1991 International Solid Freeform Fabrication Symposium

Permanent URI for this collectionhttps://hdl.handle.net/2152/64273

Proceedings for the 1991 International Solid Freeform Fabrication Symposium. For more information about the symposium, please see the Solid Freeform Fabrication website.

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 these Proceedings. 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, Greg Sanders, Robert L. Brown, Emanual Sachs, Michael Wozny, Samuel Drake, Dick Aubin, Harris Marcus, Joe Beaman, Joel Barlow, David Bourell, Rich Crawford, Kris Wood

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    1991 International Solid Freeform Fabrication Symposium Table of Contents
    (1991) Laboratory for Freeform Fabrication and University of Texas at Austin
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    Selective Area Laser Deposition from Acetylene and Methane to Increase Deposition Control
    (1991) Birmingham, B.R.; Zong, G.; Tompkins, J.V.; Marcus, H.L.
    Selective area laser deposition (SALD) has been used to deposit carbon from acetylene. Working at the relatively high pressures required to produce high deposition rates can result in explosive uncontrollable growth. Pr~vious computational modeling indicates that the energy released from the exothermic decomposition of acetylene to carbon may be responsible for this behaviour[l]. Since methane decomposes endothermically to form carbon over certain temperatures, it is possible that methane addition to the process may help control the deposition rate. The purpose of this paper is to describe SALD experiments that were performed using various partial pressures of acetylene and methane as precursor in order to determine if combining an endothermic and an exothermic reaction effects the control of the SALD process.
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    Moving Boundary Transport Phenomena in Selective Area Laser Deposition Process
    (1991) Zong, Guisheng; Marcus, Harris L.
    The overall selective area laser deposition process was modeled using the two-layer, three dimensional solid phase heat transfer with the moving boundary condition considered, gas phase mass transfer, and film growth coupled equations. A modified front-tracking finite difference method was used to solve the moving boundary heat conduction in thick deposits. The results correlate with the experimental observations.
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    Processing Problems Associated with Gas Phase Solid Freeform Fabrication Using Pyrolytic Selective Area Laser Deposition
    (1991) Zong, G.; Tompkins, J.V.; Thissell, W.R.; Sajot, E.; Marcus, H.L.
    Concerns critical to selective area laser deposition are discussed. Variables affecting deposition rate, dimensional control, and surface uniformity are analyzed. Localized growth results in undesirable morphology, and contributing factors are cited. Catalytic powders increase nucleation rate and provide superior temperature profiles resulting in good surface uniformity. Specific process control devices are investigated.
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    Selective Area Laser Deposition - A Method of Solid Freeform Fabrication
    (1991) Thissell, W.Richards; Zong, Guisheng; Tompkins, James; Birmingham, Britton R.; Marcus, Harris L.
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    Selective Laser Sintering to Produce NI-SN Intermetallics
    (1991) Weiss, Wendy; Bourell, D.L.
    A model system has been employed to investigate .the use of selective laser sintering (SLS) with a post-processing step to produce a compound having different properties than the precursor powders. The powder mixture examined consisted of95% (59% Ni and 41%8n) plus 5% ZnC12. This weight fraction of nickel and. tin produces. the intermetallic compound Ni3Sn upon equilibrium annealing. ZnCl2 was used as a wetting agent. Parts were fabricated using SLS and were then post-process annealed to create the intermetallic. Metallographic techniques and x-ray powder diffraction were used.to characterize the parts before and after annealing.
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    Selective Laser of a Copper-PMMA System
    (1991) Badrinarayan, B.; Barlow, J.W.
    The Selective Laser Sintering process was used to manufacture green copper parts from a copper-polymer mixture. PMMA was used as the polymer binder for the metal. The green part was fired in a furnace under reducing conditions to obtain a pure metal part. The metal-polymer system and the conditions used to make parts are described in this paper. The effect of laser parameters and particle sizes on part density are also discussed. Keywords: laser sintering, copper, polymer, part density, dwell time, shrinkage.
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    Selective Laser Sintering of Cu-Pb/Sn Solder Powders
    (1991) Frayre-Manriquez, J.A.; Bourell, D.L.
