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Peter McCann Architectural Models Inc. (PMAMI)
saved three weeks in the production of an architectural model of the
Technodome by cutting molds for the roof sections on a CNC Router
instead of hand carving them.
The first step in creating the model was
to import the architect’s AutoCAD drawing into Techno’s CNC
Interface
The Technodome, when it is
built, will be “the world’s largest and single- most technologically
advanced indoor attraction ever,” according to its developer. The
architectural model itself was huge, the largest PMAMI has ever
produced. The roof of the model was particularly challenging because
there were many different roof styles. Peter McCann, president of
PMAMI estimates that carving the roof molds by hand would have taken
at least five weeks. With the computer- controlled method, cutting
instructions for the milling machine were generated from the
architect’s CAD model and the roof portion of the project was
completed in only two weeks. “The model was so large we had to
divide it into sections and then glue them together,” says McCann.
“The accuracy we got with the CNC machine was so high that all the
different roof pieces fit together perfectly.”
The Technodome is the dream of Abraham
Reichmann, a member of the Toronto-based Reichmann family known for
ambitious developments. Reichmann has been shopping his Technodome
project around from city to city for nearly a decade. For a time, it
looked as if it would be built in Toronto. Currently, it seems that
Montreal will be its home. Wherever it ends up, the Technodome’s
proposed 1.2 million-square-foot space will reportedly feature
several biospheres, making it possible for a patron to go
white-water rafting and downhill skiing in the same visit. In
addition to nature attractions, it will feature disaster rides, IMAX
theatres, a 125,000-capacity sports and music arena, and massive
indoor theme zones similar to those at Disney parks. The
Technodome’s capacity is 11 million visitors per year, and its
annual budget is predicted to be $1 billion.
PMAMI got involved with the Technodome
when an architect developing a concept for the facility hired PMAMI
to produce an architectural model. With 12 employees, PMAMI is the
largest firm of its kind in Toronto. The company has been in
business since 1980, serving the model making needs of local and
international architects, industrial designers, engineers, and
manufacturers. Its 6,000 square foot facility in downtown Toronto
features a full range of model making and presentation capabilities.
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Model making services include wood and
plastics machining, laser cutting, prototype molding, casting,
vacuum forming and fabrication. Plastics and wood are the primary
materials used in the construction of models along with a wide
variety of composites and unique materials. Other in-house services
include computer animation, signage, graphics, and brochures. “We
have made many large models, but the one of the Technodome, at a
1:200 scale, measured 22 feet long by 10 feet wide by two and a half
feet tall, is the largest model we have made to date,” says McCann.
Cutting 3D Parts
PMAMI used a laser cutter to fabricate
the portions of the Technodome model that were 2D shapes, such as
walls and floors. McCann didn’t want to cut the roof pieces this
way, however, because the roof was so complex. “The roof of the
Technodome has many different roof styles, including a big dome,”
McCann says. “Breaking the roof up into hundreds of little 2D pieces
and then assembling them would have been extremely difficult.” The
alternative was to create 3D molds of the different roof shapes and
then vacuum form acrylic over the top of the molds. The acrylic
pieces could then be assembled on top of the walls fairly easily.
One option for producing the molds was
to carve them by hand out of wood. To do this, PMAMI craftsmen would
have used a band saw to rough cut the shape out of a two- to
four-inch thick piece of basswood. Next they would have used a
milling machine to carve more of the 3D shape. Then they would have
hand-carved the details. Producing the molds this way would have
taken five weeks, according to McCann. Instead he decided to look
for a computer numeric controlled (CNC) machine that would be
capable of producing architectural models.
McCann was aware of two options in CNC
equipment. The first was heavy and expensive machining centers
primarily designed for metalworking. They would deliver the accuracy
he needed, but the smallest machining centers start at $30,000 and
machines in this price range have working areas that are too small
for all but a fraction of McCann’s work. A machining center with a
table large enough to handle nearly all his work would cost in the
$100,000 price range, considerably more than he wanted to spend.
McCann ruled out most routers, on the other hand, because they could
not provide the accuracy he needs. Then McCann heard about the
Techno CNC router, which provides the best of both worlds.
Another reason McCann chose the Techno
machine was that even though it was one of the more affordable CNC
machines, it had a number of high-end features that would allow it
to produce parts with the level of the accuracy PMAMI’s work
required.
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For example, each Techno router is
constructed from extruded aluminum profiles. It has four ground and
hardened steel shafts and eight recirculating bearings in each axis.
This shaft-and-bearing system produces very smooth, play-free motion
and an extremely rigid system that produces high-quality cuts. The
machine also uses antibacklash ball screws. These screws have
excellent power transmission due to the rolling-ball contract
between the nut and screws. This type of contact ensures low
friction, low wear, and long life. The ball screws also make it
possible to produce parts to the machine resolution of 0.0005 inch.
A scaled model of the Technodome
project.
A Techno router can help create models
in various plastics, woods and composites
The first step in cutting the roof molds
for the Technodome model was to import the architect’s AutoCAD 2000
file into the CNC programming software that comes with the Techno
system. Originally designed for metalworking, it is also well-
suited for wood and foam because of its ability to generate the most
complex contours with little programming effort. In the programming
software, McCann separated the roof from the rest of the architect’s
model. Since it was a 3D wireframe model, he needed to add surfaces
to the outline of the roof because the toolpaths would be derived
from the surfaces. Next, he divided the roof into different mold
shapes that could be used to form the acrylic pieces. Most molds
produced multiple acrylic pieces.
Once this preliminary programming work
was done, McCann gave the command to software to create the
toolpaths for each of the molds. After supplying some additional
information such as feed rates and cutting speeds, the system was
ready to go. For each mold, a piece of Renshape, MDF, or a plaster
block was placed in the Techno machine. An operator hit the “start”
button and the 3D mold was carved automatically. The actual cutting
took only about one hour for most of the molds. The entire process
of programming the CNC machine and cutting all the roof molds took
two weeks.
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