Browsing by Subject "Solid Freeform Fabrication"
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Item 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.Item Calibrating Large-area Mask Projection Stereolithography for Its Accuracy and Resolution Improvements(University of Texas at Austin, 2009-09-15) Zhou, Chi; Chen, YongSolid freeform fabrication (SFF) processes based on mask image projection such as digital micro-mirror devices (DMD) have the potential to be fast and inexpensive. More and more research and commercial systems have been developed based on such digital devices. However, a digital light processing (DLP) projector based on DMD has limited resolution and certain image blurring. In order to use a DLP projector in the large-area mask projection stereolithography, it is critical to plan mask images in order to achieve high accuracy and resolution. Based on our previous work on optimized pixel blending, we present a calibration method for capturing the non-uniformity of a projection image by a low cost off-the-shelf DLP projector. Our method is based on two calibration systems, a geometric calibration system that can calibrate the position, shape, size, and orientation of a pixel and an energy calibration system that can calibrate the light intensity of a pixel. Based on both results, the light intensity at various grayscale levels can be approximated for each pixel. Developing a library of such approximation functions is critical for the optimized pixel blending to generate a better mask image plan. Experimental results verify our calibration results.Item 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.Item Design and Freeform Fabrication of Deployable Structures with Lattice Skins(2006) Maheshwaraa, Uma; Tradd, Catherine; Bourell, David; Seepersad, Carolyn ConnerFrontier environments—such as battlefields, hostile territories, remote locations, or outer space—drive the need for lightweight, deployable structures that can be stored in a compact configuration and deployed quickly and easily in the field. We introduce the concept of lattice skins to enable the design, solid freeform fabrication (SFF), and deployment of customizable structures with nearly arbitrary surface profile and lightweight multi-functionality. Using Duraform FLEX® material in a selective laser sintering machine, large deployable structures are fabricated in a nominal build chamber by either virtually collapsing them into a condensed form or decomposing them into smaller parts. Before fabrication, lattice sub-skins are added strategically beneath the surface of the part. The lattices provide elastic energy for folding and deploying the structure or constrain expansion upon application of internal air pressure. Nearly arbitrary surface profiles are achievable and internal space is preserved for subsequent usage. In this paper, we present the results of a set of experimental and computational models that are designed to provide proof of concept for lattice skins as a deployment mechanism in SFF and to demonstrate the effect of lattice structure on deployed shape.Item Direct 3D Layer Metal Deposition(2008-09-10) Ruan, Jianzhong; Tang, Lie; Sparks, Todd E.; Landers, Robert G.; Liou, FrankItem Fab@Home Model 3: A More Robust, Cost Effective and Accessible Open Hardware Fabrication Platform(University of Texas at Austin, 2011-08-17) Lipton, Jeffrey; MacCurdy, Robert; Boban, Matt; Chartrain, Nick; Withers III, Lawrence; Gangjee, Natasha; Nagai, Alex; Cohen, Jeremy; Sobhani, Karina; Liu, Jimmy; Qudsi, Hana; Kaufman, Jonathan; Mitra, Sima; Garcia, Aldo; McNioll, Anthony; Lipson, HodSolid Freeform Fabrication is transitioning from an industrial process and research endeavor towards a ubiquitous technology in the lives of every designer and innovator. In order to speed this transition Fab@Home Model 3 was created with the goal of expanding the user base of SFF technology by lowering the skill and price barriers to entry while enabling technology developers to leverage their core competencies more efficiently. The result is a device, which is modular with respect to tool heads, fabrication processes, and electronics controls, costs under $1000, and requires only a simple tool set to assemble.Item Form Accuracy Analysis of Cylindrical Parts Produced by Rapid Prototyping(2007) Tagore, G.R.N.; Anjikar, Swapnil D.; Gopal, A. VenuSolid Freeform fabrication processes are being considered for creating fit and assembly nature functional parts. It is extremely important that these parts are within allowable dimensional and geometric tolerance. The part accuracy produced by rapid prototyping process is greatly affected by the relative orientation of build and face normal directions. A systematic method is needed to find the reliability