This Proceedings of the Second Solid Freeform Fabrication Symposium that was
held at The University of Texas in Austin on August 12-14, 1991 demonstrates the very
active interest in this fully integrated approach to design, materials processing and
manufacturing. The active participation of speakers and attendees from industry,
universities and government give a clear indication of the importance that SFF in its many
variants has in the future of manufacturing. As SFF extends itself into structurally sound
parts made of polymers, metals, ceramics and their composites the number of people and
institutions involved will continue to grow exponentially. The organizers look forward to
this growth and the continued availability of the Solid Freeform Fabrication Symposium to
serve as a source of technical exchange among the researchers involved in the area.
The Symposium was organized in a manner to allow the multi-disciplinary nature of
the SFF research to be presented coherently. The initial session described the computer
interfacing required for SPF. This was followed by a session associated with polymer
research on SFF. A session on modeling SFF was then presented. Two sessions were
offered describing the latest techniques and modifications of SFF. Sessions on the
application of SFF to ceramics and metals were then presented. The final session
concentrated on the gas phase approach to SFF and to a general discussion on SFF and
where it was going. The written versions of the presented papers were incorporated into
The editors would like to thank the speakers for there prompt delivery of the manuscripts that allows the timely publication of these Proceedings. The state of the SFF art as represented by these Proceedings will serve both the people presently involved
in this research area as well as the new researchers coming into Solid Freeform Fabrication.
The editors would also like to extend a warm thank you to Nancy DeLine 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 and the
attendees for their contributions. We look forward to a continued close cooperation in
organizing the Symposium.
Organizing committee: Fritz Prinz,
Peter R. Sferro,
Robert L. Brown,
Browsing 1991 International Solid Freeform Fabrication Symposium by Title
The first stage of Rapid Prototyping life cycle as a new technology
in the marketplace is gradually ending, and the second stage has
already started. Many new vendors have introduced their products in
this field, utilized different, new technologies or improvements of
the existing ones. The first introduction of the RP concept and
Stereolithography created a stunning impression in the marketplace.
After a couple of years, as customers and users have gained much
experience and understanding or RP technology, the first enthusiasm
started making way to more serious and demanding approach. This is
very well reflected in the thorough evaluations of the different
technologies available today in the marketplace, done by customers
looking for a technology that will best fit their needs. This is
actually why most of us are here today.
It has been almost four years since the SLA - 1 ushered in the
new technology of StereoLithography, and about 2\ years since 3D
Systems introduced the SLA-250. Since then, nearly 300 systems
have been installed worldwide and are currently providing benefits
in a range of applications which might well be summarized by the
term "Rapid Prototyping and Manufacturing" or "RPM".
During the past year the accuracy of parts built with
stereoLithography has benefitted significantly from nine important
technological advances. The research and development efforts which
formed the foundation for this progress originated within the
Process, Chemistry and Software departments of 3D Systems.
The following is a listing, and brief description, of the key
features of each of these advances.
Techniques for controlling the microstructure of sprayed steel structures are
discussed in this paper. Steel is arc sprayed onto shaped substrates to form tooling. The
quality of the tool is greatly influenced by the microstructure of the material and the interlamella
regions of the deposit. This work is focused on characterizing the microstructure,
improving the state of the inter-lamella regions, and discusses our success in forming
pseudo-alloys and graded shells by mixing sprayed materials. Microstructure control has
interesting implications for other research as well, such as the MASK & DEPOSITS approach
of forming objects.
It has been proposed that a thin polymer layer applied to the
surfaces of finely divided ceramic powders would serve as a suitable
intermediate binder for Selective Layer Sintering of ceramic pans. In this
study, the effects of completeness and fraction of coa nd particle size
distribution on sintering rates and strengths of coated ridized glass are
examined. The effect of the coating as a binder during Selective Layer
Sintering as well as the binder's burnout capability during post processing
steps are also investigated.
Solid freeform fabrication technologies offer exciting possibilities for improving
product quality by direct manufacture of products. .One example of such product
improvement is the fabrication of artificial limb sockets by selective laser sintering (SLS).
Currently these sockets are produced at the University of Texas Health Science Center at
San Antonio by digitizing the residual limb with a 3D laser scanner, modifying this
geometry appropriately using a proprietary CAD system, producing a mold with a
computer-controlled milling machine, and vacuum forming the final product. This paper
describes a new manufacturing technique whereby the digital socket data from the CAD
system provide input to a SLS workstation to produce the final socket directly, without the
intermediate step of fabricating a mold pattern. The advantages of this process include
integration of the prosthesis attachment fitting and socket as one component and greater
control of local socket geometry for superior stress relief characteristics.
Afinite element heat transfer analysis is applied to the selective laser sinteringofa layered part made
frompolyroerpowder. The sinteringsubroutine in the code is based on the analyses of Scherer [l t2] and
Mackenzie and Shuttleworth . The density and conductivity of the particle bed are treated as functions of
the void fraction of the bed. The Yagi - Kunii  thermal characterization of the powder bed is used to calculate
the effective conductivity of the bed. An example is worked for ABS powder.