The Seventeenth Solid Freeform Fabrication (SFF) Symposium, held at The University of Texas in
Austin on August 6-8, 2007, was attended by almost 100 national and international researchers from
8 countries. Papers addressed SFF issues in computer software, machine design, materials synthesis
and processing, and integrated manufacturing. The diverse domestic and foreign attendees included
industrial users, SFF machine manufacturers, university researchers and representatives from the
government. The Symposium organizers look forward to its being a continuing forum for technical
exchange among the expanding body of researchers involved in SFF.
The Symposium was again organized in a manner to allow the multi-disciplinary nature of the SFF
research to be presented coherently, with various sessions emphasizing process development, design
tools, modeling and control, process parameter optimization, applications and materials. We
believe that documenting the changing state of SFF art as represented by these Proceedings will
serve both those presently involved in this fruitful technical area as well as new researchers and
users entering the field.
Two special themes for this year’s conference included an industrial perspective and design. For
the former, Terry Wohlers of Wohlers Associates presented an overview of the state of the art in
industrial practice and was followed by a panel presentation on perspectives by Joe Beaman
(University of Texas at Austin), Brent Stucker (Utah State University) and Neil Hopkinson
(Loughborough University). The special session on Design was organized by Carolyn Seeperesad.
Presentations explored design tools, fundamental research and applications in biomedical, aerospace
This year’s best oral presentation was given by David Rosen of Georgia Institute of 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. The paper title was,
“Design for Additive Manufacturing: A Method to Explore Unexplored Regions of the Design
Space”. Selected from 55 oral presentations, his presentation appears on Page 402 of this
Proceedings. The best poster presentation selected from 6 posters was given by Omer Cansizoglu
of North Carolina State University (co-authors Ola L.A. Harrysson, Denis J. Marcellin-Little, Denis
R. Cormier, Harvey A. West II). The paper title was, “Tailored Structures to Reduce Stress
Shielding in Hip Implants.”
The editors would like to extend a warm “Thank You” to Rosalie Foster for her detailed handling of
the logistics of the meeting and the Proceedings, 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 contributions, 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 SFF
community in organizing the Symposium. We also want to thank the Office of Naval Research
(N00014-07-1-0970) and the National Science Foundation (CMMI-0728118) for supporting this
meeting financially. The meeting was co-organized by the University of Connecticut at Storrs, and
the Mechanical Engineering Department, Laboratory for Freeform Fabrication and the Texas
Materials Institute at The University of Texas at Austin.
(2007) Maheshwaraa, Uma; Seepersad, Carolyn Conner; Bourell, David
Solid freeform fabrication is particularly suitable for fabricating customized parts, but it has not
been used for fabricating deployable structures that can be stored in a compact configuration and
deployed quickly and easily in the field. In previous work, lattice structures have been
established as a feasible means of deploying parts. Before fabricating the parts with a selective
laser sintering (SLS) machine and Duraform® Flex material, lattice sub-skins are added
strategically beneath the surface of the part. The lattice structure provides elastic energy for
folding and deploying the structure or constrains expansion upon application of internal air
pressure. In this paper, a procedure is presented for optimizing the lattice skin topology for
improved overall performance of the structure, measured in terms of deviation from desired
surface profile. A ground structure-based topology optimization procedure is utilized, with a
penalization scheme that encourages convergence to sets of thick lattice elements that are
manufacturable and extremely thin lattice elements that are removed from the final structure. A
deployable wing is designed for a miniature unmanned aerial vehicle. A physical prototype of
the optimal configuration is fabricated with SLS and compared with the virtual prototype.
(2007-09-05) Williams, Christopher B.; Rosen, David W.
Cellular materials, metallic bodies with gaseous voids, are a promising class of materials that offer
high strength accompanied by a relatively low mass. In this paper, the authors investigate the use of ThreeDimensional Printing (3DP) to manufacture metallic cellular materials by selectively printing binder into a
bed of metal oxide ceramic powder. The resulting green part undergoes a thermal chemical post-process in
order to convert it to metal. As a result of their investigation, the authors are able to create cellular
materials made of maraging steel that feature wall sizes as small as 400 µm and angled trusses and channels
that are 1 mm in diameter.
This paper examines the possible applications of food as a raw
material in freeform fabrication, and provides several demonstrations of
edible three-dimensional objects. The use of edible materials offers several
advantages: First, it opens the door to the application of SFF technology in
custom food industry, such as manufacturing of complex confections with
specialized geometries and intricate material compositions. For
pedagogical purposes, edible materials provide an easily accessible, nontoxic and low cost way to experiment with rapid prototyping techniques
using educational systems such as Fab@Home. For more traditional SFF
technologies, food materials with appropriate rheological properties can
serve as sacrificial, bio-degradable, bio-compatible or recyclable materials
for structural support and draft-printing. We have used the Fab@Home
personal fabrication system to produce multi-material edible 3D objects
with cake frosting, chocolate, processed cheese, and peanut butter. These
are just indicative of the range of potential edible materials and
(2007) Yasar, O.; Martin, M.; Harris, C.; Sun, S.; Starly, B.
