Spray Machines: Guns & Tips

Selecting the right tip for the right application to maximise productive.

Different spray machines require different types of guns and tips to achieve correct flow and spray pattern. If the incorrect setup is used it is possible to cause damage to the spray machine and the coating operator.

Selection of the correct tip is critical to achieving maximum productivity. This is due to the fact that the tip determines the fluid flow and the size of the spray pattern (fan size) of the coating. The correct tip produces improved results with the maximum control and minimum over spray, optimizing work times and causing less paint waste.

Choosing the right tip.

To choose the right spray tip, requires the consideration of several key factors, such as the material thickness, the sprayer's maximum flow rate and the best fan size for the project. Being able to identify when a tip is worn and replacing the tip at the right time will also improve the finish quality and project devleoment time.

For optimum performance, the sprayer must have a maximum flow rate higher than the flow rate of the tip, to be sure the flow rate of the tip is less than the maximum flow rate of the sprayer unit.

Why use a tip with a lower flow rate?

The tip slowly wears and the orifice becomes larger, resulting in an increase of coating flowing throught the tip and onto the work area. This can lead to an uneven coating of the surface and excess usage of coating material which adds to the overal project cost.

Why is spray pattern fan width also required?

The width of the spray pattern, known as the fan width, determines the area covered with each pass. For a given tip orifice, a wider fan delivers a thinner coat, less defined spray pattern, more over spray and faster coverage on broad, open surfaces. A narrower fan delivers a thicker coat, more defined spray pattern, less over spray and better control when spraying small or confined surfaces.

To maximize productivity and lower labor costs, choose a tip with the right fan size. In general, a spray tip with a larger fan size increases production with less control, and a smaller fan size decreases production with more control.

Selecting the correct gun for coating application

There are a wide variety of spray tips available for use in electrostatic coating. The type of tip used will depend on the shape of the work piece to be painted and the consistency of the paint. The object is then heated, and the powder melts into a uniform film, and is then cooled to form a hard coating. It is also common to heat the metal first and then spray the powder onto the hot substrate. Preheating can help to achieve a more uniform finish but can also create other problems, such as runs caused by excess powder.

Another type of gun is called a tribo gun, which charges the powder by (triboelectric) friction. In this case, the powder picks up a positive charge while rubbing along the wall of a Teflon tube inside the barrel of the gun. These charged powder particles then adhere to the grounded substrate. Using a tribo gun requires a different formulation of powder than the more common corona guns. Tribo guns are not subject to some of the problems associated with corona guns, however, such as back ionisation and the Faraday cage effect.

Recommended tip sizes for common coatings.

Filter Screen Typical Product Typical tip size
#30 Hi-build epoxy and high solid coatings. 25,000 +
#60 General industrial coatings. 17,000 to 23,000
#100 Decorative industrial top coats. 11,000 to 16,000
#200 Superfine finish top coats. 7,000 to 12,000

Tip Selection Charts

Get help with selecting the right tips by reviewing charts based on the most common brands.