2004 International Solid Freeform Fabrication Symposium

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Proceedings for the 2004 International Solid Freeform Fabrication Symposium. For more information about the symposium, please see the Solid Freeform Fabrication website.

The Fifteenth Solid Freeform Fabrication (SFF) Symposium, held at The University of Texas in Austin on August 2-4, 2004, was attended by over 120 national and international researchers from sixteen countries. Papers addressed SFF issues in computer software, machine design, materials synthesis and processing, and integrated manufacturing. The diverse domestic and foreign attendees included industrial users, SFF machine manufacturers, university researchers and representatives from the government. The Symposium organizers look forward to its being a continuing forum for technical exchange among the expanding body of researchers involved in SFF.

The Symposium was again organized in a manner to allow the multi-disciplinary nature of the SFF research to be presented coherently, with various sessions emphasizing process development, design tools, modeling and control, process parameter optimization, applications and materials. We believe that documenting the changing state of SFF art as represented by these Proceedings will serve both those presently involved in this fruitful technical area as well as new researchers and users entering the field.

This proceedings includes an edited transcript of a panel discussion held Tuesday afternoon at the meeting. Moderated by Harris Marcus of the University of Connecticut at Storrs, the panel topic was on the broader impacts of solid freeform fabrication. Panel members include David Alexander (Pratt and Whitney), Clinton Atwood (Sandia National Laboratory), Phill Dickens (Loughborough University, UK), and Kent Firestone (University of Texas at Austin).

This year’s best oral presentation was given by Jean-Pierre Kruth of the Katholieke Universiteit Leuven, Belgium. Selection is based on the overall quality of the paper, the presentation and discussion at the meeting, the significance of the work and the manuscript submitted to the proceedings. The paper title was, "Binding Mechanisms in Selective Laser Sintering and Selective Laser Melting". Selected from almost 70 oral presentations, his presentation appears on Page 44 of this Proceedings. The best poster presentation selected from 19 posters was given by Vito Gervasi of the Milwaukee School of Engineering. The paper title was, "Geometry and Procedure for Benchmarking SFF and Hybrid Fabrication Process Resolution" and appears on Page 493.

The editors would like to extend a warm “Thank You” to Rosalie Foster for her detailed handling of the logistics of the meeting and the Proceedings, as well as her excellent performance as registrar and problem solver during the meeting. We are grateful to Bryan Blackmur and Cindy Pflughoft who helped with Proceedings production. We would like to thank the Organizing Committee, the session chairs, the attendees for their enthusiastic contributions, and the speakers both for their significant contribution to the meeting and for the relatively prompt delivery of the manuscripts comprising this volume. We look forward to the continued close cooperation of the SFF community in organizing the Symposium. We also want to thank the Office of Naval Research (N00014-04-1- 0567) and the National Science Foundation (DMI 0412255) for supporting this meeting financially. The meeting was co-organized by the University of Connecticut at Storrs, and the Mechanical Engineering Department, Laboratory for Freeform Fabrication and the Texas Materials Institute at The University of Texas at Austin.

