Rapid prototyping large objects from parts to art

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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-by-point, 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 large-format 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.


The original Volomandra Kouros and the stereolithography replica.

For the demonstration, Materialise built a full-sized copy of a Greek kouros on the Mammoth II. Kouroi are life-sized 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 Leuven, Belgium.



After 24 hours of building, the shape of the kouros began to emerge.



Lifting the kouros out of the Mammoth.
Materialise converted the scan data to STL format and built the giant stereolithography replica. In all, it took 99 hours and 23 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 Geo-Analysis 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, 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.

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