The Fifteenth Solid Freeform Fabrication (SFF) Symposium, held at The University of Texas in
Austin on August 2-4, 2004, was attended by over 120 national and international researchers from
sixteen 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.
This proceedings includes an edited transcript of a panel discussion held Tuesday afternoon at the
meeting. Moderated by Harris Marcus of the University of Connecticut at Storrs, the panel topic
was on the broader impacts of solid freeform fabrication. Panel members include David Alexander
(Pratt and Whitney), Clinton Atwood (Sandia National Laboratory), Phill Dickens (Loughborough
University, UK), and Kent Firestone (University of Texas at Austin).
This year’s best oral presentation was given by Jean-Pierre Kruth of the Katholieke
Universiteit Leuven, Belgium. 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, "Binding Mechanisms in Selective Laser
Sintering and Selective Laser Melting". Selected from almost 70 oral presentations, his presentation
appears on Page 44 of this Proceedings. The best poster presentation selected from 19 posters was
given by Vito Gervasi of the Milwaukee School of Engineering. The paper title was,
"Geometry and Procedure for Benchmarking SFF and Hybrid Fabrication Process Resolution" and
appears on Page 493.
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 are grateful to Bryan Blackmur and Cindy Pflughoft who
helped with Proceedings production. 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 (N00014-04-1-
0567) and the National Science Foundation (DMI 0412255) 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.
The design and fabrication of components with optimized lattice microstructures is a new
approach to creating lightweight high-performance objects. This paper introduces a unique and
complete integration of design and fabrication leading to the creation of structural components
with complex composite microstructures. Rather than a solid cast component with optimized
outer shape this new approach leads to a component with an inner skeleton or microstructure
maximizing one or more properties such as the stiffness-to-weight ratio. Three dimensional
gradient materials are a natural outcome of this approach. An introduction to the design
optimization and hybrid fabrication approach will be provided in addition to research progress
and challenges through Spring 2004.
Advanced freeform fabrication techniques have been recently used for the construction of tissue
scaffolds because of the process repeatability and capability of high accuracy in fabrication
resolution at the macro and micro scales. Among many applicable tissue scaffolding materials,
polymeric materials have unique properties in terms of the biocompatibility and degradation, and
have thus been widely utilized in tissue engineering applications. Hydrogels, such as alginate,
has been one of the most important polymer scaffolding materials because of its biocompatibility
and internal structure similarity to that of the extracellular matrix of many tissues, and its
relatively moderate processing. Three-dimensional deposition has been an entreating freeform
fabrication method of biopolymer and particularly hydrogel scaffolds because of its readiness to
deposit fluids at ambient temperatures. This paper presents a recent development of biopolymer
deposition based freeform fabrication for 3-diemnsinal tissue scaffolds. The system
configuration of multi-nozzles used in the deposition of sodium alginate solutions and Poly-?-
Caprolactone (PCL) are described. Studies on polymer deposition feasibility and structural
formability are conducted, and the preliminary results are presented.
(2004) Wang, Jiwen; Shaw, Leon L.; Xu, Anping; Cameron, Thomas B.
In this paper, we describe a solid freeform fabrication procedure for human dental
restoration via porcelain slurry micro-extrusion. Based on submicron-sized dental porcelain
powder obtained via ball milling process, a porcelain slurry formulation has been developed. The
formulation developed allows the porcelain slurry to show a pseudoplastic behavior and
moderate viscosity, which permits the slurry to re-shape to form a near rectangular cross section.
A well-controlled cross-section geometry of the extrudate is important for micro-extrusion to
obtain uniform 2-D planes and for the addition of the sequential layers to form a 3-D object.
Human teeth are restored by this method directly from CAD digital models. After sintering,
shrinkage of the artificial teeth is uniform in all directions. Microstructure of the sintered teeth is
identical to that made via traditional dental restoration processes.
(2004) Li, Xiaoxuan; Wang, Jiwen; Shaw, Leon L.; Cameron, Thomas B.
In this study commercial dental porcelain powder was deposited via slurry extrusion and
laser densified to fabricate dental restorations in a Multi-Material Laser Densification (MMLD)
process. The processing conditions for laser densification of single lines and closed rings were
investigated in order to avoid warping and cracking. Multi-layer rings were also investigated to
study the dependence of bonding between layers on the laser densification conditions. The laser
densified rings showed no warping, and good bonding between layers could be achieved when
the laser densification condition was selected properly. The mechanism to achieve porcelain
rings without warping and cracking is discussed. The understanding developed will pave the way
for fabricating a physical dental restoration unit.
