The Twenty-Third Annual International Solid Freeform Fabrication (SFF) Symposium – An Additive
Manufacturing Conference, held at The University of Texas in Austin on August 6-8, 2012, was
attended by 170 researchers from 13 countries. A two-morning special session on “Societal Impacts”
emphasized the integration of additive manufacturing into culture and society. Terry Wohlers
(Wohlers Associates) presented a keynote to start the session. Of special interest were a number of
talks from China organized by Professor Wei Sun who currently holds joint appointments at Drexel
University and Tsinghua University in Beijing. Other presentations summarized activity in the US
and United Kingdom. Brent Stucker (University of Louisville) talked about international trends
including standards development. Dr. Ian Gibson from the University of Singapore closed out the
session with a 20-year perspective on the development of AM with a personal bent.
This year’s best oral presentation was entitled, “Observation and Numerical Simulation of Melt Pool
Dynamic and Beam Powder Interaction During Selective Electron Beam Melting”, authored by
Thorsten Scharowsky, Andreas Bauereiβ, Robert F. Singer and Carolin Körner from the
Friedrich Alexander Universität Erlangen. 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 107 oral presentations, the associated manuscript appears on Page
815. The best poster presentation selected from 18 posters was given by Andrew Johnson, Dr. Guy
Bingham and Dr. Candice Majewski from the University of Sheffield and Loughborough
University. Titled, “Establishing the Performance Requirements for Stab Resistant Additive
Manufactured Body Armour (AMBA)”, the article appears on Page 297 of this Proceedings.
The recipient of the International Outstanding Young Researcher in Freeform and Additive
Manufacturing Award was Dr. Christopher Williams, an assistant professor with joint appointments
in the Departments of Mechanical Engineering and Engineering Education at Virginia Tech in the
United States. Dr. Jean-Pierre Kruth won the International Freeform and Additive Manufacturing
Excellence (FAME) Award. He is a professor at the Katholieke Universitaet Leuven in Belgium.
The editors would like to
extend a warm “Thank You” to Rosalie Foster for her detailed handling of the logistics of the
meeting, as well as her excellent performance as registrar and problem solver during the meeting. We
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 (N00014-10-1-0528) and the National Science
Foundation (#CMMI-1230744) for supporting this meeting financially. The meeting was co-
organized by The University of Connecticut at Storrs, and the Mechanical Engineering Department
and the Lab for Freeform Fabrication at The University of Texas at Austin.
Electron beam melted (EBM) titanium alloy (Ti-6Al-4V) samples were built and
characterized (qualitative prior-β grain size, quantitative α lath thickness, monotonic tensile,
Vickers microhardness) to determine the effect of location and orientation on microstructure and
properties. Samples of vertical orientation, compared to horizontal, were found to have 30%
lower elongation. Orientation within the x-y plane as well as location were found to have less
than 3 % effect on mechanical properties, and it is possible a second order effect of thermal mass
contributed to these results.
(University of Texas at Austin, 2012-08-22) Rüsenberg, S.; Weiffen, R.; Knoop, F.; Schmid, H.-J.
The quality of laser sintered parts, in this work, manufactured by polymer laser sintering by
using an EOSINT P395 Laser Sintering system, depends on several steps along the process chain.
The first step is the characterization of the powder quality, whereas the rheological and physical
investigations of nylon 12 powder are shown. By changing some important influencing factors,
for example the powder ratio, the powder ageing and the moisture content, the influence on
mechanical and physical properties, density and porosity, are investigated. The composition of
the used powder is known. The previous process (storage conditions, etc.) as well as the laser
sintering process (regarding energy density, temperature, etc.) is kept constant for the duration of
this work. Regarding the post process in this work the cooling down phase is investigated as well.
With an automatically blasting system it is possible to keep the post process parameters blasting
distance and blasting time, constant. All of the tests will be performed using dry and conditioned
This work is showing the dependence on mechanical, rheological and physical parameters by
varying important influencing factors along the laser sintering process quality chain.
(University of Texas at Austin, 2012) Hoye, N.P.; Appel, E.C.; Cuiuri, D.; Li, H.
This study considers the use of the gas tungsten arc (GTA) welding process in
conjunction with ‘cold’ wire addition to give layer-wise build-up of thin walled structures,
simulating those commonly found in aerospace applications, which may in the future be
manufactured by additive means. Taguchi DOE and multiple regression analysis methods have
been applied to quantitatively establish relationships between common process parameters
including arc length, arc current, travel speed and wire feed speed and resulting weld bead
geometries and actual metal deposition rates. Mathematical expressions for build-up height,
thickness and surface roughness are presented and evaluated against experimental data, with
observations related to physical phenomena.
