The Eighth Solid Freeform Fabrication (SFF) Symposium, held at The University of Texas
in Austin on August 11-13, 1997, was attended by 200 national and international researchers.
Papers addressed SFF issues in computer software, machine design, materials synthesis and
processing, and integrated manufacturing. The continued growth in the research, application and
development of SFF approaches was readily apparent from the increased participation over
previous years and the diverse domestic and foreign attendees from industrial users, SFF machine
manufacturers, universities, and government. The excitement generated at the Symposium reflects
the participants' total involvement in SFF and the future technical health of this growing
technology. 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 computer issues,
machine topics, and the variety of materials aspects of SFF. We believe that documenting the
constantly changing state of SFF art as represented by these Proceedings will serve both the people
presently involved in this fruitful technical area as well as the large flux of new researchers and
users entering the field.
The editors would like to extend a warm "Thank You" to Glorya Gutchess 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 also acknowledge the support efforts of
Cindy Pflughoft throughout. We would like to thank the organizing committee, the session
chairmen, 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 ONR through Grant No.
NOOOI4-97-1-0453, DARPA, and The Minerals, Metals and Materials Society and the University
of Connecticut at Storrs for co-sponsoring the Symposium with the Mechanical Engineering
Department, Laboratory for Freeform Fabrication and the Center for Materials Science and
Engineering at the University of Texas at Austin.
In the industrial use ofthe Stereolithography, the precision is always a problem. Basic
phenomenon of the solidification shrink has not suffiCiently investigated This study aims at
clarifying the initial linear shrinkage ofcured resin in a minute volume. Experimental equipment
has been developed which measures the time history of the single strand in situ in a
stereolithography machine. Analysis model about the time history of a minute volume linear
shrinkage has been shown using with the measured shrinkage of a cured line segment. The
relation between the time history ofthe linear shrinkage and the temperature was measured and
the shrinkage in the minute volume after irradiation has been caused by the temperature
In recent years, important efforts have been focused on producing functional parts using
Stereolithography Apparatus ( SLA ). One of the applications is the development of rapid
polymer tooling such as dies for injection molding. For these applications, optimal thermal as
well as mechanical properties are of significance. In this paper, the mechanical behavior of the
cured resin SL5170 is discussed by use of an elastic-viscoplastic material model. Uniaxial
compression tests at different deformation rates are conducted. The stress-strain curves of these
tests are predicted by the model, and comparisons of these results with experiments show good
(1997) Papadatos, Alexandre L.; Ahzi, Said; Deckard, Carl R.; Paul, Frank W.
This work is a first step towards the prediction of the dimensions and thermomechanical
properties ofparts made with the Selective Laser Sintering (SLS) technology.
An important variation of the dimensions is found in the Z-direction of the build. This
phenomenon is known as the "Bonus-Z" where material properties differ from those in
the rest of the part due to a non-homogeneous sintering. The focus of this work is the
characterization and the modeling of the bonus-Z phenomenon, by relating it to the
energy input. The polymer powder used in this study is polycarbonate.
(1997) Tikare, Veena; Griffith, Michelle; Schlienger, Eric; Smugeresky, John
Laser Engineered Net_Shaping, otherwise known as LENSTM, is an advanced manufacturing
technique used to fabricate complex near net shaped components directly from engineering solid
models without the use of dies or machining. The ultimate objective ofthis project is to develop
predictive simulation capability which will allow the LENSTM processors to determine fabrication
conditions given the material, shape, and application ofthe final part. In this paper, we will
present an incremental achievement to meeting the ultimate goal, a model capable ofsimulating
the coarsening ofmicrostructural features under the unique thermal history to which a LENSTM
part is subjected during processing. The simulation results show how grains ofvery different
shapes and sizes form within the same deposition line. They also show that relatively minor
changes in the dynamic temperature profile results in microstructures with vastly different
characteristics. The implications ofthis work for LENSTM fabrication is that controlling the
temperature profile is essential to tailoring the microstructure of a component to its application.
(1997) AtifYardimci, M.; Hattori, Takeshi; Guceri, Selcuk I.; Danforth, Stephen C.
Fused Deposition processes involve successive melting, extrusion and solidification of
thermoplastic polymer melts. Fluid mechanics and heat transfer of neat or particle-filled
polymeric melts, viscoelastic deformation and solidification ofthe roads that are being produced,
and repetitive thermal loading of the growing part are important physical processes that control
the final quality of the part. Previous computational process models investigated deposition and
cooling processes for single and multiple filaments. In the current study, complimentary
computational models are presented for the extrusion phase of the process. Impact of liquefier
and nozzle design on thermal hardware behavior and operational stability has been quantified.
Also a detailed study of temperature field near the vicinity of deposition point is presented with
particular emphasis on dimensional analysis and deposition ofmultiple material systems.
(1997) Flach, Lawrance; Klostennan, Donald A.; Chartoff, Richard P.
A thennal model for Laminated Object Manufacturing (LOM) has been developed. The
model is based on 3-dimensional transient heat conduction in a rectangular geometry LOM part.
Heat transfer from the heated roller to the laminated part as well as heat loss to the surroundings
and the base plate are considered. It allows calculation of the transient temperature distribution
within the part during the application of a new layer as well as during other periods of the LOM
build cycle. To verify the model performance, thennocouples were embedded every 4th layer in a
20-layer ceramic part while it was being built on a standard LOM-2030. The model predictions are
in excellent agreement with the measured temperature profiles. In addition to explaining the
observed thennal behavior ofLOM parts, model predictions also have direct application to on-line
control ofthe part temperature during the build process, to be discussed herein.
(1997) Wang, Yanshuo; Dong, Jian; Marcus, Harris L.
The Virtual Reality Modeling Language (VRML) was created to put interconnected 3D
worlds onto every desktop. The 3D VRML format has the potential for 3D fax and TeleManufacture.
An architecture and methodology of using VRML format to integrate a 3D model
and Solid Freeform Fabrication system are described in this paper. The prototype software
discussed in this paper demonstrates the use of VRML for Solid Freeform Fabrication process
planning. The path used from design to part will be described.
(1997) Marsan, Anne L.; Allen, Seth; Kulkarni, Prashant; Dutta, Deba
An integrated process planning system for layered manufacturing (LM) reduces the time
between design and part fabrication and improves the quality of the final part. Process planning
for most LM processes includes part orientation, support structure generation, slicing, and path
planning. In this paper we describe an integrated process planning system we are developing. Our
software accommodates both novel and traditional design models as input, and supports a variety
of LM processes. The modules described in this paper include Solid Builder Module, which generates
a solid model from design data such as medical images, surface functions, or digital elevation
models; Orientation Module, which determines the optimal build orientation of a part and
automatically generates the support structures required; and Adaptive Slicing Module, which
adaptively slices the part.