1993 International Solid Freeform Fabrication Symposium

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https://hdl.handle.net/2152/64616

Proceedings for the 1993 International Solid Freeform Fabrication Symposium. For more information about the symposium, please see the Solid Freeform Fabrication website.

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 reception.

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

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1993 International Solid Freeform Fabrication Symposium Table of Contents
(1993) Laboratory for Freeform Fabrication and University of Texas at Austin
Selective Laser Sintering of Bioceramic Materials for Implants
(1993) Lee, Goonhee; Barlow, J.W.
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.
Measurement of the Thermal Conductivity of Powders by Two Different Methods
(1993) Sih, Samuel S.; Barlow, Joel W.
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.
Laser Sintering Model for Composite Materials
(1993) Nelson, J.C.; Vail, N.K.; Barlow, J.W.
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.
Selective Laser Sintering of A1203-
(1993) Subramanian, Kam
Synthesis, Selective Laser Sintering and Infiltration of High Super Tc Dual Phase Ag-YBa2Cu307-x Superconductor Composites
(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.
Drying of Colloidal Binder Infiltrated Ceramic Green Parts Produced by Selective Laser Sintering™
(1993) Glazer, M.; Vail, N.K.; Barlow, J.W.
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 complex shapes.
Selective Area Laser Deposition of Silicon Carbide
(1993) Tompkins, James V.
Supersolidus Liquid Phase Selective Laser Sintering of Prealloyed Bronze Powder
(1993) Gopalakrishna, B.; Bourell, David L.
Solid Freeform Fabrication of Silicon Carbide Shapes by Selective Laser Reaction Sintering (SLRS)
(1993) Birmingham, B.R.; Marcus, H.L.
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.

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