of the created product. This paper discusses the work done in this area and the effect of build orientation on the part form accuracy analysis of each specified tolerance like circularity and cylindricity. Feasible build direction that can be used to satisfy those tolerances is identified. It will help process engineer in selecting a build direction that can satisfy a mathematical model of form tolerance.Item Freeform Fabrication of Ionomeric Polymer-Metal Composite Actuators(2005-08-03) Malone, Evan; Lipson, HodIonomeric polymer-metal composite (IPMC) actuators are a type of soft electromechanically active material which offers large displacement, rapid motion with only ~1V stimulus. IPMC’s are entering commercial applications in toys (Ashley 2003) and biomedical devices (Soltanpour 2001; Shahinpoor 2002; Shahinpoor, Shahinpoor et al. 2003; Soltanpour and Shahinpoor 2003; Soltanpour and Shahinpoor 2004), but unfortunately they can only actuate by bending, limiting their utility. Freeform fabrication offers a possible means of producing IPMC with novel geometry and/or tightly integrated with mechanisms which can yield linear or more complex motion. We have developed materials and processes which allow us to freeform fabricate complete IPMC actuators and their fabrication substrate which will allow integration within other freeform fabricated devices. We have produced simple IPMC’s using our multiple material freeform fabrication system, and have demonstrated operation in air for more than 40 minutes and 256 bidirectional actuation cycles. The output stress scaled to input power is two orders of magnitude inferior to that of the best reported performance for devices produced in the traditional manner, but only slightly inferior to devices produced in a more similar manner. Possible explanations and paths to improvement are presented. Freeform fabrication of complete electroactive polymer actuators in unusual geometries, with tailored actuation behavior, and integrated with other freeform fabricated active components, will enable advances in biomedical device engineering, biologically inspired robotics, and other fields. This work constitutes the first demonstration of complete, functional, IPMC actuators produced entirely by freeform fabrication.Item Hydrocolloid Printing: A Novel Platform for Customized Food Production(University of Texas at Austin, 2009-09-18) Cohen, Daniel L.; Lipton, Jeffrey I.; Cutler, Meredith; Coulter, Deborah; Vesco, Anthony; Lipson, HodSolid Freeform Fabrication (SFF) of food has the potential to drastically impact both culinary professionals and laypeople; the technology will fundamentally change the ways we produce and experience food. Several imposing barriers to food-SFF have been overcome by recent open-source printing projects. Now, materials issues present the greatest challenge. While the culinary field of molecular gastronomy can solve many of these challenges, careful attention must be given to contain materials-set bloat. Using a novel combination of hydrocolloids (xanthium gum and gelatin) and flavor agents, texture and flavor can be independently tuned to produce printing materials that simulate a broad range of foods, with only a minimal number of materials. In addition to extensively exploring future applications of food-SFF, we also present a rigorous proof-of-concept investigation of hydrocolloids for food-SFF. A two-dimensional mouthfeel rating system was created (stiffness vs. granularity) and various hydrocolloid mixtures were characterized via an expert panel of taste testers.Item Improved Quality of 3D-Printed Tissue Constructs Through Enhanced Mixing of Alginate Hydrogels(University of Texas at Austin, 2008-09-10) Cohen, Daniel L.; Tsavaris, Andrew M.; Lo, Winifred M.; Bonassar, Lawrence J.; Lipson, HodWhile alginate hydrogel is a desirable material platform for Solid Freeform Fabrication (SFF) of cell-seeded tissue engineering scaffolds, achieving consistently high-quality results can be challenging. Local variations in the material properties cause inconsistent material deposition behavior and consequently decrease the resultant geometric fidelity of the construct. The effects of gel mixing on material property consistency, geometric fidelity, and cell viability were characterized in an attempt to improve the formulation’s compatibility with SFF processing. Material homogeneity was quantified through a novel experimental setup composed of an EnduraTEC mechanical test-frame and custom syringe-extrusion jig. Cell viability and geometric fidelity were assessed using standard protocol. The baseline mechanical stiffness of the printed samples was 16±3 kPa (n=6). We found that increasing mixing reduced material inconsistency and improved geometric fidelity, without