Airless spray painting tips.
An airless spray painting tip (nozzle) is one of the most important parts of an airless spray paint machine. The airless spray tip determines the amount of flow, the level of paint atomisation and the spray paint fan width that a airless spray paint pattern will be.
The flow of an airless spray painting machine is primarily altered by increasing or decreasing the orifice size, the opening size, of the spray tip. Airless spray paint flow rate can secondarily be increased or decreased to a much lesser extent by increasing or decreasing the airless paint pump output pressure. A downside to using increased or decreased pressure to regulate flow in and airless spray painting machine is that over atomisation causing more over spray or under atomisation causing inferior finish can result.
Most general use airless spray tips are offered for sale in thousands of an inch and in odd number of sizes e.g .007 inch, .009 inch, .011 inch, .013 inch, .015 inch, .017 inch etc.
The flow rate with water or a similar liquid at 1500 psi or 100 bar for a .017 inch spray tip is approximately .98 of a litre per minute or .26 of a US gallon per minute.
At 2000 psi or 138 bar the flow rate for a .017 in spray tip could increase to approximately 1.17 of a litre per minute or .31 of a US gallon per minute.
Spray pattern fan width of airless spray painting tips is achieved by the angle that the spray tip orifice is cut at. Airless spray tip orifice cut angles are commonly 10° 20° 30° 40° 50° and 60° 70° 80° and 90°. Certain airless spray tip manufacturers have also introduced a wide spray airless spray tip which have a 120° angle cut into the orifice to achieve spray pattern fan widths of up to 24 inches or 600 mm.
An important fact to understand is that in any given airless spray tip orifice size the flow should not increase between the narrowest 10° airless tip and the widest 120° airless spray tip. As the angle and fan with increase in an airless spray tip the same amount of paint or fluid that will flow through the narrowest angle is spread across the wider spray pattern meaning that airless spray gun speed will need to slow to achieve a similar film build and because the orifice becomes more and long dated and narrower with wider spray patterns blockages may occur more often.
Likewise when reducing the fan width in the same orifice size spray tip the same amount of paint should flow but this will be over and now area requiring faster travel of the airless spray gun to achieve the same film build that occurred with the wider airless spray tip pattern.
Most airless spray painting tips are numbered with the three digits. The first digit usually indicates the angle that the airless spray tip has been cut at which will determine the spray pattern fan width and the second two digits will indicate the nozzle opening size, in other words the orifice size in thousands of an inch.
A airless spray tip with 113 stamped indicates that it is a 10° cut with a .013 of an inch orifice.
And airless spray tip with 713 stamped indicates that it is a 70° cut again with a .0 or 13 of an inch orifice while a 719 stamped airless spray tip indicates a spray tip cut again at 70° but with a .019 of an inch orifice. Both of these airless spray tips have the same spray pattern with but be .019 of an inch opening tip will flow more material than the .013 of an inch orifice airless spray tip.
A handy rule of thumb to use to determine the width of an airless spray tip is to double the first of the three digits which indicates fan width at 12 inches or 300 mm from the surface. Placing the spray tip closer to the surface or increasing the distance from the surface will reduce or increase the spray pattern fan width. For example a 113 tip will have a 2 inch wide fan pattern, a 213 will have a 4 inch wide fan pattern, a 313 will have a 6 inch wide spray fan pattern, a 413 8 inches wide, a 513 10 inches wide, a 613 12 inches wide, a 713 14 inches wide, et cetera.
Most paint manufacturers recommend an airless spray tip size range for their products and most airless spray tip manufacturers recommend an airless spray tip size range for most general paints. A range is supplied by the airless spray tip manufacturer because paints do vary in viscosity and pigment particles size within generic paint product groups.
Water-based paints on ceilings for example could be sprayed with an airless spray tip ranging in size usually anywhere from 0.15 of an inch through to 0.19 of an inch. The .015 tip may be selected for a smaller ceiling using higher quality water-based paints with higher cost levels while a .017 of an inch or even .019 of an inch airless spray tip may be required for extremely large ceiling areas or for using using lower cost matt or flat finish water-based paint which may have coarser pigment particle sizes.
Many airless spray tip manufacturers nowadays offer fine finish airless spray tips which incorporate a pre-orifice to aid with atomisation at lower pressures and he assist with achieving a finer atomisation. The airless spray tip industry has generally standardised by using even sized orifice numbering to indicate fine finish airless spray tips such as .008 of an inch, .010 of an inch, .012 of an inch, .014 of an inch etc. Airless spray tip fan pattern with numbering generally remains the same with fine finish airless spray tips such as 10° 20° 30° etc.
Most airless spray machines will have a limit on the maximum orifice size airless spray tip they are capable of supporting and remember that all airless spray tips wear and as spray tip wear occurs the orifice size of the airless spray tip increases which reduces the angle which has been cut into the orifice to achieve a spray pattern with resulting in the spray pattern narrowing as the wear to your airless spray tip occurs.
Continuing to use a worn airless spray tip usually wastes paint and can contribute to increased overspray while creating more load for your airless spray machine which in turn can increase wear and tear on all airless spray machine components.