Rapid prototyping began as a way to produce three-dimensional
prototypes directly from digital CAD files. Yet proponents have always
maintained that faster prototyping machines and better materials could
allow companies to manufacture short-run production parts economically.
This has begun to happen. From hearing aid ear inserts and
sunglasses to jet fighter ductwork and medical implants, companies are
using direct manufacturing to reduce costs, speed new products to
market, and produce short runs without molds or dies.
Improved rapid prototyping materials play a large role in this push
into the manufacturing mainstream. In the past, such materials involved
compromises. Users could make parts fast, accurate, or durable, but
rarely an optimal combination of all three. Recently, materials
developers have been trying to bridge those tradeoffs.
DSM Somos of Elgin, Ill., a division of Dutch chemicalgiant DSM
N.V., says its new DMX-SL 100 is the first stereolithography resin to
combine durability and accuracy. According to the company, parts made
from the new resin have the durability of sintered nylon, the stiffness
of ABS, and the impact strength of polypropylene.
This is a big step up from products usually made by
stereolithography, a process known for dimensional accuracy. It uses
ultraviolet light to solidify liquid resins into solid parts.
Unfortunately, those parts are more brittle than conventional
engineering resins (such as ABS, nylon, or polycarbonate), and they
grow increasingly brittle as they age, said product development manager
Brian Bauman.
Parts made from the new DMX-SL resins, on the other hand, are as
stiff as conventional ABS, but have twice its impact strength and up to
20 percent elongation at break. Bauman said they can compete with parts
produced by other rapid prototyping systems that melt or sinter
thermoplastics. Those parts are durable, but do not have the aesthetics
or dimensional consistency of pieces made by stereolithography.
Meanwhile, Stratasys Inc. of Minneapolis introduced a metallic
prototyping material for use with the Arcam electron beam melting rapid
prototyping system from Arcam AB in Gothenburg, Sweden. Stratasys is
the exclusive North American distributor of the technology.
The metal powder ASTM F-75 cobalt chromium is commonly used in hip
and knee implants, as well as in aerospace applications. It complements
two titanium alloys already offered by Stratasys.
Electron beam melting produces parts by rapidly melting and fusing
powders. By doing this under vacuum, the parts come out fully dense and
without imperfections caused by oxidation. According to Stratasys sales
manager Kirby Quirk, electron beam melting produces cobalt chrome parts
three to five times faster than other metal additive-fabrication
methods.
This section was edited by Associate Editor Alan S. Brown.
Copyright American Society of Mechanical Engineers May 2007
Provided by ProQuest Information and Learning Company.
Subscribe to this comment's feed