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| The
new powder coating system at Herman Miller allows the company
to design workstations with a greater variety of shapes and
profiles.
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With squared
off edges, 90-degree angles and a "boxy" look, cubicle
used to be an appropriate term for the portable furniture seen in
many offices. However, at office furniture giant Herman Miller,
Inc. (Zeeland, MI) the term cubicle no longer applies. With the
rise of collaborative work and the expansion of complex technology,
the company saw an opportunity to re-examine the work environment
and resolve critical issues regarding its office furniture.
The result
is the Resolve line of workstations. The workstations have 120-degree
angles, which frame an open and inviting area that allows people
to work together easily. The design allows a greater diversity of
layouts as well as a more efficient use of space compared to previous
office furniture systems.
While Herman
Miller often used high-pressure laminates to finish the medium-density
fiberboard (MDF) used to construct its office furniture, the company
was unable to use high-pressure laminates with the Resolve line.
Why was this the case? High-pressure laminates only bend in one
plane, but the Resolve line's multiple curves and waterfall profile
(as opposed to a straight edge) meant the laminates would have to
be bent in multiple planes.
So, the company
developed a process called Formcoat™, a trade name for the
thermal cure powder coating process used to coat the MDF. The powder
process allows the designers more freedom in the shapes and curves
they can use. "There is not an easy way to do complex shapes
with high-pressure laminates," said Rich Saddler, a finishing
engineer at Herman Miller. "So, powder coating fit with this
product. Since then, we've started to expand into other product
lines."
Developing
a Powder System
As powder coating has become the preferred method for finishing
MDF furniture with multiple curves and waterfall profiles, Herman
Miller needed to find a supplier to build a system for the company.
The company turned to ITW
Gema to build a state-of-the-art system.
The foundation
of the powder coating system is the ColorMagic cylinder and Chameleon
Color Management System, a new color change technology that provides
users with quick and clean powder changes. By automating parts of
the cleaning process, the color management system reduces the time
required to convert from one color to another. A programmable logic
controller (PLC) system is used to automate cleaning by managing
the internal purging and cleaning of the suction tubes, powder pumps,
powder hose and gun. It does this by pulsing compressed air over
the gun exterior and powder path. This process works so effectively
to free the guns of powder that color contamination is virtually
eliminated.
Mr. Saddler
admits that powder coating on MDF is an evolving process. "We're
still in the infancy stages of powder coating on wood," he
stated. "We're probably now where powder coating of steel was
30 years ago. We learn something new every day about the wood, the
process and the materials. But, every day we're learning means that
next week we have more of a knowledge base to deal with production
issues." The company has learned a great deal about different
woods, density profiles, sanding and other process variables. And,
Herman Miller has learned that it definitely needs a higher quality
of MDF to withstand the heat generated by the UV curing process.
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As an example
of this learning process, Saddler recalls troubles with an 8 x 15-inch
board that was coming out of the powder application process lighter
than necessary. "We thought that the pre-heat oven was drying
the board out, and we were losing our conductivity," Mr. Saddler
explained. "We started to reduce the pre-heat temperatures
lower and lower trying to get the powder to attract better. Then,
one of my technicians suggested that we try to raise the pre-heat
oven's temperature, and it worked. It turned out that it wasn't
a moisture issue of the board becoming too hot and drying out. It
was a temperature issue of not being hot enough when we applied
the powder. It was too cool, and the powder wouldn't stick to it."
The powder
process also helps Herman Miller employ a variety of just-in-time
manufacturing techniques. Herman Miller uses 100% Sierra Pine MDF
manufactured in Medford, OR. It is shipped via railroad car to nearby
Grand Rapids, MI, and then delivered on a daily basis to the powder
coating facility in Holland, MI. It sits in inventory for perhaps
a day before it starts the process that includes routing, sanding,
powder coating, assembling and packing. Raw board can come into
the production area at 8 a.m. and be shipped out by 4 p.m. on that
same day.
To powder coat
the MDF, the board is hung on a rack and heated in a pre-heat oven
before it is ready to enter the powder coating booth. There are
15 PG2-AX guns in the booth, which are turned on and off automatically
by the PLC. This is accomplished via a part recognition system on
the entrance to the booth as parts pass through a profile, which
is identified and recorded in the PLC.
Quick
Color Changes
Time is of the essence when performing a color change. "She
has to be efficient and quick because there are parts coming,"
said Mr. Saddler. "You can't dilly-dally at this point in time."
The first step is to pump air through the hoses in order to clean
out any of the old powder in the hoses. The operator can spray the
powder directly from the powder manufacturer's original shipping
container. This improves color change time by eliminating the process
of using hoppers as well as other equipment usually required to
reclaim powder.
"I've
been very happy with it," proclaimed Mr. Saddler. "We're
able to do quick color changes both in the reclaim and the non-reclaim
mode." The ColorMagic enables Herman Miller to do a color change
in 12 min in a reclaim environment and 6 min in a non-reclaim environment.
Herman Miller estimates that in the reclaim application, it gets
50% first-pass transfer efficiency and greater than 95% reclaim
efficiency, which means that there is very little waste.
The company
saves valuable time with the color management system because of
the easy cleaning process. Mr. Saddler says that the operators don't
even have to use a vacuum. The booth is simply blown down with compressed
air. "That is not the case with a traditional stainless steel
powder coating booth," he stated. "You would have to vacuum
that." Vacuuming isn't necessary because the clear booth material
is non-conductive. Consequently, the powder does not attract to
the booth walls when the booth is electrostatically charged.
In nearly a
year of operation, Herman Miller has not had any significant down
time with the powder coating system. But it's the functionality
of the process and the end result that please him most. "We
are spraying horizontal work surfaces - things that people use five
days a week," said Mr. Saddler. "So we need to have that
scratch-resistance, stain-resistance and color stability in order
to meet what the customers' expectations are of a high-pressure
laminate surface."
