Rapid prototyping large objects -- from parts to art
Most companies use technologies such as stereolithography, selective laser sintering, and
fused deposition modeling to make parts for such small consumer products as telephones,
toasters, and track shoes. A typical rapid prototyping part is less than ten inches in length.
Because most rapid systems build parts by depositing, solidifying, or sintering material point-bypoint, making larger objects takes a long time, and in many cases, large objects won’t fit the
fabber’s building chamber. For instance, the largest part that a 3D Systems’ SLA-7000
stereolithography machine or a Stratasys FDM Titan can make is only 24 inches long (600mm).
(See “2002 U.S. Rapid Prototyping Equipment Roundup.”)
But what if you need to build models larger than two feet across? The approach taken by most
companies is to build larger parts in sections and then glue them together. But building multiple
pieces takes time, and assembling them can be tricky.
The Materialise Mammoths
To meet customer demand for larger parts, Materialise of Belgium has built three custom largeformat stereolithography machines. The Mammoth I has a building capacity of 2,100mm by
640mm by 490mm (82.6 inches by 25.2 inches by 19.2 inches). The Mammoth II can build
parts as large as 2,150mm by 620mm by 500mm (84.6 inches by 24.4 inches by 19.7 inches).
And the newest, the Mammoth III, can build parts 2,100mm by 650mm by 600mm (82.6 inches
by 25.6 inches by 23.6 inches). Each Mammoth employs multiple lasers and uses a formulation
of DSM’s Somos 9100 resin that it calls PolyPox. Materialise demonstrated the capabilities of
the Mammoths recently, as part of a project sponsored by the European Union to explore the
possibility of using waste powder created in marble quarrying to manufacture replicas of
statues. The idea behind the project is to use rapid prototyping models as masters for
duplication by powder-injection molding with a marble-powder composite.
For the demonstration, Materialise built a full-sized copy
of a Greek kouros on the Mammoth II. Kouroi are lifesized statues of idealized young men, sculpted in ancient
Greece between 650 B.C. and 500 B.C. to mark graves
or as gifts in temples to the gods. Only a few dozen of
these statues remain, and their stylistic progression from
idealized to more realistic representation helps art
historians delineate the transition from the Archaic to the
Classical period of Greek art.
The Volomandra Kouros, on display in the National
Archeological Museum in Athens, stands almost six feet
tall and is dated to 550-570 B.C. For the EU project, the
Greek company Geo-Analysis S.A. of Thessaloniki,
scanned the statue and sent the files to Materialise in
Leuv
en,
Belgi
um.
The original Volomandra Kouros and
the stereolithography replica.
Materialise converted the scan data to STL
format and built the giant stereolithography After 24 hours of building, the shape of the kouros
replica. In all, it took 99 hours and 23 began to emerge.
minutes to build the kouros. Sixteen
kilograms of stereolithography resin were
used. To save resin and minimize building
time, Materialise built the statue as a shell
with a wall thickness of five millimeters.
The resulting copy makes it clear that the
real challenge to duplicating art lies not in
the limitations of rapid prototyping but
rather in the difficulty of collecting good
scan data. The technicians from GeoAnalysis faced precisely the same problems
met by companies doing full-body scans of
people to create computer games or action
figures. While it’s easy to scan geometric
shapes, the human form, with all its curves, Lifting the kouros out of the Mammoth.
is more difficult to capture. The
stereolithography statue duplicated flaws in the scan data along with the features of the original.
Building statuary, however, won’t be the primary mission for the Mammoths. Materialise says it
has experienced growing demand, particularly from automotive companies, for single-piece
prototypes of such large parts as instrument panels, bumpers, and interior trim items. Contact:
Materialise NV, Technologielaan 15, 3001 Leuven Belgium Telephone: (32) 16 39 66 11
Fax: (32) 16 39 66 00 Web site: http:// www.materialise.be.
More typically, the Mammoths are used to build
large automotive parts such as this instrument
panel.