SAMPE Journal - November/December 2021 - 65

INTRODUCTION
Large Format Additive Manufacturing (LFAM)
presents unique challenges to reliably producing
defect-free parts. Novel build orientations and
non-planar slicing methods enable efficient use
of material and provide manufacturing engineers
additional degrees of freedom to control critical
process parameters.
Audience
The process parameters investigated and exhibited
herein require a basic understanding of Additive
Manufacturing (AM) and extrusion-based, layered
material deposition as a subcategory of 3D printing.
This paper is intended to address Applications
Engineers and AM Technicians by elaborating
on process techniques while Design Engineers
can utilize the resulting Design for Additive
Manufacturing (DfAM) guidelines. Equipment
Engineers and manufacturing management will be
updated on advances in feasibility.
Purpose
Traditional filament-fed or extrusion-based AM
technology naturally forms a secondary subset of
equipment and applications when applied over
increasing working volumes. Large Format Additive
Manufacturing (LFAM) covers an expanding range
of AM processes, though thermoplastic extrusion
is the most widely practiced and commercially
available.
While this paper addresses major concerns
of a small LFAM user group, largely from heavy
industry, LFAM technology development can
be transferrable to smaller equipment. This is
particularly true for automation technology and
software-driven solutions.
DESCRIPTION OF SYSTEMS
The study and practice of LFAM warrants an
understanding
of AM's
physical
phenomena
that are exaggerated as the AM processes scale
in volume and deposition rate. Large format
systems can be self-defined as the systems where
challenges present themselves due to size scale.
In this paper, thermoplastic LFAM systems are
primarily considered with phenomena based on
thermoplastic processing fundamentals.
System Sizes and Configurations
Material deposition rate must relate proportionally
to the working volume. The maximum printable
cross-section of this volume determines the
potential object that may be outlined or traversed
in a discrete printed layer. Being a time-dependent
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Figure 1. Ingersoll MasterPrint®, large format AM system printing composite
tooling at 44 kg (97 lb) per hour, 65% of rated throughput.
process, the extruder's throughput rate must be
sufficiently fast to satisfy layer deposition within a
maximum layer time limit with an auxiliary benefit
to production efficiency. While some throughput
exceptions exist for uniquely sparse geometry or
extreme efficiency of material use, those thin or
skeletonized geometry types are often avoided as
they present less familiar production risks.
Robotic arm LFAM systems commonly range
from 7 kg to 65 kg (15 lb to 145 lb) of material
throughput per hour with workzones from 1 to
8 m3 in volume. Degraded accuracy will often
disqualify a robot arm from practical use beyond 2
m of reach. Integrated linear rails or other mobile
configurations can provide expanded volumes and
increased flexibility.
Larger systems are found as gantry-based
positioners with three linear geometry axes (XYZ)
and have been equipped with extruders offering
upwards of 225 kg (500 lb) of material throughput
per hour. Gantry dimensions often range from 3 m
by 3 m by 2 m (LWH) to 18 m by 6 m by 3 m (LWH)
or larger.
Process Characteristics
With thermoplastics, pelletized feedstock
materials allow for the greatest economy while
providing an open material platform both for
materials experimentation and to tailor the
material selection for performance and budget
requirement.
These
engineered
products
are
most often compounded with chopped fiber fill
(carbon or glass) to add strength and dimensional
stability through temperature changes. Pellet-fed
LFAM systems also benefit from continuous feed
mechanisms such as conveying between storage
NOVEMBER/DECEMBER 2021
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SAMPE JOURNAL | 65
http://www.sampe.org
SAMPE Journal - November/December 2021

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