A current challenge impeding the growth of bone tissue engineering is the lack of
functional scaffolds of geometric sizes greater than 10mm due to the inability of cells to
survive deep within the scaffold. It is hypothesized that these scaffolds must have an
inbuilt nutrient distribution network to sustain the uniform growth of cells. In this
paper, we seek to enhance the design and layered fabrication of scaffold internal
architecture through the development of Lindenmayer systems, a graphical language
based theory to create nutrient delivery networks. The scaffolds are fabricated using the
Texas Instruments DLP™ system through UV‐photopolymerization to produce
polyethylene glycol hydrogels with internal branch structures. The paper will discuss
the Lindenmayer system, process planning algorithms, layered fabrication of samples,
challenges and future tasks.
(2007) Eosoly, S.; Ryder, G.; Tansey, T.; Looney, L.
This paper investigates the applicability of selective laser sintering (SLS) for the manufacture of
scaffold geometries for bone tissue engineering applications. Porous scaffold geometries with
open-cell structure and relative density of 10-60 v% were computationally designed and
fabricated by selective laser sintering using polyamide powder. Strut and pore sizes ranging from
0.4 - 1 mm and 1.2 -2 mm are explored. The effect of process parameters on compressive
properties and accuracy of scaffolds was examined and outline laser power and scan spacing
were identified as significant factors. In general, the designed scaffold geometry was not
accurately fabricated on the micron-scale. The smallest successfully fabricated strut and pore size
was 0.4 mm and 1.2 mm, respectively. It was found that selective laser sintering has the potential
to fabricate hard tissue engineering scaffolds. However the technology is not able to replicate
exact geometries on the micron-scale but by accounting for errors resulting from the diameter of
the laser and from the manufacturing induced geometrical deformations in different building
directions, the exact dimensions of the manufactured scaffolds can be predicted and controlled
indirectly, which corresponds favorably with its application in computer aided tissue engineering.
(2007-09-05) Janaki Ram, G.D.; Yang, Y.; Stucker, B. E.
A new method of depositing hard and wear resistant composite coatings on metal-onmetal bearing surfaces of titanium implant structures is proposed and demonstrated. The method
consists of depositing a Ti/TiC composite coating (~ 2.5 mm thick) on titanium implant bearing
surfaces using Laser Engineered Net Shaping (LENS®). Defect-free composite coatings were
successfully produced at various amounts of the reinforcing TiC phase with excellent interfacial
characteristics using a mixture of commercially pure Ti and TiC powders. The coatings consisted
of a mixture of coarser unmelted/partially melted (UMC) TiC particles and finer, discreet
resolidified (RSC) TiC particles uniformly distributed in the titanium matrix. The amounts of
UMC and RSC were found to increase with increasing TiC content of the original powder
mixture. The coatings exhibited a high level of hardness, which increased with increasing TiC
content of the original powder mixture. Fractographic studies indicated that the coatings, even at
60 vol.% TiC, do not fail in a brittle manner. Various aspects of LENS® deposition of Ti/TiC
composite coatings are addressed and a preliminary understanding of structure-property-fracture
correlations is presented. The current work shows that the proposed approach to deposit
composite coatings using laser-based metal deposition processes is highly-effective, which can
be readily utilized on a commercial basis for manufacture of high-performance implants.
Automated manufacturing technologies such as freeform fabrication can greatly
reduce the cost and complexity of infrastructure required to manufacture unique devices
or invent new technologies. Multi-material freeform fabrication processes under
development have the potential to automatically build complete functional devices
including electronics. Making this technology available to creative individuals will
revolutionize art and invention, but requires extensive simplification and cost reduction
of what is still a laboratory technology. The combination of a Fab@Home Model 1
personal fabrication system and commercially available materials allows the
demonstration of simple and inexpensive freeform fabrication of functional embedded
electrical circuits, and useful devices. Using this approach, we have been able to
demonstrate an LED flashlight, functional printed circuit boards in 2-dimensions and 3-
dimensions that are actually entirely printed, and a child’s toy with embedded circuitry.
These results, and the materials and methods involved in producing them will be
presented in detail.
The authors are developing a laser sintering process to fabricate highly porous
models with such high porosities as 90% and more. In the process, water-soluble filler is
mixed with designated plastic powder and leached out after laser sintering process is
finished to generate pores where the grains used to exist. Previously, the authors
reported successful application of this technology on a tissue engineering scaffold.
However, relationship between process parameters and obtained results has not been
clarified. This paper reports experimental investigation into effects of optimizing
process parameters such as mixture, grain size of the filler on resultant porosity, pore
size and process resolution