JEC COMPOSITES MAGAZINE - Issue #134 - May/June 2020 - 22

MANUFACTURlNG 3D printing

This large demonstration part printed on
the LSAM MT is one of
twenty similar parts
which when combined
become a production
mold for a large yacht
hull.

Thermwood offers a full line of LSAM sizes to fit almost any application.

nology. Although the market is not huge,
quite yet, virtually all large-scale additive
manufacturing machines sold in the USA
in the last year or two have come from one
company located in Southern Indiana. This
company is Thermwood Corporation. They
call their system LSAM (pronounced L‐
Sam), which stands for Large-Scale Additive
Manufacturing. With Thermwood machines,
both the print and trim are done on the same
machine. As indicated above, their machines
are printing and machining parts every day.
The print process, which is pellet rather than
filament fed, produces parts that are quite
solid, fully fused, homogeneous and can hold
vacuum as well as a piece of glass.
This ability to sustain vacuum is critical
to most aerospace tooling. The process,
equipment and related software are quite
refined and intended for serious industrial
production.
This equipment routinely processes a
variety of materials, from room-temperature
materials such as ABS and polycarbonate

22

to high-temperature materials such as PPS,
PSU, PESU and Ultem.
Truly large robust machines
Images of this equipment have been available
online for some time now, but these images
do not properly convey the scope and size of
the actual machines.
These machines are built from thick steel
plate, laser cut, tabbed, welded and annealed
into an incredibly strong structure. They are
almost 6m tall with both a print gantry and a
trim gantry mounted on the same machine.
A 6m-long table system weighs 32.6 metric
tons (MT) and the 12m machine weighs
over 46.3MT. The print gantry itself weighs
almost 4MT and the print head itself weighs
between 1,245 and 1,361kg depending on
the melt core installed.
Despite the weight and mass, the print head
and trim head can move at speeds of more
than 0.9 metre per second and hold accuracies measured in thousandths of a cm. These
are truly large, robust machines.

	 jec composites magazine / N°134 May - June 2020

53 patents
The print process and print head design
used in these systems are quite unique and
currently covered by 53 patents.
To understand this a bit better, let's first look
at the print process.
LSAM machines print at room temperature
using rather large print beads. The system
uses pelletized polymers as feedstock and
can run virtually any thermoplastic material
available today. The bead is printed as round
but is flattened by a temperature-controlled
compression wheel into a bead that is 5mm
thick by 21mm wide. Once printed, the bead
begins to cool, but it does not cool evenly.
The outside surface cools first. At some point,
the outside surface of the bead has cooled
enough to just support the next bead, but the
inside of the bead is still quite hot. When the
next layer is printed, it quickly melts through
the cooled surface crust and the compression
roller fuses the new hot bead with the still
hot centre of the previous bead, generating a
solid, homogeneous, void-free structure.
An important fact about this process is that
the print time per layer depends on how long
it takes for the polymer to cool enough to
support the next layer. Polymer cooling and
not print head output determines how fast
a layer can be printed. Different polymers
cool at different rates. Polymers printed at
high temperatures cool faster than polymers
printed at lower temperature. An added
reinforcement in the polymer also affects
the cooling rate. A carbon fibre-reinforced
polymer cools quicker than a glass fibre-filled
material, for example.
Polymer cooling determines how much time
you have to print a layer. At that point, the
print head output determines how much
bead can be printed in the layer time available. The greater the print head output, the
larger the part that can be printed.
The standard LSAM print head uses a 40mm
melt core that can generally print most polymers at about 91kg/h.
This translates to about 12m of print bead
per minute. High-temperature polymers
generally have a 1 ½ to 2 minute layer time,
which translates to 18 to 24m of print bead
per layer. Lower temperature materials will
generally double that.
JEC COMPOSITES MAGAZINE - Issue #134 - May/June 2020

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