Browsing by Subject "stereolithography"
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Item Accuracy of Stereolithography Parts: Mechanism and Modes of Distortion for a "Letter-H" Diagnostic Part(1995) Pang, Thomas H.; Guertin, Michelle D.; Nguyen, Hop D.Rapid Prototyping and Manufacturing (RP&M) users need to compare the accuracy of various commercially available RP&M materials and processes. A good diagnostic test for both material and the fabrication process involves a 4-inch long "letter-H" diagnostic part. This diagnostic part, known as "H-4", was developed to measure the inherent dimensional characteristics ofvarious RP&M build materials. It is also less dependent on the calibration status of particular RP&M machines, and is excellent for the purpose of generating simple but meaningful accuracy information, which can be used to further understand the mechanism and the modes of distortion in RP&M materials. H-4 parts were prepared and built in Stereolithography Apparatus (SLA) using Ciba-Geigy epoxy based resins SL 5170 and SL 5180, and results were compared to acrylate based SL 5149. Experimental data involving the magnitude, mechanism, and the modes of distortion for these three resins are analyzed in this paper.Item Accurate Rapid Prototyping(1991) Levi, HeimThe first stage of Rapid Prototyping life cycle as a new technology in the marketplace is gradually ending, and the second stage has already started. Many new vendors have introduced their products in this field, utilized different, new technologies or improvements of the existing ones. The first introduction of the RP concept and Stereolithography created a stunning impression in the marketplace. After a couple of years, as customers and users have gained much experience and understanding or RP technology, the first enthusiasm started making way to more serious and demanding approach. This is very well reflected in the thorough evaluations of the different technologies available today in the marketplace, done by customers looking for a technology that will best fit their needs. This is actually why most of us are here today.Item Application of Stereolithography in the Fabrication of Rehabilitation Aids(1995) Jayanthi, Suresh; Harwin, William; Keefe, Michael; Kumar, VijayFree form fabrication methods have a great potential to significantly improve the design and manufacture of equipment for people with physical disabilities, such as quadriplegia through spinal cord injury, arthrogryposis, or cerebral palsy. Depending on the nature of the disability a device may need to be designed or adapted. A person with quadriplegia, for example, may benefit from an assistive device that maps existing head movements, into the movements of a spoon between a plate and his/her mouth. To be comfortable and effective a person Iuay need a headband that can connect to a suitable linkage. Stereolithography lends itself well to the fabrication of such one-of-akind devices. Since the fabrication process time is considerably less than conventional approaches a greater number of iterations can be performed during the design to arrive at the most compatible device for a particular disability. Some rehabilitation devices are fabricated to establish the viability and linlitations of this approach. This paper details the efforts underway to integrate stereolithography with the needs of rehabilitation engineering.Item Composites with Gradient Properties From Solid Freeform Fabrication(1998) Gervasi, V.R.; Crockett, R.S.TetraCast is a build style developed by Milwaukee School ofEngineering involving stereolithography patterns produced with an open cellular structure inside a surface shell. Composites are created using this pattern as a host fora filler material, generally epoxy matrices loaded with various fibers or microspheres. Regions within a singleobjectrrray be separated by thin barriers, allowing filling with different matrix materials.to create regiollsof differing.local properties. The internal structure can also be continually graded in thickness to prodUl::e composites with properties ranging from that ofthe fillermaterial to that ofthe TetraCast material (currently stereolithography epoxy or FDM ABS)Item Controlling the Microstructure of Arc Sprayed Shells(1991) Fussell, P.S.; Kirchner, H.O.K; Prinz, F.B.; Weiss, L.E.Techniques for controlling the microstructure of sprayed steel structures are discussed in this paper. Steel is arc sprayed onto shaped substrates to form tooling. The quality of the tool is greatly influenced by the microstructure of the material and the