When purchasing spraying equipment, choosing the best technology for your application is vital. In order to select the best one, it’s essential to understand the difference between air spray, airless and air-assisted airless technologies.
Air Spray
Air spray systems use high-pressured air created by a compressor to atomise the material being sprayed. It is often used for low to medium-viscosity materials. Air spray results in much finer atomisation compared to over types of spraying, this results in a very smooth finish but with more overspray.
There are three options for supplying fluid to an air spray gun:
- Pressure-feed guns
- Gravity-feed guns
- Siphon-feed guns
Pressure-feed guns are usually fed through a hose from a low-pressure pump or pressure tank, they are used in industrial applications to move large amounts of fluid through the system. The benefit of pressure-feed is that you have control of air and fluid pressure. Pressure-feed can atomise and deliver higher viscosity material.
Gravity-feed guns have a cup mounted above the centreline to enhance the fluid using gravity. Gravity is more suited for jobs using smaller amounts of material, such as touch-ups or repairs. Gravity is commonly used for applying wood stains and automotive finishing. With Gravity, you are limited to how much paint you can deliver at a time as the nozzle determines if the paint will be able to flow through the gun.
Siphon-feed guns have a cup mounted below the front of the gun. They are used for handling small amounts of material, frequent small-volume colour changes and low production rates. The suction is created by air flowing from the aircap, which draws material from the cup to the fluid nozzle.
Airless Spraying
Airless spraying atomises, or breaks up material into small droplets without the use of compressed air. In an airless system, fluid is pumped under high pressure through a spray tip. The tip size and pressure are what determine the flow rate of the material. High pressure creates a complete pattern- the higher the material viscosity, the more pressure from the pump is required.
There are many benefits to airless spraying:
- When using different tips in conjunction with your machine you can spray a wide variety of materials.
- Airless spraying is one of the fastest methods of paint application, which makes it perfect for large jobs.
- Airless units tend to be more portable since they don’t need a compressor.
Some drawbacks of airless spraying:
- Not all the material sticks to the intended surface, this is called overspray. This results in wasted material.
- You must properly maintain the machine to ensure proper function and longevity.
- You must flush out the pump in order to maintain the machine.
- When storing the machine, you need to use Pump Armour.
Air-assisted Spraying
Air-assisted spraying uses a high-pressure fluid for atomisation and compressed air at the cap for pattern control. Air-assisted spraying atomisation is created by hydraulic force, so it atomises the centre of the pattern. A spray tip determines the pattern size and flow rate. Air fills out the pattern, and an aircap completes the pattern, eliminating tails on the spray pattern.
The benefits of air-assisted are:
- You can get a slightly finer finish compared to airless. By adding assist air into the fluid stream, you achieve a finer break up and finish than you get using airless paint sprayers. This makes it better suited for fine-finish jobs.
- They waste less material than airless sprayers typically do.
- You need less fluid pressure to break up the same material compared to airless.
Some cons of air-assisted are:
- They typically will not come in high-ratio pumps. This creates limitations in their ability to properly spray high-viscosity material.
- Air-assisted requires an airline which creates an additional line to have to work with when spraying.
- The air-assisted guns are a little more expensive than airless guns, this is due to using atomisation air.
If you would like any further advice about which spray equipment is best for the job tht you're doing, please get in touch.