The Twenty-Sixth Annual International Solid Freeform Fabrication (SFF) Symposium – An Additive
Manufacturing Conference, held at The University of Texas in Austin on August 10-12, 2015, was
attended by 388 researchers from 19 countries. The organizers are pleased that 175 of the attendees
were students, representing 45% of the audience. The number of oral and poster presentations
increased to 289 this year, an increase of almost 50% over 2014. The meeting was held on the camps
of The University of Texas at Austin in the AT&T Executive Education and Conference Center.
The meeting consisted of a Monday morning plenary, 25 parallel technical sessions and a poster
session. This year’s best oral presentation was entitled, “Thermographic Measurements of the
Commercial Laser Powder Bed Fusion Process at NIST”, authored by B. Lane, S. Moylan, E.
Whitenton and L. Ma from the National Institute of Standards and Technology. Selection is based
on the overall quality of the paper, the presentation and discussion at the meeting, the significance of
the work and the manuscript submitted to the proceedings. Selected from 256 oral presentations, the
associated manuscript appears on Page 575. The best poster presentation selected from 33 posters was
given by L.B. Bass, N.A. Meisel and C.B. Williams from Virginia Polytechnic Institute and State
University. Titled, “Exploring Variability in Material Properties of Multi-Material Jetting Parts”, the
paper is included in the Proceedings on Page 993. Posters are judged based on the quality and
organization of the poster as well as the discussion of the poster by the author during the poster
The recipient of the International Outstanding Young Researcher in Freeform and Additive
Manufacturing Award was Dr. Ibrahim T. Ozbolat from The Pennsylvania State University. Dr.
Richard J.M. Hague from the University of Nottingham won the International Freeform and
Additive Manufacturing Excellence (FAME) Award.
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 (N00014-15-1-0071) and the National Science
Foundation (CMMI-1536671) for supporting this meeting financially. The meeting was co-organized
by The University of Connecticut at Storrs, and 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.
(University of Texas at Austin, 2015) Torossian, Kevin; Bourell, David
A snap-fit is a mechanical joint system whose mating parts exert a cam action, flexing until one
part slips past a raised lip on the other part, preventing their separation. The use of snaps in
additive manufacturing (AM) is an approach for assembling components of parts too large to
build in one piece in AM. There are broadly two types of snap-fits possible to encounter,
permanent and non-permanent, depending on the design geometry. An experimental study
was carried out to evaluate the mating/dismounting force for snap-fits regarding several
geometrical parameters for additive manufacturing. The design chosen for this study has been
established from the start to work on only one design. The parameters chosen for experimental
investigation were the mating angle, the separation angle and the inner diameter of the mating
part. All in all, fifteen pairs were designed and additive manufactured for evaluation. The force
required to insert and separate the snap components was recorded and compared to the value
based on a derived equation.
(University of Texas at Austin, 2015) Lade, Robert K. Jr; Hippchen, Erik J.; Rodgers, Luke; Macosko, Christopher; Francis, Lorraine F.
The fundamentals of fluid flow in 3D printed, open microchannels created using fused
deposition modeling (FDM) are explored. Printed microchannels are used in microfluidic devices
and have potential applications in embedding electronics in plastic substrates. However, FDM
parts possess rough surfaces, and in this study, surface topography is shown to have an important
impact on flow behavior, causing the liquid to travel down the channel with a characteristic
‘pulsing’ movement. We also analyze the influence of print orientation on capillary flow, where
microchannels printed in specific orientations are shown to exhibit different flow dynamics.
(University of Texas at Austin, 2015) Dumene, Richard L.; Kennedy, Paul; Williams, Christopher B.; Sweeney, Dennis; Earle, Greg
Embedding of integrated systems via Additive Manufacturing (AM) offers the potential to save
weight, space, and time in the production of electronics and vehicles. Of specific interest are
embedded electrical systems that operate in the radiofrequency (RF) range as they have great
potential utility in communication systems and aircraft avionics including navigation. However,
systems in this frequency range pose unique manufacturing challenges such as the need to
minimize impedance discontinuities in the system. In this work, the authors explore various
techniques for embedding RF structures such as antennas and filters via a multi-material jetting
AM process. Specifically, the dielectric constants and loss tangents of Vero White and Tango
Black polymers were determined to facilitate the design of RF structures with these materials. It
is shown that measurements of S-parameters of the resultant embedded RF structures approach or
match the performance of non-embedded electronics.