interlamella regions of the deposit. This work is focused on characterizing the microstructure, improving the state of the inter-lamella regions, and discusses our success in forming pseudo-alloys and graded shells by mixing sprayed materials. Microstructure control has interesting implications for other research as well, such as the MASK & DEPOSITS approach of forming objects.Item Design Considerations for Mask Projection Microstereolithography Systems(University of Texas at Austin, 2013) Lambert, Phillip M.; Campaigne, Earl A. III; Williams, Christopher B.Mask projection microstereolithography (MPµSL) uses a dynamic mask and focusing optics to digitally pattern UV light and selectively cure entire layers of photopolymer resin. These systems have been shown to be capable of creating parts with features smaller than 10µm. In this paper, the authors analyze existing MPµSL systems using functional decomposition. Within the context of a morphological matrix, these systems’ design embodiment decisions are compared and the resulting performance tradeoffs are quantified. These embodiment decisions include the dynamic mask, UV light source, projection orientation, and supporting optics. The aim of this work is to provide a design guide for the realization of future MPµSL systems.Item Design of Stereolithography Trees for Use in the Investment Casting of Stereolithography Patterns(1996) McDowell, Christopher S.; Boomer, Mark C.Item Digital Light Processing (DLP): Anisotropic Tensile Considerations(University of Texas at Austin, 2017) Aznarte, E.; Ayranci, C.; Qureshi, A.J.Digital light processing (DLP) 3D printing is an additive manufacturing (AM) process used to produce layered parts via photopolymerization. Anisotropy is a common characteristic of parts produced by DLP. Furthermore, printing conditions affect widely the resulting mechanical properties. This paper shows the effect of three printing factors on the final mechanical properties of specimens manufactured using DLP 3D printing. A series of ISO compliant tensile test specimens were designed, printed and tested. The properties analyzed were the elastic modulus, ultimate tensile strength, ultimate strain and printing time. Preliminary findings on design guidelines for Vat Photopolymerization processes are presented in addition to the economic effect of the studied parameters in terms of the total printing time.Item Dimensional Issues in Stereolithography(1998) Winmill, David L.; Hoopes, Daniel M.; Jayanthi, Suresh S.New stereolithography photopolymers have recently been introduced that provide a wider range of functional properties similar to those of high-density polyethylene. One of the important criteria for these materials is the dimensional accuracy and stability in end-use applications as mold masters or the actual functional parts. This work investigates the dimensional stability of one of these new materials with varying amounts of exposure during build. The effect of aging on the part dimensions is reported. The result of environmental humidity extremes at ambient temperature on part dimensions is investigated and compared for parts made from two different families of stereolithography resins, namely DuPont Somos® 7100 and Somos® 8100.Item Direct Laser Sintering of Metals(1993) Carter, William T.; Jones, Marshall G.The use of a directed laser bealn source to selectively sinter multiple layers of binderless metal powder for the purposes of rapid prototyping is described. The work in this paper is restricted to -325 mesh iron powder, which was sintered using a C\V 50 W Nd:YAG laser to approximately 3.5% density. A subsequent post-treatlnent was perfornled to achieve a fully dense saulple. It is envisioned that such a system can be used to manufacture functional metallic prototypes directly from CAD without part-specific tooling.Item Dynamic Resolution Control in a Laser Projection Based Stereolithography System(University of Texas at Austin, 2015) Pan, Yayue; Dagli, ChintanIn a typical Additive Manufacturing system, it is critical to make a trade-off between the resolution and build area for applications in which varied dimensional sizes, feature sizes, and accuracies are desired. The lack of the capability in adjusting resolution dynamically during building processes limits the use of AM in fabricating complex structures with big layer areas and small features. In this paper, a novel AM system with dynamic resolution control by integrating a laser projection in vat photopolymerization process is presented. Theoretical models and parameter characterizations are presented