(University of Texas at Austin, 2012-08-22) Krauss, H.; Eschey, C.; Zaeh, M.F.
A lot of strategies exist to monitor and control additive layer manufacturing processes.
Basically one can distinguish between coaxially monitoring the process zone and monitoring the
complete layer currently being built. Since Selective Laser Melting is a thermal process, a lot of
information about the process and in consequence about the resulting part quality can be gathered
by monitoring the temperature distribution of a complete layer and its temporal evolution. It
depends on the geometrical configuration of parts being built and the quality of the powder layer
deposition. In this paper, process errors originating from insufficient heat dissipation are
investigated as well as the limits for detecting pores and other irregularities by observation of the
(University of Texas at Austin, 2012-08-15) Elliott, A.M.; Ivanova, O.S.; Williams, C.B.; Campbell, T.A.
The addition of quantum dot (QD) nanoparticles to additive manufacturing (AM) media
provides the opportunity to create artifacts with complex geometry that also have unique optical
characteristics. However, the addition of nanoparticles can significantly alter the rheology of a
material and make it difficult to process in an AM context. In this study, quantum dots were
added to a photopolymer resin in varying mass ratios to photopolymer, and their effects on the
viscosity, surface tension, and jetting ability of the suspension were investigated. Results show
that printability was not significantly affected by the presence of quantum dots in mass
concentrations less than or equal to 0.5%. The nanosuspensions were deposited via inkjet to
demonstrate the feasibility of creating optically-unique artifacts.
(University of Texas at Austin, 2012-08-15) Kleszczynski, S.; zur Jacobsmühlen, J.; Sehrt, J.T.; Witt, G.
Laser Beam Melting as a member of Additive Manufacturing processes allows the
fabrication of three-dimensional metallic parts with almost unlimited geometrical complexity and
very good mechanical properties. However, its potential in areas of application such as aerospace
or medicine has not yet been exploited due to the lack of process stability and quality
management. For that reason samples with pre-defined process irregularities are built and the
resulting errors are detected using high-resolution imaging. This paper presents an overview of
typical process errors and proposes a catalog of measures to reduce process breakdowns. Based
on this systematical summary a future contribution to quality assurance and process
documentation is aspired.
(University of Texas at Austin, 2012-08-15) Yuan, Mengqi; Bourell, David
Part bed surface thermal gradients (x-y plane) are usually present in laser sintering (LS)
fabricators. The purpose of this study was to investigate various means to reduce these
thermal gradients. Several experiments were conducted using a FLIR™ infrared camera to
examine the thermal profile of the part bed during the LS operation. Experiments included
thermal profile characterization of the part bed with different nitrogen shielding gas flow rates,
assessment of the proper experimental settings, and a temperature profile record of the part bed
from the warm-up to the cool-down stage. A series of experiments were conducted using the
laser as a heat source to preheat part bed surface cold spots to decrease the thermal gradients,
which effect was limited by the natural low thermal conductivity of nylon 12 powder and large
heat convection. Moreover, manifolds were mounted below the piston to provide warm
nitrogen down draft flow during the LS operation.
(University of Texas at Austin, 2012-08-15) Rodriguez, Emmanuel; Medina, Francisco; Espalin, David; Terrazas, Cesar; Muse, Dan; Henry, Chad; MacDonald, Eric; Wicker, Ryan B.
A thermal imaging system using an infrared (IR) camera was incorporated in the
fabrication process of an Arcam A2 Electron Beam Melting system to provide layer-by-layer
feedback and ensure quality and defect free products. Using the IR camera, build chamber
surface temperature profiles were imaged and analyzed, providing information used to modify
build settings for the next build layer. Individual part temperatures were also monitored and
modified to achieve a more uniform bed temperature. The thermal imaging information can also
be used as a quality control tool to detect imperfections during the build. Results from the
integration of the camera in the system as well as use of the thermal images in process
monitoring and control is described.
(University of Texas at Austin, 2012-08-15) Baumers, M.; Tuck, C.; Wildman, R.; Ashcroft, I.; Rosamond, E.; Hague, R.
As a single-step process, Additive Manufacturing (AM) affords full measurability
with respect to process energy inputs and production cost. However, the parallel character of
AM (allowing the contemporaneous production of multiple parts) poses a number of problems
for the estimation of resource consumption. A novel combined estimator of build-time, energy
consumption and production cost is presented for the EOSINT M270 Direct Metal Laser
Sintering system. It is demonstrated that the quantity and variety of parts demanded and the
resulting ability to utilize the available machine capacity impact process efficiency, both in
energy and in financial terms.
