rack, so that the water content of the paper can be quickly increased, so as to reduce static electricity and maintain normal printing

a comprehensive method can also be adopted to eliminate paper static electricity, which combines raising the temperature and water content of the paper with the use of electrostatic eliminators, so that the effect is better. The main measures are:

1. Install air conditioning equipment in the printing workshop, and adjust and maintain the printing workshop at a constant temperature and humidity according to the strength of paper static electricity. Generally, the workshop temperature is adjusted between 18 ℃ - 20 ℃, and the relative humidity of the air is maintained between 60-65%. If the paper is heavily charged, the relative humidity of the air can be adjusted to 80-85%

2. Install an electrostatic eliminator on the printing machine to eliminate the static electricity of the paper. The electrostatic eliminator is adjustable. It can eliminate the static electricity of the paper by adjusting the voltage and frequency. When the static electricity of the paper is large, use high voltage and high frequency. When the static electricity of the paper is small, reduce the voltage and frequency

3. Use isotope emitters to eliminate printing static electricity. The principle of isotope emitters and electrostatic eliminators to eliminate static electricity is basically the same, both of which ionize some air molecules into ions. Because the ions have different charges, when the paper passes through the ion space, part of the electrostatic charge will be neutralized, so as to achieve the purpose of eliminating static electricity

to sum up, static electricity causes equipment protection costs, high brush efficiency and quality, and also increases the loss of paper. Therefore, the correct understanding and understanding of printing static electricity, and take corresponding measures to overcome and eliminate, can ensure the smooth progress of printing, and achieve the purpose of improving production efficiency and quality

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