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Tuscarora Inc. has reduced the labor
time for manufacturing foam samples from hours to minutes in some
cases. Previously, prototypes of the company's molded foam products
were carved by hand, requiring between one hour and eight hours of a
skilled craftsman's time. Now, after CNC machines are programmed
from CAD geometry, they automatically cut the prototypes.
Programming and setup takes about 20 minutes, while actual cutting
takes 10 minutes to four hours, depending on the complexity of the
part. The machines operate unattended except for loading the foam
stock and removing finished pieces. "It's a huge labor savings
because the prototype makers are free to do other work while the
machine is in operation," says Bill Brokob, manager of Tuscarora's
western region technical center in Colorado Springs, Colorado.
Another benefit of the CNC machines is improved accuracy, especially
for the complex 3D shapes that Tuscarora's customers are now
requiring.
Tuscarora Inc. is one of the world's largest manufacturers of custom
molded products made from expanded foam plastic materials. The
company designs and manufactures interior protective packaging and
material handling solutions as well as molded plastic and
thermoformed components. Its customers are major manufacturers in
the high technology, consumer electronics, appliance, and automotive
industries. Tuscarora currently serves more than 2,500 customers
located in the United States, Canada, Mexico, and the United Kingdom
from 30 locations. The company is divided into a foam molding group,
an integrated materials group, a thermoforming group, and an
automotive group, and an engineering services group.
Product protection and beyond
Tuscarora's foam molding group utilizes
a variety of materials such as expanded polystyrene (EPS), expanded
polyethylene (EPE), expanded polypropylene (EPP), copolymers such as
ARCELŪ, and R-MERŪ, and hi-heat resins. These raw materials are
injected as beads into molds, then heated with steam which causes
them to expand and solidify into the finished shape. The resulting
molded foam shapes protect and cushion fragile products better than
virtually any other interior packaging or material handling product
available today. Molded foam plastics are also cost-effective,
resulting in less packaging labor and smaller carton sizes. In
addition to packaging applications, Tuscarora's molded foam plastics
are used for products and components with a long service life. For
example, foam's unique properties make it an excellent insulation
component in building construction, refrigeration, and shipping
containers. Recently Tuscarora has begun to offer an innovative
molded foam assembly chassis for electromechanical devices that uses
molded EPP foam to replace sheet metal and traditional fasteners.
The complexity of molded foam products produced by Tuscarora has
increased in recent years, driven by similar changes in the
complexity of its customers' products. "Nothing is square any more,"
says Brokob. As customers create products with more graceful curves,
Tuscarora's designers must match those shapes in the packaging
components they create. |
The use of solid modeling has helped
them do this. Many customers now provide CAD models of their
products. Tuscarora engineers import the models into their CAD
system, Pro/ENGINEER, and design the foam packaging components
around the customer's geometry.
Most customers request one or more
prototypes for testing prior to having the foam parts manufactured.
Previously, prototypes were produced by hand. Working from drawings,
a prototype maker drew lines indicating the general shape of the
part on a block of foam, then used a Bridgeport milling machine to
carve out the part. Some fine-tuning was usually required, so he
chipped away at the foam with hand tools until it fit the customer's
product. This was a slow process, requiring anywhere from one to
eight hours, depending on the complexity of the part. It was also
somewhat inaccurate. "We could hold a tolerance of 1/16 inch at best
working by hand," says Brokob.
Another limitation of making prototypes by hand became evident as
the shape of customers' products became more aesthetic. "It was
impossible to follow those curves accurately when we were cutting
prototypes by hand," Brokob adds. "If we had two end caps, for
instance, one for the right side of a monitor and one for the left,
the two sides wouldn't always match." This problem was complicated
by the fact that as the shapes were getting more complex, customers
were also raising the bar on the accuracy of the prototypes. "Some
of our more high tech customers have started to demand highly
accurate prototypes," Brokob says. "If they want five samples for
testing and verification, they want them to be virtually
indistinguishable from each other. Hand samples are all different."
