Electrostatic spraying includes electrostatic spraying paint and electrostatic powder spraying.
1. Principle of electrostatic painting
The atomized paint particles are negatively charged in the DC high voltage (80-90kV) electric field, and under the action of the electric field force, they fly to the surface of the positively charged workpiece to form a paint film. This process is called electrostatic painting.
2. Characteristics of electrostatic spray painting
advantage
(1) High production efficiency and good working conditions The production efficiency is more than 10 times higher than that of manual painting, and it effectively gets rid of the heavy labor of manual painting (painting), especially suitable for large-scale assembly line operations;
(2) High-quality paint film, good adhesion, especially uniform and smooth paint film;
(3) Saving paint generally saves about 60% of paint compared with manual painting.
shortcoming
(1) A complete set of painting equipment is required, which requires a large investment;
(2) The process operation is more complicated.
3. Electrostatic painting equipment
Mainly refers to the spray booth and Spray Gun.
1) The spray booth should be determined according to the size, shape and batch of the workpiece. Large plate-shaped workpieces, large batches, optional
Use a through-type spray booth (matched with a rotary Spray Gun); for small and medium-sized workpieces, large quantities, you can choose an Omega-style spray booth (matched with a rotary spray disc).
It should be noted here that the light in the electrostatic spray booth must be sufficient, and the general illumination can reach 800 lux. It is recommended to set up searchlights at the four corners of the spray booth. At the same time, it should be considered that the light is dimmed due to the vibration of the equipment and the excessive paint fog. Second, attention should be paid to the ventilation of the equipment. Generally, the wind speed for ventilation is 0.6m/min. Considering the air duct, the paint will gradually adhere to the fan, which will affect the ventilation effect, so the wind speed can be appropriately increased to 0.8m/min during design.
2) Spray guns Electrostatic Spray Guns (or spray discs) should generally be driven by air. The speed of the wind motor can reach more than 4000r/min, and there is no cable grounding to avoid high voltage leakage. The speed is high, the sprayed paint mist particles are small, and the paint film is smooth and clean. The working characteristics of the turntable spraying disc and Omega spray booth are: the workpiece is transmitted and operated in the Ω shape in the spray booth, and the paint mist thrown out by the turntable is absorbed by the surrounding workpieces, and the effect is better than that of the through type. The structure of the rotary cup electrostatic Spray Gun is shown in the figure
4. Electrostatic painting process
The pass-through spray booth uses a rotary cup Spray Gun, and the process parameters for spraying amino paint are as follows:
1) The working voltage is 75kV for amino paint and 70kV for acrylic paint;
2) The resistivity of paint liquid is 10-50MΩ·cm;
3) Paint viscosity Amino paint 24s, acrylic paint 22s, (the above viscosities are all measured by Tu-4 viscometer) (also called Tu 4 cups, north and south tide note). If the viscosity
4) The appropriate amount of paint delivery is 40ml/min. If it is too large, the atomization will not be good, if it is too small, it will not be coated;
5) The distance between the Spray Gun and the workpiece should be 30cm. Too far away is inefficient, too close is unsafe;
6) The optimal running speed of workpiece conveying is 0.8m/min;
7) Spray gun speed is above 2800r/min. For alkyd paint 4000r/min or more. The speed is low, the paint atomization particles are large, and the paint film is not smooth.
Omega spray booth and rotary spray disc can be carried out with reference to the above parameters.
5. Paint materials for electrostatic spraying
1) Ultra-fast drying amino baking paint "ultra-fast drying" means that the paint is painted under the standard state, that is, 0.25mm thick tinplate is painted at a humidity of (65±5)% and 25°C, and the film thickness is 20-23μm When it is baked , it only takes 3 minutes to dry completely. The general paint takes 100 minutes to fully dry. This kind of paint film has a bright and bright appearance, and its performance can meet the standard. The manufacturer of this paint is Zhangjiakou Paint Factory.
2) Metal flash paint This amino metal flash paint is characterized by beautiful appearance, good gloss and elegant color. The main manufacturer is Jinan Paint Factory.
3) Peacock blue amino enamel paint is bright in color, strong in hiding power, and easy to dry. It can be dried in less than 30 minutes at 120°C. The main manufacturer is Guangdong Foshan Chemical Factory. In addition, Tianjin, Shanghai, Wuhan , Zhangjiakou and Jiangxi are also produced.
6. Electrostatic spray paint application
It is mainly used in parts of automobiles, bicycles, tractors, and agricultural transport vehicles.
