Electrostatic Spray Coating(Micro Fabrication Techniques )

By 1- Ahmed Abubakr 2- Mostafa Amer

Outline!Basic Idea of Electrostatic Spray

CoatingCharging MethodsCoating MaterialsAdvantages Limitations

Basic Idea of Electrostatic Spray Coating

Charging Methods(1-Corona Discharge)

Charging Methods(2-Conduction Method)

Charging Methods(3-Induction Method)

Coating Materials

Key Properties

Resistivity Conductivity

Flammability

Coating Materials: materials (or paint or photoresist) used to coat the object or target.

Coating Materials(Resistivity & Conductivity)

Optimum range for resistivity to spray best is 20-200 megaohms.cm

Lower resistivity materials may require special fluid tube or hose configurations to prevent them from shorting out.

If the coating material is too resistive a higher conductive solvents are used to reduce the resistivity.

Coating Materials(Resistivity & Conductivity)

Coating Materials(Flammability)Coating materials have a flashpoint

temperature rating to indicate the temperature at which vapors from the material are flammable.

How easily these vapors can be ignited ?!Flammable materials may ignite if an

uncontrolled electrical discharge (spark) occurs.

Note: any metallic or otherwise electrically conductive object is in the vicinity should be properly electrically grounded

AdvantagesSaves material because it utilizes overspray and

reboundReduces clean-up and maintenance time.Increases production rates Reduces equipment wear because lower air and

fluid pressures are used.Eliminates secondary operations in some cases

because of wrap-around.Better atomization because like charges repel

each other causing the spray pattern to open upbetter using less air pressure

LimitationsUniformity of coverage will vary depending on

the size and contour of the object.The product to be sprayed must be a conductor.

Parts which are not conductors can be sprayedby having parts immersed in a special solutionto make them conductors.

Conveyors, as well as the product, must begrounded at all times.

Electrostatic spray guns are limited to the amount of fluid they can efficiently charge in agiven period of time.

References 1- Basic electrostatic spray finishing,

Retrieved from: http://www.elliottequipment.com/MediaLibraries/ElliottEquipment/PDFs/Ask%20Elliott/ELECTR_1.PDF

2- Electrostatic Spraying, Retrieved from: http://infohouse.p2ric.org/ref/50/49414.pdf

Questions!