(University of Texas at Austin, 2015) Khoshnevis, Behrokh; Yuan, Xiao; Zahiri, Behnam; Xia, Bin
This paper reports on the experiments with the Contour Crafting Automated Construction process using
sulfur concrete as the choice of construction material. Sulfur concrete has numerous terrestrial applications and
is potentially an ideal construction material for planetary construction. On Mars, sulfur can be found in
abundance and the range of temperature variation on the planet is within the safe zone for the structures to be
built and survive over reasonable length of time with sulfur concrete. Several experiments have been performed
at centimeter and meter scales. A FEA simulation model for the behavior of sulfur concrete based structures
has been developed. Experimental results were compared with the results of simulation.
(University of Texas at Austin, 2015) Meyers, Sebastian; Kruth, Jean-Pierre; Vleugels, Jef
Three-dimensional reaction bonded silicon carbide (SiSiC or RBSC) parts have been
produced by direct selective laser sintering (SLS). Unlike previously investigated processing
routes, which make use of a sacrificial polymer binder to form green parts, the parts in this work
are built by scanning subsequent layers composed of a mixture of silicon and silicon carbide
powders. A fibre laser is used to selectively melt the silicon under an inert argon atmosphere,
resulting in porous preforms of sufficient strength for further handling and processing. After
impregnation with a graphite suspension and infiltration with liquid Si at 1450°C, highly dense
reaction bonded silicon carbide parts are obtained.
(University of Texas at Austin, 2015) Velu, Rajkumar; Singamneni, Sarat
Biocompatible and osteoconductive characteristics expected of materials used for bone grafting
applications identified Polymethyl methacrylate (PMMA) and β-Tri Calcium Phosphate (βTCP) combinations to be potential biopolymer composite options. Together with additive
manufacturing methods such as selective laser sintering (SLS), these materials options would
also bring about the benefits of free from fabrication. While earlier research laser sintering
PMMA+β-TCP composites experimentally proved the combination to be promising, the
resulting microstructures are indicative of varied coalescence and consolidation with varying
amounts of β-TCP. Considering the differential thermal properties, it becomes necessary and
interesting to evaluate the possible role of the filler material in altering the nature of the thermal
fields. This paper presents results of numerical and experimental work carried out investigating
the thermal fields of laser sintered PMMA+β-TCP composites.
(University of Texas at Austin, 2015) Yang, Li; Lassell, Austin; Perez Vilhena Paiva, Gustavo
In this study, the effect of various parameters including the voltage, current, polishing time,
temperature and electrode spacing on the electropolishing quality of Ti6Al4V samples made via
electron beam melting was investigated using specialty designed research setups. The
relationships between these process parameters and the surface roughness of the parts were
(University of Texas at Austin, 2015) Monroe, J.G.; Ibrahim, O.T.; Thompson, S.M.; Shamsaei, N.; Bian, L.; Elwany, A.
A titanium alloy (Ti-6Al-4V) flat-plate oscillating heat pipe (FP-OHP) was fabricated
using Selective Laser Melting (SLM). The 50.8 x 38.1 x 15.75 mm3
FP-OHP consisted of four
integral layers of capillary-sized, circular mini-channels (1.52 mm in diameter). The post-SLM
prototype was de-powdered using pressurized air and a novel layer-by-layer, plug-and-pressurize
design/approach. A vacuum-grade port was threaded into the FP-OHP, and the heat pipe was
charged with acetone (~70% by volume) then hermetically sealed. Experiments were conducted
to characterize the thermal performance and functionality of the multi-layered FP-OHP. Results
indicate that the acetone-filled FP-OHP operates and can provide for an 800% increase in
effective thermal conductivity relative to pure Ti-6Al-4V. The build integrity of the FP-OHP was
investigated by shearing along its width to inspect the channel-area surface using field emission
scanning electron microscopy (SEM) and laser triangulation for channel topography. The mean
surface roughness was found to be approximately 45 micrometers and characterized by partiallymelted, abraded particles. This study demonstrates the appeal of additive manufacturing for
fabrication of customized heat transfer media traditionally challenging to realize.
(University of Texas at Austin, 2015) Cunico, Marlon Wesley Machado; Cunico, Miriam Machado; de Carvalho, Jonas
The additive manufacturing technologies has been facing an extraordinary growth during that last years, mainly as
consequence of the increase of low cost FDM technologies into the marketing. In contrast with that, one of the main
disadvantages of this sort of equipment is the final object finishing. For that reason, the main goal of this work is to
present and characterise the post-processing which was introduced in the marketing as smoothing. In addition, a
concise overview about the theory beneath this process is presented besides an experimental study that evaluates the
impact of this process for the main mechanical properties of object.