05 Spray Applications and Defects TC 2012 [Compatibility Mod

7/26/2019 05 Spray Applications and Defects TC 2012 [Compatibility Mod

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Training CenterAkzoNobel Aerospace Coatings

Spray EquipmentSpray Equipment


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2012 AkzoNobel NV. All rights reserved. Aerospace Coati ngs | Spray app li cati ons and defects 2

Types of spray guns / equipment

Conventional

HR/RP

HVLP

Airless

Air-mix

Electrostatic


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How did everything start?

The dentist Dr. Allen DeVilbissinvented in 1888 in Toledo, Ohio,a sprayer for liquids, to clean andrinse the patients mouth andthroat.


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Conventional spray equipment

Gravity feedSuction feed


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Used by nearly all airlines and manufacturers

Air pressure (inlet spray gun): 3.0 - 4.5 bar

Nozzle diameter: 1.2 - 1.8 mm

Distance gun - substrate: 15 - 25 cm


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Advantages

Controlled atomizing air pressure and paint flow

Easy to clean

Less expensive

Texture look possible (cabin coatings)

Disadvantages

Low paint efficiency (30- 70 % loss of paint)

Creates a lot of over spray

Less suitable for large aircraft painting/ time consuming


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HR/RP/ HVLP spray guns

HR = High Return

RP = Reduced Pressure

HVLP = High Volume Low Pressure

Gravity feed

Suction feed

Air pressure (inlet spray gun): 2.0 - 3.0 bar




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HR/RP/ HVLP spray guns

Advantages

Meets (European) legislation

Controlled air pressure (similar like conventional)

Less over spray

Texture-look possible

High paint efficiency

Disadvantages

Less suitable for large aircraft painting/ timeconsuming

Consult user manual


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Airless spray equipment


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Manufacturers made an efficient improvement byintroducing airless application

Paint pressure: 150 -180 bar

Nozzle diameter: 6.11 - 6.13 (60o, 0.011 inch)


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6.


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Advantages

Can operate within wide range of viscosities

High output (up to 5 liters/ min)/ higher working speed

Less over spray and bounce back compared to air spray

Reduced pressure loss (long hoses/ working on heights)

Disadvantages

Tip must be changed to alter fan width

Paint output cannot be easily controlled Higher risk blocking of the nozzle/ tip

Cannot be used with the application of mica


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Air-mix spray equipment


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Air-mix is combination of:

Airless

Air-assist

Developed to reduce the inconveniencesof Airless and air-assist

Air-mix is a brand name of Kremlin


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Air pressure: 2.0 4.0 bar

Paint pressure: 60 - 120 bar

Nozzle diameter: 09.134 - 09.154



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Advantages in comparison to conventional

Higher working speed

Improved working conditions

Advantages in comparison to airless

Lower purchasing price

Lower working pressure

User friendly


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Electrostatic spray equipment


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Electronic charging

Combines the features / advantages of existing spray equipment, air spray,

airless and air assisted airless with an electronic charge


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Electronically charging the paint creates a 'field' where the paint material is

attracted to the substrate resulting in less over spray


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Xs3 Air spray



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Graco PRO Xs3 (Xs3 = 60 kV/ Xs4 = 85kV)air-assisted electrostatic spray gun

Air pressure: 5.0 - 5.5 bar

Paint pressure: 1.0 - 2.5 bar

(paint flow rate 240 - 340 ml / min.)




