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.

Browse

Now showing 1 - 20 of 85

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.
SLS Processing of Functionally Gradient Materials
(1997) Jepson, L.; Beaman, J. J.; Bourell, D. L.; Wood, K. L.
A developing SLS process, known as Multiple Material Selective Laser Sintering, will allow the material composition of a component to be varied in a controlled manner. This process could allow the fabrication of functionally gradient materials (FGMs) in which a blended interface exists. Two potential applications of FGMs are the reduction of thermal stresses in metal/ceramic joints and the matching of material properties to functional requirements. A tungsten carbide/cobalt system has been examined in which the ceramic/metal ratio has been varied in an attempt to control the hardness/fracture resistance _ratio. An FGM powder bed was manually fabricated using a discrete banding technique. Results of traditional SLS processing of this powder bed are presented.
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".
Layered Micro-Wall Structures from the Gas Phase
(1997) Messia, David; Pegna, Joseph; Lee, Woo Ho
The use of3-D LCVD with volumetric rate feedback was investigated in the fabrication ofmicromechanical wall structures. These were constructed by recursive laser scanning and resulted in layered wall composed ofrecursive line deposition. Experiments were designed to uncover the relationship between scan rate, volumetric deposition rate, pressure and laser powerfor pyrolytic graphite from an ethylene precursor. Results point to a conduction dominated heat transfer which greatly limits the volumetric deposition rate at the wall. This also results in a highly unstable deposition process, since volumetric deposition increases by orders ofmagnitude as soon as rod growth is initiated. An unexpected results ofthis work is the ability to grow rods at an angle to the laser axis, with good control ofthe linear growth rate. This is achieved by adaptive laser scanning during rod growth.
The Role of Materials Processing Variables in the FDC Process
(1997) Rangarajan, Sriram; Qi, Gang; Banyopadhyay, Amit; Dai, Cheng; W. Han, Joon; Bhargava, Parag; Wu, Suxing; Safar, Ahmad; Danforth, Stephen. C.
The Fused Deposition of Ceramics (FDC) is based on the commercially available Fused Deposition Modeling (IDMTM) technique developed by Stratasys Inc. The FDC process is being currently developed to make complex ceramic parts in an automated fashion. Although the current focus is on making SisN4 parts, this technique has been successfully used to make electroceramic (such as PZT) and metallic (such as stainless steel) parts. As feedstock for the IDC process, filaments loaded with 55 vol% GS-44 Si3N4 is being used. For the filament to be used in the IDC process, it must possess a unique combination of physical, rheological and mechanical properties. In this paper, we investigate the role played by some of the process variables on these properties. Our current processing sequence to make filaments is as follows - coating of powders with a surfactant, compounding the ceramic and binder, extrusion into filaments and finally treatment of filaments to achieve requisite properties. The study has resulted in improvements to the quality of the filament which can be used for automated FDC. The effect of moisture, agglomerates and filament aging on FDC will be discussed.
Low-cost Machine Vision Monitoring of the SLS Process
(1997) Gibson, Ian; Ming, Ling Wai
During the building of a part using SLS, it is common practice to adjust the temperature parameters. It is important to control these parameters because ifthey are too high then part breakout is difficult. Ifthey are too low then parts have poor material properties. One method of controlling these parameters is by observation through the process chamber window. Any adjustment can be determined by examining the colour ofthe cross-section in process. By using a machine vision system to determine colour variation, it is possible to calculate temperature or laser power adjustments necessary to maintain consistent part quality.
Measurement of Residual Stresses in Parts Created by Shape Deposition Manufacturing
(1997) Klingbeil, N.W.; Zinn, J.W.; Beuth, J.L.
Residual stress build-up is a concern in any solid freeform fabrication process involving successive deposition of uncured or molten material, due to differential contractions caused by solidification or curing. The most detrimental effect of residual stresses is typically part warping, which can lead to unacceptable losses in part tolerance. In many processes residual stress build-up is a fundamental barrier to the consistent manufacture of high-quality artifacts. In this paper, two methods of measuring residual stresses in parts created by Shape Deposition Manufacturing (SDM) with microcasting are described. First, a technique for measuring warping in deposited plateshaped specimens is detailed, which can be used to determine residual stress resultants as well as to quantify gross effects of processing changes on residual stress magnitudes. Next, x-ray diffraction procedures are described by which residual stresses in deposited layers can be measured at discrete in-plane locations as a function of depth. Measured results for 308L stainless steel deposits determined from each method are interpreted in the context of residual stress modeling results obtained numerically in a separate research effort. The measured results provide insight into the effects on residual stress of both the material deposition path and the discrete droplet-bydroplet nature of the microcasting deposition process. The insights provided here may also be applicable to other processes involving successive material deposition.
