Download - Infrared Vs
-
7/26/2019 Infrared Vs
1/3
Infrared vs. Convection Curing
Many manufacturers face the challenge of product
piling up around their painting department, waiting to
cure. After all, depending on the paint being used, it
can take anywhere from a few minutes to a few hours
to achieve the degree of curing required for the
product to move to the next step of your
manufacturing process.
ne of the best ways to help reduce a bottleneck due
to slow throughput in your painting process is to reduce
the time it takes to cure your paint.
!ypical methods for speeding up the curing process
include Infrared curing and convection heat. "oth
options have their pros and cons, which we will review
so you can better determine which might be right for
your application.
Convection Curing
#or a variety of reasons, convection heat is one of the
most common methods of curing coatings. Convection
heating involves elevating the temperature of the
ambient air surrounding a product in order to speed upcuring. $olvent%based coatings& cure time can often be
reduced by '( percent or more using convection heat.
ne of the primary bene)ts of convection heating is
the opportunity for a low%cost initial investment. *aint
booths can be purchased with an elevated heat option
for curing, making the overall cost very reasonable.
$imilarly, convection curing ovens typically can be
purchased at a lower initial cost than infrared ovens.
An additional bene)t of convection heat is that it will
work with a large variety of coatings+as a general rule
of thumb, though, you should check with your coating
representative to make sure it&s a viable option.
A )nal bene)t of convection heat, in comparison with
infrared, is that convection will work with a greater
variety of product shapes.
Infrared Curing
Infrared curing involves infrared waves penetrating
through the coating and curing throughout. #or this to
happen most eciently, the infrared waves should
have a direct line to the surface that you are trying to
cure. !hat&s why infrared curing is best for -at
surfaces If your product has a lot of angular, round, or
non%-at surfaces, this method can present challenges.
!he largest bene)t of infrared curing is how much
faster it can cure a coating as compared with
convection curing. !his is due to the temperature
elevations associated with infrared curing. /epending
on the wavelength of infrared being used,
temperatures can be elevated in seconds up to a few
thousand degrees. !he end result is a rapid curing
time.
In addition to rapid curing, infrared can also have a
lower operating cost. In the convection method, a lot of
energy is used to elevate and maintain temperature in
a paint booth or oven. !his results in higher operating
costs. $ince infrared uses energy waves to elevate
temperature, curing begins almost immediately and
very little energy is wasted in the curing process.
An additional bene)t of infrared curing is that it can be
used to spot cure. $ince infrared curing uses energy
waves, you can purchase infrared panels that allow for
curing targeted areas. !his can be a useful application
for spot repair work when you want to accelerate the
curing time.
Infrared curing, though, can be used on fewer types of
coatings than convection. !his is largely because it
depends on the infrared waves to be able to pass
through the coating and re-ect o0 the substrate
causing heat elevation of the coating.
1o matter which technology you are leaning toward, it
is always recommended to have a coating baked using
that method as a 2trial run3 prior to deciding on an
equipment investment.
If a coating has certain properties, like being
excessively re-ective, the infrared waves may not
e0ectively penetrate the coating and may not cure the
coating well. Additionally, certain substrates will absorb
infrared waves, reducing the re-ection of the wave
back through the coating, which can signi)cantly
reduce the curing e0ectiveness of infrared.
/ue to the potential challenges of coatings, substrate
materials, and product con)gurations you should
always have your product tested to see if infrared
curing can potentially work for you. In fact, no matter
which technology you are leaning toward, it is alwaysrecommended to have a coating baked using that
method as a 2trial run3 prior to deciding on an
equipment investment to determine if you can improve
production time.
Making a /ecision
"efore you decide which tool might be ideal for you, it
is smart to coordinate with your coating representative
to verify whether convection or infrared curing will
work, evaluate the production improvement potential
of either solution, and evaluate the cost di0erences in
initial investment and operating costs.
4ltimately, convection and infrared curing both have
good uses. 5hich method will work well for your
application will depend on the substrate of your
products, the coating you apply, the amount you want
to invest, and your production priorities.
-
7/26/2019 Infrared Vs
2/3
6lectrostatic *ainting 5hat 7ou 1eed to 8now
6lectrostatic painting is often not well understood in
the paint and coatings industry.