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    2004 International Solid Freeform Fabrication Symposium Table of Contents
    (2004) Laboratory for Freeform Fabrication and University of Texas at Austin
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    Design and Fabrication of Components with Optimized Lattice Microstructures
    (2004) Gervasi, Vito R.; Stahl, Douglas C.
    The design and fabrication of components with optimized lattice microstructures is a new approach to creating lightweight high-performance objects. This paper introduces a unique and complete integration of design and fabrication leading to the creation of structural components with complex composite microstructures. Rather than a solid cast component with optimized outer shape this new approach leads to a component with an inner skeleton or microstructure maximizing one or more properties such as the stiffness-to-weight ratio. Three dimensional gradient materials are a natural outcome of this approach. An introduction to the design optimization and hybrid fabrication approach will be provided in addition to research progress and challenges through Spring 2004.
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    Multi-Nozzle Biopolymer Deposition for Freeform Fabrication of Tissue Constructs
    (2004) Khalil, S.; Nam, J.; Darling, A.; Sun, W.
    Advanced freeform fabrication techniques have been recently used for the construction of tissue scaffolds because of the process repeatability and capability of high accuracy in fabrication resolution at the macro and micro scales. Among many applicable tissue scaffolding materials, polymeric materials have unique properties in terms of the biocompatibility and degradation, and have thus been widely utilized in tissue engineering applications. Hydrogels, such as alginate, has been one of the most important polymer scaffolding materials because of its biocompatibility and internal structure similarity to that of the extracellular matrix of many tissues, and its relatively moderate processing. Three-dimensional deposition has been an entreating freeform fabrication method of biopolymer and particularly hydrogel scaffolds because of its readiness to deposit fluids at ambient temperatures. This paper presents a recent development of biopolymer deposition based freeform fabrication for 3-diemnsinal tissue scaffolds. The system configuration of multi-nozzles used in the deposition of sodium alginate solutions and Poly-?- Caprolactone (PCL) are described. Studies on polymer deposition feasibility and structural formability are conducted, and the preliminary results are presented.
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    Solid Freeform Fabrication of Artificial Human Teeth
    (2004) Wang, Jiwen; Shaw, Leon L.; Xu, Anping; Cameron, Thomas B.
    In this paper, we describe a solid freeform fabrication procedure for human dental restoration via porcelain slurry micro-extrusion. Based on submicron-sized dental porcelain powder obtained via ball milling process, a porcelain slurry formulation has been developed. The formulation developed allows the porcelain slurry to show a pseudoplastic behavior and moderate viscosity, which permits the slurry to re-shape to form a near rectangular cross section. A well-controlled cross-section geometry of the extrudate is important for micro-extrusion to obtain uniform 2-D planes and for the addition of the sequential layers to form a 3-D object. Human teeth are restored by this method directly from CAD digital models. After sintering, shrinkage of the artificial teeth is uniform in all directions. Microstructure of the sintered teeth is identical to that made via traditional dental restoration processes.
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    Laser Densification of Extruded Dental Porcelain Bodies in Multi-Material Laser Densification (MMLD) Process
    (2004) Li, Xiaoxuan; Wang, Jiwen; Shaw, Leon L.; Cameron, Thomas B.
    In this study commercial dental porcelain powder was deposited via slurry extrusion and laser densified to fabricate dental restorations in a Multi-Material Laser Densification (MMLD) process. The processing conditions for laser densification of single lines and closed rings were investigated in order to avoid warping and cracking. Multi-layer rings were also investigated to study the dependence of bonding between layers on the laser densification conditions. The laser densified rings showed no warping, and good bonding between layers could be achieved when the laser densification condition was selected properly. The mechanism to achieve porcelain rings without warping and cracking is discussed. The understanding developed will pave the way for fabricating a physical dental restoration unit.
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    Design and Manufacture of an Attachment Fitting for Transtibial Prosthetic Sockets Using Selective Laser Sintering
    (2004) Burhan, Danny; Crawford, Richard
    The focus of this work is using selective laser sintering to manufacture transtibial prosthetics sockets with compliant features to relieve contact pressure in sensitive areas. Each of these sockets requires an integrated attachment fitting to connect to the pylon and foot using standard hardware. Several design concepts of an attachment fitting are presented and compared. The design concepts were tested using a tensile test machine and analyzed using ground reaction force data to ensure a structurally sound connection. The resulting design employs standard hardware while maintaining the integrity of the connection for a normal gait cycle.