(University of Texas at Austin, 2012) Seepersad, Carolyn Connor; Govett, Tyler; Kim, Kevin; Lundin, Michael; Pinero, Daniel
Because additive manufacturing (AM) is a relatively novel industry, with the first
commercial machines introduced in the late 1980s, many designers are unaware of the
capabilities of AM technologies. Many engineers also find it difficult to utilize AM because of a
lack of “Design for AM” knowledge in the public domain. Reliable information on material
properties, dimensions and tolerances, and other process-related specifications is often scattered
throughout the literature, if it is publicly available at all. The objective of the research reported
in this paper is to begin to create a designer's guide for dimensioning and tolerancing parts that
are additively manufacturing using selective laser sintering (SLS) technology. The guide is
based on a series of experiments designed to determine the limiting feature sizes for various
types of features fabricated in commercially available SLS machines. The features include slits,
holes, letters, mating gears, and shafts built in a preassembled state. The impact of part
thickness, orientation, clearance, and dimensions on the resolvability of features is examined.
Results are reported in a series of matrices that relate realizable feature sizes to other important
variables such as part thickness.
(University of Texas at Austin, 2012-08-15) Moylan, Shwan; Slotwinski, John; Cooke, April; Jurrens, Kevin; Donmez, M. Alkan
Historically, standardized test parts are used to quantitatively evaluate the performance of a
machine or process. While several different additive manufacturing (AM) test parts have been
developed in the past, there are no current standard test parts. This paper reviews existing AM
test parts, discusses the purposes of the studies, and describes important features and
characteristics found in these test parts. A new test part intended for standardization is proposed.
This part incorporates the most useful features seen in previous test parts. These features are
designed to highlight process capabilities and test machine accuracy. The design has been
validated through builds by several AM processes.
(University of Texas at Austin, 2012-08-18) Doubrovski, E.L.; Verlinden, J.C.; Horvath, I.
Despite the broad coverage concerning the technological challenges, little research has been performed
on the methods that enable designers to deal with Additive Manufacturing. At present, the challenge is to
generate Design for Additive Manufacturing knowledge which goes beyond traditional solutions and to ensure
that this knowledge is complete, correct and up to date. This paper reports on the employment of a wiki
environment to support open-ended knowledge management. We applied this solution in an undergraduate
prototyping course focused on exploring visual properties using AM structures. The results of the 32 students
encompass unexpected designs while the knowledge on the wiki encompassed i) AM processes, ii) procedures,
iii) artifacts. This forces us to rethink what should constitute DfAM.
(University of Texas at Austin, 2012-08-15) Barclift, Michael W.; Williams, Christopher B.
In Objet’s PolyJet process, part layers are created by selectively inkjetting photopolymers
onto a build substrate and then cured with ultraviolet lamps. With an eye towards using PolyJet
as a manufacturing process to fabricate end-use products, the authors examine the sensitivity of
part material properties to variation in process parameters. Specifically, a design of experiments
is conducted using a full-factorial design to analyze the effects of three parameters on the
specimens’ tensile strength and tensile modulus: the in-build plane part orientation (X-Y), the
out-of-build plane part orientation (Z), and the distance between specimens. Results show that
part spacing has the largest effect on the tensile strength, but the three parameters produced no
statistically significant effects on the tensile modulus. Orienting specimens in XZ orientation
with minimal part spacing resulted in the highest tensile strength and modulus. Whereas,
orienting specimens in the YZ orientation at the farthest part spacing led to the lowest
(University of Texas at Austin, 2012) Cheverton, Mark; Singh, Prabhjot; Smith, Scott; Chan, Kwok Pong
A modified multi-layer lithography process is used to additively manufacture highresolution netshape ceramic structures by photopolymerizing a ceramic-polymer slurry using
structured light patterns. This paper will discuss the development of a low-cost, high speed
manufacturing process method for the fabrication of piezoelectric ceramic transducer elements in
the 1-25 MHz frequency range. The key considerations in the development of the process
including the selection and optimization of slurry materials for the deposition of PZT 5H
materials, optical exposure parameters, debinding/sintering profiles, process monitoring, and
post manufacturing processing. Ongoing work includes improvements to the materials
properties, improved throughput and geometric fidelity.