for the developed AM system. Accordingly, the process planning and mask image planning approaches for fabricating models with varied dimensional sizes and feature sizes have been developed. Multiple test cases based on various types of structures have been performed.Item Effect of Process Parameters and Shot Peening on the Tensile Strength and Deflection of Polymer Parts Made Using Mask Image Projection Stereolithography (MIP-SLA)(University of Texas at Austin, 2017) Madireddy, G.; Montazeri, M.; Curtis, E.; Berger, J.; Underwood, N.; Khayari, Y.; Marth, B.; Smith, B.; Christy, S.; Krueger, K.; Sealy, M.P.; Rao, P.Mask Image Projection Stereolithography (MIP-SLA) is an additive manufacturing technique in which a liquid photopolymer resin is hardened from exposure to ultraviolet (UV) light. Shot peening is a surface treatment to improve the mechanical properties of components. The goal of this work was to quantify the effect of SLA print process parameters, namely layer height and UV exposure, and shot peening on the longitudinal tensile strength of ASTM D638 Type 5 test artifacts. Test parts were created using a central composite experimental plan on a B9 Creator desktop SLA machine. Deflection of the pseudo-Almen strips after shot peening was measured using a digital camera to identify desired peening condition. Post-shot peening tensile strength was measured for the ASTM D638 Type 5 parts. Shot peening generally decreased the strength of MIPSLA parts.Item Electronics Integration in Conformal Substrates Fabricated with Additive Layered Manufacturing(University of Texas at Austin, 2009-09) Castillo, Sylvia; Muse, Dan; Medina, Frank; MacDonald, Eric; Wicker, RyanA three-dimensional (3D) accelerometer sensor system with microprocessor control was fabricated using a previously developed integrated layered manufacturing system that combines conductive ink dispensing with stereolithography (SL). The electronics are integrated into a conformal substrate that is press-fit into a helmet for the purpose of detecting Traumatic Head Injury (THI) when an excessive acceleration to the head is measured. Applications include monitoring the health of soldiers or athletes. Traditional fabrication of electronics is implemented with a 2 dimensional printed circuit board (PCB), which are not well suited for rugged installations in curved locations such as the interior of a helmet. The advantage of layered manufacturing for the integration of electronics is the ability to fabricate in a conformal substrate - conforming to the curved, complex, and often flexible shapes dictated by the human body.Item An Experimental Study of the Parameters Affecting Curl in Parts Created Using Stereolithography(1993) Horton, Leslie; Gargiulo, EdwardItem Exploring Variability in Shape Memory Properties of Stereolithography Printed Parts(University of Texas at Austin, 2016) Choong, Y.Y.C.; Saeed, M.; Eng, H.; Su, P.-C.; Wei, J.Shape memory polymers (SMPs) are smart materials that can change shape and revert to their permanent shape upon external stimulus. Most fabrications of SMPs are based on conventional methods which limit design freedom, hence additive manufacturing presents an alternative to expanding more possibilities for applications. In this study, curing process parameters were optimized for printing of photopolymerized thermoset SMPs by the stereolithography process. Tert-butyl acrylate (tBA) and di (ethylene glycol) diacrylate (DEGDA) were copolymerized with variations in crosslinkers to create networks with well-separated transition temperatures (Tg) that varied in a range from 43.6 to 74.1°C. A fold-deployable shape memory test was performed and revealed that free-strain recovery and retention deteriorate with increasing Tg. Nevertheless, the SMPs can undergo at least 20 repeated fold-deploy cycles before failure. These results are intended to provide better understandings in processing SMPs via stereolithography, while exploring variability in Tg widens the range of possible applications.Item Fast Recoating Methods for the Projection-based Stereolithography Process in Micro- and Macro-Scales(University of Texas at Austin, 2012) Pan, Yayue; Chen, Yong; Zhou, ChiThe purpose of this paper is to present a recoating method for the development of a direct digital manufacturing (DDM) process that can be an order of magnitude faster than other currently available DDM processes. In the mask-image-projection-based Stereolithography (MIP-SL) process, projection light controlled by a Digital Micromirror Device (DMD) can quickly cure liquid photopolymer