1997 International Solid Freeform Fabrication Symposium

Permanent URI for this collectionhttps://hdl.handle.net/2152/69898

Proceedings for the 1997 International Solid Freeform Fabrication Symposium. For more information about the symposium, please see the Solid Freeform Fabrication website.

The Eighth Solid Freeform Fabrication (SFF) Symposium, held at The University of Texas in Austin on August 11-13, 1997, was attended by 200 national and international researchers. Papers addressed SFF issues in computer software, machine design, materials synthesis and processing, and integrated manufacturing. The continued growth in the research, application and development of SFF approaches was readily apparent from the increased participation over previous years and the diverse domestic and foreign attendees from industrial users, SFF machine manufacturers, universities, and government. The excitement generated at the Symposium reflects the participants' total involvement in SFF and the future technical health of this growing technology. 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 computer issues, machine topics, and the variety of materials aspects of SFF. We believe that documenting the constantly 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 the large flux of new researchers and users entering the field.

The editors would like to extend a warm "Thank You" to Glorya Gutchess 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 also acknowledge the support efforts of Cindy Pflughoft throughout. We would like to thank the organizing committee, the session chairmen, 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 ONR through Grant No. NOOOI4-97-1-0453, DARPA, and The Minerals, Metals and Materials Society and the University of Connecticut at Storrs for co-sponsoring the Symposium with the Mechanical Engineering Department, Laboratory for Freeform Fabrication and the Center for Materials Science and Engineering at the University of Texas at Austin.

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1997 International Solid Freeform Fabrication Symposium Table of Contents
(1997) Laboratory for Freeform Fabrication and University of Texas at Austin
An Analysis Technique for Layered Manufacturing Based on Quasi-Wavelet Transforms
(1997) Lee, Cheol H.; Thomas, Charles L.
An analysis technique based on the Wavelet transform (WT) has been recently introduced that allows the spatial frequency content of objects produced by layered manufacturing (LM) techniques to be interpreted in terms ofmanufacturable features. (Lee and Thomas, 1997) Using Haar's wavelet as a basis function, layers with vertical edges are modeled exactly. Using analysis, a 3D model can be transformed, filtered, and inverse transformed resulting in an image ofthe part as it would look if constructed from layers of a specific thickness. In order to extend this analysis to construction techniques using higher order edges (ruled surface edges or curved edges), the quasi-wavelet transform (QWT) is introduced. QWT analysis is conceptually the same as WT analysis, except that the basis function can be selected by the user, allowing exact analysis of layered manufacturing techniques using higher order construction algorithms. This work is supported by a grant from the University ofUtah Research Foundation.
Automated Fabrication of Monolithic and Ceramic Matrix Composites via Laminated Object Manufacturing (LaM)
(1997) Klosterman, Don; Chartoff, Richard; Osborne, Nora; Graves, George
This report summarizes recent developments in a research program for fabricating advanced monolithic and ceramic matrix composite parts using Laminated Object Manufacturing (LOM). Both silicon carbide (SiC) and SiC/SiC composites are discussed. The LOM process is used to produce green forms that are then densified using various post processing operations. The monolithic ceramic LOM process was advanced through the implementation of an automated solvent spray bonding step, significant improvement in decubing with new software, and an intensive round ofmechanical characterization. The LOM process for making CMC green forms is fully developed. This entailed implementing a process for making suitable SiC fiber preforms, a laser cutting capability, a decubing strategy, and a binder resin cure procedure. Further research is ongoing for the post processing pyrolysis and reaction bonding steps as discussed herein.
Bonding Methods for Laminated Tooling
(1997) Walczyk, Daniel F.; Dolar, Nathanael Y.
Laminated tooling consists of an array of stacked laminations that are mechanically clamped or bonded together, depending on the requirements of the manufacturing process. Various manufacturing processes that can benefit from tooling constructed oflaminations include sheet metal forming, thermoforming, composites molding, metal extrusion, injection molding, resin transfer molding, and compression molding. When bonding of the laminations is required (e.g., incorporation of conformal cooling passages for injection molding temperature control) then laminations can be joined together by diffusion bonding, brazing and using adhesives. However, for a tooling engineer to effectively design a laminated tool, the physical and mechanical properties of these joints must be known. Consequently, a set of experiments is outlined for determining the tensile, shear, and peel strengths, tensile and shear elastic moduli, thermal contact resistance, and specific permeability (for gasses or liquids) ofthe aforementioned bonded joints for both steel and aluminum laminations. Some preliminary results with aluminum and future work are presented.
