Recently, I paid a visit to ExOne's sand printing operation just south of Seattle in Auburn, WA. ExOne (Nasdaq: XONE) specializes in large-scale 3D printers for rapid fabrication of metal parts. And when I say large, I mean HUGE--the maximum print size is roughly two cubic meters. The machine itself is taller than a person, and check out the size of the material feed:
These pictures are of ExOne's sand 3D printer. The machine uses a binder jetting process using inkjet-like technology. First, a roller deposits a thin layer of specially treated foundry sand. Next, a print head selectively deposits a glue across the print bed. The roller then adds another fine layer of sand and the process repeats until completion.
The printed part is then used by a foundry for sand casting metal parts. See the gallery below for an example mold. Molten metal flows through the hole in the top of the mold and soon encapsulates the core, creating a hollow metal part. Note that each mold is consumed in the production of a single part, so to make 10 objects you need 10 molds.
Note that these parts are highly fragile - dropping one would almost certainly destroy it. The cost of printing is incredibly cheap compared to other 3D printing technologies as measured by print volume: only $0.20 per cubic inch. I couldn't afford to sells prints for that rate from my desktop-class Ultimaker!
As you might imagine from the machine size, the cost of one of these sand printers starts around $750,000. Ford Motor Company reportedly owns three ExOne sand 3D printers, but the company is mostly pursuing a service bureau business model.
Thanks again to Sean for spending time with me, and for the 3D printed dragon!