This Proceedings of the Sixth Solid Freeform Fabrication (SFF) Symposium, held at The
University of Texas in Austin on August 7-9, 1995, was attended by over 150 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. To avoid parallel sessions, a poster
session was organized. 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 area
as well as the large flux of new researchers and users entering the field.
Several important issues surfaced during a plenary discussion at the end of the meeting.
Considerable interest was expressed in the availability of related topics on the worldwide web. In
response, The University of Texas at Austin Laboratory for Freeform Fabrication homepage
(http://shimano.me.utexas.edu/sffl) now includes links to all sites currently published by our home
page, including all locations submitted at the meeting. This current list of web locations is also
included at the end of this proceedings volume. We will be pleased to update the list by notification
of one of the Symposium Proceedings editors.
Another issue which would benefit a majority of SFF researchers is formation of a research
infrastructure manufacturing network. Interest was expressed in the formation of a library of
"public domain" .STL files. Clemson University has created this, and Elaine Persall is the contact
person. contact information is in the participant index.
The editors would like to extend a warm "Thank You" to Sue Ferentinos 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
Vicki Lehmeier and 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.
N00014-95-1-0424, ARPA, and The Minerals, Metals and Materials Society for co-sponsoring the
Symposium with the Mechanical Engineering Department and the Center for Materials Science and
Engineering at the University of Texas at Austin.
Organizing Committee: Dick Aubin, United Technologies Research Center;
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;
Michael Cima, Massachusetts Institute of Technology;
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, University of Connecticut at Storrs;
Sean O'Reilly, Ford Motor Company;
Fritz Prinz, Stanford University;
Emanuel Sachs, Massachusetts Institute of Technology;
Greg Sanders, Lost Foam International;
Susan Smyth, General Motors Corporation;
Ralph Wachter, Office of Naval Research;
Michael Wozny, Nat'l Institute of Standards and TechnoIogy
Browsing 1995 International Solid Freeform Fabrication Symposium by Issue Date
(1995) Ullett, Jill S.; Rodrigues, Stanley J.; Chartoff, Richard P.
The linear shrinkage of an acrylate and an epoxy based stereolithography resin was
measured during cure. A helium-cadmium (He-Cd) laser cured strands of resin as is done in the
stereolithography process using two exposures. The exposure time was held constant while the
delay time between exposures was varied. It was found for both resins that the final cure depth and
linear shrinkage were a function of delay time
Stereodeposition techniques are well suited for the Solid Freeform Fabrication of dense ceramic
components. As opposed to forming a pattern in a particle bed or polymer bath, stereodeposition
processes deposit material directly onto the previously created layer. The key to stereodeposition is
a material's ability to be dispensed as a fluid, yet rapidly stiffen to hold the shape of the object.
This is accomplished by either solidification of a thermoplastic binder upon cooling from a melt
(Fused Deposition) or by polymerization of a binder (Reactive Stereodeposition). We are
developing both techniques for the production of functional ceramic and engineering polymer
A key issue in developing a successful stereodeposition system is controlling the rate of bead
transformation from liquid to solid. Control is critical to achieving high resolution and low surface
roughness of the finished product, but is made complex by the large number of parameters
involved. These include binder parameters (surface tension, gelling characteristics), slurry
parameters (viscosity, particle loading and size distribution), and process parameters (deposition
rate, temperature). Current efforts at the University of Arizona are focused on modeling and
controlling the deposition and transformation of ceramic slurries used in the Reactive
Selective Laser Sintering (SLS) is a leadingtechnology in the important new area of Solid
Freeform Fabrication (also ca1ledR.apid Prototyping). Selective Laser Sintering produces freeform
parts directly from a CAD model by building the parts up in layers from a powder. A laser is used
to selectively melt each layer of powder to form the part. The laser beam is scanned across the
powder using two galvanometer scanners. The energy delivery system (laser, optics, scanner and
controls) is a critical component technology of SLS. Projects with the objective of improving the
energy delivery system are underway at Clemson University
A variety ofsolid freeform fabrication (SFF) techniques have been developed to
produce prototype parts directly from a computer-aided drawing (CAD) without any hard
tooling, dies or molds . Most ofthese techniques use polymer, wax, or paper materials
to produce the parts.
These techniques, with SOlne lnodifications, can be used to rapidly prototype
functional ceramic parts. Once developed, these techniques could also be used to
manufacture small quantities of ceralnic parts on a just-in-time basis. Fabrication using
conventional techniques is a costly, titne-consuming, and inflexible process when a few
ceramic prototypes or when small quantities of parts are needed.
