2013 International Solid Freeform Fabrication Symposium

Permanent URI for this collectionhttps://hdl.handle.net/2152/88473

Proceedings for the 2013 International Solid Freeform Fabrication Symposium. For more information about the symposium, please see the Solid Freeform Fabrication website.

The Twenty-Fourth Annual International Solid Freeform Fabrication (SFF) Symposium – An Additive Manufacturing Conference, held at The University of Texas in Austin on August 12-14, 2013, was attended by 219 researchers from 12 countries. The meeting consisted of plenary and parallel technical sessions. Three special topics were organized into single plenary sessions: “Cyber- enabled Manufacturing Systems for AM”, “Qualification, Verification and Certification” and “Micro- and Nano-AM”.

This year’s best oral presentation was entitled, “Lattice Boltzmann Simulations of Multiple Droplet Interactions during Impingement on the Substrate”, authored by Wenchao Zhou, Drew Loney, Andrei G. Fedorov, F. Levent Degertekin and David W. Rosen from the Georgia Institute of Technology. Selection is based on the overall quality of the paper, the presentation and discussion at the meeting, the significance of the work and the manuscript submitted to the proceedings. Selected from 102 oral presentations, the associated manuscript appears on Page 606. The best poster presentation selected from 16 posters was given by Monica Cadena, Alejandro Hinojos, Sara M. Gaytan, David Bentley, Francisco Medina and Ryan Wicker from The University of Texas at El Paso. Titled, “Characterization of 17-4 PH SS Fabricated by Powder Bed Fusion”.

The recipient of the International Outstanding Young Researcher in Freeform and Additive Manufacturing Award was Dr. April Cooke, presently employed by Paramount Industries, a 3D Systems Corporation Company. Dr. David Rosen won the International Freeform and Additive Manufacturing Excellence (FAME) Award. He is a professor at Georgia Institute of Technology.

The editors would like to extend a warm “Thank You” to Rosalie Foster for her detailed handling of the logistics of the meeting, as well as her excellent performance as registrar and problem solver during the meeting. We are grateful to Mr. Lars Jacquemetton for handling the logistics of proceedings manuscript review as well as most other aspects of the proceedings undertaking. We would like to thank the Organizing Committee, the session chairs, the attendees for their enthusiastic participation, 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 additive manufacturing community in organizing the Symposium. We also want to thank the Office of Naval Research (N00014-13-1-0420) and the National Science Foundation (CMMI-1331096) for supporting this meeting financially. The meeting was co-organized by The University of Connecticut at Storrs, and the Mechanical Engineering Department and the Lab for Freeform Fabrication under the aegis of the Advanced Manufacturing Center at The University of Texas at Austin.


