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
Modeling, design and fabrication of tissue scaffolds with intricate architecture,
porosity and pore size for desired tissue properties presents a challenge in tissue engineering.
This paper will present the details of our development in designing and fabrication of the
interior architecture of scaffolds using a novel design approach. The Interior Architecture
Design (IAD) approach seeks to generate scaffold layered freeform fabrication tool path without
forming complicated 3D CAD scaffold models. This involves: applying the principle of layered
manufacturing to determine the scaffold individual layered process planes and layered contour;
defining the 2D characteristic patterns of the scaffold building blocks (unit cells) to form the
Interior Scaffold Pattern; and the generation of process tool path for freeform fabrication of
these scaffolds with the specified interior architecture. Feasibility studies applying the IAD
algorithm to example models and the generation of fabrication planning instructions will be
At the Freiburger Materialforschungszentrum we have developed a new process (3DBioplotting
TM) that permits most kind of polymers and biopolymers to be used in 3D scaffold
design, including hydrogels (e.g. collagen, agar), polymer melts (e.g. PLLA, PGA, PCl) and twocomponent systems (e.g. chitosan, fibrin). Cells can be incorporated within the construction
process, making this an ideal Rapid Prototyping technique for Organ Printing. Tailor-made
biodegradable soft or hard scaffolds can so be fabricated in a short time using individual
computer-tomography data from the patient. In-vitro tests showed promising results and in-vivo
experiments are now under observation.
(2004-08-04) Cohen, D. L.; Malone, E.; Lipson, H.; Bonassar, L. J.
The objectives of this work are the development of the processes, materials, and tooling to
directly “3-D print” living, pre-seeded, patient-specific implants of spatially heterogeneous
compositions. The research presented herein attempts to overcome some of the challenges to
scaffolding, such as the difficulty of producing spatially heterogeneous implants that require
varied seeding densities and/or cell-type distributions. In the proposed approach, living implants
are fabricated by the layer-wise deposition of pre-cell-seeded alginate hydrogel. Although
alginate hydrogels have been previously used to mold living implants, the properties of the
alginate formulations used for molding were not suitable for 3-D printing. In addition to changing
the formulation to make the alginate hydrogels “printable,” we developed a robotic hydrogel
deposition system and supporting CAD software to deposit the gel in arbitrary geometries. We
demonstrated this technology’s capabilities by printing alginate gel implants of multiple materials
with various spatial heterogeneities, including, implants with completely embedded material
clusters. The process was determined to be both viable (94±5% n=15) and sterile (less than one
bacterium per 0.9 µL after 8 days of incubation). Additionally, we demonstrated the printing of a
meniscus cartilage-shaped gel generated directly from a CT Scan. The proposed approach may
hold advantages over other tissue printing efforts [5,9]. This technology has the potential to
overcome challenges to scaffolding and could enable the efficient fabrication of spatially
heterogeneous, patient-specific, living implants.
Precision tools with structural resolution reaching the 20 micrometer range can be generated
on an industrial scale by “laser micro sintering”. Components featuring aspect ratios above 12
and a roughness Ra down to 1.5 micrometers have already been produced from sub micrometer
grained metal powders. The components can be generated either firmly attached to a substrate or
fixed in an easily separable mode. If supporting structures are employed, undercuts up to 90° are
feasible, without, a process parameter dependent maximum angles of undercut below 90° are
The process has been introduced into the market, labeled microSINTERING by
In pursuit of the goal of producing complete electromechanical systems entirely via solid freeform fabrication, we are
developing a library of mutually compatible, functional, freeform elements. Several essential elements – actuation, sensing,
and control electronics - still remain to be incorporated into this library. Conducting polymers (CP) are a class of materials
which can be used to produce all of these functionalities. Meanwhile, research into actuatable “smart” materials has
produced other candidate materials for freeform fabricated actuators that are compatible with our library. We have
succeeded in manually producing air-operable actuators that have processing and operating requirements that are
compatible with our power source and mechanical component library elements. A survey of candidate actuator materials is
presented, experiments performed with two types of actuator materials are described, and complete SFF-producible actuator
devices are demonstrated.
