HVLP automatic guns are widely used in industrial painting processes where controlled paint application, stable spray patterns, and efficient material use are important. The atomization process inside an HVLP gun is based on the interaction between fluid flow and compressed air.
As paint exits the nozzle, compressed atomizing air breaks the fluid into smaller particles. These particles are then shaped into a spray pattern using additional air jets. Understanding each stage of this process helps explain how HVLP automatic guns create a consistent and controlled spray.
Fluid Flow Through the Nozzle Centre Hole
The process begins with the paint passing through the nozzle centre hole. This central opening guides the fluid flow out of the gun.
The fluid exits the nozzle as a concentrated stream before it is broken up by air. The stability of this initial fluid flow is important because it affects the quality of atomization and the consistency of the final spray pattern.
Atomizing Air Through the Annular Orifice
Around the nozzle centre hole is the annular orifice. This opening allows compressed atomizing air to flow around the fluid stream.
The atomizing air surrounds the paint as it leaves the nozzle. Its role is to provide the energy needed to break the liquid stream into smaller droplets.
How Atomization Is Created
Atomization is created by the speed difference between the air and fluid flow.
The compressed air moves at a different speed than the paint stream. This velocity difference creates shear forces that break the fluid into ligaments and droplets. As a result, the continuous liquid stream becomes a spray mist.
This stage is essential for achieving the required droplet size and spray quality. Proper balance between fluid flow and atomizing air is needed to create stable atomization.
Face Holes
Face holes support the stabilization and cleaning function of the spray process.
They help stabilize the atomization zone near the nozzle and keep the area around the fluid outlet cleaner during operation. This supports consistent spray behavior and helps reduce the risk of paint buildup at the nozzle face.
Shape Air Jets
Shape air jets are used to create and control the final spray pattern.
The pressure of the shape air jets on both sides of the spray cone forms the spray pattern. By influencing the cone from both sides, the air jets can transform the spray into the desired shape, such as a flatter and wider pattern suitable for coating surfaces.
Correct adjustment of shape air is important for controlling the width, symmetry, and stability of the spray pattern.
Atomization Zone
The atomization zone can be divided into three main stages: primary atomization, jet breakup, and secondary atomization.
In the primary stage, the liquid core begins to destabilize as it exits the nozzle. During jet breakup, the liquid stream breaks into ligaments and larger droplets. In the secondary stage, these structures continue to break down into finer droplets within the spray boundary.
This gradual breakup process creates the final droplet distribution that reaches the coated surface.
Conclusion
The atomization process in HVLP automatic guns depends on the controlled interaction between paint flow and compressed air. Paint flows through the nozzle centre hole, atomizing air exits through the annular orifice, and the speed difference between air and fluid creates atomization.
Face holes help stabilize and clean the spray area, while shape air jets define the final spray pattern. Together, these elements create a controlled spray mist that allows precise and repeatable paint application in automatic coating processes.