SAMPE Journal - January/February 2023 - 55

the entire width of a printed tow is sufficiently
heated and compacted during printing.
The system features a cooling system consisting
of a pneumatic compressed air manifold leading to
two adjustable cooling ducts, shown in Figure 2. A
firmware-controlled valve allows for activation and
deactivation of the cooling ducts for programmed
application of cooling air. This system was
implemented to rapidly rigidize the commingled
material after deposition, as needed. This feature
is important for printing non-geodesic print paths.
When making a turn, the cooling is turned on and
the nozzle temperature is lowered, which reduces
tow shearing and increases the tackiness of the
matrix. This results in an increase in positional
fidelity as the material is able to rigidize faster
and form a bond to the previous layer, or to the
substrate, more quickly.
For this study a consolidation force
measurement system was added to the apparatus.
This system is comprised of 4 cantilever load cells
supporting the print bed, as shown in Figure 3. All
four load cells are controlled by a
single Arduino microcontroller,
which is interfaced with a
computer to display and record
the load cell measurements. The
microcontroller is programmed
to output a summation value
of the 4 load cells. Using two
different calibration weights of
known mass, the accuracy of
the system was found to be ±
5g. Additionally, no noticeable
variation in load measurement
was detected when positioning
the calibration weights at
different locations on the
print bed. The consolidation
force
measurement system
was installed to determine the
actual consolidation force being
applied during printing rather
than relying only on the spring
constant and programmed
deflection. In addition, the force
measurement system allows
the exploration of variations in
consolidation force experienced
between different layers of
multi-layer prints.
Process Parameters
For this study process
parameters were developed
www. sampe.org
JANUARY FEBRUARY 2023
|
Figure 3. Active consolidation force measurement system supporting the
print bed.
based on prior research findings coupled with
early experimentation using the composite
placement system8,10
. The initial consolidation
force was programmed based on values used
in prior research and was set to be about 10 N9
Similarly, the programmed layer height was set to
.
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SAMPE JOURNAL |
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SAMPE Journal - January/February 2023

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