The Twenty-ninth Annual International Solid Freeform Fabrication (SFF) Symposium – An Additive
Manufacturing Conference, held at The University of Texas in Austin on August 13-15, 2018, was
attended by 680 researchers from 18 countries. The number of oral and poster presentations increased
to 517 this year. The meeting was held on the Hilton Austin in the downtown area and consisted of a
Monday morning plenary, 59 parallel technical sessions, and a poster session.
The conference attendance continued to grow, reflective
of the interest at large in the area.
The recipient of the International Outstanding Young
Researcher in Freeform and Additive Manufacturing
Award was Dr. Guha Manogharan from Penn
State University. Dr. Chee Kai Chua from Nanyang
Technological University in Singapore received the
International Freeform and Additive Manufacturing
Excellence (FAME) Award.
There are 212 papers in the conference proceedings. Papers marked “REVIEWED” in the title area
were peer reviewed by two external reviewers. We have sequentially numbered the pages of the papers to facilitate citation. Manuscripts for
this and all preceding SFF Symposia are available for free download below and at the conference website: http://
The editors would like to thank the Organizing Committee, the session chairs, the attendees for their
enthusiastic participation; and the speakers both for their significant contribution to the meeting and
for the relatively prompt delivery of the manuscripts comprising this volume. We look forward to the
continued close cooperation of the additive manufacturing community in organizing the Symposium.
We also want to thank the Office of Naval Research (N00014-18-1-2558) and the National Science
Foundation (CMMI-1826959) for supporting this meeting financially. The meeting was co-organized by
the Mechanical Engineering Department/Lab for Freeform Fabrication under the aegis of the Advanced
Manufacturing and Design Center at The University of Texas at Austin.
The 2019 SFF Symposium is set for August 12-14, 2019 in Austin, Texas USA.
Browsing 2018 International Solid Freeform Fabrication Symposium by Issue Date
(University of Texas at Austin, 2018) Leite, M.; Frutuoso, N.; Soares, B.; Ventura, R.
One of the main drawbacks of large-scale FDM is fabrication time, due to the use of a single deposition
head. In this paper we propose a novel approach to tool-path generation for a system with multiple collaborative
independent deposition heads. This system allows the size of the parts to increase considerably in comparison to
regular FDM systems without the corresponding time increase. However, to enable the tool-path generation, the
conventional process planning must be changed.
Once the machine configuration is defined, (e.g. number and size of heads), the regions are attributed to
each head as either static or dynamic. Then the layer is divided into domains, assigned to each head. A
centralized tool-path planner then generates tool-paths, accounting for collisions and optimizing the fabrication
time in the layer. The process repeating for all layers.
Examples of this approach show reduced fabrication time and larger part dimensions than conventional
(University of Texas at Austin, 2018) Zhang, Shanshan; Lane, Brandon; Whiting, Justin; Chou, Kevin
This study investigates the thermal conductivity of metallic powder in laser powder-bed
fusion (LPBF) additive manufacturing. The intent is to utilize a methodology combining laser flash
testing, finite element (FE) heat transfer modeling, and an inverse method to indirectly measure
the thermal conductivity of nickel-based super alloy 625 (IN625) and titanium alloy (Ti64) powder
used in LPBF processes. A hollow test specimen geometry was designed and built with LPBF
enclosing the un-melted powder to mimic the powder bed conditions. The specimens were then
flash heated in a laser flash system to measure their transient temperature response. Next, a
developed FE model and a multi-point optimization algorithm were applied to inversely analyze
the thermal transient, and extract the thermal diffusivity and conductivity of the powder enclosed
in the specimens. The results indicate that the thermal conductivity of IN625 powder used in LPBF
ranges from 0.65 W/(m·K) to 1.02 W/(m·K) at 100 °C and 500 °C, respectively. On the other hand,
Ti64 powder has a lower thermal conductivity than IN625 powder, about 35 % to 40 % smaller.
However, the thermal conductivity ratio of the powder to the respective solid counterpart is not
much different between the two materials, about 4 % to 7 %, which is largely temperature
(University of Texas at Austin, 2018) Link, Martin; Haefele, Tobias; Abele, Eberhard
The advantages of selective laser melting lie in the production of complex, small
components in small batches. For large-volume components, the use of additive manufacturing
(AM) processes is limited by the available installation space, low build rates, and high material
costs. For the production of large and less complex workpieces, conventional manufacturing
processes such as milling are more economical. The background of this study was to combine both
processes to decrease manufacturing times. For this purpose, a body made of 316L (1.4404) steel
powder was printed using selective laser melting on conventionally manufactured stainless-steel
base bodies. The use of multi-materials enables optimized machinability in the respective
manufacturing process. This paper examines the hardness properties of multi-material samples and
uses micrographs to analyze the microstructure of their connection area. A complete connection
between hybrid components made of comparable materials was determined.
(University of Texas at Austin, 2018) Nezhadfar, Pooriya Dastranjy; Soltani-Tehrani, Arash; Sterling, Amanda; Tsolas, Nicholas; Shamsaei, Nima
The booming interest in Additive Manufacturing (AM), is seeing a rising number of
industries and research entities adopting this technology into their manufacturing practices. Of
particular interest is Laser Powder Bed Fusion (L-PBF) process, a common AM method for
fabricating metallic components. However, one obstacle is the high cost of powder feedstock. A
popular tactic to offset this cost is to reuse the powder between prints, but there is no in-depth
understanding of how the powder feedstock may change or affect the mechanical properties of the
produced parts. By incorporating unique powder/part characterization methods, this study
quantifies the rheological properties of continually recycled 17-4 precipitation hardening (PH)
stainless steel (SS) powder through successive printing of mechanical test specimens. The AM
specimens are subjected to tensile tests, to correlate mechanical behavior to changing powder
quality, including particle size/shape distribution, flowability, and density.
