Analysis of spraying atomization method and utilization rate!

The improvement of the utilization rate of liquid spray coatings is one of the most important issues in the coating industry.

Traditional high pressure atomization 

The spraying air pressure of a traditional high-pressure spray gun is generally 4.

HVLP high flow low pressure atomization 

HVLP (High Volume Low Pressure) high-flow low-pressure spraying technology is the most advanced modern spraying technology in the coating industry

The HVLP environmental protection paint-saving series spray guns are characterized by saving paint (the actual use saves 15-30% paint compared to traditional spray guns) and reducing pollution.

RP low flow and medium pressure atomization 

RP (Reduced reduced; Pressure hood air pressure) paint-saving high-efficiency series spray gun atomization technology combines the advantages of traditional spray guns and HVLP spray guns.

Nitrogen spray 

The traditional air spraying technology uses compressed air as the carrier of the paint, while the heated nitrogen spraying technology uses heated nitrogen with a purity of 99.

Figure: Four 20% pursued by nitrogen spraying technology

Electrostatic spraying 

In the assembly line operation, the technology that relies on the electric field to transfer the paint to improve the utilization rate of the paint has been rapidly popularized
.
Generally, solvent-based paints use internal power-up technology.
Water-based paints have external power-up and several different internal power-up methods due to conductive factors.
Spraying in small spaces such as the interior of the car body generally uses magazines, turbochargers, etc.
Electric or hidden pole needles are externally powered, and small-scale industrial sprayed water-based paints also have an internally insulated power-on method
.
Automatic spraying generally uses high-voltage generators to generate electric charges, and manual spraying is represented by built-in turbine power generation and electrostatic generators
.
Technologies such as electrostatic ring and water-based built-in grounding electrode needle have basically tapped the full potential of water-based paint electrostatic manual spraying
.

At present, the painting rate of large areas using electrostatic spraying is above 75%, but electrostatic spraying must pay special attention to safety design.
The energy of the electrostatic needle, the grounding of the spray booth facilities, and the protection of the insulation technology of the water-based paint system must be strictly in accordance with the specifications
.

Electrostatic field atomization 

The traditional air paint atomizer mainly uses aerodynamic air pressure to spray paint, and then uses the air paint atomizer to spray atomized particles onto the car body
.
Therefore, paint particles will be sprayed from the car body by air, resulting in lower coating efficiency
.
Therefore, technologies such as low air flow technology, static electricity and rotary cup auxiliary transmission were born, and their promotion and application have shown a good effect of saving paint
.

The highest level of improvement in the utilization rate of spray paint completely cancels air atomization, and the paint is naturally adsorbed on the product by the electrostatic field.
Toyota Motor released such a car paint atomization device last year
.
The new airless spray paint atomizer uses electrostatic spray paint (electrostatic atomization), and this electrostatic particle coating method uses gravity to make the paint adhere to the car body (electrostatic spray)
.
Electrostatic atomization and electrostatic spraying technology greatly reduces the number of scattered atomized particles and achieves a spraying efficiency of more than 95%.
At present, the equipment has entered the practical stage
.
With a large number of deployments, the Toyota Group can reduce carbon dioxide emissions by about 7%, bicycle paint consumption and VOC emissions will be reduced, and the operating cost of the spray paint production line will be greatly reduced
.

The tip of the airless paint atomizer has a rotating cylindrical head to optimize the amount of paint sprayed
.
Electrostatic atomization technology was originally used in beauty treatment devices and other equipment that sprays tiny liquids, but Toyota used it in automobile manufacturing
.
Specifically, the tip of the paint sprayer is cylindrical, with about 600 special grooves inserted into the tip, the grooves are rotated to generate centrifugal force, so that the paint flows into the grooves and atomizes through static electricity
.

High-precision current control realizes the feasibility of short-distance spraying
.
The unevenness of the sheet metal parts of the body itself will cause the distance between the cylindrical head and the body to fluctuate, and the current will be unstable
.
However, the airless spray paint atomizer will continuously monitor the changes in current and automatically control the voltage to keep the distance between the cylindrical head and the body about 10mm
.
Therefore, electrostatic atomization and electrostatic spraying become possible under a fixed current, which in turn suppresses the change of paint particle size, resulting in high-quality spraying
.

Picture: The paint reaches the surface of the workpiece by the action of the electrostatic field after being thrown out from the groove

Printing and spraying technology 

At present, various forms of coating construction methods have been developed that can make the utilization rate of coatings close to 100%, such as electrophoresis, powder spraying, etc.
, but 100% of liquid spraying is still in the stage of preliminary exploration and partial trials, such as the spraying of FAW Hongqi body patterns , Dürr, ABB, SAMES have jointly developed a new technology without overspray in cooperation with coating suppliers and users, which has been successfully applied to the mass production of two-color car roofs
.
In addition, furniture can also easily achieve decorative effects.
Spraying equipment without overspray sprays all paint on the product surface like printing, achieving 100% paint spatter-free and clear borders, fast color change, and customized surface design
.

Figure: The precise spraying path makes the surface spray paint and coating have a clear boundary

The technical principle of each type of spraying equipment will be different, but the ultimate goal is to maximize the utilization of paint and spraying effect.
Different spraying techniques can be selected according to the actual use
.