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Xs4 AA Air-assisted



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The Graco PRO AA Xs4 (85 kV) air-assisted airless electrostaticspray gun

Pressure: 150 - 180 bar

Nozzle diameter: 6.11- 6.13 (60o, 0.011 inch)



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Advantages

High transfer efficiency

Less over spray

Preferred in regular maintenance hangars

Disadvantages

Expensive equipment

Less suitable painting smaller parts

Cleaning must be done extremely well


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General safety instructions

Read and understand safety instructions

Equipment and A/C thoroughly grounding

All persons wear: shoes with conductive soles

Special gloves

Never flush the lines while ES is on

Habit of turning ES off immediately after spraying


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Comparison transfer efficiency

Conventional air spray: 30 %

Airless spray: 50 %

Electrostatic spray: 70 %

Airmix: 65 %

HVLP: 70%

HR/RP: 70 %

Roller coat: 95 %

Note: above figures are based on correctly adjusted spray equipment


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05 Spray Equipment


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Training CenterAkzoNobel Aerospace Coatings

Spray DefectsSpray Defects


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Spray defectsSpray defects

Overspray

Sags and runs

Foaming/ pinholing

Hazing/ poor gloss

Orange peel Cratering and fish eyeing

Poor opacity

Poor adhesion


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Overspray


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Spray gun too far from the job

Air pressure too high (over atomization)

Waving with the gun

Not triggering at the end of each lap

Incorrect routing resulting in poor melt in Incorrect viscosity (too much thinner)

No air movement

Overspray


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Sags and runs in paint coat


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Addition of too much thinner

High film build on overlaps

Spray-gun too close to the surface being painted

Incorrect fluid tip, needle or air-cap (poor atomization)

Slow application resulting in high film build Spraying too thick layer in one coat

Spraying irregular thickness

Insufficient flash-off between coats



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Foaming/ pinholing


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Foaming/ pinholing

Too high absolute humidity (combination relative humidity andtemperature)

Solvent entrapment caused by air flow exceeding

0,5 m/. which can result in premature skinning

Too high viscosity of the paint

Too high film thickness

Insufficient flash-off between coats


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Foaming/ pinholing


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Foaming/ pinholing


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Hazing/ poor gloss


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Moistures substrate Cold substrate

Too quick evaporation solvent

Differences in temperature of paint versus surface to bepainted

Unstable circumstances during paint process and drying ofthe paint system

Too quick covering of not fully cured painted surfaces withplastic

Hazing/ poor gloss


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Application over incompatible substrate

Not adhering to recommended flash-off times

Incorrect use of accelerators or reducers

Using shelf life expired products

Hazing/ poor gloss


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Orange peel


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Incorrect viscosity (insufficient solvent)

Air pressure too low

Incorrect gun set-up (poor atomisation)

Paint dust in primer coat

Insufficient flow of primer system

Orange peel


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Cratering and fish eyeing


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Not properly stirring or shaking of the paint Solvent, evaporation leaving contamination on the surface

Use of contaminated air

Air born contamination

Poor cleaning/ degreasing (wipe-on-wipe-off method)

Contamination from skin contact after cleaning

Not degreasing before sanding

Cratering and fish eyeing


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Poor opacity


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Addition too much thinner Not stirring or shaking the material sufficiently to achieve total

dispersement

Low film thickness

Incorrect gun set-up (over atomization)

Too short flash-off time between coats, flash-off / drying timedepends on temperature and humidity

See the technical data sheet for the correct flash-off time

Poor opacity


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Poor adhesion


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Poor preparation (cleaning) Surface contamination

Not tacking off

Exceeding stated re-coat times

Incorrect system selection

Dry application of primer systems

Poor adhesion


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Standard paint shop equipment

Paint shaker


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Temperature & relative humidity meter



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Tack-rags



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Rulers



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Flow cups ie. ISO cup,Zahn cup etc.



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Stopwatch



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Layer th ickness meter



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Gloss meter



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Technical data sheets



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Depends on: Skill

Dedication

Experience

Proper tools and equipment Good housekeeping

Teamwork

Painting an aircraft successful ly


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A good paint job will be achieved with:

Good HousekeepingPersonal cleanliness Preciseness


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Teamwork is essential for a good paint job!


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05 Spray Applications and Defects

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05 Spray Applications and Defects TC 2012 [Compatibility Mod

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