The Eleventh Solid Freeform Fabrication (SFF) Symposium, held at The University of
Texas in Austin on August 8-10, 2000, was attended by over 100 national and international
researchers. Papers addressed SFF issues in computer software, machine design, materials
synthesis and processing, and integrated manufacturing. New sessions on ceramic materials and
multiple materials SFF were added to this year’s program. 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
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 computer issues,
machine topics, and the variety of materials aspects of SFF. We believe that documenting the
changing state of SFF art as represented by these Proceedings will serve both the people presently
involved in this fruitful technical area as well as new researchers and users entering the field.
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 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 (N00014-00-1-0674) and the National Science Foundation (DMI-0003777) 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.
A machine vision system, based on CCD camera, is used to control the molten pool size during the gas tungsten arc welding (GTAW) process. The technique is tested by making a metallic part with a complex 3-D network of conformal channels on a hybrid rapid prototyping machine based on welding and milling. The test part demonstrated manufacturing flexibility and new technological opportunities required for prototyping injection mold tools. The real metallic part made in a layered fashion had good surface quality, dimensional accuracy, and high density.
Solid Freeform Fabrication to date has largely been applied in prototype fabrication or fabrication of patterns for conventional manufacturing methods. However, many opportunities exist for using SFF for manufacturing the actual product. In particular, those applications that require or can be enhanced by custom geometric design seem to be well suited for SFF techniques. In this paper we describe the design of a prosthesis socket for a below-the-knee amputee. This socket is specifically designed to provide compliance in selected areas to enhance the comfort of the wearer. Additionally, the socket contains an integrated pylon fitting that provides a structurally superior connection while also improving the comfort of the wearer. The socket was manufactured using selective laser sintering, mated to a pylon and foot, and fitted to the patient for gait analysis. The results of the analysis indicate an improved fit is possible with manufacture by SLS.
(2000) Jiang, T.; Lin, F.; Kaltman, Steven I.; Sun, W.
A CAD-based approach to generate three-dimensional anatomical modeling and its application in analysis and rapid prototyping for surgical reconstruction is presented. The process of modeling technique, starting from processing computed tomography segmentation profiles, reverse engineering to reconstruct 3D anatomical model, and rapid prototyping to fabricate physical models are described. Methods of applying the least-square fitting criteria to simplify CT or MRI anatomical data, to generate NURBS based curves, surfaces, and solids, and to develop a CAD-based anatomical modeling for femur are introduced.
Feasibility of using finite element method for femur structural analysis and using rapid prototyping to reproduce tactical medical model for surgical reconstruction is also discussed.
Solid Freeform Fabrication was recently used to identify the dismembered body of a woman found in rural Wisconsin. Skin from the face of the victim had been removed, making visual identification impossible. A model of the skull was constructed by Laminated Object Manufacturing (LOM), using data extracted from CT scans of the victim’s head. Forensic anthropologists performed a facial reconstruction directly on the LOM model, which was then photographed and distributed. The computer model was further manipulated and served as supplemental data to investigators preparing the reconstruction. An identification from one of the distributed photographs led to the arrest of a suspect and a subsequent conviction. This is the first example that we are aware of where SFF has been used in an active criminal case, and the successful results show a promising future for SFF as a forensic tool.
An experimental study of the deformation phenomena during laser bending of 0.5 mm metal sheets is presented here. The thermal gradient mechanism, i.e. ratio of the laser beam diameter to the sheet thickness less than unity, was used to bend the samples. The sheets, which are made of 304 stainless steel, 1100 aluminum and 1010 carbon steel, were scanned with a
focused CO2 laser beam for several times. Optical power of the laser ranged from 64 to 95 W and its maximum traverse speed was 15 mm/s. Results are presented as plots of the bending angle vs. number of scans (i.e. 2θ-N curves). Understanding of this novel forming process is crucial in order to find applications for it in the rapid prototyping field.
(2000) Hui, Du Zhao; Kai, Chua Chee; Sen, Chua Yew; Gek, Loh-Lee Keow; Tiak, Lim Ser
A closed loop process is proposed for making sheet metal prototyping parts by using advanced computer aided techniques and computer controlled machines. The key aspect of this process is the method used to fabricate and modify the sheet metal
forming tools, which are not necessarily for mass production but should be suitable for short run production or design evaluation of sheet metal products where the prototyping cost and lead-time are greatly reduced. Various approaches are investigated in the preparation of the tooling for onward embossing on a sheet metal. The three indirect approaches use Selective Laser
Sintering (SLS), Stereolithography(SLA), and high speed Computer Numerical Controlled (CNC) milling to build the masters from computer data models. And the masters are then served in the vacuum casting process to generate the non-ferrous
tooling. The direct approach uses DTM’s RapidSteel to produce the metal tooling without going through any secondary process. Comparisons on quality, leading time and cost are presented.
Rapid freeze prototyping (RFP) is a solid freeform fabrication process that builds an ice part by rapidly freezing water in a layer by layer manner. One advantage of this process is the ability to build ice parts faster than other SFF processes. The factors that affect the speed of contour building and interior filling in RFP are identified. The influence of these factors is
analyzed through heat transfer and material flow analyses. A model based on heat transfer analysis is proposed to determine the maximum achievable speed of contour building under stable conditions. Experiments are conducted to validate the performance of the proposed model for determination of building speed.
Lost-foam (also known as Expendable Pattern Casting, EPC) is an ever-growing metalmcasting technique, capable of producing complex metal components without parting lines. Mold preparation for lost-foam casting is typically accurate, but expensive and slow. The goal of this research was to develop a new approach for producing rapid lost-foam molds. With this new approach, patterns generated by SFF technology are used to form indirect composite lost-foam molds. Ultimately, our objective is to produce these molds quickly, accurately, and inexpensively. This new approach to lost-foam mold-making will be explained as well as the
results of one trial.
(2000) Fuhrman, Brian T.; Duty, Chad E.; Jean, Daniel L.; Lackey, W. Jack
Laser Chemical Vapor Deposition-Rapid Prototyping (LCVD-RP) is a relatively new manufacturing process. Its capabilities are ideally suited for the manufacturing of a type of electron emitter called an integrated-grid thermionic emitter. The integrated-grid thermionic emitter is composed of wagon wheel-like structures of alternating layers of boron nitride and molybdenum on tungsten. The goal of this paper is to determine the feasibility of using LCVDRP technology to manufacture advanced thermionic emitters.