One of the most widely used application devices in industrial spray painting – especially in shipyards, heavy carpentry, metal furniture and similar sectors – is the airless spray system, in its various versions: airless, air-assisted airless, electrostatic airless and heated electrostatic airless.
The principle is well known: the coating material is fed by a high-pressure pump, which determines the material flow rate and pressure (up to about 350 bar).
The real heart of the system is the tungsten carbide spray tip, which defines both the spray angle and the amount of product applied. Assuming a constant feed pressure, the only way to adjust the main spray parameters is to choose and replace the tip. For this reason, tip selection is crucial and must take into account several factors:
- orifice size,
- type and viscosity of the coating,
- geometry and size of the surface to be coated,
- degree of tip wear.
One parameter that is often underestimated is tip wear, which depends mainly on working pressure and on the abrasiveness of the coating material.
If a worn tip is used, the original spray fan – defined as the spray width at a distance of about 30 cm from the surface – is drastically reduced (sometimes by up to 50%). The consequences are immediate:
- a narrower fan means more passes are needed to cover the same area;
- more passes mean a higher paint flow per unit area;
- overall, this can lead to paint consumption increases of up to 30%, together with longer application times.
A simple way to assess the wear of an airless tip is to spray the coating used in production at a distance of 30 cm from a test panel and measure the spray width. This value can then be compared with the code engraved on the tip, which specifies the nominal fan width and flow rate at a given pressure.
Regularly checking spray width and replacing worn tips when they no longer match their rated fan pattern is one of the most effective and low-cost actions to reduce material consumption, cycle time and rework in the spray painting department.