Static Eliminator in Printing Industry
As we all know, the electrostatic phenomenon is mainly manifested on the surface of the object, and printing is performed on the surface of the object. In the printing process, due to frequent collisions and frictions between different substances, almost all objects involved in the printing process are electrostatically charged. If it does not come out, it will not pass when the circuit is tested, resulting in defective products. The static electricity in the printing industry will be very large, mainly due to the increase and accumulation of static electricity generated by the static electricity of the object itself after printing (multiple frictions). The harm of static electricity to the printing industry is mainly in two aspects: dust collection and color streaking. For the technological process of the printing industry, the process of eliminating static electricity is mainly divided into the following three parts:
- De-static treatment of semi-finished products before printing.
- Control the increase and accumulation of static electricity during the printing process.
- Static electricity elimination during segmentation and storage after printing finished products.
Why should static elimination be performed before printing?
For the printing industry, their main substrates are plastic and paper, and these materials themselves have strong static electricity and are insulators that are not suitable for conducting static electricity itself to other media, so it is easy to use static electricity once it is charged. The accumulation of static electricity makes the substrates attract each other instead of being peeled off and entering the printing machine in turn. Therefore, it is very necessary to remove static electricity from the surface of the substrate before printing. There are two main ways to remove static electricity in this link:
- Increase the electrical conductivity of the material itself, but the service life is very short and the cost is high.
- Remove dust and static electricity while taking out the substrate, to ensure that the substrate can be peeled off smoothly and then enter the printing machine one by one, and then perform the static elimination action again at the paper inlet of the printing press. In order to ensure that the substrate itself does not have static electricity before printing to ensure that there is no cross-color phenomenon in the subsequent printing process.
Since the static electricity of the object to be eliminated has been guaranteed before printing, why is it still necessary to remove static electricity during the printing process? At present, the main printing processes in the domestic market are divided into three types: emboss printing, offset printing, and screen printing. In their printing process, many frictions are generated, so that the static electricity on the surface of the object will be much higher. If the static electricity is not well controlled during printing, it is easy to cause electrostatic ink shifts and cross-color phenomena on the printed matter. , And in the printing process, due to high-speed friction, peeling will generate static electricity and the accumulation of static electricity can easily lead to air discharge, resulting in electric shock or fire. So how can we control the generation and elimination of static electricity in the printing process? It is to ensure that the substrate has no static electricity before contacting it, and also that there is no static electricity on the surface of the finished printed matter. This process is very cumbersome and simple. In other words, it is necessary to ensure that there are absolutely enough negative ions in the printing process to give the object to be eliminated.
Why does the finished printed matter need to dissipate static electricity?
This problem is very simple to prevent the finished printed matter from being placed and stored neatly after being divided. The solution is to install static elimination equipment when dividing.
How to eliminate silence during printing?
Chemical elimination method
The chemical elimination method is generally to coat a layer of antistatic agent on the surface of the substrate to make the substrate conductive. The application of the chemical elimination method is very limited. If chemical components are added to the paper during papermaking, it is likely to have adverse effects on the quality of the paper, such as reducing paper strength, adhesion, tightness, tension, etc. Therefore, chemical elimination is generally not used.
Physical elimination method
The physical elimination method is to use the inherent characteristics of static electricity without changing the properties of the material. The method of eliminating static electricity is the static elimination method commonly used in industrial production at present.
- "Grounding" elimination method. This is the simplest method, which is to use a metal conductor to connect the object to be eliminated static electricity to the ground, so that it forms a potential difference with the ground, and the charge leaks through the ground, but this method has little effect on insulators.
- Humidity control elimination method. The surface resistance of the printed material decreases with the increase in the relative humidity of the air, because
Therefore, increasing the relative humidity of the air can improve the conductivity of the paper surface and accelerate the leakage of electric charges. The suitable environmental conditions of the printing workshop are: the temperature is about 20°C, and the relative humidity is above 70%. 4. Introduction and selection principles of static elimination equipment. The static eliminators commonly used in printing factories include induction type, high-voltage corona discharge type, radioisotope type, and ion current static eliminator. Among them, the first two have been widely used due to their advantages of low price, convenient installation and use, and no atomic radiation. Now they are analyzed as follows.
Inductive static eliminator
The inductive static eliminator is the inductive static eliminator brush. Its working principle is: when the tip of the static eliminator is close to the charged body, it can induce a charge whose polarity is opposite to that of the static electricity on the charged body, and form a very large amount near the tip. Strong electric field, after the electric field ionizes the air, the generated positive and negative ions move to the tip of the charged body and the dissipator respectively under the action of the electric field, thereby neutralizing the static electricity.
High voltage discharge static eliminator
High-voltage discharge static eliminators can be divided into the electronic type and high-voltage transformer type according to different structures. The difference in electrical polarity can be divided into unipolar and bipolar. In the printing process, the static elimination method combining induction type and high voltage discharge type can be used, which can completely and effectively eliminate static electricity.