This Proceedings of the Fourth Solid Freeform Fabrication Symposium, held at The
University of Texas in Austin on August 9-11, 1993, reaffirms the dynamic nature of the
research area. The interest shown by researchers over the wide range of disciplines and sub-
disciplines that make up Solid Freeform Fabrication (SFF) highlights this technical Symposium.
The speakers addressed problems in computer software, in machine design, materials synthesis
and processing, and SFF in integrated manufacturing. The exponential growth in the research,
application and development of SFF approaches was readily apparent from the attendees from
industrial users, SFF machine manufacturers, universities, and government. This Symposium is
the first where real progress toward structurally sound samples and parts was demonstrated as
SFF moves from "feelie" to "non-structural" to "structural" real parts over a range of materials.
This advancement in the state-of-the-art of SFF will continue to drive the exponential growth of
the area. The excitement amongst the Symposium participants will continue to serve as the
catalyst for the continued growth and the availability of Solid Freeform Fabrication. The
Symposium organizers look forward to its being a continued source of technical exchange among
the growing body of researchers involved in SFF.
The Symposium was organized in a manner to allow the multi-disciplinary nature of the
SFF research to be presented coherently, with various sessions emphasizing computer aspects,
machine topics, and the variety of materials aspects of SFF. Application-related efforts were
scattered throughout the Symposium. To avoid parallel sessions a poster session was organized,
and the panel session on SFF was held in the evening, after a visit with Texas barbecue. The
dynamic panel discussion on Future Directions in SFF was led by Marshall Burns, Michael J.
Cima, Tom Latham, Greg Sanders and Joel W. Barlow. The written versions of the presented
papers are incorporated into these Proceedings. The editors would like to thank the speakers for
their timely delivery of the manuscripts that expedited the publication of these Proceedings. The
constantly changing state of the SFF art as represented by these Proceedings will serve both the
people. presently involved in this fruitful area as well as new researchers and users coming into
Solid Freeform Fabrication.
The editors would also like to extend a warm thank you to Renee Loyless-May for her
extensive efforts in the detailed handling of the logistics of the meeting and the Proceedings. We
would also like to thank the organizing committee, the speakers, the session chairmen, panel
members, and the attendees for their enthusiastic contributions. 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. N00014-93-1-0371, ARPA, and The Minerals, Metals and
Materials Society for co-sponsoring the Symposium as well as DTM Corporation for hosting the
Organizing Committee: Dick Aubin, United Technologies;
Joel W. Barlow, The University of Texas at Austin;
Joseph J. Beaman, The University of Texas at Austin;
David L. Bourell, The University of Texas at Austin;
Robert L. Brown, The Gillette Company;
William Coblenz, ARPA;
Richard Crawford, The University of Texas at Austin;
Samuel Drake, University of Utah;
Steven Fishman, Office of Naval Research;
Harris L. Marcus, The University of Texas at Austin;
Fritz Prinz, Carnegie Mellon University;
Emanuel Sachs, Massachusetts Institute of Technology;
Greg Sanders, General Motors Corporation;
Sean O'Reilly, Ford Motor Company;
Ralph Wachter, Office of Naval Research;
Michael Wozny, Rennselaer Polytechnic Institute
Browsing 1993 International Solid Freeform Fabrication Symposium by Title
The DIGIBOT 3D Laser Digitizer is a high performance 3D input device which
combines laser ranging technology, personal computing, and Microsoft Windows in an
attractive desktop package.
With its full four-axis scanning capabilities, the DIGIBOT provides a simple,
accurate, and quick way to copy or inspect complex, sculpted surfaces. The DIGIBOT
provides an effective solution for many industrial and academic problems involving 3D
design, inspection, replication, analysis, and visualization/animation. By measuring
sequential points and producing a standard list of x/y/z coordinates, the DIGIBOT
interfaces to any CAD/CAM/CAE imaging or animation software that reads 3D points,
contours, or triangular facets.
Solid Freefonn Fabrication (SFF) is a class of manufacturing technologies aimed at the
production of mechanical components without part-specific tooling or process planning. Originally
used for creating modelsfor visualization, many industrial users of SFF technologies are realizing
the greater potentialofSFF as legitimate manufacturing processes for producing patterns and, in
some cases, functional.parts. Thus, SFF is becoming an important aspect of the product
realization process in these industries.
Solid Freefonn Fabrication arose from the dream of "push-button" prototyping, in which
solid reproductions of three-dimensional geometric models are created automatically under
computer control. Perhaps more than any other class of manufacturing technologies, computer
software development has been an integral part of the emergence of SFF. As SFF technologies
evolve toward the ability to create functional parts, computer issues gain more importance.
