CPT International 02/2019

Production of a 3-D pattern and
its advantages
Strassacker uses voxeljet‘s 3-D printing
service to produce, among other things,
positive and tooling less patterns for
bronze casting. In order to achieve this,
they send the 3-D data set of an artwork
to the voxeljet service center in
Friedberg near Augsburg. Here, the
CAD data is checked and further uploaded
into the VX1000 3-D printing system.
In the subsequent Binder-Jetting
process, the recoater moves over the
1,000 x 600 x 500 millimetre building
platform and spreads a 150 micrometre
thin layer of the plastic polymethyl methacrylate
(PMMA). Then, the print head
bonds the PMMA with a binder through
polymerisation wherever the artwork is
to be created. After each of these two
steps, the building platform is lowered
by one layer thickness and the recoater
and print head process the next layer.
This process produces the CAD data
layer by layer with a resolution of up to
600 dpi.
Once the print is finished, voxeljet
employees remove the model from the
The elaborate interlaced geometries
can only be realized
through the use of additive
processes, such as the voxeljet
binder jetting. Making a cast
blank with conventional
molding techniques would
be impossible.
The production of complex
model geometries is now
easily possible. Even the
gating system can be printed.
job box, remove unbound plastic powder
which can be reused 100 %,
infiltrate the components with wax to
further smoothen the surface and send
the positive pattern to Strassacker. 3 to
5 days after the placed order the pattern
is on-site at Strassacker and ready
for further processing.
The casting process at Strassacker
can then take its regular course. With a
significant advantage: no silicone negative
mold has to be created. The supplied
PMMA pattern can then be
immersed directly in ceramic to build a
shell and burnt out in the furnace at
700 °C. The PMMA material burns out
without leaving any residue, leaving
just the ceramic mold, into which the
liquid metal can then be poured.
In combination with 3-D printing,
the investment casting process opens up
completely new design possibilities.
Complex geometries that would have
been unthinkable in the past are now
possible in the near future. Added to
that, the gating system can also be printed
directly. This saves time and delivers
consistent casting results.
Chiselling and patination
Once the casting process has been completed,
the chiselling and patinating
work begins. A service that Strassacker
customers particularly appreciate. In
intensive cooperation with the artist, the
final appearance of an artwork is created
mutually. With custom-made tools,
the chisellers precisely carve out intricate
shapes and structures. Multi-piece cast
parts are joined by a specially developed
welding process without any visible
welds on the finished work of art. The
Bambi also gets its highly polished surface
here. Last but not least, the patinater
gives the work its colour by anticipating
the natural oxidation process using
chemical reactions. A high level of craftsmanship
and expertise is required to create
the subtlest of nuances in colour.
The future of sculpting
Nobody can exactly say, what the future
holds for the art of sculpting. But
change is clearly audible. There are
already a significant number of
open-minded artists using new, digital
technologies. This change will be of particular
benefit when it comes to conceptualizing
new artistic works. It allows
drafts to be drawn up and developed
using a computer in cases where manual
shaping techniques would be insufficient.
Innovative artists are constantly
striving to shift boundaries and develop
something new. The path they take to
achieve their vision is not the priority.
Decisive is the transformation into reality.
3-D printing gives artists the opportunity
to truly innovate. This is why 3-D
printing has already become firmly established
in sculptors’ repertoires and will
continue to gain market share.
It could also be conceivable that in
the distant future the model pre-acceptance
could take place using Virtual Reality
glasses. This would allow customers
to view the finished artwork in size,
colour and shape in three-dimensional
space before it actually is fabricated.
Peter Mühlhäußer is certain: “This would
be a practical relief that could solve
many problems in advance. It continues
expanding the dynamic creative dialogue
between artist and craftsman.”
Until then, it remains to be seen
what new, unique, 3-D-printed projects
will emerge at Strassacker in the near
future with the help of Binder Jetting
from voxeljet. One thing is for sure:
next time you get to see another Bambi
Award celebration, you’ll certainly
know, where the Bambi originated.
www.voxeljet.com
CASTING PLANT & TECHNOLOGY 2/2019 71