    Solid Freeform Fabrication (SFF) as an overall approach in the manufacturing field has been applied to very different areas and on different materials systems including polymers, ceramics, metals and vapor phase. Even though it is clear that polymers have enjoyed a rapid and successful advance in terms of applications, research in the other areas have shown potential applications as well. In this paper, Cu-Sn/Pb solder and Cu-Sn blends have been used as starting material for the Selective Laser Sintering (SLS) manufacture of SFF objects. The general properties of the objects thus produced are presented. In particular, density and microstructural characterizations results are discussed..
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    Controlling the Microstructure of Arc Sprayed Shells
    (1991) Fussell, P.S.; Kirchner, H.O.K; Prinz, F.B.; Weiss, L.E.
    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.
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    Microstructural and Mechanical Properties of Al2O3/P2O5 AND Al2O3/B2O3 Composties Fabricated by Selective Laser Sintering
    (1991) Lakshminarayan, Uday; Marcus, H.L.
    The feasibility of processing ceramic powders by Selective Laser Sintering has been reported in an earlier paperl . Material systems we have investigated include alumina based systems with ammonium phosphate or boron oxide as low temperature binders which are the systems discussed in this paper. With bOth systems, a secondary heat treat.rJ1ent is necessary to realize the high temperatute properties of the materials. This paper will focus mainly on the mechanical properties of the composite bodies. In particular, the influence of particle size, powder mix composition, laser parameters and secondary heat treat.rJ1ent on density, strength and dimensional stability of the final product will be discussed.
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    Effect of Polymer Coatings as Intermediate Binders on Sintering of Ceramic Parts
    (1991) Vail, N.K.; Barlow, J.W.
    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.
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    Three Dimensional Printing: Form, Materials, and Performance
    (1991) Cima, Michael J.; Sachs, Emanuel M.
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    A Framework for Thermal Spray Shape Deposition: The MD* System
    (1991) Weiss, Lee E.; Prinz, Fritz B.; Siewiork, Daniel P.
    This paper present.s t.he framework for a solid-freeform-fabrication syst.em based on thermal spray shape deposition t.o build mult.i-mat.erial st.ruct.ures by incremen tal build-up of t.hin cross-sect.ional layers. The basis of theMD* System (recursively, Mask and Deposit.) is to spray each layer using disposable masks to shape each layer. A thermal spray approach has the potential to build dense parts with desirable mechanical properties. Metal. ceramic, plastic, laminate, and composite structures can be deposited. Since l11asking enables selective deposition wit.hin a layer, complet.e assemblies composed of different mat.erials can be creat.ed in a single process. For example, int.egrated electronic/mechanical structures are feasible.
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    The Electrostatic Application of Powder for Selective Laser Sintering
    (1991) Melvin, Lawrence S. III; Beaman, J.J.
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    Design of a High Temperature Workstation for the Selective Laser Sintering Process
    (1991) Das, Suman; McWilliam, John; Wu, Benny; Beaman, J.J.
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    Fabrication of Prosthetic Socket by Selective Laser Sintering
    (1991) Rogers, W.E.; Crawford, R.H.; Beaman, J.J.; Walsh, N.E.
    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.
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    Advances in Stereolithography Accuracy
    (1991) Jacobs, Paul F.; Richter, Jan
    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.
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    Selective Laser Sintering as a Rapid Prototyping and Manufacturing Technique
    (1991) Kent, Nutt
    With accelerating growth and competition in today's global marketplace, manufacturers face the daunting tasks of meeting changing market needs, maintaining market share, and reasserting a technological edge. Now, more than ever, adopting new technologies is a key component in ensuring the successful outcome of new projects--and in producing longterm market success.
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    Laminated Object Manufacturing (LOM): A Simpler Process
    (1991) Feygin, Michael; Hsieh, Brian
    With Laminated Object Manufacturing (LQM) process, three dimensional objects are manufactured by sequentially laminating and cUtting two-dimensional cross-sections. The.rnediumused.inLOMprocess isaQhesive-coatedsheet• materials.. As seen in Figure 1, the sheetmateria.l carries the adhesive either on one sideQr both sides, or it cQntains the adhesive ill itself, like woven composite material impregnated with bonding agent. The adhesive,which can be pre-coatedonto>material or be deposited prior to bonding, enables layers of sheet material to be attached to each other so as to construct a three-dimensional object.
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