Properties of Near-Net Shape Metallic Components Made by the Directed Light Fabrication Process
(1997) Lewis, Gary K.; Milewski, John O.; Thoma, DanB.; Nemec, RonB.
Rheology and Solid Freeform Fabrication: Modeling Material Flow in Deposition Techniques
(1997) Crocket, R.S.; Calvert, P.D.
Rapid Tooling by Powder Casting Transferred from RIP Model -Manufacturing Conditions Pursuing Zero Shrinkage
(1997) NOGUCHI, Hiroyuki; NAKAGAWA, Takeo
High accuracy is being sought in the rapid manufacturing of long life metal dies and molds by transferring from layer laminated models. Powder casting serves as a promising rapid tooling method as it enables high density filling and thus controls dimensional shrinkage to a considerable extent during sintering and infutrating This study aims to study the relation between the tooling conditions and dimensional changes of powder casting and fmd the conditions at which dimensional changes are minimum. In the experiments performed, a golf ball model was chosen as an exampIe of a small mold and results show that dimensional changes can be controlled to below 0.1%, which will facilitate practical application. By subjecting the cast powder to vibrations after adding the binder to achieve higher density, and adding fme copper powder to a mixture of two different size stainless steel powders for dimensional adjustments, almost zero shrinkage control in rapid tool making was realized.
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.
Shrinkage, Weight Loss and Crack Prevention During Binder Burn Out of Components Produced" by Fused Deposition of Ceramics (FDC)
(1997) Bhargava, P.; Bandyopadhyay, A.; Rangarajan, S.; Qi, G.; Dai, C.; Wu, S.; Danforth, S.; Safari, A.
In the present study the sequential stages ofthe previously established binder bum out (BBO) route were characterized by obtaining precise shrinkage and weight loss measurements from interrupted runs. A DoE (Design of Experiments) approach was adopted to systematically investigate the effect of process variables; such as the heating rates during critical segments, part dimensions and environment (flowing nitrogen vs vacuum) on the shrinkage, weight loss and cracking during binder bum out. A stepwise TGA was performed to study the effect of ramp rate and dwell time on the kinetics of binder bum out, and an experiment was conducted to determine optimum wicking conditions. The results from this study have been used to maximize the weight loss and minimize the cracking during binder bum out cycle for FDC parts with different sizes.
Rapid Fabrication of Disposable Fixtures for Correct Assembly of Split Build Rapid Prototyped Parts
(1997) Kadakia, Samit R.; Novac, Andrei S.; Roosendaal, Mark D. Van; Thomas, Charles L.; Smith, Norman T.; Balogh, Matthew
The size of part that can be produced in a single build on any ofthe commercially available Rapid Prototyping systems is limited by the size ofthe particular machine's build envelope. Parts which exceed the dimensions ofthe build envelope are split into sections that fit the machine's envelope and these sections are fabricated separately. Assembly ofthe sections into an accurate three dimensional object often requires the creation of a fixture. This fixture ensures correct positional and angular orientation ofthe sections during assembly. This paper discusses the fabrication ofsuch fixtures using Shapemaker II, a Solid Freeform Fabrication process developed at the University ofUtah. Using Shapemaker II, large fixtures (4 ft. by 8 ft. or even larger) can be created in just a few hours. While the fixture is reusable, given the low cost ofthe fixture, it can be considered a throwaway item.
SL 5410: High Humidity, Water, and Heat Resistant Resin for Stereolithography
(1997) Pang, Thomas; Figueroa, Israel; Fong, John; Melisaris, Anastasios; Wang, Renyi; Hanna, Stephen; Nguyen, Hop; Guertin, Michelle; Phan, Cathy
A new Stereolithography (SL) resin, CibaTool® SL 5410, which imparts good humidity and heat resistance, was released in July, 1997. This epoxy based resin for SLA-500 was developed mainly to eliminate the relatively weak resistance to high humidity and high heat that the first generation ofresins suffered from. Namely, with this new resin, strength ofQuickCast part and solid parts can now be maintained under high relative humidity. Even when immersed into water, part strength of SL 5410 is essentially preserved. Thermomechanical properties have also improved significantly relative to those of SL 5180. Heat deflection temperature and Tg values increased by +15°C to +40°C, to as high as 88°C and 105°C, respectively, for SL 5410, when parts were additionally thermally postcured. Improvements in mechanical properties are also included in this paper. These property enhancements were achieved while further improving part accuracy, vertical surface finish, and productivity. Productivity may increase by as much as 2.5-fold over SL 5180. Also, SL 5410 requires no predip delay, hence cutting the overhead time. These newly achieved resin characteristics for SL 5410 are expected to improve the ease-of-use in today's applications, and open new fields of applications in the near future.
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.
Net shape Functional Parts Using Diode Laser
