Paint Spray Finishing and the different types of equipment, a quick simple guide to the different spray options available. We could talk so much about the differences, the benefit of one piece of kit over another. There is mountains of information available and we do not profess to be the oracle, we are however very happy to discuss individual needs and we will always help to give the best advice, we are bale to put people in touch with the spray equipment suppliers. We supply equipment from Aristospray and supply the Q-Tech & Tritech products from spray guns, airless or air assisted spray pumps, HVLP and consumables such as spray tips and filters.
Conventional SprayingÂ
This is the most flexible and adaptable method. The finishing material is transported and dispersed with compressed air. The finishing material is fed forward to the paint nozzle. The flow is controlled by a needle valve, operated via the spray-gun trigger. When the trigger is depressed, the compressed air valve is opened first. The needle is then drawn back, and
the finishing material can pass through the paint nozzle. The paint meets the jets of air beyond the nozzle and is atomized in the form of tiny droplets. Spray breadth and spray pattern (spray cone) are regulated by the amount of air supplied to the air nozzle. The finishing material is fed to the nozzle by suction or pressure generated by a pump or pressure vessel. The correct spray nozzle must be selected, according to the method used. The amount of finishing material can be roughly regulated by adjusting the pressure in the lacquer container and the size of the hole in the spray
nozzle. Fine adjustment is achieved by changing the length of stroke of the paint needle. The disadvantages of conventional spraying are the relatively slow production rate, fairly high
paint consumption and high environmental load.
HVLP
In recent years, conventional spraying has been modified to reduce overspray. The spray gun and nozzle have been modified to atomise the paint using a large volume of air at low
pressure, the High Volume, Low Pressure (HVLP) method.
AIRLESS SPRAYING
This method offers certain advantages compared with conventional spraying, but is not as flexible when it comes to regulating spray-field width. Atomization of the lacquer is less satisfactory and in some cases inadequate. It is a rapid method with a minimum of overspray. With airless spraying, the finishing material is fed forward to the spray-gun nozzle under high pressure (as much as 200 bar). It is atomized as it passes through the spray gun nozzle. Pressure is generated by a piston pump. Spray width and paint/lacquer quantity are adjusted by replacing the spray-gun nozzle. Better atomization can be obtained by using a “pre-nozzle“, which makes the spray cone less elliptical (to achieve a less diffuse spray pattern). Airless spraying is now widely used when applying waterborne finishes with automated spray coating systems.
Air Assisted SprayingÂ
Airmix, Air-Plus, Air assist etc. are combinations of the methods described above. Nowadays, this is one of the most commonly used spraying methods in the wood finishing industry, thanks to fine atomization and minimum overspray. The combination comprises:
A high-pressure pump featuring an adjustable pressure of 15-45 bar ( far less than for airless spraying ). The pump pulls the paint from an open container ( some can be fitted with a hopper )
The pump is fitted with a high pressure fluid hose and an air nozzle for the air atomisation and fan pattern adjustment, the fan adjustment shapes the spray field. The air pressure used to atomise the paint / lacquer generally is very low, perhaps no more than 0.5 – 2 bar. The coating is fed from the pump to the spray gun via a thin hose. The air pressure to the pump can be adjusted on the spray pump.