Build Style Decision Support for Stereolithography
(1997) McClurkin, Joel E.; Rosen, David W.
When building parts in a stereolithography apparatus (SLA), the user is faced with many decisions regarding how the part will be built. The quality of the build can be controlled by the user via changing one of several build style variables, including part orientation, cross sectional layer thickness, and laser hatch density. A user will probably have preferences for the part build (Le., accuracy or speed), but may not understand how to vary the build style variables to produce the desired results. A method based on response surface methodology and multi-objective decision support is described in this paper for relating build goals to three build style variables, and the use ofthese relationships in providing decision support for building a part on a SLA. The method is applied to the build style of a circuit breaker handle.
CAD and Control Technologies for Computer-Aided Manufacturing of Laminated Engineering Materials
(1997) Choi, Sangeun; Hebbar, Ravi; Zheng, Yong; Newman, Wyatt S.
This paper presents recent progress in software, material handling and tangent-cutting control in support of Computer-Aided Manufacturing of Laminated Engineering Materials(CAM-LEM). Progress in CAD focuses on the definition of a new layered file format for describing 3-D solids in terms of thick slabs with ruled-surface edges. For material handling, we present new algorithms for automatic generation of mask hole patterns used in selective-area vacuum gripping, which is required for our laminated assembly process. Finally, we present recent results of object fabrication using thick-slab, tangent-cut layers
CAM-LEM Processing: Materials Flexibility
(1997) Liu, z. E.; Ko, T. C.; Bes, J.; Cawley, J. D.; Heuer, A. H.
The cut-then-stack paradigm of computer-aided manufacturing of laminated engineering materials (CAM-LEM) offers choice of feedstock material, ease of handling finely divided (and therefore sinterable) powders, and the ability to mix materials. This combination of features was exploited to process fluidic devices. CAM-LEM processing was used to render the Part in aluminum oxide, silicon nitride, and stainless steel.
The Clemson Intelligent Design Environment For Stereolithography-Cides 2.0
(1997) Kirschman, Jill S.; Kirschman, Charles F.; Fadel, Georges M.; Greenstein, Joel S.
There are a large number of commercial Rapid Prototyping (RP) devices available today. All ofthese machines begin with a Computer-Aided Design (CAD) model, which is tessellated, sliced and then built layer-by-Iayer on the RP device. All ofthese operations, except the actual building ofthe part, are completed on a computer. Therefore, many improvements to the RP processes can be achieved through software, without affecting the RP devices or the warranties on them. This has led to the development of a front-end software product to support the task of preparing the part to be built. The Clemson Intelligent Design Environment for Stereolithography (CIDES) is a user-centered interface between the CAD system and RP systems, primarily the Stereolithography Apparatus (SLA). CIDES 2.0 is designed to provide a variety oftools which are valuable to the users ofRP systems, including the ability to view and modify tessellated (STL) files, generate supports, and slice STL files into layer (SLI) files for use on an SLA. It also provides the ability to view SLI and merged (V) files. Furthermore, CIDES offers additional translation capabilities that make it valuable for other RP processes. The package has proven useful in the Laboratory to Advance Industrial Prototyping (LAIP) at Clemson University. CIDES 2.0 is a new X Windows-based release based on the original version ofCIDES with many additional features. A new HumanComputer Interface is the major improvement to this release.
A data format providing side wall orientation and adaptive slicing for use in stepless rapid prototyping
(1997) Fang, Wei; Siang Ngooi, Chan; Gong, Haiqing
Current Rapid Prototyping systems mainly use 2D layers building techniques that result in the 'staircase' effect on slanted surface. A new method has been developed to eliminate the 'staircase' effect and to improve the surface quality by extending the 2D layers to 3D layers building. In this approach, a new data format, Layer Transfer Interface (LTI), is introduced to generate layers having slanted side wall. It provides a faster slicing algorithm and accurate reconstruction of 3D objects. This format is independent of any particular RP machines. Furthermore, adaptive slicing has been achieved using this format and implemented on a fiveaxis milling RP system.
Deflection and the Prevention of Ingress within Laminated Tooling for Pressure Die-Casting
(1997) Soar, R.C.; Dickens, P.M.
Wrthin the context ofrapid tooling, we are currently assessing the fundamental limitations oflaminated tooling for pressure die-casting (PDC) applications. The use ofindividual laminates to form a die-cast tool presents it own problems, namely the prevention of excessive deflection that may lead to the ingress of pressurised molten aluminium between laminates. Ultimate solutions lie with bonding and clamping techniques of which work is already underway. This paper describes an initial study to establish the fundamental laminated die behaviour in extreme die-casting environments.
