We have been using
stereolithography (SLA) and FDM (fusion deposition modeling) for rapid prototyping for quite some time at Omnica. SLA is still the best method for
large parts, but for most of the rapid prototyping we do, Fused Deposition Modeling, and more recently, Polymer-Jet 3D printing is what we use most often. The parts that these newer "additive
manufacturing" methods produce, work quite well as accurate patterns for our urethane molding shop, "one- off" models, and in some cases, robust components.
In 2004 we purchased our first Stratasys FDM printer. It was costly, but there were so many advantages of owning one, we made the decision to invest in the relatively new
process. In the past few years, these and other 3D printers have become much more affordable. We now have five rapid prototyping machines.
All five 3-D printers offer real speed and cost benefits to our
customers.
The two refrigerator-sized FDM machines are the Elite and 1200ES Dimension models made by Stratasys. They build parts layer by layer, with strands
(0.007"-0.0013") of tough ABS plastic. Thickness of the layers depends on the build speed, but since the filaments are relatively coarse, parts that come directly from the FDM machines can be
"cosmetically challenged". They are not quite smooth enough to be used as silicone mold patterns or finished prototypes with minimal post finishing. Useful applications are tool handles, custom
fixtures and rugged internal working components of finished products.
Both printers have a smallish envelope build size but it doesn't limit the size of the parts we can produce. A real advantage of ABS is that it is easily and effectively joined
by solvent bonding, a process of chemically melting and joining parts together that results in a solid piece when the solvent evaporates.
It is the method we used when we built a sixteen-inch model of the Omnica sphere for the MD&M Show. We designed the three lobes of our logo as nested parts (like rose petals),
and built them concurrently. We solvent-bonded them together, sanded, and then painted the completed sphere afterwards. It looks like it was constructed as a single unit. The Stratasys
representative at the show was so impressed; he photographed it for his colleagues.
The auto industry uses larger versions of the machines to in-expensively build holding fixtures and templates. As another useful application, businesses can sometimes avoid the
heavy cost of injection molding by using FDM and ABS plastic to produce low volume articles.
The Objet PolyJet™ printers, an EDEN 330 and an Alaris 30, have nearly ten times finer resolution than the Dimension printers. Rather than using an extruded
filament to build models, the PolyJet (Polymer-Jet 3D Printing) builds thin layers with liquid polymer which are UV-cured after each pass of the applicator head. The fine layer thicknesses result
in parts that are easy to smooth and finish. They can build with special high durometer (hard) materials, and others which are typically used to simulate silicone and rubber. The Objet printing
process can produce parts with walls less than 1/32" thick, a critical benefit that for us is especially important. In the medical device field many handheld products require finely featured thin
wall sections.
Our highest resolution printer is the Solidscape Modelmaker II. It about a third the size of its roommates and is a high resolution (0.0005" layer thickness
build) 3D wax printer used to create high-resolution wax models for investment casting. This machine builds the most precise models on the market
today by depositing micro droplets similar to the inkjet printing process. We have discussed details of the machine in the past, but as a recap, here they are: 1) The fragile thermoplastic
wax-like material can be used for investment casting or as direct casting patterns for silicone, RTV, and epoxy molds, 2) It is capable of extremely detailed and intricate parts, 3) The printer is
used extensively in the jewelry industry.
