The Fabricator - November 2013

How Do the Application Guns Work?

Liquid. Conventional spray guns for liquid coatings rely on highly pressurized compressed air ( 2 to 3. 5 bar) to propel atomized coating material to the surface. ;ese guns have a low transfer e;ciency when compared to more modern paint application guns and may not be approved for use in some areas.

However, they are relatively inexpensive and easy to maintain.

High-volume, low-pressure (HVLP) spray guns also atomize the paint like a conventional spray gun, but use low-pressure air, usually less than 0.7 bar, to propel the paint onto the object. ;e lower velocity of the air results in less paint jetting through the spray gun’s air nozzle and allows for a more controlled application. Higher application rates are then possible.

Other spray gun technologies are airless spray guns that force the paint through a smaller nozzle and electrostatic-based guns that rely on paint being “attracted” to the object to be coated. (In electrostatic application, a charge is applied to the liquid coating while it is being atomized. In turn, the coating is attracted to any surface that is grounded, which happens to be the workpiece. Obviously, this approach works very well with metal workpieces.) For new users of paint technology, conventional or HVLP spray guns are typically the choice for paint application.

Powder. Powder coatings rely on the charging of material for application as well. Today’s market primarily uses corona guns to do this.

;ese guns impart a strong electrostatic charge on the powder material as it leaves the spray gun via compressed air. As the powder coating is discharged, it is attracted to the grounded metal part hanging from a metal rack. It is necessary for the rack to have some area of exposed metal to ensure a solid grounding for good electrostatic powder application.