(1997) Manzur, Tariq; Roychoudhuri, Chandra; Dua, Puneit; Hossain, Fahmida; Marcus, Harris
Manufacturing processes, such as cutting, drilling, soldering, marking, forming 3Dsintered parts from metal powders and laser vapor deposition, are now well established practices using matured high power lasers like Nd:YAG, C02 and Excimer lasers(l). These lasers are bulky, inefficient and expensive. Semiconductor diode lasers, if wavelength is not a disadvantage, hold the potential of creating a major cost/convenience breakthrough in these and other new manufacturing processes such as growing integrated opto-electronics devices etc. They have the potential to initiate a mini industrial revolution because they are compact, have high wall-plug efficiency (50%) and above all, they can be mass produced (like computer chips). It is important to note that almost all laser material processing can be carried out ifthe intensity available can cover the range from 103 to 107 W/cm2 . Fortunately, microscopic as they may be, even low power diode lasers emit reliably at 106 W/cm2 . The hurdle that needs to be solved is coupling energy from a large number of diodes to obtain high total power without losing much oftheir inherent brightness and yet keep the system cost low. Price of high power laser diodes have already come down dramatically over the last five years; further reduction is expected as the volume market keeps increasing rapidly. Current commercial devices are mostly oftwo types: (1) fiber coupled arrays and (2) two-dimensional stacked arrays. We are using both types. We believe, the ultimate high brightness and high total power at low cost will be achieved by 2D array ofbroad area surface emitting lasers. We will present the results of our various activities using 30W (980 nm, spot size - 600 ~m), 10 W (860 nm, spot size - 50 ~m) and 60 W (810 nm, spot size - 700 ~m) fiber-coupled cw diode laser and 50 W (930 nm spot size -700 ~m) free space diode lasers on: (1) fabricating 3D SLS parts directly from metal/ceramic powders using CAD/CAM design, (2) laser assisted selective area vapor phase deposition of amorphous SiC and ShN4-rod, (3) Pb and Ag soldering ofsimple electronic parts, (4) surface hardening ofstainless steel ribbon. INTRODUCT
Layered Manufacturing Material Issues for SDM of Polymers and Ceramics
(1997) Kietzman, J. W.; Cooper, A. G.; Weiss, L. E.; Schultz, L.; Lombardi, J. L.; Prinz, F. B.
Shape Deposition Manufacturing (SDM) is a solid freeform fabrication process which enables the manufacture of structural parts from engineering materials. This paper discusses the requirements and constraints for SDM part and sacrificial support materials, including chemical and physical compatibility, mutual adhesion, low shrinkage, machinability, and support material removability. Polymers and ceramics processed by SDM include polyurethanes, epoxies, polyurethane foams, photocurable acrylics, and green alumina ceramics. SDM compatible support materials include waxes, water-soluble polyacrylate soldermasks, and water-soluble thermoplastics. This paper details the selection of SDM part and support material combinations for the fabrication of polymer prototypes and polymer molds for ceramic prototyPes.
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.
Validation of Rapid Prototyping Material for Rapid Experimental Stress Analysis
(1997) Schley, C.; Smith, G.F.
The paper will detail the validation work carried out on various Rapid Prototyping (RP) materials to determine their suitability for the application of Thermoelastic Stress Analysis. The overall objective is to drastically reduce the product design cycle, by providing "real experimental data" for correlation with Finite Element Analysis (FEA), prior to any expensive manufacturing process. In order to achieve this the homogeneity of the Rapid Prototyping material has to be established to ensure a valid transfer of results from model to actual part.
Rapid Prototyping of Functional Metal and Ceramic Components By The Multiphase Jet Solidification (MJS) Process
(1997) Kupp, Donald; Eifert, Harald; Greul, Matthias; Kunstner, Matthias
The need to generate high-quality conceptual models ofmanufacturing components and limited application functional components has driven the development ofRapid Prototyping (RP) in the last fifteen years. Recently, however, it has become increasingly obvious that an RP system that can produce fully functional components in materials other than polymers would be beneficial. In order to fulfill the requirements for the direct production ofmetallic and ceramic components for functional testing and application, the development ofnew processes and materials are key development areas at the Fraunhofer Institute for Applied Materials Research (IFAM) and the Fraunhofer Resource Center-Delaware (FRC-DE). For the free-form fabrication of ceramic and metal parts, the Multiphase Jet Solidification (MJS) process has been developed for producing metal and ceramic components. The MJS process extrudes metal and ceramic based binder systems (such as A120 3, SiC, stainless steel, and Ti), forming the desired component layer by layer. As in powder injection molding, after a part is formed by MJS, the binder phase is removed chemically or thermally and the remaining powder compact is sintered to final density. This paper presents the MJS technique and outlines a variety ofpotential applications.

Browse

Browsing 1997 International Solid Freeform Fabrication Symposium by Issue Date