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DeVilbiss JGA Maintenance And Troubleshooting Manual

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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 test 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 the examples then look at the
corrective measures before you apply paint to the
workpiece.
Having examined the vertical spray pattern for uniformity of shape and size, now turn the air cap through 90
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 spray pattern.
This will highlight how well the material is distributed throughout the spray pattern. If the run-out is more obvious at the
centre or at the ends then this indicates a problem.
TYPICAL GOOD PATTERN RUN-OUT
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)
Banana Pattern
?
Air cap horn hole dirty or
damaged
?
Test spray pattern, rotate
o
180
and test again to
isolate horn hole cause
location
?
Clean air cap thoroughly
?
Replace air cap if necessary
Single Split Pattern
?
Too much air for fluid
quantity used
?
Reduce air pressure at
regulator
?
Increase fluid flow by
changing fluid tip size
opening needle control
knob
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
STATIC PATTERN TEST
(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 a piece of brown paper (approx. ½ metre /
20" square) onto the spray booth wall at shoulder
height.
(3) Having set the gun at the recommended inlet or
atomising air pressure, hold it at he correct target
distance and spray at the paper without moving the
gun.
Intermittent Spray Fan or
Fluttering
?
Air in the fluid passageways
?
Insufficient paint in the cup
?
Fluid tip loose
?
Fluid needle packing or packing
screw loose
?
Cup vent hole clogged
Heavy Top or Bottom
Pattern
?
Fluid tip or cap dirty or
damaged
?
Test spray pattern, rotate 180
and test again to isolate cause.
?
Clean both items thoroughly
?
Replace Fluid tip or Air cap if
necessary
Centre Heavy Ellipse
?
Bad air or paint setting
?
Viscosity too high – thin with
solvent
?
Fluid flow too high – reduce
?
Air pressure too low – increase
Ball End Heavy Pattern
?
Too much fluid flow
?
Change fluid tip for smaller size
?
Reduce flow using fluid needle
control
?
Reduce fan size using fan
control
TYPICAL BAD PATTERN RUN-OUT
o
o
and static spray

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  Summary of Contents for DeVilbiss JGA

  • Page 1 HOW DOES YOUR SPRAY GUN SHAPE UP? No matter how experienced the sprayer, merely (1) Ensure that you have the correct Air Cap, Fluid triggering and moving a gun in space will not Tip and Needle set-up on the gun to match the reveal any of the performance characteristics vital material being applied.
  • Page 2 MAINTENANCE & TROUBLESHOOTING PAGE 1 Spray gun Maintenance and Troubleshooting Guide (JGA) IMPORTANT: Before using the gun for the first time, tighten the needle packing until the needle starts to bind. Then loosen the packing nut just WARNING enough so that the needle moves freely.
  • Page 3 MAINTENANCE & TROUBLESHOOTING PAGE 2 SPRAY FAULTS Condition Cause Correction Improper spray pattern Gun Improperly adjusted. Readjust gun, follow instructions carefully. Clean air cap. Dirty air cap Clean Fluid tip obstructed Lubricate (see lubrication section) or Sluggish needle loosen packing nut. Heavy top or bottom pattern Material build-up on air cap, partially Soak cap or tip in suitable solvent and wipe...
  • Page 4 MAINTENANCE & TROUBLESHOOTING PAGE 3 SPRAY FAULTS Condition Cause Correction Split spray pattern enough material high Reduce air pressure or increase fluid flow atomisation pressure by turning fluid needle adjusting screw counterclockwise increase fluid pressure on pressure feed container. Excessive bounce-back Too much atomisation air pressure Reduce air pressure Gun too far from surface...
  • Page 5 MAINTENANCE & TROUBLESHOOTING PAGE 4 MAINTENANCE & TROUBLESHOOTING PAGE 4...
  • Page 6 MAINTENANCE & TROUBLESHOOTING PAGE 5 GUN FAULTS Condition Cause Correction Will not spray No air pressure at gun Check air supply and air lines Internal mix or pressure feed air cap used Change to proper suction feed air cap with suction feed Fluid pressure too low with internal mix Increase fluid pressure at tank cap and pressure tank...
  • Page 7 MAINTENANCE & TROUBLESHOOTING PAGE 6 GUN FAULTS Condition Cause Correction Paint build-up on fluid tip Fluid tip not fitted correctly in gun head Tighten to correct torque Fluid tip/needle leakage Check for damage or blockage Paint build-up on Air cap Damaged air cap holes Replace with new Air cap Gradual build-up of bounce-back on gun...
  • Page 8: Spray Gun Cleaning

    MAINTENANCE & TROUBLESHOOTING PAGE 7 Without a hose cleaner, remove excess material from cup or Spray Gun Cleaning tank and clean. Set up cup, tank or pump to operate with clean cleaning solvent. Turn off atomisation air to gun. Trigger gun Suction Feed Clean Up: into waste container.
  • Page 9 MAINTENANCE & TROUBLESHOOTING PAGE 8 JGA Spray Gun Maintenance Schedule A. Every Shift 1) Check front air cap face and all air cap holes are free from damage. Replace if necessary 2) Check fluid tip external profile is undamaged. Replace if necessary 4) Check fluid needle is seating correctly in fluid head allowing no seepage.