The Design and Construction of a Medical System to Optimize the Endoscopic Ultrasound Procedure
(1997) Daruwala, Darius P.; Johnson, Christopher M.; Jacobsen, Donald R.
This project involved the use ofrapid prototyping to produce a model of a section ofthe gastrointestinal (GI) tract which could be used for practice ofthe Endoscopic Ultrasound (EUS) procedure. Computed Tomography (CT) scans were obtained from Dr. Donald Jacobsen, Assistant Professor ofRadiology at the Medical College ofWisconsin in Milwaukee. Apart from the final testing, the entire project was performed at the Milwaukee School ofEngineering's Rapid Prototyping Center. To convert the CT scans into files that are compatible with the rapid prototyping machines, a software developed by Materialise, N.V., was used. The rapid prototype models were used as master patterns for molds so that a polyurethane material with similar properties to human tissue could be used for actual simulation. Finally, these polyurethane models were placed in an enclosure and surrounded by a gelatin to simulate fatty abdominal tissue. The system was tested at Froedtert Memorial Lutheran Hospital under the supervision of Dr. Anthony Bohorfoush in conjunction with the Medical Physics Department ofthe Medical College ofWisconsin.
Direct Selective Laser Sintering and Containerless Hot Isostatic Pressing for High Performance Metal Components
(1997) Das, Suman; Wohlert, Martin; Beaman, Joseph J.; Bourell, David L.
A novel net shape manufacturing method known as SLSIHIP that combines the strengths ofselective laser sintering (SLS) and hot isostatic pressing (HIP) is presented. Direct selective laser sintering is a rapid manufacturing technique that can produce high density metal components of complex geometry with an integral, gas impermeable skin. These components can then be directly post-processed to full density by containerless HIP. The advantages of in-situ HIP encapsulation include elimination of a secondary container material and associated container-powder interaction, reduced pre-processing time, a short HIP cycle and reduction in post-processing steps compared to HIP of canned parts. Results of research conducted on Inconel 625 superalloy, Ti-6AI-4V and Monel are presented. This research is funded by DARPAlONR contract N00014-95-C0139 titled "Low Cost Metal Processing Using SLSIHIP".
Direct SLS of powder compositions used for self-propagating high-temperature synthesis
(1997) Shishkovsky, IV.; Makarenko, A.G.; Petrov, A.L
The conditions of a direct selective laser sintering (SLS) were resea;rched experimental in a volume and by layers for the eutectic and near-eutectic powder compositions, which usually used for the self-propagating high-temperature synthesis (SHS) technology. It was shown a possibility to realise during SLS process a control exothermic reaction of combustion exactly in the focus ofew-Iaser beam on Nd-YAG. The necessary parameters of a laser influence (a power, scan velocity and diameter'of the laser beam), a dispersion and composition of the powder mixtures were determined for the such regime. The 3D parts from intermetallic compounds were created without any post-process procedures, that expands the functional opportunities ofthe sintering models.
Direct-Write Fabrication of Integrated, Multilayer Ceramic Components
(1997) Dimos, D.; Yang, P.; Garino, TJ.; Raymond, M.V.; Rodriguez, M.A.
The need for advanced (electronic) ceramic components with smaller size, greater functionality, and enhanced reliability requires the ability to integrate electronic ceramics in complex 3-D architectures. For rapid prototyping and small-lot manufacturing, traditional tape casting and screen printing approaches are poorly suited. To address this need, we are developing a direct-write approach for fabricating highly integrated, multilayer components using a micropen to deposit slurries in precise patterns. With this technique, components can be constructed layer by layer, simplifying fabrication. It can also be used to produce structures combining several materials in a single layer. The parts are either cofired or sequentially fired, after each layer is deposited. Since differential shrinkage can lead to defects in these multilayer structures, we are characterizing the sintering behavior ofindividua1layers. This technique has been used to fabricate devices such integrated RC filters, multilayer voltage transformers, and other passive components. The direct-write approach provides the ability to fabricate multifunctional, multimaterial integrated ceramic components (MMICCs) in an agile and rapid way.
Effects of Processing Conditions on Prototypes Reinforced with TLCPs for Fused Deposition Modeling
(1997) Gray IV, R. W.; Baird, D. G.; Bohn, J. H.