resin in a whole area; a fast recoating method is required for achieving truly high-speed fabrication. We investigate the bottom-up projection system in the MIP-SL process. For the macro-scale MIP-SL process, a two-way linear motion approach has been developed for the quick spreading of liquid resin into uniform thin layers. In comparison, a direct pull-up motion can be used in the micro-scale MIP-SL process. The system design and related settings for achieving a fabrication speed of a few seconds per layer are presented. Additionally, the hardware, software, and material setups for fabricating three-dimensional (3D) digital models are presented. Experimental studies using the developed testbed have been performed to verify the effectiveness and efficiency of the presented fast MIP-SL process.Item FFF at Ford Motor Company(1993) O'Reilly, Sean B.Ford's effort in Free Fonn Fabrication (FFF) began in 1987 with the fontation of an internal consortium, Calp)sed of a dozen different activities, whose purpose was to evaluate and apply, where possible, this errerging tecl:mology. Each of the consortium members agreed to contribute sare rroney and, rrore irrportantly, one or rrore people to work on this project. By the following year (1988) the first rrachine, an SLA-1, had been installed at the Alpha Msmufacturing Develq:ment Center and fomed the cornerstone of the FFF Lab.Item The Finishing of Stereolithography Models Using Resin Based Coatings(1995) Reeves, P.E.; Cobb, R.CThe use of StereoLithography (SL) can produce accurate prototype models with complex internal and external features. However, a major problem to commercial use is the poor surface finish caused mainly by 'stair stepping' which is inherent in layer manufacturing. Models are often finished by hand but this is labour intensive, highly selective and causes inaccuracies in the model geometry. A three-year research project has been undertaken to address these issues and to investigate a range of surface coatings and mechanical finishing processes applied to SL models. This paper describes some initial findings using resin coatings applied to both cured and uncured SL parts.Initial findings suggest that excess resin retained after part stripping can result in a lower surface roughness than parts thoroughly cleaned prior to post curing.Through the addition of photocurable and epoxy based resins to parts in both the un-cured, green and cured states, surface roughness has been seen to be reduced by up to 50% on complex parts.Item Free Form Fabrication of Metallic Components Using Laser Engineered Net Shaping (Lens)(1996) Griffith, M. L.; Keicher, D. M.; Atwood, C. L.; Romero, J. A.; Smugeresky, J. E.; Harwell, L. D.; Greene, D. L.Solid free form fabrication is one ofthe fastest growing automated manufacturing technologies that has significantly impacted the length oftime between initial concept and actual part fabrication1 2. Starting with CAD renditions of new components, several techniques such as stereolithography3 and selective laser sintering4 are being used to fabricate highly accurate complex three-dimensional concept models using polymeric materials. Coupled with investment casting techniques, sacrificial polymeric objects are used to minimize costs and time to fabricate tooling used to make complex metal castings5 • This paper will describe recent developments in a new technology, known as LENSTM (Laser Engineered Net Shaping)6 7 8 9, to fabricate metal components directly from CAD solid models and thus further reduce the lead times for metal part fabrication. In a manner analogous to stereolithography or selective sintering, the LENSTM process builds metal parts line by line and layer by layer. Metal particles are injected into a laser beam, where they are melted and deposited onto a substrate as a miniature weld pool. The trace ofthe laser beam on the substrate is driven by the definition ofCAD models until the desired net-shaped densified metal component is produced.Item Full-Densification of SLS Parts by Re-Melting(2004-08-04) Niino, T.; Yamada, H.Among commercially available rapid prototyping processes, SLS is the most effective in terms of adaptability of various materials. However, rapid prototyped parts by the process are always porous and the physical properties of the parts are different from dense parts which is to be used in final product. This paper introduces a post process that can densify SLS processed plastic parts to almost 100%. An SLS processed polystyrene part is densified and, resultantly, a much stronger and transparent part is obtained.