1992 International Solid Freeform Fabrication Symposium

Permanent URI for this collectionhttps://hdl.handle.net/2152/64274

Proceedings for the 1992 International Solid Freeform Fabrication Symposium. For more information about the symposium, please see the Solid Freeform Fabrication website.

This Proceedings of the Third Solid Freeform Fabrication Symposium, held at The University of Texas in Austin on August 3-5, 1992, again 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 that uses SFF, SFF machine manufacturers, universities, and government gives 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. To avoid parallel sessions a poster session was organized. The initial session emphasized the computer interfacing required for SFF. This was followed by a session associated with materials related research on SFF. Two sessions were offered describing the latest techniques and modifications of SFF. These sessions were highlighted by a spirited panel discussion led by Robert L. Brown, Emanuel Sachs, and Joel Barlow, on "where is SFF going?" The final session concentrated on machine issues in SFF. The written versions of the presented papers are incorporated into these Proceedings. The editors would like to thank the speakers for their prompt delivery of the manuscripts that allows the timely 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 Carolyn Medina 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 and DARPA for co-sponsoring the Symposium and DTM Corporation for hosting the reception.

Organizing committee: Dick Aubin, United Technologies; Joel 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, DARPA; 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; Peter R. Sferro, Ford Motor Company; Ralph Wachter, Office of Naval Research; Michael Wozny, Rennselaer Polytechnic Institute