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    Fabrication of Bone Substitute Material by Rapid Prototyping
    (2004) Ott, A.; Heinzl, J.; Janitza, D.; Pelzer, R.
    Bone tissue engineering has gained much attention in recent years. A key requirement in this field is the development of scaffold structures, on which cells adhere. This can be done by fabricating scaffolds by direct procedures like 3D-printing or by indirect procedures like casting. With the 3D-printing process different structures were build up by using hydroxyapatite powder (HA) and a special binder material. Afterwards the printed 3D structures were sintered. For the casting process molds have been made of different resins by stereolithography and other processes using polymers and waxes. These structures were filled by a suspension of HA. By heating the resulting polymer/ceramic composite to a specific temperature it is possible to combust the polymer or wax. By further heating the remaining body, the HA is sintered. Compared to the 3D printing a better resolution can be obtained here. But there are restrictions regarding the ratio of polymer and the HA ceramic during the heating process which means a limitation for the level of porosity.
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    Orthopedic Surgery Planning Based on the Integration of Reverse Engineering and Rapid Prototyping
    (2004-08-30) Ahn, Dong-Gyu; Lee, Jun-Young; Yang, Dong-Yol
    This paper describes orthopedic surgical planning based on the integration of RE and RP. Using symmetrical characteristics of the human body, CAD data of the original bone without damages for the injured extent are generated from a mirror transformation of undamaged bone data for the uninjured extent. The physical model before the injury is manufactured from RP apparatus. Surgical planning, such as the selection of the proper implant, pre-forming of the implant, decision of fixation positions and incision sizes, etc., is determined by a physical simulation using the physical model. In order to examine the applicability and efficiency of surgical planning technology for orthopedics, various case studies, such as a proximal tibia plateau fracture, a distal tibia comminuted fracture and an iliac wing fracture of pelvis, are carried out. As a result of the examination, it has been shown that the orthopedic surgical planning based on the integration of RE and RP is an efficient surgical tool.
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    Accurate Heart Model for Pacemaker Development in SFF
    (2004) Crockett, R. S.; Horvath, T.; Koch, M.; Yang, M.
    Medical imaging combined with SFF techniques were used to create detailed CAD and physical heart models for commercial development of Pacemakers. Using a data set of 2D optical slice images of the human heart at 1mm spacing obtained from the Visible Human Project, a 3D CAD model was constructed by masking the features of interest in each slice. Normals on the resulting .stl file were inverted to create a single-piece mold, which was built in starch using 3D Printing. Flexible silicone was cast into this mold, and the starch was dissolved away to produce the final physical heart model. The resulting model simulates the mechanical properties of an actual heart, with medically accurate internal and external details including major veins & arteries, coronary sinus, etc.
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    Multiple Material Micro-Fabrication: Extending Stereolithography to Tissue Engineering and Other Novel Applications
    (2004-08-04) Wicker, Ryan; Medina, Francisco; Elkins, Chris
    A design for modifying an existing 3D Systems stereolithography (SL) apparatus 250/50 was developed to accommodate multiple material fabrication for building multi-material, multifunctional and multi-colored prototypes, models and devices. The machine was configured for automated access to an intermediate washing, curing, and drying unit that eliminated contamination between material vats and maintained accurate platform registration throughout the build process. Three vats were arranged on a rotating vat carousel, and each vat was adapted to actively maintain a uniform, desired level of material by including a recoating device and a material fill and removal system. A single platform was attached to an elevator mechanism (zstage) to traverse the platform to and from the vats and the washing, curing, and drying unit. The platform was mounted to the z-stage via an automated rotary stage to rotate the platform about a horizontal axis, thus providing angled building, washing, curing, and drying capabilities. A horizontal traversing mechanism was also designed to be optionally included to facilitate manufacturing between multiple SL cabinets, related SL apparatuses and/or other alternative manufacturing technologies. For micro-fabrication, linear and rotary stages were selected that provided ±1.0 µm repeatability and 0.1 µm resolution and ±2 arc sec repeatability and 0.13 arc sec resolution, respectively. The multi-material SL design presented here is capable of utilizing existing SL resins for manufacturing multiple material mechanically and electrically functional models as well as hydrogels, biocompatible materials, and bioactive agents for a variety of biofunctional, implantable tissue engineering applications including nerve regeneration and guided angiogenesis.