The recent developments in rapid production tooling have all but made the need for
prototype tooling disappear. There are several approaches that are now as fast and
inexpensive as prototype tooling, and after part approval can continue to run in high volume
production applications. The newest of these approaches is an indirect spray forming process
invented by Dr. Kevin McHugh of the Idaho National Engineering and Environmental
Laboratories (INEEL). The advantages of RSP Tooling can be found in its accuracy, finish,
cost and speed compared to the other rapid tooling processes .
The commercialization effort for this spray forming process started in February of
2002. The beta production machine was operational in November, 2003, and started to
produce production tooling in March, 2004. Since that time tooling has been manufactured
and run for many forming applications. In all but the simplest tools the process has proven to
be less expensive and faster than standard machining of tools or any other rapid production
tooling process. Research and development of the process has continued both at INEEL and
at RSP Tooling, LLC making the process faster, more accurate and less expensive to operate.
This research has also generated a better understanding of the underlying metallurgy of the
(2004) Kinsella, M. E.; Lilly, B.; Carpenter, B.; Cooper, K.
Experiments have been performed with injection mold inserts made using solid freeform
fabrication processes in an effort to further study such applications for economic production of
small quantities of parts. Static friction coefficients were determined for HDPE and HIPS against
P-20 steel, sintered LaserForm ST-100, and stereolithography SL 5170 using the ASTM D 1894
standard. Injection mold inserts were constructed of the same three materials and were used to
inject cylindrical parts using HDPE and HIPS. Ejection forces were measured, and a model was
used to calculate ejection forces and apparent coefficients of static friction. Statistical analyses
were used to determine the effects of packing time, cooling time and packing pressure on
ejection force for the three insert types. This paper compares experimental and calculated
ejection forces, compares standard friction test results to calculated apparent coefficients of
friction, summarizes the statistical results, and comments on the feasibility of using rapid tooled
inserts for injection molding.
The potential of various manufacturing methods was evaluated for producing nickel-titanium
graded composition material. The selected test case examined attachment brackets that join
nickel-based metallic thermal protection systems to titanium-based launch vehicle structure. The
proposed application would replace nickel-based components with graded composition
components in an effort to alleviate service induced thermal stresses. Demonstration samples
were produced by laser direct metal deposition, flat wire welding, and ultrasonic consolidation.
Microstructure, general bond quality, and chemistry were evaluated for the components.
Tool steel parts built by laser powder deposition often present a heterogeneous distribution of
properties caused by the complex structural transformations that occur during the deposition
process. A model describing these transformations has been developed. It couples finite element
heat transfer calculations with transformation kinetic theory to predict the final microstructure
and properties of the material and their variation across a laser powder deposited part.
Pre-heating is often used to reduce the residual stresses and the risk of thermal distortion and
cracking. However, this changes the heat transfer conditions and affects the final microstructure
and properties. In this work the proposed model was used to evaluate the effects of substrate preheating on the final hardness distribution. The results show that the final hardness depends
considerably on the initial temperature of the substrate.
(2004) Boillat, Eric; Glardon, Rémy; Matthey, Marc
Producing injection tooling with cooling channels of almost any form seems to be one of the most
promising advantages of Layered Manufacturing Techniques (like Selective Laser Sintering). It could
be efficiently exploited to achieve higher productivity or better quality parts in injection molding.
Unfortunately, at the present time, the lack of data-processing tools to design optimal cooling systems
still prevents us from fully benefiting from this new potential.
The first objective of this paper is to present a methodology for the optimal design of cooling systems
in three-dimensional injection molds. Our optimization process is based on a finite element model of
the mold and on the standard gradient method.
In the second part of this paper, we compare a conventional mold and a mold equipped with a cooling
system optimized by means of the proposed methodology. The comparison is carried out thanks to
an appropriate protocol. The conclusion is that the optimization of the cooling system doubled the
productivity of the mold.