When
you think of dipping parts into a tank to coat them, some of the first words that
probably come to mind are electrocoating or small parts. But, not all dip coating
processes fit into the electrocoating or small parts categories.
Borroughs Corp. (Kalamazoo,
MI) is an example of a company with such a process. It uses a waterborne dip coating
process to coat a significant portion of its parts. The company manufactures industrial
and retail shelving with approximately a 50/50 split between the two. The dip
line is used to coat shelves, dividers and other "smaller" parts for
the shelving assemblies.
Why
Dip Coating?
Small parts are often dip coated in bulk because it is more efficient than racking
each individual part. While Borroughs is racking each part that is coated, it
still finds dip coating shelves and dividers to be more efficient than spraying
them. According to John McDonald, superintendent of quality at Borroughs, "It's
a less expensive way to paint the product and get a decent coat on it. Plus, the
waterborne coating is less expensive than the solvent-borne."
The dip line is actually
comprised of two conveyors that move side by side. This setup allows two tanks
to be used for coating at the same time without taking up any more floor space.
In all, there are 11 tanks with eight colors that can be moved on and off line,
which allows Borroughs to change colors in about 4 minutes.
Waterborne
Dip Coating
In addition to the dip line, Borroughs has two spray lines that use solvent-borne
coatings. Several years ago though, the company replaced the solvent-borne coatings
on the dip line with a waterborne dip coating from Jamestown Paint because it
was more environmentally friendly and could provide a thicker coating.
The waterborne coating
has proven to be an excellent addition to Borroughs' coating arsenal, meeting
or exceeding all of the specifications of the solvent-borne coatings. While Borroughs
is pleased with the waterborne dip coating, it is even more pleased with the service
that its paint supplier has provided for a number of years.
 |
| Due to the
nature of its product, Borroughs has to change colors frequently. The unique system
shown in these pictures allows tanks to be towed on and off line. The result:
Borroughs can change colors in approximately 4 minutes.
|
One of the most significant
aspects of the supplier's service is the recycling of drippings from the waterborne
dip line. Borroughs has paper-lined troughs under each conveyor. The first section
of these troughs are sloped toward the dip tank so that the drippings will flow
back into the tank. The other sections of the troughs are sloped so that the paint
drippings flow into containers, which are used to collect any of the colors Borroughs
uses. These containers are then sent back to the supplier where the paint is reformulated
into the gray that Borroughs uses for a number of products. Borroughs is now recycling
about 9,000 gal of paint per year at a savings of $74,000 per year.
Another important part
of the service that Jamestown provides is paint analysis. Borroughs has seven
750-gal tanks and one 350-gal tank on its waterborne dip line. Each tank will
use anywhere from 500-10,000 gal/yr of paint. That means the paint in some tanks
is sitting for a long time before it is used. Therefore, the supplier performs
a solvent analysis every month to make certain that the colors are stable.
Also, viscosity tests are
performed regularly. While parts are hung at a 30-deg angle to get the appropriate
paint runoff and ensure a good coating, maintaining the proper paint viscosity
is very important. "If the paint is too thick, you don't get coverage around
the holes in the shelves," said Mr. McDonald. "The paint will just run
around the holes. If it's too thick, you will get streaks. Also, you'll get blisters
on the bottom and the side. Therefore, we keep close tabs on the viscosity. If
it's too thin or watery, you get a very thin coating over the whole part."
One other important aspect
of the service that Borroughs gets from its paint supplier is color adjustment.
Color control is crucial for Borroughs because it must match parts from different
processes using different paints. Therefore, Borroughs' paint supplier tests part
samples for color match every week. "Jamestown will be sent samples. Sometimes
we'll take samples and e-mail the readings to its lab. Then, they'll look it over
and fax or e-mail back the necessary adjustments. We only do additions with the
recommendation of our paint supplier," stated Mr. McDonald.
Borroughs is extremely
pleased with the quality of its waterborne coating, but it's the relationship
with its supplier that makes the use of the coating such a success. "We've
been with Jamestown for more than 20 years. The relationship has been really good,"
proclaimed Mr. McDonald. "They have been very responsive, jumping on any
question or situation. They've been in here a number of times, constantly monitoring
the situation. They've done a very good job."
