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State-of-the-art Paint System
Pretreatment Makes Vending
Machine One Tough Customer
Fawn
Manufacturing's vending machines needed a finish that could withstand harsh
climates, rugged weather and tough customers. It found a pretreatment
package it liked and made it better, which made for a high-quality, durable
powder coating finish that stood up to the most demanding environments....
By Beverly A. Graves, Editor
Every
day, people the world over slide coins into vending machines in
anticipation of a soda, sandwich, coffee or bag of chips. Most vending
machines in the United
States are staged in protected venues like
cafeterias, schools, sports arenas and similar places. However, in places
such as Western Europe, Asia and South America,
most of the vending machines are outdoors. Also, vending machines are more
prevalent on those continents. Even so, according to industry studies,
consumers everywhere spend more on vended merchandise than they spend on
movies, videos, CDs or professional sports.
Learning
this, Fawn Manufacturing (Des
Moines, IA)
realized it needed to find a tougher finish than the solvent-borne liquid
paint it was using to coat its vending machines. The finish had to endure
not only temperature and weather extremes, but also climatic conditions
such as salt air, high winds and varying altitudes. In areas such as South
America, where environmental regulations are not as strict or as strictly
enforced as in Europe or the U.S., Fawn also had to consider
the effects of air pollution combined with the extreme climatic conditions.
For
two years Fawn researched various coatings but focused primarily on powder
coatings. It surveyed liquid and powder coating systems at its competitors'
businesses as well as lines at companies manufacturing consumer durable
appliances. It also purchased a small powder coating booth "so its
employees could learn the ins and "outs of powder coating.
Once
the final decision was made to go with powder coating, Fawn put its full
energy into developing a world class finishing line. Milbank Systems headed
the project, working with Fawn to design the entire layout of the automated
system from racking stations to curing oven. Fawn had seen what was out
there and had many ideas on how to make its finishing system better.
Fawn
added stages to the "traditional" iron-phosphate pretreatment
line in order to achieve the higher quality paint finish it needed on its
vending machines. "We personalized the entire system," noted Mr.
Bruntz, president and CEO, "however, we felt
that optimizing the cleaning line was one of the most important things we
could do to ensure superior adhesion and a premium paint finish."
One
of the major requirements Fawn insisted upon was a top-rate pretreatment
system. Mr. Bruntz, along with the engineers on the project, believed that
to achieve a quality powder coated finish, the best pretreatment was
imperative. Dubois Chemical Co., which had been the pretreatment supplier
for the old finishing system, was assigned the task of developing the new
pretreatment for the powder coating line.
Electronic eyes at the entrance to the powder coating booth determine what
size and shape of part is entering the booth and triggers the proper spray
guns to turn on and off at the appropriate interval.
In
the first stage of the iron-phosphate spray pretreatment, parts spend 60
sec in the 140F Ferroterj. The first stage removes
shop oils and metalworking fluids. This is followed by a second 60-sec
stage of the same solution at the same temperature and concentration. The
second stage simply continues the cleaning process. The third and fourth
stages are 42-sec counterflowing tap-water
rinses.
The
fifth stage is Secure iron phosphate for 90 sec at 130-140F. In addition to
phosphating, the process also provides some
cleaning action. The coating is heavier than ordinary phosphate coatings,
enhancing paint adhesion and corrosion protection.
The
sixth stage is another 42-sec tap-water rinse followed by the sealer, ICA
503. This sealant stage lasts 30 sec and is maintained at a pH of 4.5-5.5.
The seventh and final stage is a 30-sec DI rinse at a pH of 5.5. As parts
exit the washer, they travel through a DI halo rinse and then dry off.
The
premium paint finish is achieved in one of three Nordson
Excel 2003 powder coating booths, which can be rolled on and off line as
needed. These booths are set up in the environmentally controlled powder
coating room, which is maintained at 60F and less than 70% humidity.
Paint
"The
first booth is dedicated to Fawn's signature color, black. The second booth
in line is dedicated to a black textured coating, another Fawn trademark.
Sherwin-Williams collaborated with Fawn in developing this coating, which
is unique to Fawn's vending machines. In these two booths, powder is
reclaimed and mixed with virgin powder for reuse. In the third booth, a
variety of colors is applied. All paints applied in this third booth are
sprayed to waste. Very little powder is actually sprayed in this booth, so
reclamation is not economical.
Automated
spray guns are set up in all three booths; however, manual touchup is used
after each automated pass to ensure that all Faraday cage areas are coated.
The
spray booths feature a 99.9% efficient, centrally located side-draft
cartridge collector reclaim system that allows for highly uniform airflow
inside the booth and through all the openings. This provides for a clean operating
environment and maximum transfer efficiency. This is important to Fawn,
considering the design of its parts, which have many recessed areas that
harness Faraday cage areas.
The
booths employ Versa Screen 10c control system which provides gun triggering,
gun movement and booth control. Each booth has a 10-inch touch screen that
allows operators to enter control parameters at the booth. The system also
controls other parameters in the booth such as dew point; cartridge filter
pressure; final filter pressure; powder level; motor status; fire
detection; line speed; sieve and transfer control and cartridge blow-down
sequence.
Each
booth features one Sure Coat manual spray gun for touchup and eightP Versa Spray II automated guns. The spray gun
system provides precise control for optimal powder charging. Sensors at the
entrance to each booth identify parts and trigger on and off only the guns
necessary to coat the particular part entering the booth. This system helps
Fawn reduce energy costs and paint waste. It also improves the finish
quality on its vending machines by minimizing edge buildup. The system has
a user-adjustable automatic feedback current control. This provides Fawn
with more operating flexibility and higher transfer efficiency, since it delays
back ionization and automatically maintains gun current and voltage at an
optimum level regardless of the gun-to-part distance. "It allows us to
effectively powder coat the deep recesses in our parts," noted Joe
Ayers, vice president of manufacturing. "And the manual guns ensure
that we cover all areas of the vending machines."
Overview
of the powder coating environmental room with its three roll-on/roll-off
powder coating spray booths. Only one booth is in operation at a time,
spraying either black smooth, black textured or a
color powder coating.
Complete
coverage and the ability to control coverage were the reasons Fawn
implemented this new system. The system had to be able to supply a finish
that could withstand the outdoor elements that most of its vending machines
faced. This new system allowed the company to apply a pretreatment that
would give the powder coating better adhesion. And the powder coating
system provided the means to apply powder coating in all areas of the
parts, even Faraday cage areas.
"We believe we set
the standard in everything we do," stated Mr. Bruntz. "Our
pretreatment and powder coating line are no exception. We did a little more
when it came to pretreatment to make sure we would achieve the highest
quality paint finish possible. I believe we have set the standard with our
system."
Source: Gardner Publications, Inc.
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