This paper discusses three aspects of software design for SFF: processing of geometric
data, global and local control of SFF processes, and computer-based analysis and design for SFF
manufacturing. The discussion of geometric processing issues focuses on accuracy and
completeness of input models, and the algorithms required to process such models. The interplay
between the physics of SFF processing and the desired output geometry is discussed in terms of
the development of model-based control algorithms for SFF. These two areas, geometric
processing and control, are necessary for the practical implementation of any SFF technology.
However, for SFF to realize its potential as an alternative for manufacturing functional parts,
engineers must be provided with analysis and design tools for predicting mechanical properties,
ensuring dimensional accuracy, choosing appropriate materials, selecting process parameter
values, etc. For each of these three different but related areas of software design, the state-of-theart
is assessed, contemporary research is summarized, and future needs are outlined.
Since the introduction ofrapid prototyping technology as a tool for time
compression and concurrent engineering in the design and manufacturing process, many
enhancements and refinements have been made based on the experience ofusers and
manufacturers ofrapid prototyping equipment. These improvements contribute
significantly to faster production of quality output from rapid prototyping systems.
There are diverse control and material selection parameters that affect prototype
models built using the Fused Deposition Modeling (FDM®) process. This paper reviews
the role of several ofthese parameters in the process. Data will be presented to help the
user choose the appropriate material for specific applications including density, tensile
stiffhess, flexural stiffhess, tensile strength, flexural strength, tensile ductility, shock
resistance, and hardness.
Nanocomposites in which the constituents are mixed on a nanorneter scale can
provide important advantages in the Selective Laser Sintering (SLS) and Selective Laser
Reactive Sintering (SLRS) processes. The larger surface area and grain boundaries in the
nanocolnposites compared to that in the conventional microcomposites are expected to
enhance the solid state diffusion during laser irradiation as well as during any other
subsequent processes. Our strategy is to design and develop nanocomposites in which one
nanosize cOlnponent has a lower melting point than the other nanosize component, either of
which can serve as the matrix phase. The nanoscale dispersion of the low melting
component can aid the sintering process during SLS or SLRS. Nanocomposite powders of
AI203-COOx, Ab03-NiO, A1203-CO and A1203-Ni have been synthesized by sol-gel
processing and are evaluated by SLS.
Geometry processing for layer-based Solid Freeform Fabrication consists of at least two
steps: slicing the geometry to obtain the part contours for each layer, and scan-converting the
layers for laser scanning (or other device-dependent in-layer processing). This paper discusses
the generation of contour files directly from Constructive Solid Geometry (CSG) representations
for the Selective Laser Sintering process. Previous work at The University of Texas focused on
slicing CSG representations composed of quadric primitives. This paper extends previous work
at UT to include the torus, a fourth degree surface, as one of the CSG primitives. Slicing a torus
results in a fourth degree equation in two variables, which represents a curve in two-dimensional
real space. For. some special cases, this fourth degree equation may be sub-divided into two
second degree equations. For the cases where the fourth degree equation cannot be sub-divided,
a method is presented to approximate the fourth degree curve with second degree curve
The use of a directed laser bealn source to selectively sinter multiple layers of
binderless metal powder for the purposes of rapid prototyping is described. The
work in this paper is restricted to -325 mesh iron powder, which was sintered
using a C\V 50 W Nd:YAG laser to approximately 3.5% density. A subsequent
post-treatlnent was perfornled to achieve a fully dense saulple. It is envisioned
that such a system can be used to manufacture functional metallic prototypes
directly from CAD without part-specific tooling.
Colloidal ceramic binders have been used to strengthen ceramic
green shapes produced by Selective Laser Sintering. This paper
focuses on the effectiveness of the colloid infiltration with
respect to the physical properties of the colloidal binder. Mass
gains, strength gains, and dimensional changes resulting from
infiltration were monitored. Controlled drying experiments were
conducted to predict the factors influencing drying times for
(1993) Agarwala, Mukesh K.; Bourell, David L.; Wu, Benny; Beaman, Joseph J.
Mechanical properties of Bronze-Nickel composites produced by Selective Laser Sintering (SLS)
were evaluated by constant displacement tension tests. These were studied as a function of SLS
process parameters - laser power density, scan speed, scan spacing, scan direction and layer
thickness. The strength data was then correlated to the microstructure and the part bulk density. To
further enhance the part densities and the mechanical properties, post-SLS sintering was studied.
The relationships between SLS process parameters, post-SLS sintering parameters and the
resulting microstructures, part bulk density and the mechanical properties will be described.