The drawbacks of hand production led Tuscarora to consider using a
CNC machine to cut the foam samples. As the company looked into
this, they found that one option was to purchase a heavy and
expensive machining center primarily designed for metalworking.
"These machines cost about $75,000 and are more heavy duty than we
need for cutting foam," says Brokob. Further investigation revealed
a more suitable alternative, a Techno CNC router from Techno-Isel,
New Hyde Park, New York. This machine was designed for production
routing and drilling on a wide variety of materials including wood,
plastic, MDF, solid surfacing materials, and nonferrous metals. Its
$25,000 price was affordable and its 0.003 inches/foot absolute
accuracy and 0.0005-inch resolution and repeatability met
Tuscarora's accuracy requirements. The company selected a Techno
system with a 48-inch by 40-inch table size and a z-axis height
extension of 19-7/8 inches.
Labor-saving process
Now, after modeling a new foam part in
Pro/ENGINEER, the designer exports the solid model directly into
Pro/ENGINEER's CAM program. This eliminates the step of creating
drawings for the prototype maker, as was done in the past, because
the CAM program generates toolpaths for the Techno machine directly
from the CAD geometry. Tuscarora has set up its CAM program so that
it's "almost just the push of a button," as Brokob says, to generate
toolpaths. Once this is done, the CAM file is exported into the ICAM
post processor that creates the actual code that drives the Techno
machine. Total programming time, from when the Pro/ENGINEER model is
imported into the CAM program until the machine code is complete,
ranges from 10 to 15 minutes.
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Another five minutes are needed to cut
the foam stock to the right size and attach it to the Techno
machine. The operator then hits the "start" button and the sample is
then carved automatically. It takes only 10 minutes per side to cut
simpler pieces, while more complex pieces may take up to four hours
per side. One key advantage of using the CNC machine instead of
cutting prototypes by hand is that it frees the prototype makers to
do other work. The machine does not require any supervision, except
to remove the finished piece and attach a new foam block to repeat
the process. "It's a significant labor savings," says Brokob.
"Instead of spending one to eight hours cutting foam by hand, we
just attend to the machine as necessary, which takes minutes. We
quite often turn on the machine when we leave for the day, and when
we come back the next morning, one side of a part is done."
After prototypes have been machined,
they are checked against the customer's product. This is another
area where Tuscarora sees an advantage to using a Techno CNC
machine. Since parts are cut directly from CAD data, the shape of a
prototype matches the shape of the customer's product perfectly,
something that was almost impossible to achieve in the past. "The
improvement in accuracy is an important part of customer
satisfaction," notes Brokob. "It also differentiates us from the
other competitors who are still working by hand."
Tuscarora was so pleased with the CNC method of prototype production
that the company eventually equipped each of its regional technical
centers with Techno machines. The western regional center has three
CNC machines devoted to making foam prototypes, and there are 10 in
the entire company. Having multiple machines has been very helpful
during times when one center has trouble meeting a big order. The
company simply emails the machine code to other technical centers,
which can be producing the parts within minutes.
Tuscarora has been pleased with the reliability of its Techno
machines. Part of their reliability is due to the materials used in
their construction. For example, each machine uses anti-backlash
ball screws. These screws have excellent power transmission due to
the rolling ball contact between the nut and screws, and this type
of contact ensures low friction, low wear, and long life. In
addition, the machine is constructed on steel stress relieved bases
with hardened steel linear ways, and ballscrews with servomotors
standard. The shaft-and-bearing system produces very smooth,
play-free motion and is an extremely rigid system that produces
high-quality cuts.
Using CNC machines to manufacture foam prototypes has paid off for
Tuscarora in a number of ways: more efficient use of labor, more
accurate samples, better satisfied customers, and a competitive
advantage. "It has become more and more important that we supply
highly accurate prototypes," says Brokob. "With the Techno machines,
we can fulfill this requirement in a cost-effective manner."
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