SAMPE Journal - November/December 2021 - 83

and failure. Similarly, in the case of foams, as
material cools, the size of the layer height and bead
width shrink, changing the proper spacing and
placing defects throughout the structure. Rather
than purging the transition material, it can be
printed into a non-critical portion of the structure.
Although this would remove defects from purging, it
would modify the overall mechanical performance
of the structure. Therefore, studies are currently
being conducted to determine the impact of the
material transition on the mechanical properties
throughout the transition zone. For instance, it
has been found that in the transition zone from CF
ABS to neat ABS, a 96.68 cm^3
material is deposited, and mechanical properties
may vary depending on filler content and base resin
dominating in this zone17
. Understanding how the
transition occurs and the mechanical properties of
the structure changes enables engineers to switch
materials ahead of time such that the unstable
mechanical properties appear in a non-critical
section of the structure.
CONCLUSION
BAAM extrusion-based printing can often
manufacture large structures at a lower cost
and faster rate than traditional manufacturing.
However, the structures have been limited a single
material, which limits the ability to have different
local mechanical properties across the structure.
Equipping the BAAM with a dual material system
enables articles to be designed and printed with
rigid and stiff exteriors with foam interiors, as
well as different stiffness materials for custom
impact and compression
Department of Energy and administered by the Oak Ridge Institute for Science
and Education.
This research was supported in part by an appointment to the Oak Ridge
National Laboratory Higher Education Research Experience (HERE) Program,
sponsored by the U.S. Department of Energy and administered by the Oak
Ridge Institute for Science and Education.
Large scale AM machine used in this research was sponsored by Cincinnati
Inc., OH, USA. Feedstock materials used in this work were provided by Techmer
PM., TN, USA.
(5.9 in3) volume of
responses. Currently
the dual hopper design is limited by temperature
because both materials need to have similar
processing conditions. The system also needs
to account for a purge and/or transition zone to
fully transition between materials. In future work,
values for calculating the volume required to fully
transition between materials will be determined
and integrated into the slicing software such to
minimize the waste during multi-material prints.
ACKNOWLEDGMENTS
Research sponsored by the U.S. Department of
Energy, Office of Energy Efficiency and Renewable
Energy, Advanced Manufacturing Office, under
contract DE-AC05-00OR22725 with UT-Battelle,
LLC.
This research was supported in part by an
appointment to the Oak Ridge National Laboratory
Advanced Short-Term Research Opportunity
(ASTRO) Program, sponsored by the U.S.
www. sampe.org
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