Some important factors influencing powder spraying efficiency
Posted by: admin | on August 21, 2012
Spray Gun Positioning
All powder coating processes necessitate the powder, suspended in its air flow, being as close as possible to the object. The force of electrostatic attraction between powder particles and the object decreases by the square of the distance between them (D2), and only when that distance is just a few centimeters will the powder be drawn towards the object. Careful positioning of the spray gun also assures that small and large particles are deposited on the object in the same proportions found in the virgin powder.
In order to increase spraying efficiency it remains advantageous to suspend objects as close together as possible along the conveyor line. This reduces the amount of powder that is recycled thus preventing an excess of finer particles returning to the powder reservoir. To achieve the same coating thickness on all objects, however, spacing must be adapted according to the size of the objects, as the following diagrams illustrate:
- When the distance is too small, objects are not evenly coated:
- By increasing the distance, the coating thickness is even on all objects:
- A small object will produce a higher concentration of fields and subsequently receive a thicker coating than a larger object adjacent to it.It is advantageous to hang objects of equal size next to each other along the conveyor.
Hanging objects correctly on the conveyor is of greater importance to successful conventional electrostatic spraying than it is to friction charged powder spraying.