Thinking About Spray Applications? March 01 2017
For a serious woodworker, there comes a point when it makes sense to move to a spray finish, maybe due to the size of a project or a wish to make things go faster. The next question is, what type of spray gun? Below is a description of the major spray gun categories to get you started on your shopping.
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Conventional Spray Guns
The traditional high-pressure guns are powered by compressed air (commonly 35 to 45 psi). These guns have been used for the last century.
Turbine HVLP (high volume, low pressure)
The technology was introduced in the 1950s, but it didn’t receive wide acceptance until the 1980s when tougher environmental laws made it make sense. Instead of compressed air, a Turbine HVLP uses a high volume of air supplied by a turbine blower to atomize liquids. Reducing the pressure creates a soft spray with much less bounce-back and waste than high-pressure conventional spray guns. Turbines with more fans, or stages, supply higher volume and more pressure.
With this technology introduced in the late 1980s, compressed air is converted in the body of the gun to high volume and low pressure. It too produces a soft spray with very little bounce-back and waste. HVLP spray guns have a higher transfer efficiency than conventional spray guns. Due to its soft spray velocity, about two-thirds of the liquid material is deposited on the sprayed surface; conventional spray guns deposit only about a third.
Airless (hydraulic – atomization)
These spray guns are powered by a pump that pushes liquid material through a very small spray-nozzle orifice at up to 3,000 psi. A very large volume of liquid material can be sprayed with airless systems. The atomization is not as fine as with other systems; that’s why orange peel can be pronounced with this system. Airless spray guns aren’t often used to spray clear finishes onto fine wood.
Air-Assisted Airless and Air Mix
These types of spray guns are powered by both medium-pressure (800 to 1,000 psi) pumps and compressed air. About 80% of the spray pattern is achieved through hydraulic atomization while 20% results from the impingement of low-pressure air.