How Spray Gun Works

Understanding the Working Principle of Your Spray Gun.

What is a Spray Gun?

A spray gun is a device that sprays or applies a liquid to the surface of an object through different motions. It is often used for spraying and cleaning, as in the case of a water spray gun, or for spraying items, as in the case of a paint spray gun. Spray guns are used in a wide range of applications and can spray metal, wood, stone, clay (ceramics), porcelain, plastic, glass, or textiles, to name a few. Spray guns have gradually replaced traditional brushes as the most popular way of spraying because of their good spraying effect, wide range of applications, and high spraying efficiency.

Classification of spray guns

Spray gun is divided into 2 categories, airless spray guns and air spray guns.

1.  Airless spray gun

High-pressure airless spray gun is divided into three types: ordinary type, long handle type, and automatic high-pressure spray gun.

(1)   Ordinary type is the most common high-pressure spray gun, composed of the following diagram(Take HVBAN’s H131 as an example), including these parts: 1-Nozzle seat; 2-Saddle assembly; 3-Needle cap; 4-Gun handle sheath; 5-Needle; 6-Gun body; 7-Gun body nut; 8-Gun core push rod (pin); 9-Limit valve seat; 10-Retract nut M5; 11-Gun body screw; 12-Gun trigger assembly; 13-PTFE gasket; 14-Inserted gun filter; 15-Gun handle inner spring; 16-Gun handle; 17-Gun limit valve plate; 18-Gun joint assembly.

Technical Diagram of a Common High-pressure Spray Gun.

(2)   The long-handle type, on the other hand, is suitable for spraying large objects that are not easily accessible, such as the hull of a ship. Its composition is shown below and includes these parts: 1-rotary joint; 2-seal; 3, 24, 28-spring; 4-strainer 5; 17, 19, 36, -gasket; 6, 8, 10, 38-washer; 7-handle; 9-rear swivel body; 11-nut; 12, 26-pin; 13-front swivel body; 14-nozzle washer; 15-nozzle; 16-nozzle nut; 18, 37-connector; 20-gun valve seat; 21-lock nut; 22-joint rod; 23- Tail sleeve; 25-Sleeve; 27-Support sleeve; 29-Connection sleeve; 30-Compression nut; 31-Sealing ring; 32-Guide ring; 33-Trigger; 34-Screw; 35-Gun body; 39-Handguard rod; 40-Handguard; 42-Spool.

Technical Diagram of a Long-handle Airless Spray Gun.

(3)  The basic structure of an automatic high-pressure spray gun is similar to that of the ordinary high-pressure spray gun, but the opening and closing of the gun do not have to be done manually. It is controlled by the cylinder at the rear of the gun, which is favorable for the automation of airless spraying. The composition is shown below, including parts are: 1, 2-O-ring seal; 3-piston; 4-gun body; 5-tightening screw; 6-handle; 7-seal screw; 8, 18-gasket; 9, 29-seal; 10-pressure ring; 11-connection screw; 12, 22, 31-spring; 13, 15-connector; 14, 26, 28-nut; 16-gun spool; 17-gun valve seat; 19-gun valve spool; 20-gun valve seat pull pin; 21 -Tip nut; 23-Tip jacket; 24-Tip; 25-Washer; 27-Attachment nut; 30-Nut; 32-Piston cap.

Technical Diagram of an Automatic High-pressure Spray Gun.

2.   Air spray gun

The air spray gun is divided into an electrostatic spray gun and a manual spray gun. The manual spray gun is divided into the siphon spray gun, gravity manual spray gun, and pressure-fed manual spray gun. However, because the application of the scene is not as extensive as the airless spray gun, there will not be a detailed description.

Airless spray guns are used in a wide range of applications, let's focus on the airless spray gun.

The Principle of Airless Spray Gun Painting.

The working principle of the airless spray gun

The work of an airless spray gun consists of spraying pressurized paint. We can break down the working process of an airless spray gun into 4 steps:

• The paint passes through the filter under pressure.

  
  

• The material continues to pass through the gun.

  
  

• The material spray stream passes through the tip orifice.

  
  

• The airless tip ensures fine atomization.

In a nutshell, it works on the principle that pressurized paint is forced through a specific-sized opening in the airless tip, which creates atomization due to the pressure difference between the paint and the atmosphere.

 

Material of Airless Spray Gun Components

As you can see from the above, airless spray guns need to spray pressurized paint, so there are certain requirements for the material of some important parts, especially for the gun body, needle valve, and tip.

Most of the gun bodies of airless spray guns are made of aluminum, needle valves and valve seats are machined from high-quality steel, and the tips are tungsten carbide. The special materials of these components ensure that the airless gun works properly under high pressure.

Understanding the structure of the spray gun, you must want to ask, among so many parts, which one has the most direct impact on the spraying effect? That would be the airless spray tip! Many spray guns come with multiple interchangeable tips, and the tips come in different sizes to fit different-sized projects. So let's take a look at how to choose a tip.

The Airless Tip: A Critical Component for a Flawless Finish.

Selection of spray tip

The choice of the tip depends mainly on its orifice size and shape. Please note:

1.The shape of the tip determines the fan width at a certain spraying distance.

2.The orifice diameter of the tip determines the flow rate. You can choose the appropriate orifice size according to your desired flow rate (see table below).

Orifice range（inch）	Specific orifice（inch）	Flow rate（L/min）
0.09-0.15	0.009	0.27
0.010	0.42
0.012	0.61
0.015	0.8
0.17-0.22	0.017	1.02
0.019	1.29
0.020	1.59
0.022	1.89
0.25-0.32	0.025	2.27
0.027	2.65
0.029	3.07
0.031	3.52
0.032	3.97

When purchasing tips, you'll notice each one has a three-digit number. Let's decode what these digits mean using the example of a tip labeled 215:

The first digit, when doubled, indicates the spray pattern fan width. For a 215 tip, it’s 2 x 2 = 4, so it has a 4-inch fan width when sprayed 12 inches from the surface.

The last two digits represent the orifice size in thousandths of an inch. For a 215 tip, it’s 0.015 inches.

Knowing this, you will be able to quickly pick out the airless spray tip you need when making your purchase. After explaining so much about the principles and knowledge of spray guns, let's finally take a look at the rules for using airless spray guns.

Rules for Spraying

1.  Distance: The gun should be held approximately 12 inches (30.5 cm) from the surface and pointed straight (horizontally and vertically) at the surface. This will give the best spraying results;

2.  It is best to move the gun at a constant speed while spraying;

3.  Make sure there is a consistent overlap when spraying. Airless spraying should have a 25%-50% overlap;

4.  Keep the gun's trajectory parallel to the surface of the object;

5.  Keep the gun body perpendicular to the surface of the object; tilting at an angle will result in wasted paint;

6.  Don't just use your wrist to move the gun, forearms and shoulders should also be powered;

7.  When spraying outside the air, pay attention to the direction of the wind, and the unsprayed surface should be below the wind in order to bring flying paint and rebound to the unsprayed surface;

8.  Adjust pressure when spraying: It is desirable to spray at the lowest pressure that will fully atomize the paint within the appropriate range. The correct procedure should be to set the pressure control to low pressure and slowly increase it until the paint is fully atomized. If the spray shape has finger or tail marks, the pressure should be increased.

Conclusion

That's all there is to know about spray guns, and we hope that after reading this article you'll have a general understanding of spray guns. Contact HVBAN with any questions or if you have an airless spray gun you would like to buy, we are happy to answer them.