SAMPE Journal - November/December 2021 - 12

FEATURE / CONTINUOUS FIBER 3D PRINTING
Figure 1. Current version of the
Continuous Composites CF3D® End
Effector and Motion Platform
(Version 0.7).
One such technology, under development by
Continuous Composites of Coeur d'Alene, ID, is
called Continuous Fiber 3D Printing (CF3D®
).
The founders of this small business understood
the merits of the Additive Manufacturing process
while recognizing the mechanical drawbacks
associated with extrusions containing little or no
fibrous reinforcement. In response, Continuous
Composites was founded in 2015 based on
foundational patents for the CF3D®
process filed
starting in 20129. Work began in 2015 on finding
technical solutions to additive manufacturing
using continuous fibers. More recent efforts at
Continuous Composites,
in
cooperation
.
with
Lockheed Martin, and sponsored by the US Air
Force Research Labs (AFRL), are looking to adapt
their process for use with carbon fibers10
CF3D® Description
CF3D® is
akin
to AFP in
that a robotically
manipulated end-effector disperses impregnated
tows of composite tape which are compacted
onto previously placed material. Figure 1 shows
the current generation CF3D®
CF3D®
is also unique from AFP in that resin
is applied within the head just prior to extrusion.
This feature replaces costly slit tape with dry fiber
tows and liquid resin; permitting fiber volume
adjustments to be made as the part
is being
processed. The current SOTA has extruded fiber
volumes up to 56vol%.
Fully curing (with glass fiber) or solidifying
(with carbon fiber) the composite on-the-fly offers
the unique ability to manufacture parts without
the need for tooling other than a flat project plate
on which to start the additive process. The cost
savings benefits of this feature are obvious and
will be explored more extensively when Aerospace
Applications and Future CF3D®
Development is
covered.
Continuous Composites is not the only
innovator
targeting
continuous
fiber
additive
manufacturing. Markforged has also developed 3D
printing systems for use with continuous carbon
fibers where the resin systems are thermoplastic11
This capability is not addressed in this paper.
.
head attached to a
Fanuc motion platform. As with AFP, the CF3D®
head also feeds tow(s) at controlled rates and
includes automated tow cutting at preprogrammed
locations. CF3D®
differs from AFP in that the tow is
snap cured using an ultraviolet source. With glass
fiber reinforcement this ultraviolet light source
can instantaneously cure the liquid resin during
the extrusion process. When using carbon fiber
the light source is capable of only partial cure
of the resin. The current state-of-the-art (SOTA)
with carbon fiber requires an oven postcure to
complete the resin's cure. Continuous Composites
is working with material suppliers to formulate
resin systems, suited to carbon fiber, that calls
for little or no thermal postcure requirement.
These developments will be discussed in CF3D®
Development Discussion.
12 | SAMPE JOURNAL | NOVEMBER/DECEMBER 2021
Material Options
The fundamental principles of CF3D®
work with
any continuous fiber and liquid polymer. The
continuous fiber can be structural or functional
utilizing carbon, aramids, ceramics, and glass.
Additionally, resins can also be multimodal, relying
on traditional thermosets or thermoplastics and
be doped with additives for additional property
changes or functionality.
In CF3D®
, the matrix material starts in the
print head as liquid resin and solidifies nearly
instantaneously as it discharges from the print head.
The snap cure property allows geometries and fiber
orientations that are not possible with traditional
techniques as well as the ability to be moldless and
out of autoclave (OoA). Continuous Composites
has chosen to focus on high-end applications
such as aerospace, which require high mechanical
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