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
Selective Laser Sintering (SLS) process is employed for fabrication of biocerarnics
for orthopedic implants. Hydroxyapatite and Calcium Phosphate ceramics are coated with
polymer as a intermediate binder by using a spray drier. Polymer coated materials are
SLS processed to make green parts, which are infiltrated and fired to remove the polymer.
SLS processed green parts of hydroxyapatite have low density due to the small particle
size with large specific surface area. This paper discusses the possibilities and problems in
free-form fabrication of bioceramic.
The thermal diffusivities and thermal conductivities of powders, especially PMMA-coated
silicon carbide, at various temperatures, have been tested by two different dynamic methods, the
water-bath method and the laser-heated method. The thermal conductivity data found by these two
techniques are found to be consistent with each other.
A computer model for the sintering of ceramic/polymer composite
materials has been established based on empirical sintering rate data. The
model calculates sintering depths which result from variations in the
operating parameters which include laser power, beam speed, scan
spacing, scan vector length, and initial temperatures of the powder and
surroundings. Sintering depths measured in multiple layer parts made of
polymer coated ceramic powders are compared to sintering depths
calculated by the sintering model.
(1993) Agarwala, Mukesh K.; Bourell, David L.; Manthiram, Arumugam; Birmingham, Britton R.; Marcus, Harris L.
Fine, homogeneous dual phase Ag-YBa2Cu307-x composite powders were prepared by a simple
colloidal sol-gel co-precipitation technique. Silver did not react with or degrade YBa2Cu307-x.
Bulk porous samples of pure YBa2Cu307-x and Ag-YBa2Cu307-x were made from powders by
Selective Laser Sintering. The porous parts were further densified by infiltrating silver into pores,
resulting in a dense, structurally sound dual phase superconducting composite. Laser processing
parameters were varied to obtain optimum microstructure. The laser sintered parts required oxygen
annealing after infiltration to restore the orthorhombic, superconducting structure. X-ray
diffraction and Tc measurements indicate some impurity phases present in samples processed
under aggressive laser conditions.
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
This paper describes an investigation ofthe production ofsilicon carbide shapes by
Selective Laser Reaction Sintering (SLRS). One type ofSLRS process, which combines
laser sintering of silicon with acetylene decomposition, is briefly outlined, and the
mechanisms important to the process are discussed. A series oftest shapes are made at
different acetylene pressures to determine pressure effects on conversion to silicon
carbide. X-ray diffraction spectroscopy is used for bulk analysis ofthe shapes, and Auger
electron spectroscopy is used for surface analysis. The results indicate that acetylene
pressure does have a strong effect on silicon conversion to silicon carbide, and SLRS can
be used successfully to make silicon carbide shapes.