Presentation on theme: "Presented By: Jennifer Erle Amberlee French Sarah Bennett Josh Hamilton John Schmitt."— Presentation transcript:
Presented By: Jennifer Erle Amberlee French Sarah Bennett Josh Hamilton John Schmitt
Powder coating is a dry finishing process, using fine particles of paint, which are electrostatically charged and sprayed onto a workpiece. Once the powder is applied, the part is cured, causing the powder to adhere to the surface.
Fine particles are fluidized in a feed hopper Powder is vacuumed into the spray gun A second burst of air increases the particle velocity Particles are then charged by high velocity friction Spray gun applies powder to the grounded workpiece Coated part is then oven cured
Dimensions: 0.4m x 0.4m x 0.4m Bed dimensions based on 50 lbs of powder Pick-Up Tube Diameter: D = 0.02 m Fluidization of the particles prevents clogging
1) Terminal velocity for the smallest particle size : v t = 4.41×10 -3 m/s 2) Reynold’s number : Re = 2.81×10 -3 3) Volume fraction of the powder particles for minimum fluidization : w = 0.41 4) Velocity in the pick-up tube : v tube = 48.52 m/s
The volume flow rate at the tip of the gun was tabulated: v powder = 250 m/s A guntip = 3.142×10 -4 m 2 V guntip = 0.079 m 3 /s The second burst of compressed air volume flow rate was calculated: V 2ndburst = 0.063 m 3 /s
Oven temperature: 300 °F Time for complete cure: 20 minutes Curing causes a chemical reaction that bonds the powder coating to the workpiece.
No solvents are used Over-spray (up to 98%) can be reused More resistant to chipping, cracking, and fading Corrosion and chemical resistant Coating does not run, drip, or sag Thick coatings are easily done Simple clean-up and maintenance
Thin coatings are difficult to produce Storage and handling of the powder requires special climate controls Color matching is somewhat more difficult Cure temperatures may be too high Difficult to coat sharp corners
Key concepts involved in powder coating: Fluidized Bed Mass Balance Bernoulli Equation Stoke’s Law Specific calculated properties: Terminal velocity in fluidized bed Velocity in pick-up tube Volume flow rate of second burst of air
Presented By: Jennifer Erle Amberlee French Sarah Bennett Josh Hamilton John Schmitt Questions ?