(University of Texas at Austin, 2012) Pan, Yayue; Chen, Yong; Zhou, Chi
The purpose of this paper is to present a recoating method for the development of a direct digital
manufacturing (DDM) process that can be an order of magnitude faster than other currently available
DDM processes. In the mask-image-projection-based Stereolithography (MIP-SL) process, projection
light controlled by a Digital Micromirror Device (DMD) can quickly cure liquid photopolymer resin in a
whole area; a fast recoating method is required for achieving truly high-speed fabrication. We investigate
the bottom-up projection system in the MIP-SL process. For the macro-scale MIP-SL process, a two-way
linear motion approach has been developed for the quick spreading of liquid resin into uniform thin layers.
In comparison, a direct pull-up motion can be used in the micro-scale MIP-SL process. The system design
and related settings for achieving a fabrication speed of a few seconds per layer are presented.
Additionally, the hardware, software, and material setups for fabricating three-dimensional (3D) digital
models are presented. Experimental studies using the developed testbed have been performed to verify the
effectiveness and efficiency of the presented fast MIP-SL process.
(University of Texas at Austin, 2012-08-22) Mireles, Jorge; Espalin, David; Roberson, David; Zinniel, Bob; Medina, Francisco; Wicker, Ryan
Studies have been conducted to improve previous work performed in developing a Fused
Deposition Modeling for metals (FDMm) system used for applications in electronics and
fabrication of 3-dimensional metallic structures. A FDM 3000 system was modified to achieve
controlled deposition of eutectic Bi58Sn42 and non-eutectic Sn60Bi40 materials. Toolpath
command modifications were required to achieve controlled deposition of metals. Results are
presented which include a redesigned metal deposition head, computer modeling of fluid flow,
and finally examples of the successful deposition of metal alloys. Additionally, FDMm-fabricated metal samples were prepared and analyzed using optical and scanning electron
microscopy. Controlled deposition of metals using FDMm allows for parts that can be used for
jigs and fixtures, electroforming mandrels, encapsulation molds, dies, electronic joining
applications, as well as printing 3-dimensional electronic circuitry.
(University of Texas at Austin, 2012-08-15) Espalin, David; Ramirez, Jorge; Medina, Francisco; Wicker, Ryan
A multi-material, multi-technology FDM system was developed and constructed to
enable the production of novel thermoplastic parts. Two legacy FDM systems were modified
and installed onto a single manufacturing system to allow the strategic, spatially controlled
thermoplastic deposition of multiple materials during the same build. Additionally, a build
process variation utilizing more than two extrusions tips was employed to deposit
thermoplastic materials using variable layer thicknesses and road widths. The hardware and
control software is discussed as well as the potential applications of multi-material polymeric
parts. Benefits of multiple material FDM include: 1) achieving aesthetic requirements by
using polymers of different colors, and 2) attaining desired properties (e.g., bulk
tensile/compressive/flexural strength, weight, thermal conductivity) by strategically
combining layers and regions within layers of polymers that display different properties.
Parts produced using the build process variation exhibited internal road with 1200 ± 39µm
road width and 497 ± 11µm layer height while the contours measured 269 ± 18µm road width
and 133 ± 3µm layer thickness. Additionally, for a 50.8mm by 50.8mm square section
(25.4mm tall), the build process variation required 4.0 hours to build while the original
strategy required 6.2 hours constituting a 35% reduction in build time.
(University of Texas at Austin, 2012-08-16) Jones, Jason; McNutt, Phil; Tosi, Riccardo; Perry, Clinton; Wimpenny, David
Remanufacturing is one of the most efficient ways of recycling worn parts because it
consumes only a fraction of the energy, cost, and material required for new parts.
Remanufacture of engineering components typically entails serial labor intensive and
operator skill sensitive processes, often requiring parts to move between
manufacturers and subcontractors. Unfortunately the logistics and quality assurance
measures required for effective remanufacturing currently restrict its implementation
primarily to high value components (e.g. turbine blades, blisks, etc.). This research
reports progress toward an integrated production system which combines laser
cladding, machining and in-process scanning in a single machine for flexible and lean
(University of Texas at Austin, 2012) Scharowsky, T.; Baureiβ, A.; Singer, R.F.; Körner, C.
Selective electron beam melting (SEBM) is an additive manufacturing method used to
produce complex parts in a layer-by-layer process utilizing Ti6Al4V powder. To improve the
very good properties of built parts even more and to use the full capacity of the process, the
fundamental understanding of the beam powder interaction is of essential relevance.
Numerical simulations and observation with a high speed camera of powder melting show the
strong melt pool dynamic and its lateral extent clearly. Furthermore, the immediate effect of
beam parameters, e.g. beam current and velocity, on the melting behavior of the powder can
be resolved in time steps of a few milliseconds.