Solid freeform fabrication of ceralnic parts offers numerous advantages over
conventional processing. Prototypes can be prepared rapidly and cost-effectively. Design
changes can be made easily and inexpensively. Larger nUlnber of design options can be
investigated. Parts can be designed and engineered to take advantage ofthe stronger
properties of ceramics, while minimizing the weaker ones. Typically, ceramic parts are
made using an existing design, regardless ofthe material used for the original part. The
ability to rapidly prototype a ceralnic component will contribute to concurrent
engineering, a popular design process being used today.
Lone Peak Engineering (LPE) is developing three SFF processes for ceramics based on:
1. Selective Laser Sintering (SLS)
2. Fused Deposition Modeling (FDM)
3. Lalninated Object Manufacturing (LOM™)
TMLOM is a registered trademark of Helisys, Inc. Torrance, CA
This paper discusses preliminary results with the SLS and FDM processes. LPE's ceramic
LOM based process has been reported at this symposium  as well as at other meetings
and in different publications .
(1995) Pang, Thomas H.; Guertin, Michelle D.; Nguyen, Hop D.
Rapid Prototyping and Manufacturing (RP&M) users need to compare the accuracy of various
commercially available RP&M materials and processes. A good diagnostic test for both material and the
fabrication process involves a 4-inch long "letter-H" diagnostic part. This diagnostic part, known as "H-4", was
developed to measure the inherent dimensional characteristics ofvarious RP&M build materials. It is also less
dependent on the calibration status of particular RP&M machines, and is excellent for the purpose of generating
simple but meaningful accuracy information, which can be used to further understand the mechanism and the
modes of distortion in RP&M materials. H-4 parts were prepared and built in Stereolithography Apparatus (SLA)
using Ciba-Geigy epoxy based resins SL 5170 and SL 5180, and results were compared to acrylate based SL 5149.
Experimental data involving the magnitude, mechanism, and the modes of distortion for these three resins are
analyzed in this paper.
A two-stage method has been devised for free form fabrication of nickel,
iron and copper based alloy parts with shape and property control equal or
superior to investment castings in the same base alloys. A major advantage
of the approach is the ability to utilise commercially available selective laser
sintering systems with virtually no modification from their standard
configurations for plastic model generation. We have demonstrated the
essential feasibility of shape, dimension and property control for complex,
low production volume rocket engine components and for tools and dies in
higher volume commercial production situations. This presentation is limited
in scope to a brief overview of our recent progress.
(1995) Yardimci, M. Atif; Guceri, Selcuk I; Danforth, Stephen C.
Fused Deposition ModelingTM utilizes the simple idea of melting, extrusion and
resolidification of thermoplastic filaments. The introduction of particulate materials,
especially ceramics and metals, will widen the range of capabilities of the process. The
present study is directed to the development of a family of numerical models for the
FDM and Fused Deposition of Ceramics processes. These models in turn would help to
predict the operation windows of the FDM/FDC. Time-dependent mesh generation and
parameter file generation are incorporated into the developed two-dimensional model.
Finite element method is used in order to address heat transfer issues regarding the
solidification ofthe thermoplastic binder
(1995) Melvin III, Lawrence S.; Beaman Jr., Joseph J.
A sieve feed system has been designed for use with the Selective
Laser Sintering process. The sieve feed system uses
electrostatic charge to help apply polymer powder to a green
powder bed. The sieve feed system was found to help the
application of polymer powder as measured by a 10 to 15%
increase in final part density. The sieve feed system has
many potential applications, including material property design,
and material mixing during the sintering process.
(1995) Mathewson, Brian B.; Newman, Wyatt S.; Heuer, Arthur H.; Cawley, James D.
This paper describes a machine and process for automated fabrication of functional 3-D
laminated engineering components, ceramics in the present example. A laser cuts successive layers
of a part derived from a CAD model description out of unfired tape-cast ceramic sheets
vacuum-clamped to an x-y sled. A material-handling robot uses a selective-area gripper to extract
only the desired part outlines from the surrounding waste material, then stacks the slices to build the
part. This system design enables rapid manufacture of functional engineering components with
arbitrarily complex internal and external geometries from virtually any material available in sheet
The Standard for the Exchange of Product Model Data (STEP), ISO 10303, is a developing
International Standard for the exchange of product information between many different engineering
and manufacturing applications. This paper describes an architecture and methodology, using
STEP, that integrates a heterogeneous environment of CAD and Solid Freeform Fabrication (SFF)
systems. The prototype software discussed in this paper demonstrates the use of STEP to provide
CAD product data to a SFF system. The architecture described in this paper also addresses the role
of the STEP standards in an environment where STL and other SFF part data formats must also be