adversely affecting cell viability: the printed construct quality was drastically improved by increasing mixing well beyond previously established limits.Item Laser Aided Direct Rapid Prototyping(1997) Franceschini, Robert; Napravnik, Lee; Mukherjee, Amar; Sankaranarayanan, Srikanth; Kar, AravindaWe describe a multilevel design hierarchy applicable to the VLSI-like layered manufacturing technology of Solid Freeform Fabrication (SFF) called Laser Aided Direct Rapid Prototyping (LADRP). We discuss the interfaces between the abstraction levels and the requirements of the standard languages needed for the interfaces. We provide experimental verification for the thickness design rule and indicate other possible design rules applicable to this process. We then present a software tool called a Slicer that takes a three-dimensional description of a solid body and creates 2.5D layers for the SFF process. Our current implementation is based on a boundary representation of solids described by the Unigrafix solid modeler.Item Maximizing the Strength of Fused-Deposition ABS Plastic Parts(1999) Rodriguez, J. F.; Thomas, J.P.; Renaud, J. E.Fused-Deposition (FD) creates parts using robotic extrusion of set.D.i-liquid .polymer fiber, which molecularly bonds with neighboring fibers via thermal-dlffuslo.n bonding. T~e strength ofthe. part depends on the bulk polymer strength, themesostructure ~flber layout, vOid geom~try, extent of fiber bonding), and thefiber-t~-fiber ~ond strength. The ~nfluence of these factors on the mechanical strength of FD-ABS.plasttc parts IS reported.along with the.FD process variable settingsfor maximum strength. Substantial increases in transverse strength are achieved at the optirnal settings and additional increases can be achieved by post..fabrication annealing. Keywords: Stratasys, fused-deposition, ABSplastic, functional parts, strength, mesostructure, polymer diffusion.Item Mechanism for Determination of G-factors for Solid Freeform Fabrication Techniques Based on Large Heat Input(2005) Dwivedi, Rajeev; Zekovic, Srdja; Kovacevic, RadovanA major class of Solid Freeform Fabrication (SFF) methods for metal deposition are based on large heat input. The geometry and microstructural properties of the deposition depend primarily on the heat input and the subsequent distribution at the substrate. On one hand the insufficient heat may lead to the inadequate melting of the metal, on the other hand overheating and heat accumulation leads to the overmelting, resulting in the deformation of the build up geometry. The heat distribution is governed by the available heat sink . For a better control of the process, the estimation of heat sinks and the subsequent control of the energy input allows a better control of the process. A parameter G-factor that estimates the heat sink based on the local geometry of a part has been introduced. The estimation of G-factor is based on the simulation and the experimental results. Also a mechanism to determine the G-factor for various substrate geometries has been introduced.Item A Model for Error Propagation in the Surface Profile for Solid Freeform Fabrication(2005-08-26) Dwivedi, Rajeev; Zekovic, Srdja; Kovacevic, RadovanItem Morphing Based Approach for Process Planning for Fabrication of Geometries and the Control of Material Composition(2004-08-04) Dwivedi, Rajeev; Kovacevic, RadovanThe inherent limitation of most of the solid freeform fabrication is the deposition in form of layers. Artificial imposition of the process for the desired geometric morphology and the functional gradience of material limits the accuracy of the workpiece. Mathematical morphing of geometry and the material gradience allows a smooth variation across the part geometry and the material composition of the part. The paper describes a framework for process planning and implementation of fabrication of geometries and control of the material composition. Simulation results for the suggested approach are described in the paper.Item Multi-Material Food Printing with Complex Internal Structure Suitable for Conventional Post-Processing(University of Texas at Austin, 2010-09-23) Lipton, Jeffrey; Arnold, Dave; Nigl, Franz; Lopez, Nastassia; Cohen, Dan; Norén, Nils; Lipson, HodSolid Freeform Fabrication (SFF) of food provides an exciting application for additive manufacturing technologies. A variety of materials has been used to demonstrate food printing. However, these materials were not suited for traditional food processing techniques (Baking, slow cooking, frying, etc) and thus eliminating the majority of today‟s consumed food. We demonstrated new materials suitable for baking, broiling and frying. Turkey, scallop, celery were processed and modified using transglutaminase to enable them to