Tribo guns also are used for powder application. With this method, the powder material picks up a positive charge while rubbing against the gun’s interior
Teflon® walls.
An operator needs less experience to apply powder coatings in an e;cient
and e;ective manner than someone applying liquid coatings.
What Are the General
Oven Requirements?
Liquid. Because most liquid coatings can air-day, ovens aren’t necessarily needed. However, if a manufacturer wants to speed up drying times, it needs an
oven that is capable of heating between 130 and 170 degrees F.
Powder. Powder coatings need a much hotter oven to melt the particles so
that they can flow and react chemically to form a smooth finish on the workpiece. Most powder coatings reach this stage in an oven heated to 350 to 400
degrees F. For a proper curing, the substrate must be at this temperature for at
least 10 minutes.
On some occasions a manufacturer can use the same oven for drying liquid
coatings and curing powder coatings (as long as both coating chemistries are
compatible with each other). ;e key is scheduling parts headed through the
oven so that the temperature can be adjusted accordingly for specific coating
jobs.
Why Use a Liquid Coating?
;is coating technology is prevalent for many reasons:
• It can be cured quickly, resulting in faster production cycles.
• It is cost-e;ective in the sense that the initial investment for the equipment is much less than for powder coating equipment (although liquid
material is more expensive than powder and can’t be reclaimed).
• ;e coating can be used to finish parts containing sensitive materials, such
as a metal cylinder with a rubber seal, because it does not require dramatically high temperatures to dry.
• It can be used to finish very large parts that are not able to fit into an oven
or can’t be moved easily.
• A thin coating is achievable. It can routinely be applied as thin as 0.5 mil.
• It provides an automotive-quality finish (although this performance advantage over powder coatings has been narrowed greatly over the years).
Why Use a Powder Coating?
Users of powder coatings turn to this
technology for a few specific reasons:
• As soon as the workpiece has
cooled after curing, the part
doesn’t require overly protective handling and immediately
can be sent to downstream processes such as assembly or packaging.
• It is very durable. It is commonly
used for outdoor applications
ranging from outdoor furniture
to agricultural.
• ;e process does not emit
VOCs, which means local air
quality regulations aren’t likely
to be an issue for the manufacturer undertaking powder
coating. Additionally, the material can be reclaimed, if the right
equipment is installed, which
limits the amount of waste material that has to be placed into
the waste stream.
• Although it requires a large upfront investment, the long-term costs of
applying powder are less than those for a liquid system. In some instances,
the price of liquid material may be four times more.
Michael Hornbaker is technical sales support manager; Loren Keene is a regional sales manager; Randy Krawiec is liquid technician; Rob Tesmer is technical and sales support manager; and Todd Wilken is service and powder lab
supervisor at Wagner Systems Inc., 300 Airport Road, Unit 1, Elgin, IL 60123,
630-503-2400, www.wagnersystemsinc.com.
