How Does Your Spray Gun Shape Up?
No matter how experienced the sprayer, merely triggering and moving a gun in space will not reveal any of the performance characteristics vital to a top quality finish. A simple brief static spray pattern will immediately highlight any potential problems before the gun is used on the painstakingly prepared workpiece or vehicle.
Follow the procedure explained below and compare the pattern to our examples. If your result resembles examples 2-8, then look at the corrective measures before you apply paint to the workpiece.
1. Ensure that you have the correct air cap, fluid tip and needle set-up on the gun to match the material being applied.
2. Tape up a piece of brown paper - approx. 20” (1/2m) square - onto the spray booth wall at shoulder height.
3. Having set the gun at the recommended inlet or atomizing air pressure, hold it at the correct target distance and spray at the paper WITHOUT MOVING THE GUN.
Normal Pattern - Ready To Spray
- Good balance and uniformity
- Symmetrical pattern shape
- Good working height and width
- Uniform distribution of material
- (Verify by horizontal spray out)
Intermittent Spray Fan Or Fluttering
- Air in the fluid passageways
- Insufficient paint in cup
- Fluid tip loose
- Fluid needle packing or packing screw loose
- Cup vent hole clogged
- Air cap horn hole dirty or damaged
- Clean air cap thoroughly
- Replace air cap if necessary
- Test spray pattern, rotate 180° and test again to isolate horn hole location
Heavy Top Or Bottom Pattern
- Fluid tip or air cap dirty or damaged
- Test spray pattern, rotate 180° and test again to isolate case
- Clean both items thoroughly
- Replace fluid tip or air cap if necessary
Center Heavy Ellipse
- Bad air or paint setting
- Viscosity too high, thin with solvents
- Fluid flow too high – reduce
- Air pressure too low – increase
Double Split Pattern
- Too much air for fluid quantity used
- Reduce air pressure at regulator
- Increase fluid flow by changing fluid tip size or opening needle control knob
Ball End Heavy Pattern
- Too much air flow
- Change fluid tip for smaller size
- Reduce flow using fluid needle control
- Reduce fan size using fan control
STATIC PATTERN TEST - PATTERN RUN OUT
Having examined the vertical spray pattern for uniformity of shape and size, now turn the air cap through 90° and static spray a horizontal pattern making sure you trigger for long enough to load the shape with material. Then watch to see the formation of the run-outs of material across the full width of the sprayed pattern. This will highlight how well the material is distributed throughout the spray pattern. If run-out is more obvious at the center or at the ends then this indicates a problem.