Technology and application of the hottest air mixi

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Technology and application of air mixing spraying machine

[Abstract] this paper describes the principle and process parameters of air mixing spraying, introduces the characteristics of air mixing spraying, and puts forward the precautions in the operation process

[Key words] coating equipment, transformer

1, preface

transformer coating generally adopts dip coating, drenching coating, air spraying, high-pressure airless spraying and other methods; For large components that are difficult to dip and drench, air spraying is usually used, and airless spraying is used in a few cases. However, the utilization rate of air spraying coating is less than 50%, or even only 30%. Compressed air consumption is large, and a large amount of paint mist is generated, which seriously pollutes the environment. The utilization rate of high-pressure airless spraying coating is about 60%. The coating film is prone to sagging and paint mist is also large. Air mixed spraying not only overcomes the shortcomings of both, but also has obvious advantages

2. Principle of air mixed spraying

air mixed spraying is invented by combining the advantages of air spraying and airless spraying. Its key points include: (1) the coating is pressurized to 4 ~ 5MPa by a special spraying machine with a certain pressure ratio, and then sprayed through the nozzle. (2) The compressed air after filtration and pressure regulation is sent to the air cap and ejected through a specially designed hole. Part of the compressed air participates in the atomization process of the paint, that is, the expanded atomized paint is further atomized to make it finer and more evenly distributed. The other part of the compressed air forms a wind curtain around the fan-shaped paint mist flow of the paint, which limits the flow direction of the paint mist around and restricts its application to the workpiece. In a word, the atomizing force of mixed gas spraying comes from two aspects: one is from the liquid, which atomizes after the coating is suddenly decompressed and expanded under pressure; The second comes from the flow of gas, that is, compressed air, which promotes the further atomization of the coating. These two elements together are called twin atomization. This spraying method is called air mixed spraying method

3. Mixed gas spraying process parameters

mixed gas spraying machine is used for transformer coating, and the use effect is good. After production verification, the process parameters are determined as follows:

gas supply pressure: 0.4 ~ 0.6MPa

pump pressure: 0.3 ~ 0.4MPa

auxiliary gas pressure: 0.15 ~ 0.2MPa

spray amount: 1.2l/min

spray width: 400mm

spray distance: 250 ~ 300mm

4.Precautions for operation

in order to improve the quality of the coating, To ensure the use effect, according to the production experience and experience, the following operation precautions are put forward:

a) the dust reduction in the operating environment shall not affect the appearance of the film, and the temperature shall not be lower than 0 ℃

b) before using the coating, filter it, stir it evenly, and control the viscosity within 25 ~ 30s

c) when spraying silver powder paint, remove the spray gun for filtration to prevent high data accuracy and stop the spray gun from blocking

d) when starting and cleaning the pump, the pump speed should not exceed 40 stroke/min, and the pump pressure should be 0.05 ~ 0.07MPa

e) the air supply pressure shall not exceed 0.6MPa

f) air mixing coating should not be used for pipe radiator and other workpieces

g) the thickness of one-time spraying is 20 ~ 50un, and the number of spraying layers should be controlled as required during construction

h) in order to prevent sagging, it is necessary to control the paint viscosity and spraying distance

5. Application of mixed air spraying

through a period of production and application, it is proved that mixed air spraying has the following significant advantages:

A) improve the coating quality

mixed air spraying method can obtain a high-quality decorative coating surface, and the key to obtain such a surface is the atomization effect of spraying. Good atomization effect depends on two aspects of spray flow. One is the fineness of each coating droplet after the coating is atomized, that is, the size of each droplet diameter; The second is the uniform distribution of the paint mist composed of these paint droplets over the entire paint mist flow width. Due to the double atomization principle, the mixed air spraying method has achieved satisfactory results in both aspects

due to the good atomization effect of air mixing spraying, the atomized droplets of the coating are fine and evenly distributed; The obtained film is more uniform, flat and meticulous than air spraying method, which can effectively overcome the film defects such as sagging and "virtual smoke", so it has been widely used in various industrial departments since the 1990s

b) paint saving

production practice has proved that air mixed spraying saves 20 ~ 40% of paint than air spraying, and 10 ~ 15% of paint than high-pressure airless spraying. The reason is that the coating pressure used in air mixing spraying is smaller than that of high-pressure airless spraying, and the pressure of compressed air used is much smaller than that of air spraying (0.1 ~ 0.2MPa). Under such working conditions, 1. It is suitable for making electrical parts with heat resistance, fire resistance and high dimensional stability. The initial velocity of the paint sprayed from the nozzle is much lower than that of high-pressure airless spraying, and the initial velocity of compressed air is also greatly reduced, so that there is an annular wind curtain outside the fog flow to restrict the flow of paint mist to escape around. These two factors determine that the air mixing spraying method greatly reduces the flying of the escaping paint mist, which is more than 20 times less than that of air spraying

c) improve production efficiency

because the air mixing spray gun has a large amount of paint spraying, which is 10 times that of the air spray gun; The width of paint mist flow is 400mm, while the air spraying range is only 70 ~ 100mm; The thickness of one film of air mixing spraying can reach 20 ~ 50um, and the air spray gun is only 10 ~ 15um, which can reduce the number of relevant inspections of raw and auxiliary materials, assessment and evaluation of suppliers on a regular basis during construction; Therefore, air mixed spraying has high production efficiency

d) improve the working environment

because the coating pressure of air mixing spraying is much smaller than that of high-pressure airless spraying, the initial velocity of the coating sprayed through the nozzle is much lower than that of high-pressure airless spraying, and the spray paint mist flow hardly rebounds; At the same time, due to the effect of wind curtain, the dissipation of paint mist is limited; These two factors determine that the paint mist is greatly reduced during operation. After on-site inspection, the paint mist produced by the air mixing spraying machine is more than 20 times lower than that of the air spray gun. The concentration of toluene and xylene is 5 times lower, which effectively improves the working environment

e) it has good processability

it is characterized by wide viscosity adaptability, many types of applicable coatings, reduced amount of thinner, easy operation, and therefore easy to promote and apply

although the mixed air spraying method has many advantages, it also has shortcomings, such as the one-time investment is close to high-pressure airless spraying, and the equipment and pipelines need to be cleaned before work every day

6. Summary

production practice has proved that the air mixing spraying machine has the advantages of good film quality, paint saving, high production efficiency, less paint mist and good processability. It is especially suitable for the coating of large components. It is a relatively advanced coating equipment at present, and has a good prospect in the promotion of transformer coating

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