The focus of this work is using selective laser sintering to manufacture transtibial
prosthetics sockets with compliant features to relieve contact pressure in sensitive areas. Each of
these sockets requires an integrated attachment fitting to connect to the pylon and foot using
standard hardware. Several design concepts of an attachment fitting are presented and
compared. The design concepts were tested using a tensile test machine and analyzed using
ground reaction force data to ensure a structurally sound connection. The resulting design
employs standard hardware while maintaining the integrity of the connection for a normal gait
(2004) Ott, A.; Heinzl, J.; Janitza, D.; Pelzer, R.
Bone tissue engineering has gained much attention in recent years. A key requirement in this
field is the development of scaffold structures, on which cells adhere. This can be done by
fabricating scaffolds by direct procedures like 3D-printing or by indirect procedures like casting.
With the 3D-printing process different structures were build up by using hydroxyapatite powder
(HA) and a special binder material. Afterwards the printed 3D structures were sintered.
For the casting process molds have been made of different resins by stereolithography and other
processes using polymers and waxes. These structures were filled by a suspension of HA. By
heating the resulting polymer/ceramic composite to a specific temperature it is possible to
combust the polymer or wax. By further heating the remaining body, the HA is sintered.
Compared to the 3D printing a better resolution can be obtained here. But there are restrictions
regarding the ratio of polymer and the HA ceramic during the heating process which means a
limitation for the level of porosity.
This paper describes orthopedic surgical planning based on the integration of RE and RP.
Using symmetrical characteristics of the human body, CAD data of the original bone without
damages for the injured extent are generated from a mirror transformation of undamaged bone
data for the uninjured extent. The physical model before the injury is manufactured from RP
apparatus. Surgical planning, such as the selection of the proper implant, pre-forming of the
implant, decision of fixation positions and incision sizes, etc., is determined by a physical
simulation using the physical model. In order to examine the applicability and efficiency of
surgical planning technology for orthopedics, various case studies, such as a proximal tibia
plateau fracture, a distal tibia comminuted fracture and an iliac wing fracture of pelvis, are
carried out. As a result of the examination, it has been shown that the orthopedic surgical
planning based on the integration of RE and RP is an efficient surgical tool.
(2004) Crockett, R. S.; Horvath, T.; Koch, M.; Yang, M.
Medical imaging combined with SFF techniques were used to create detailed CAD and physical
heart models for commercial development of Pacemakers. Using a data set of 2D optical slice
images of the human heart at 1mm spacing obtained from the Visible Human Project, a 3D CAD
model was constructed by masking the features of interest in each slice. Normals on the
resulting .stl file were inverted to create a single-piece mold, which was built in starch using 3D
Printing. Flexible silicone was cast into this mold, and the starch was dissolved away to produce
the final physical heart model. The resulting model simulates the mechanical properties of an
actual heart, with medically accurate internal and external details including major veins &
arteries, coronary sinus, etc.
(2004-08-04) Wicker, Ryan; Medina, Francisco; Elkins, Chris
A design for modifying an existing 3D Systems stereolithography (SL) apparatus 250/50 was
developed to accommodate multiple material fabrication for building multi-material, multifunctional and multi-colored prototypes, models and devices. The machine was configured for
automated access to an intermediate washing, curing, and drying unit that eliminated
contamination between material vats and maintained accurate platform registration throughout
the build process. Three vats were arranged on a rotating vat carousel, and each vat was adapted
to actively maintain a uniform, desired level of material by including a recoating device and a
material fill and removal system. A single platform was attached to an elevator mechanism (zstage) to traverse the platform to and from the vats and the washing, curing, and drying unit. The
platform was mounted to the z-stage via an automated rotary stage to rotate the platform about a
horizontal axis, thus providing angled building, washing, curing, and drying capabilities. A
horizontal traversing mechanism was also designed to be optionally included to facilitate
manufacturing between multiple SL cabinets, related SL apparatuses and/or other alternative
manufacturing technologies. For micro-fabrication, linear and rotary stages were selected that
provided ±1.0 µm repeatability and 0.1 µm resolution and ±2 arc sec repeatability and 0.13 arc
sec resolution, respectively. The multi-material SL design presented here is capable of utilizing
existing SL resins for manufacturing multiple material mechanically and electrically functional
models as well as hydrogels, biocompatible materials, and bioactive agents for a variety of biofunctional, implantable tissue engineering applications including nerve regeneration and guided