What causes a bad spray pattern from the tip?

When spraying foam and polyurea, bad spray patterns from the tip can occur. What are the causes?

Your Spray Pattern Is Affected by Several Elements:

Gun, tip, and Reactor type, distance and angle to the surface, temperature and pressure, applicator skills...in some cases, a bad spray pattern caused by the tip can occur. In this article we explain the most likely causes.

When spraying foam and polyurea, a bad spray pattern can occur, possible leading to additional problems such as bad finishing and material waste. It is important to take the appropriate action to restore the desired spray pattern as soon as possible. To correct your spray pattern, you should know the possible causes of a bad spray pattern from the tip.


Causes of a bad spray pattern

  1. Tip is partially plugged.
    Matter can build up at the inside of the tip, partially plugging the tip and causing a bad spray pattern. To clear the blockage, you should remove the tip and clean it. Do not use a metal object, as this could damage the tip.

  2. Pressure is too low.
    If the pressure at the spray tip is too low, the spray pattern will have a rough surface and an inconsistent cell structure. To increase the pressure, you should turn the pressure knob clockwise.

  3. Pressure is too high.
    A high mix pressure increases the area of overspray and with it the material waste, the amount of clean-up required, and the operational costs. Turn the pressure knob counterclockwise to decrease the pressure.

  4. Temperature is too high.
    High temperature can lead to an inconsistent spray pattern.

  5. Filters in proportioner or gun are plugged.
    Matter can build up at the filters of the gun, blocking the material and resulting in a shrinking spray pattern. Remove and clean the filters or replace them completely if needed.

  6. Tip is too large or worn out.
    If the tip is too large or worn out because of intensive usage, it needs to be replaced with a tip with a size appropriate for the material being sprayed.

  7. Too much containment air around the air cap.

  8. Dirty ports in mixing module.


Need help fixing a bad spray pattern?

If you notice constant fluctuations in the spray pattern or the appearance of the foam, you should stop your spraying activities until the cause is determined. Need help with your spray foam and polyurea equipment? Contact Graco’s product specialists. We offer a complete range of single component sprayers and pumps, plural component proportioners, and blasting equipment.


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