be slow cooked or deep-fried after printing. Mutli-material constructs of turkey meat and celery were successfully printed. A cookie recipe was modified to be printable while retaining shape during baking. By adding cocoa powder to the modified recipe a second, visually and differently tasting material was created. A complex shape of the cocoa modified material was printed within a block of the modified material. The complex internal geometry printed was fully preserved during baking.Item Polymer Matrix Nanocomposites by Inkjet Printing(2005-08-03) McMorrow, Brain; Chartoff, Richard; Lucas, Pierre; Richardson, WadeThis paper describes work on a continuing project to form functional composites that contain ceramic nanoparticles using a Solid Freeform Fabrication (SFF) inkjet printing method. The process involves inkjet deposition of monomer/particle suspensions in layers followed by curing each layer in sequence using UV radiation. The reactive monomer is hexanediol-diacrylate (HDODA); the polymer forming reaction proceeds by a free radical mechanism. The liquid monomer containing nanoparticles is essentially a printing ink formulation. Successfully suspending the particles in the monomer is critical. We have developed a surface treatment method for forming stable suspensions of the nanoparticles so that they remain discrete throughout the processing sequence. The SFF process involves careful control of the polymer cure so that the interface between layers is seamless and residual stresses in the composites are eliminated. An immediate use for such composites is in optical applications as gradient refractive index lenses (GRIN). GRIN lenses have planar surfaces, eliminating the need for costly grinding and polishing. The planar surfaces also eliminate optical aberrations that result at the edges of spherical lenses and diminish the accuracy of focus. If the appropriate nanoparticles are fully dispersed they will modify the polymer's refractive index without interfering with light transmission. The effect is additive with volume concentration. Using 'inks' of different compositions in a multiple nozzle inkjet printer allows the formation of composites with precise composition gradients. Since an object is built one planar layer at a time, changes can be made readily both within each layer and from layer to layer. Inkjet printing with picoliter resolution is ideal for this task. Working with SiC nanoparticles in HDODA as a model system for demonstrating the inkjet deposition process, nanocomposite films with a linear concentration gradient varying from 0 to 4.5% (wt) were fabricated on Silicon wafers. These composites are 30 layer films, which total 140µm in thickness. Each layer in the composite is about 5 µm in thickness. Analytical methods for characterizing the dispersion of the nanoparticles in the composite and some of the salient optical properties of the composites also were established. The status of the program is reviewed in this paper.Item Rapid Freezing Prototyping with Water(1998) Zhang, Wei; Leu, Ming C.; Ji, Zhiming; Yan, YongnianRapid Freezing Prototyping (RFP) with water is a novel solid freeform fabrication technique that can generate three-dimensional ice objects by depositing and rapidly freezing water layer by layer. The support where necessary is made of brine whose. freezing point is lower than. pure water. After building the part, the support can be removed by utilizing the melting temperature difference between brine and water. Preliminary experiments have shown that the ice patterns produced by this technique can be used for design visualization and silicone molding. This paper will present the concept and some experimental results of the RFP process as well as potential applications.Item Software Testbed for Selective Laser Sintering(1991) Crawford, Richard H.; Beaman, J.J.; Das, SumanComputer software plays an important role in the implementation of Solid Freeform Fabrication (SFF) technologies. This paper describes a software testbed for processing part geometry for a particular SFF technology, selective laser sintering (SLS), that is built around the separation of the slicing and rasterization operations to accommodate geometric information from a variety of sources. The paper also discusses the process control software being developed for a new high-temperat rkstation for SLS of metal powders. This program features a high-resolution data rmat, the ability to interpolate to achieve a desired resolution, and a menu-driven user interface with graphical feedback and process simulation capabilities.Item Solid Freeform Fabrication An Advanced Manufacturing Approach(1990) Bourell, D.L.; Beaman, J.J.; Marcus, H.L.; Barlow, J.W.; Bourell, D.L.; Beaman, J.J.; Marcus, H.L.; Barlow, J.W.