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    1992 International Solid Freeform Fabrication Symposium Table of Contents
    (1992) Laboratory for Freeform Fabrication and University of Texas at Austin
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    Machine Issues Associated with Solid Freeform Fabrication
    (1992) Beaman, Joseph J.
    Before we begin a discussion of machine issues it is important that we categorize exactly what we mean. There are differences between the design of a research piece of equipment as compared to a commercial piece of equipment. A research piece of equipment has to have the flexibility to demonstrate a success pattern. A commercial piece of equipment, on the other hand, assumes that you have a stable platform and you are now trying to assess how broad a success path you have (Figure 1). In fact, you are trying to make that path as broad as possible so that the machine will not fail and will always work the same way. This particular talk, and my expertise, is much more along the lines of design of a research piece of equipment. What I will be talking about today are machine issues associated with developing a success path in Solid Freeform Fabrication. The machines we will be talking about have to have the flexibility to operate in a wide variety of ways with a wide variety of experiments.
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    Rapid Prototyping Using FDM: A Fast, Precise, Safe Technology
    (1992) Walters
    This paper outlines the use of FDM to speed product design and to streamline the manufacturing process. Time compression, the ability to quickly reduce the time it takes to get new products to market, has increased the pressure on all phases of the manufacturing process. Manufacturers must find and implement time saving systems without sacrificing quality.
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    Adaptive Laminated Machining for Prototyping of Dies and Molds
    (1992) Vouzelaud, F.A.; Bagchi, A.
    Adaptive laminated machining is the fusion of slicing a solid model into layers and producing parts by CNC milling machines. Unlike other solid freeform fabrication processes which create the part by addition of material, adaptive laminated machining can create solid parts by selectively removing in layers. The research issues and practical limitations on shape and manufacturability are thus different from other processes. However, the biggest advantage is the ability to obtain a solid metal part such as a die or a mold directly. In this paper, the concept of this technique, and initial results and parts produced in Clemson will be presented. In addition, future research needs and issues will be discussed.
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    Rapid Prototyping Using 3-D Welding
    (1992) Dickens, P.M; Pridham, M.S; Cobb, R.C.; Gibson, I.; Dixon, G.
    Rapid prototyping systems are based, almost exclusively on polymer, or paper materials. The dimensions of the parts produced are limited by the volume of the processing area within the machine, and parts tend to warp or distort due to shrinkage and lack of support. Also the mechanical properties of the part are restricted to those of the processable materials and thus, in many cases, required 'engineering properties' cannot be obtained
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    Manufacturing Mechatronics Using Thermal Spray Shape Deposition
    (1992) Beck, James E.; Prinz, Fritz B.; Siewiorek, Daniel P.; Weiss, Lee E.
    A new technology for manufacturing mechatronics is described. The technique is based on recursive masking and deposition of thermally sprayed materials. Using these methods, mechanical structures can be created that embed and interconnect electronic components. This results in highly integrated mechatronic devices. A simple, electromechanical artifact was designed and produced to assess the feasibility of these techniques. The details and limitations of this project will be discussed. Areas of future research are identified which are aimed at realizing the full potential of this emerging manufacturing process.
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    Stereophotolithography: A Brand New Machinery
    (1992) Allanic, A.L.; Medard, C.; Schaeffer, P.
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    Generating Topological Information from a "Bucket of Facets"
    (1992) Rock, Stephen J.; Wozny, Michael J.
    The STL de facto data exchange standard for Solid Freefonn F*brication represents CAD models as a collection of unordered triangular planar facels. No topological connectivity information is provided; hence the term "bucket of facet." Such topological information can, however, be quite useful for performing model validity checking and speeding subsequent processing operations such as model slicing. lfhis paper discusses model topology and how to derive it given a collection of unordered tri,ngular facets which represent a valid model.
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    Metal Parts Generation by Three Dimensional Printing
    (1992) Michaels, Steven; Sachs, Emanuel M.; Cima, Michael J.
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    Rapid Prototyping at Zero Gravity for In-Flight Repairs and Fabrication on Space Station Freedom
    (1992) Roberts, Floyd; Lomshek, David; Brower, William E.
    The ability to perform in-flight rapid prototyping would be of great benefit to NASA in two ways. First, repair parts could be fabricated from CAD designs beamed up from earth based laboratories which might allow a failed experiment to proceed. The mission specialists themselves, under the creative influence of space flight, might design a new part or tool and fabricate it on board in a matter of hours. Second, with metal casting and ceramic sintering facilities on board, rapid prototyping would allow manufacturing in space. This paper presents some test criteria for evaluating two of the rapid prototyping techniques, stereolithography and fused deposition, in microgravity conditions. Effects of the variation of head speed and strip width for the fused deposition process on the resulting mechanical properties are presented. The mechanical strength of the polyamide test bars increased with both increasing head speed and strip width. Increasing head speed would be desirable in microgravity applications.
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    Relating Operating Parameters between SLS Machines which have Different Scanner Geometries and Laser Spot Sizes
    (1992) Nelson, J.C.; Barlow, J.W.
    As the number of SLS machines in operation increases, the opportunities to share operating parameters with other SLS operators also increases. However, if the machines are not identical down to the spot size of the laser beam, the quality of parts made on each machine can be different. The most likely differences between two SLS machines are the laser spot size and the scanning radius of the optics. The total energy flux to the powder surface is a function of the spot size and the scan speed. The algorithms defined to correct for machine differences are verified both experimentally and numerically using a one-dimensional empirical SLS model.
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    Microstructural Elements of Components Derived from 3D Printing
    (1992) Cima, M.J.; Lauder, A.; Khanuja, S.; Sachs, E.
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    The Materials Advantage of the SLS Selective Laser Sintering Process
    (1992) Kimble, Luke L.
    The rapid prototyping market continues to progress in tenns of processes and materials used for the creation of conceptual and functional parts and prototype tooling. As this market continues to mature, the market leaders win be able to offer rapid prototyping processes and materials that provide parts which are accurate, have good surface finish, and provide properties which support fqnctional applications.. The materials used for these parts will be. polymers, metals, and ceramics. '. The strength oithe SLSTM Selective Laser Sintering Process is the. potential to use a wide variety of powdered materials for the creation of models, patterns, and some fonns of prototype tooling. ,This paper will cover the types of materials currently used in the SLS process and their inherent advantages.and discuss current research into the development of new materials.
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    Fundamentals of Stereolithography
    (1992) Jacobs, Paul F.
    It has only been a little over four years since the introduction of the first StereoLithography system, the SLA-1. From early 1988 until J.une 1992 over 300 SLA-1, SLA-250, SLA-190 and SLA-500 units have been sold by 3D Systems. These machines, currently operating in 20 countries on five continents, amount to about 90 percent of all the rapid prototyping systems now in use.
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    Laser Tracking Control Implementation for SFF Applications
    (1992) Wu, Ying-Jeng Engin; Beaman, Joseph J.
    From a three-dimensional computer graphic model, Solid Freeform Fabrication produces solid objects directly without special tooling and human handling. In order to increas process productivity and accuracy, a time-efficient laser tracking control technique is needed. Based on the minimum time optimal control solution, the desired laser scanning control system is designed and implemented. To obtain uniform solidification during timeefficient tracking which has variable speed, laser power intensity is also controlled in real time by an acousto-optic modulator.
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    A Case Study in Rapid Prototyping
    (1992) Aubin, Richard F.
    Since the first quarter of 1988, Pratt & Whitney (P&W), a Division of United Technologies Corporation (UTC), has been involved in the development for the use of rapid prototyping technologies that use a "layer-by-Iayer" building approach. Based on over 4 1/2 years experience with Stereolithography, this paper will address three aspects of our experience including: Implementation, Current Operations, and Future Plans
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    Preliminary Experience with Selective Laser Sintigrapbic (SLS) Models of the Human Temporal Bone
    (1992) Levy, Richard A.; Guduri, Sashidhar; Crawford, Richard H.
    To assess the accuracy of three-dimensional models of the human temporal bone generated from computed tomographic (CT) data.
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    Application of Factorial Design in Selective Laser Sintering
    (1992) Deng, Xioaming; Beaman, Joseph J.
    Selective Laser Sintering (SLS) is a complex process involving many process parameters. These parameters are not all independent. A factorial design technique is utilized to study the effects of three main process parameters, laser power, laser beam scanning speed, and powder packing density as well as their interactions on the sintering depth and fractional density. The results of this investigation provide useful information for the further experimental analysis of the process parameters and for selecting suitable parameters for SLS process.
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    Development of a Selective Laser Reaction Sintering Workstation
    (1992) Birmingham, B.R.; Tompkins, J.V.; Zong, G.; Marcus, H.L.
    The purpose of this paper is to describe the design and operation of a Selective Laser Reaction Sintering workstation developed at The University of Texas. The workstation allows the study of solid freeform fabrication of reaction sintered materials on a research scale. The mechanical and control systems of the workstation are detailed, and Selective Laser Reaction Sintering as a technique is discussed including example material systems that are currently under study.