!o help clarify the electrostatic process, I want to
discuss what electrostatic painting is and how it works,
things you should consider, and how to determine if it
is the right )t for you.
!he electrostatic method is used in liquid and powder
coating, but I will focus on liquid coatings in this post.
5hat It Is, 9ow It 5orks
6lectrostatic painting is a process in which an
electrostatic charge is applied to both the substrate
and to the coating through the tip of the spray tool in
order to achieve eciency in painting the surface by
preventing overspray.
!he coating is pro:ected by an electrostatic charge
from a high%volume, low%pressure ;9 spray gun or
airless paint sprayer to the grounded, conductive
surface to be painted.
!he charged paint is attracted to the charged surface
in such a way that the pain essentially wraps around
the target and rather than leading to overspray.
!his translates into a high transfer eciency and
reduction of coating waste. !ypical ranges of
electrostatic transfer eciency are anywhere from ?(
to @( percent, depending on the target type and other
factors.
!his paint savings is often what makes electrostatic an
attractive solution, but there are a lot of things to
consider with electrostatic coating, such as the
coatings you use, the intended target, your equipmentmaintenance tendencies and safety.
Coatings and 6quipment
!he coatings you want to use are an important
consideration because of the unique requirements of
electrostatic equipment.
In the electrostatic process, the charged paint is
attracted to the charged surface in such a way that the
pain essentially wraps around the target and rather
than leading to overspray.
5aterborne coatings, for example, require special
spray guns when used for electrostatic painting. !his is
because waterborne coatings are conductive and tend
to carry a charge that can cause issues with
2grounding out3 when they are sprayed.
rounding out means that the electric charge+rather
than charging the paint at the tip of the gun+simply
passes back through the coating into the pressure pot
and, if the pressure pot is grounded, into the earth.
!his provides none of the bene)ts of electrostatic
application.
!he waterborne%speci)c electrostatic spray gun will
have an isolation block as part of the equipment to
prevent the electric charge from trying to return to the
pressure tank and ultimately stops the waterborne
coating from grounding out.
!his can be a highly expensive downside if you
routinely change between solvent% and water%based
coatings on your :obs because you will need two
di0erent types of electrostatic guns.
Additionally, many unique complications can occur with
this specialiBed process, so it is always best to have
someone test the equipment tested in your work area,
with your coating and under your normal
circumstances. 6lements such as humidity, the
grounded target, the coating itself and the solvent you
use can vary from one work area to the next and a0ect
the spray application.
It is also important to note that certain solvents are
more likely to work well with a solvent%based
electrostatic gun because they are less conductive
than other solvents. $ee the table below for more
information.
4ltimately, the goal is to have the coating be as
nonconductive as possible. !hat is why solvents like
xylene and toluene are good for electrostatic painting
they are nonconductive, which minimiBes the likelihood
of your coating grounding out.
8eeping in mind the unique requirements of
electrostatic coating, for the most part you can spray
:ust about any coating, but certain coatings like Bincs
will not take a negative charge well and therefore will
not be able to deliver the improved transfer eciency
electrostatic brings.
$urface Materials
!he surface you intend to paint also plays a signi)cant
role in determining if electrostatic spraying is a good
method to use.
*lastic, wood or )berglass surfaces won&t conduct a
charge without a preparation coating, for example. !his
means you will have to apply a prep coating before
your intended coating to allow for electrostatic
application.
-
7/26/2019 Infrared Vs
3/3
Additionally, electrostatic application is sub:ect to a
phenomenon called the #araday Cage 60ect. !he
#araday Cage 60ect describes the tendency for
negatively charged particles to want to attract to the
nearest positively charged surface.
In electrostatic painting, this e0ect means that the
paint will want to adhere to the sides of the surface
material but not penetrate into any corners. 5ith this
in mind, an applicator needs to remember to turn the
electricity to the gun o0 in order to achieve thoroughcoverage.
$hop and 6quipment Maintenance
Another area to consider before investing in
electrostatic painting is how well you maintain your
shop and equipment.
6lectrostatic equipment is a lot more expensive than
9