With the widespread application of technology, high-voltage static electricity has rapidly developed in China. There are already multiple manufacturers of electrostatic spraying equipment in China, producing various types of electrostatic spraying equipment.

Among numerous manufacturers of electrostatic spraying equipment, Huzhou Electric Meter Factory was the first to successfully develop and officially mass produce a new type of powder electrostatic discharge under the guidance of relevant researchers from the Chinese Coatings Society; Friction electrostatic spray gun.

Compared with commonly used high-pressure spray guns, this type of spray gun has many characteristics and advantages. This article compares two types of friction electrostatic spray guns when applied.

1、 Powder Charging and Electric Field of Friction Gun

Powder coating is charged inside the friction gun, and its charge does not come from the corona discharge at the electrode tip, but from the collision, friction, contact, and clutch between the powder and the gun wall. That is to say, it uses the principle of frictional electrification to make the powder charged.

The mixture of powder particles and air flows through the friction gun and is ejected from the muzzle by the pressure of the airflow. Charged powder particles form a spatial electric field, the strength of which is determined by the spatial charge density and the geometric shape of the electric field, including the amount of charge on the powder particles, the proportion of powder in the gas powder mixture, and the spray pattern of the spray gun.

The gas powder mixture sprayed by the spray gun gradually increases in volume, decreases in charge density, and weakens the electric field due to the decrease in air pressure and the repulsive force of the same charge. The electric field of the friction gun is strong at the muzzle, and gradually decreases from the muzzle to the workpiece. The direction of electric field weakening is consistent with the direction of airflow, and the direction of powder force is the same as the direction of airflow.

2、 Characteristics of Friction Electrostatic Powder Spray Gun

Friction guns have their own characteristics due to their different charging methods and electric fields from high-voltage guns. These characteristics have demonstrated superiority in electrostatic spraying.

1. The powder of the friction gun is charged due to the friction between the powder and the gun wall, which determines that the friction gun does not require high voltage in electrostatic spraying; Static electricity generator. Thus saving equipment investment by 10-30%, especially for small sizes, the savings ratio is even higher. Although the energy consumption of an electrostatic generator is not high, over time, the energy consumption of an electrostatic generator can also be considerable.

2. It is safer to use a friction gun for spraying because there is no high-voltage electrostatic generator in the spraying equipment. A well-designed high-voltage electrostatic generator will not cause personal injury accidents, but the stimulation of high-voltage electric shock will always make people nervous. In addition, there are no metal electrodes inside the friction gun, so there will be no spark discharge caused by electrode short circuit during spraying, which will ignite the gas powder mixture. This is even more important when spraying on the inner walls of pipelines or the interior of containers.

3. Spraying with a friction gun is very convenient. Firstly, the friction gun does not connect to high-voltage cables, making it easy to hold; Secondly, it is less affected by the spraying distance, and the friction gun is closer or farther away from the workpiece, resulting in similar spraying effects.

4. Spraying small workpieces or workpieces with complex surface shapes with a friction gun is much superior to high-pressure guns.

5. There are no metal electrodes inside the friction gun, so there will be no electrode powder accumulation phenomenon, which avoids the detachment of powder accumulation on the electrode and ensures a smooth and even surface of the powder layer.

6. A friction gun can spray thicker coated wires, which cannot be compared to conventional high-pressure guns.

3、 Comparison of Technical Performance between Grinding Gun and High Pressure Gun

1. The performance of electric field spray guns for two types of guns is closely related to the electric field. To understand the differences in performance between the two guns, first compare the differences in electric field between the two guns. The electric field of the friction gun is formed by the space charge of the powder particles, and due to the small distance between the guns, the electric field is relatively uniform.

The electric field of a high-voltage gun is a typical non-uniform electric field. The electric field is strong near the needle, the potential gradient is large in the direction of the needle, and the electric field is weak near the workpiece. In addition, the electric field range of high-voltage guns is much larger than that of friction guns.

2. In the electrostatic spraying of the spray gun, the current output by the electrostatic generator is not completely increased by the powder or carried to the workpiece, or carried to the ground by the powder. And a part of the current does not flow through the powder as a medium and flows into the space outside the workpiece or the earth, forming the so-called ion wind current.

Different spray guns have different ion wind currents. For friction guns, the charge generated by friction is carried to the workpiece or ground through powder as a medium, while high-voltage guns have strong ion wind currents. This is one of the reasons why the spraying effect is not very good when using a high-pressure gun for spraying, although the spraying current is high.

3. It is difficult to comprehensively compare the spraying effects of two guns. Here we will only compare a few main indicators. These comparison results are inferred from the difference in electric fields between the two guns and have been confirmed in practice.

① The coating thickness can be sprayed uniformly using high-pressure guns and friction guns. However, it is difficult to spray thick coatings using high-pressure guns. When spraying with a high-pressure gun, reverse ionization (also known as reverse breakdown) phenomenon will occur when the powder layer thickens. During a spraying experiment using a high-pressure gun, not only did pits and pockmarks appear on the surface of the powder layer, but several regular patterns also appeared; Snowflakes;, Its diameter is as large as 1 centimeter.

