Electrostatic
The main benefit of using electrostatic charge, field and effect, is to improve dramatically the transfer efficiency, which is the quantity of material we can get on the part Vs the quantity delivered in the coating process.
The electrostatic coating process uses physical properties of electricity to improve the paint coatings. The whole surface of the part to be painted attracts the negatively charged paint droplets.
The electrostatic field can reach 100,000 V with a very low current (approximate value of 100 µA in internal charge).
It is created by a low voltage generator, providing a signal to a high voltage transfomer, called an High Voltage cascade.
This effect can be used for liquid & powder paints in spray guns (Airspray or Airmix® technology) & rotary bell atomizers.
The Electrostatic second effect on a liquid spray, is to reduce the average diameter of the droplets consequently to the voltage applied. It helps to harmonize the size and reduce it, leading to a better and uniform finishing quality, and especially with higher viscosities (varnish, waterborne paints) above 100MPa.s
Added to existing liquid spray Technologies, electrostatic will improve the paint particle size (more homogeneous and finer) and add transfer efficiency in the coating process, increasing the thickness or the application speed.
Paint particles charged are in an electrostatic field which generates an electrostatic force proportional to the charge and the field value. So the force applied to the particle will depend on its own charge and the physical location where it will see an electrostatic field with a different level.
this explains that we have a better efficiency with direct charge (more charges on the particle), higher field and lower distance. It also explains the wraparound effect, because even behind parts there is a field and paint is attracted.
Equilibrium of forces applied on each particles are the following:
- dynamic speed given by the mean of spray (air and pressure effect, rotary bell effect) and reduced by the friction inside the air
- weight of the particle
- electrostatic force
Depending on the timing, these 3 nature of forces will get more or less important.
Electrostatic effect and Weight are stable, and depend on the particle, when speed is decreasing when the particle gets closer to the surface.
Weight will move basically the spray down to the ground, and high speed will limit the electrostatic effect around the part. With a low speed we can get the maximum attraction effect, electrostatic force being the highest, and with high particle speed, we get a rebound on the surface and a poor quantity of particles staying on the surface (low transfer efficiency).
With a HIGH transfer efficiency and also side coating with the wraparound effect.
Less orange peel effect, even thicknesses & improved brightness due to the size harmonization and reduction of the droplets.
VOC (Volatile Organic Compounds), organic chemicals that have a high vapor pressure at ordinary room temperature & can be harmful to human health & the environment.
Paint waste reduction leads to cost savings in the material quantity but also the treatment of wastes in the booth.
Less time is required to process the same surface area, leading to a higher productivity of an existing line.
It can prevent from new line investment when production output needs to be increased while just adding electrostatic effect on the coating process.