Electron Beam Additive Manufacturing requires to improve electron gun characteristics to
become a highly competitive manufacturing process. Our work targets the optimization of
beam focusing to reduce the beam spot size, to improve the beam deflection system resulting
in higher positioning accuracy, to refine thermal stability by minimizing heat induced drifting
and to introduce a new powder delivery device which can be synchronized to beam parameters.
Heisenberg's uncertainty principle states that if a position of a particle is precisely known, its
momentum becomes less accurate and vice versa. Therefore, it will be required to conceive
gun parameters optimizing the balance of opposing laws. Our goal is to deliver an open
platform electron beam additive manufacturing machine which utilizes the results presented in
(University of Texas at Austin, 2018) Nie, Xiaojia; Zhang, Hu; Zhu, Haihong; Hu, Zhiheng; Zeng, Xiaoyan
The newly designed alloy compositions for selective laser melting (SLM) have
aroused great interest. In this study, zirconium modified Al-Cu-Mg alloys were
fabricated by SLM. Results show that crack-free samples with relative density of nearly
100% were obtained by optimizing the processing parameters. With the increase of
scanning speed, the relative density decreases due to insufficient energy input. In
addition, the microstructure transforms from homogeneous to bio-modal, the reason is
the unstable flows caused by the high scanning speed. The small hatching space will
provide more energy input and preheat, leading to the coarse surface.
(University of Texas at Austin, 2018) Ho, Jason; Lough, Cody S.; Mulligan, Phillip; Kinzel, Edward C.; Johnson, Catherine E.
A Shaped Charge (SC) is an explosive device used to focus a detonation in a desired
direction, and has applications in demolition and oil extraction. The focusing relies on a void in
the explosive mass, shaped by a metal liner that becomes a projectile during detonation. Additive
Manufacturing (AM) allows greater design freedom and geometric complexity for the liner portion
of the SC. Specifically, hierarchical structuring and functional grading can potentially provide
greater velocity, directionality, and efficiency. In this work, Selective Laser Melting (SLM) is used
to explore different geometries for an SC liner made out of SS 304L. These are detonated using
the explosive Composition C-4 to evaluate performance metrics, depth and standoff, and are
observed using high-speed imaging. The work shows the potential for advanced shaped charges
produced using SLM.
(University of Texas at Austin, 2018) Simeunovic, A.; Hoelzle, D.
Control of material metering in material extrusion based additive manufacturing
modalities, such as positive displacement direct-write, is critical for manufacturing accuracy. However, in positive displacement direct-write, transient flows are poorly controlled
due to capacitive pressure dynamics - pressure is stored and slowly released over time from
the build material and other compliant system elements, negatively impacting flow rate startups and stops. Thus far, modeling of these dynamics has ranged from simplistic, potentially
omitting key contributors to the observed phenomena, to highly complex, making usage in
control schemes difficult. Here, we present nonlinear and linearized models that seek to
both capture the capacitive and nonlinear resistive fluid elements of positive displacement
direct-write systems and to pose them as ordinary differential equations for integration into
nonlinear and linear control schemes. We validate our theoretical work with experimental
flow rate and material measurements across a range of extrusion nozzles and materials to address different feature sizes and diverse applications spanning tissue engineering, electronics
fabrication, and food science. As part of this experimental work, we explore the contribution
of the bulk system compliance and the build material compliance to these dynamics. We
show that all models accurately describe the measured dynamics, facilitating ease of integration into future nonlinear and linear control systems. Additionally, we show that while build
material compliance may be nearly entirely reduced through appropriate system design, the
compliance from build material alone is significant enough to require feedback control to
fully control material delivery.
(University of Texas at Austin, 2018) Mohammed, Mazher Iqbal; Wilson, Daniel; Gomez-Kervin, Eli; Vidler, Callum; Rosson, Lucas; Long, Johannes
This study demonstrates the EcoPrinting principal, which makes use of renewable energy to
realise a low carbon footprint means of recycling waste plastics into feedstock for Fused Filament
Fabrication (FFF) 3D printing. We present our work to date to encapsulate this principal in a singular
device, which comprises a nanogrid solar/battery storage unit, a custom made filament extrusion
device and modified FFF 3D printer system. We demonstrate that our system is capable of reforming
ABS plastics found in electronic waste and converting these into functional items through a melt
extrusion and additive manufacturing process. We successfully demonstrate the efficacy of the system
to operate using solar derived energy and using the resulting filament to 3D print functional pipe
connector components. We conclude Ecoprinting holds considerable potential as a sustainable means
of converting waste plastics into functional components. Finally, the portable and self-sufficient
nature of the system, Ecoprinting could feasibly could be applied as a cost effective aid solution for
vulnerable communities in low socio-economic environments.
(University of Texas at Austin, 2018) Kelly, S.; Paterson, A.M.J.; Bibb, R.J.
Research has shown that wrist splints can be made using Additive
Manufacturing (AM) with a similar or greater performance than splints created using
traditional manufacturing methods. By using AM, many of the problems associated with
traditional splinting such as poor aesthetics and poor ventilation could be mitigated.
However, work to date typically reviews splints with singular pattern designs (e.g. Voronoi
patterns), which have structural and safety implications if similar but untested patterns are
created. Using Design of Experiments (DOE) design rules were to enable clinicians to
confidently design splints alongside their patients.
Design rules were created by investigating variables of cut out patterns using DOE
methods. Finite Element Analysis (FEA) of various combinations of cut out variables was