The anti ionization phenomenon of the powder layer damages the surface smoothness and the gloss of the cured coating, even leaving pinholes. The anti ionization phenomenon is caused by the strong electric field of the high-voltage gun. There is no such strong electric field in the friction gun, so there will be no anti ionization phenomenon. A friction gun can spray thick coatings with high surface quality.

② The uncured adhesion of the powder layer requires sufficient adsorption force between the powders, otherwise the powder will detach from the powder layer. The adsorption force between powders is not the Coulomb force generated by free charges, but rather the gravitational force between bound charges generated by the polarization of powder particles.

The magnitude of this gravitational force is determined by the strength of powder polarization. The high-voltage gun has a strong electric field, high polarization strength of the powder, high density of bound charges generated, strong attraction between powders, and strong adhesion of the powder layer. The powder layer sprayed with a high-pressure gun will not detach from the powder layer even if it is left for seven, ten, or even longer before solidification.

The adhesion of the powder layer sprayed with a friction gun is smaller, but it can still fully meet the needs of spray production, which has been confirmed by engineering practice.

③ Powder deposition rate is a technical indicator determined by multiple factors, and it is not a constant in spraying. The deposition rate will decrease as the powder layer thickens.

There is no unified standard for sedimentation rate in China, and it is not strict to say whether the sedimentation rate is high or low in general. In order to correctly evaluate the advantages and disadvantages of electrostatic spraying equipment, a unified and universally recognized technical specification should be formulated. The powder deposition rates of the two guns are not easy to compare carefully.

But it can be said that the powder deposition rate of the friction gun is higher than that of the high-pressure gun when spraying with small powder amounts and close range spraying, especially for spraying small parts and workpieces with complex surface shapes.

④ Ability is a technical indicator reflecting the production capacity of spraying equipment, which is determined by sedimentation rate and powder spraying amount. If the powder spraying amount of the two guns is similar, the coating ability of the friction gun produced by Huzhou Electric Meter Factory can be compared with the high-pressure gun used for workpieces at 40-60KV and spraying distance of 200-300mm.

By comparing the two types of guns above, it can be said that the friction gun has many advantages, but it cannot completely replace the high-pressure gun. Both types of guns have their own advantages and applicability, and designers should pay attention to this when selecting electrostatic spray guns.

4、 Precautions

According to the charging principle, electric field, and structural characteristics of the friction gun, the following points should be noted when using the friction gun:

1. The air should be thoroughly purified, filtered, oil-free, waterless, and dust-free, which is the same as high-pressure guns and should be even stricter.

2. The charged friction gun is affected by the composition and performance of the powder coating. When spraying with different powders, a trial spraying should be carried out first, and the formal spraying should be carried out when the effect is good.

3. Attention should be paid to the application range of the grinding gun's powder dosage, as exceeding the range will affect the spraying effect.

4. The friction gun generates two types of charges during spraying, one carried away by the powder and the other accumulated on the gun body. If this part of the charge is not guided to the ground in a timely manner, high voltage will appear on the gun body and it will also affect the charging of the powder. Therefore, when spraying with a friction gun, it is necessary to reliably connect the ground wire connected to the gun body to the ground.

Source: Network

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Yongji Industrial Co., Ltd. is located in; Hometown of Chinese Coatings& mdash;— Shunde, Guangdong, covering an area of nearly 10000 square meters, is a high-tech outward oriented powder coating production enterprise that integrates research and development and operation.

The company was founded in 1997, and we have always adhered to the principle of 'riding'; User first, quality first; Our business philosophy is that in 2003, the company fully passed the ISO9001-2000 international quality management system certification. In 2004, it was evaluated by the National Quality Evaluation Center as; Chinese Quality Credit Enterprise;, The Yongji brand, built with high-quality products and excellent services, has won a good reputation among customers. In July 2018, the company underwent a comprehensive upgrade and passed the ISO9001:2015&ISO14001:2015 Quality&Environmental Management System certification.

Since its establishment, the company has maintained healthy, stable, and rapid growth. From two small production lines and a small factory with more than ten people in the early stages of construction, it has developed into a modern enterprise with an experienced and skilled technical and management team, with an annual output of over 15000 tons and annual sales exceeding 200 million yuan.

We are customer-centric, market-oriented, and have gathered top talents in industry technology management from both domestic and foreign sources, committed to the corporate philosophy of technological innovation. We have established long-term and stable partnerships with well-known domestic enterprises such as Midea, Hisense Kelon, TCL, and Jilong. Our products are exported to well-known foreign enterprises such as Malaysia and Indonesia, and our exports are showing a rapid growth trend.

Looking ahead to the future, the company will continue to adhere to the development policy of efficiency, coordination, health, and science, with the goal of maximizing the overall value of the enterprise, further improving the organizational structure and management mode of the enterprise, and making it; Yongji Powder; Become the most valuable brand in China's powder coating industry.