Ink-Jet
Printing refers to an entire class of machines that
employ ink-jet technology. The first was 3D Printing
(3DP), developed at MIT and licensed to Soligen Corporation,
Extrude Hone, and others. The ZCorp 3D printer, produced
by Z Corporation of Burlington, MA (www.zcorp.com) is
an example of this technology. As shown in Figure 6a,
parts are built upon a platform situated in a bin full
of powder material. An ink-jet printing head selectively
deposits or "prints" a binder fluid to fuse
the powder together in the desired areas. Unbound powder
remains to support the part. The platform is lowered,
more powder added and leveled, and the process repeated.
When finished, the green part is then removed from the
unbound powder, and excess unbound powder is blown off.
Finished parts can be infiltrated with wax, CA glue,
or other sealants to improve durability and surface
finish. Typical layer thicknesses are on the order of
0.1 mm. This process is very fast, and produces parts
with a slightly grainy surface. ZCorp uses two different
materials, a starch based powder (not as strong, but
can be burned out, for investment casting applications)
and a ceramic powder. Machines with 4 color printing
capability are available. (fig. 6)
3D
Systems' (www.3dsystems.com) version of the ink-jet
based system is called the Thermo-Jet or Multi-Jet Printer.
It uses a linear array of print heads to rapidly produce
thermoplastic models (Figure 6d). If the part is narrow
enough, the print head can deposit an entire layer in
one pass. Otherwise, the head makes several passes.
Sanders
Prototype of Wilton, NH (www.solid-scape.com) uses a
different ink-jet technique in its Model Maker line
of concept modelers. The machines use two ink-jets (see
Figure 6c). One dispenses low-melt thermoplastic to
make the model, while the other prints wax to form supports.
After each layer, a cutting tool mills the top surface
to uniform height. This yields extremely good accuracy,
allowing the machines to be used in the jewelry industry.
Figure 6 : Spectrum Z510