Polypropylene (PP) composite strands, reinforced with thermotropic liquid crystalline polymers (TLCPs), were generated using a novel dual extrusion process which allowed for the use of a TLCP with a significantly higher melting temperature than that of the PP. Pregenerated TLCPtpp microcomposite strands were reprocessed using a second novel process to produce a wen-controned monofilament composite for use in a FDM 1600 rapid prototyping system in order to build complex geometries. Uniaxial parts were built to determine the effect of differing material compositions and processing temperatures, in order to develop an oPerating window for the optimal mechanical properties. By adjusting the lay down pattern of orientable materials, the final mechanical properties of the part could be engineered independent ofthe material. To understand the effect ofthe reprocessing steps on the pregenerated microcomposites, the final mechanical properties ofthe monofilament composite were compared with those ofthe pregenerated strands.
Empirical Similitude Method for the Functional Test with Rapid Prototypes
(1997) Cho, Uichung; Wood, Kristin
Rapid prototyping has the potential to improve the performance of the design process both in cycle time and resources. Such improvements may be realized through the timely visual, ergonomic, and functional information provided by solid freeform fabrication (SFF) parts. Of these information classes, functional information is perhaps the least realized with current technology. A number of technical issues have limited functional testing of SFF parts, including sensor fusion, range of prototyping materials, part size etc. Our focus here concerns the material issues of functional testing, especially the potential differences in prototyping material choices to actual production materials. For example, to derive accurate functional information of non-polymeric products from polymeric rapid prototypes, an improved similitude method that can overcome the distortion of material characteristics is necessary. In this paper, a new similitude method that utilizes specimen test data is introduced. This method develops a mathematical transformation between prototype and product behavior through specimen testing. This transformation replaces the role ofthe scale factor of the traditional similitude method, and provides a basis for relating prototypes to proposed production parts, even under dependent loading and material conditions. Computational and experimental results of a structural design provide verification ofthe new method.
Extrusion Freeform Fabrication of Bone-Like Mineralized Hydrogels and Muscle-like Actuators
(1997) Zengshe, Liu Paul, Calvert
Extrusion freeform fabrication has been used to build shapes from agarose, polyacrylamide and polyacrylic acid hydrogels. Contraction and bending can be induced by pH change or application ofa voltage between embedded electrodes. Mineral reinforcement can be induced by incorporating salts into the gels and allowing them to react.
Extrusion Freeforming of Nylon 6 Materials
(1997) Lombardi, John L.; Calvert, Paul D.
Numerous commercial rapid prototyping (RP) processes are capable offabricating complex shaped components. These processes build prototypes "from the ground up" by first reducing a CAD design ofthe desired prototype to a series ofgeometrical slices followed by the precise sequential deposition ofraw material layers upon one another. Unfortunately, these RP processes are limited to producing prototypes from polYmers that exhibit inferior mechanical properties compared to commercial engineering thermoplastics. Consequently, there are significant advantages in extending the materials processing capabilities ofRP technology into the realm ofproducing tough, high strength functional prototypes from engineering polYmers.
Fabrication of In-situ SiC/C Thermocouples by Selective Area Laser Deposition
(1997) Sun, Lianchao; Jakubenas, Kevin J.; Crocker, James E.; Harrison, Shay; Shaw, Leon L.; Marcus, Harris L.
With the intrinsic nature to process relatively small features, selective area laser deposition (SALD) is a potential technique to fabricate complex shaped macro-components with in-situ high-resolution micro-devices. In this study, SALD was used to deposit in-situ silicon carbide/carbon (SiC/C) thermocouples on alumina and silicon carbide substrates with a C02 laser. Tetramethylsilane (TMS) and acetylene (C2H2) were chosen as precursors for deposition of the silicon carbide and carbon lines respectively. The electromotive force (emf) ofthe deposited thermocouple was measured and found to respond sensitively to temperature variations from room temperature to 800°C. The effect ofthe deposition parameters on the product morphology was also investigated.
FDM of ABS Patterns for Investment Casting
(1997) Blake, Paul; Fodran, Eric; Koch, Martin; Menon, Unny; Priedeman, Bill; Sharp, Stephen
This paper will evaluate the suitability offused deposition modeling (FDM) of acrylonitrile butadiene styrene (ABS) patterns for use in investment casting. The focus is on integration with existing foundry practices. It is a combined industry/university project with the case studies performed at the industrial sites with university produced patterns. Process parameters, ash handling and casting issues are addressed.

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