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    2013 International Solid Freeform Fabrication Symposium Table of Contents
    (2013) Laboratory for Freeform Fabrication and University of Texas at Austin
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    Ranking Model for 3D Printing
    (University of Texas at Austin, 2013) Perez, Mireya A.; Ramos, Jorge; Espalin, David; Hossain, Mohammad S.; Wicker, Ryan B.
    The capabilities of desktop additive manufacturing (AM) machines were evaluated based on the ability to produce a standard component. This work also developed a model/method for evaluating and ranking AM technologies based on select criteria that can facilitate purchasing decisions. A standard part was adapted and printed on each machine, and evaluated in various ways to provide machine-specific input data for the model. The research highlights the differences between AM units and suggests a method by which to evaluate the differences. With the rapid proliferation of desktop additive manufacturing units, a quantitative ranking system was developed to rate these units so that the consumer, for example, can use this model to assist with decision making during purchase. Although the focus of the work was on desktop systems, the approach can be applied across other AM technologies.
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    Design and Assessment of an AM Vending Machine for Student Use
    (University of Texas at Austin, 2013) Meisel, Nicholas A.; Williams, Christopher B.
    Due to prohibitive costs, access to Additive Manufacturing (AM) technologies at academic institutions tends to be limited to upper-level courses that feature significant project-based coursework, such as capstone design. However, with the decreasing cost of desktop-scale AM technology, there is potential to improve student access to such technologies throughout a student’s undergraduate career, and thus provide more opportunities for AM education. In this poster, the authors present the design and implementation of an AM “vending machine” that is powered by desktop-scale extrusion-based AM systems. The resulting machine allows for unrestricted student use of AM equipment, and thus provides ample opportunity for informal learning regarding AM. The results of a formal assessment of student use of the machine are presented.
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    Potentials of Additive Manufacturing to Prevent Product Piracy
    (University of Texas at Austin, 2013-08-16) Jahnke, U.; Lindemann, C.; Moi, M.; Koch, R.
    Infringements of intellectual and industrial properties rights in terms of imitations of products are continuously increasing. Massive economic and reputational damages are consequences for concerned companies. One solution to this problem can be the use of Additive Manufacturing (AM) technologies. This production technology enables complex designed products and specific product properties due to the use of different manufacturing processes and materials, which can help preventing product piracy safety measures of products can highly benefit from these capabilities, which have not been possible yet. The layer wise process allows, for example, to implement identifiable marks under the parts surface and to adjust mechanical properties in a certain way. The use of AM can strongly reduce the economic efficiency of plagiarism. This paper will present approaches to product piracy prevention by the use of AM focusing on the tagging of products, preventive measures as well as the interplay of these types.
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    Selective Laser Sintering of Negative Stiffness Mesostructures for Recoverable, Nearly-Ideal Shock Isolation
    (University of Texas at Austin, 2013) Klatt, Timothy; Haberman, Michael; Conner Seepersad, Carolyn
    Honeycomb materials are well known for providing lightweight stiffness, strength, and energy absorption capabilities. For most honeycomb materials, energy absorption occurs when individual cells collapse progressively. Although it is possible for honeycombs with very low relative density to collapse via elastic buckling, honeycombs with typical relative densities collapse due to plastic yielding and buckling of the cell walls, such that the energy absorption is nonrecoverable. In this paper, mono-stable negative stiffness unit cells are investigated for constructing honeycomb mesostructures with high levels of recoverable energy absorption. Negative stiffness is achieved by incorporating curved beams into each unit cell. When subject to transverse loading, the curved beams exhibit negative stiffness behavior as they transition from one curved geometry to another in a snap-through type of motion that absorbs energy elastically at a relatively constant plateau stress. The plateau stress at which this energy absorption occurs can be tailored via the geometry of the unit cell. Preliminary experiments indicate that the structures can absorb significant amounts of energy by requiring nearly-constant-force to increase deformation as the structure transitions between snap-through configurations. Unlike traditional honeycombs, the negative stiffness mesostructures are self-resettable and therefore reusable. Using SLS as a means of fabrication, they can also be customized for specific shock events and even functionally graded to offer shock isolation for transient loads of various amplitudes.
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    Impact and Influence Factors of Additive Manufacturing on Product Lifecycle Costs
    (University of Texas at Austin, 2013-08-16) Lindemann, C.; Jahnke, U.; Moi, M.; Koch, R.
    At first sight the direct costs of Additive Manufacturing (AM) seem too high in comparison to traditional manufacturing. Considering the whole lifecycle costs of parts changes the point of view. Due to the modification of the new production process and new supply chains during a parts lifecycle, producing companies can strongly benefit from AM. Therefore, a costing model for assessing lifecycle costs with regard to specific applications and branches has been developed. The costing model represents the advantages of AM monetary. For the evaluation of this model and the influence factors, different case studies have been performed including different approaches in part redesign. Deeper research is and will be carried out with respect to the AM building rates and the comparability of various AM machines, as these facts are hardly comparable for end users. This paper will present the methodology as well as the results of the case studies conducted over the whole product lifecycle.
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    Multiple-Material Topology Optimization of Compliant Mechanisms Created via Polyjet 3D Printing
    (University of Texas at Austin, 2013) Meisel, Nicholas A.; Gaynor, Andrew; Williams, Christopher B.; Guest, James K.
    Compliant mechanisms are able to transfer motion, force, and energy using a monolithic structure without discrete hinge elements. The geometric design freedoms and multi-material capability offered by the PolyJet 3D printing process enables the fabrication of compliant mechanisms with optimized topology. The inclusion of multiple materials in the topology optimization process has the potential to eliminate the narrow, weak, hinge-like sections that are often present in single-material compliant mechanisms. In this paper, the authors propose a design and fabrication process for the realization of 3-phase, multiple-material compliant mechanisms. The process is tested on a 2D compliant force inverter. Experimental and theoretical performance of the resulting 3-phase inverter is compared against a standard 2-phase design.
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    Combining Additive Manufacturing and Direct Write for Integrated Electronics – A Review
    (University of Texas at Austin, 2013) Perez, K. Blake; Williams, Christopher B.
    Direct write (DW) of conductive materials in the context of Additive Manufacturing (AM) enables embedded electronics within fabricated parts. Previous works use manual, hybrid, and native material patterning systems to deposit conductive materials in parts fabricated by different AM technologies. This capability could eliminate cabled interconnects and redundant electronics packaging, resulting in a significant reduction of mass and assembly complexity. In this paper, the authors explore applications of DW of conductive traces in the context of AM, review prior work in the integration, and analyze the technical roadblocks facing their hybridization. Barriers to integrating the two technology classes include material, process, and post-process compatibilities.
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    3D Printing of Electro Mechanical Systems
    (University of Texas at Austin, 2013) Aguilera, Efrain; Ramos, Jorge; Espalin, David; Cedillos, Fernando; Muse, Dan; Wicker, Ryan; MacDonald, Eric
    Recent research has focused on the fabrication freedom of 3D printing to not only create conceptual models but final end-use products as well. By democratizing the manufacturing process, products will inevitably be fabricated locally and with unit-level customization. For 3D printed end-use products to be profoundly meaningful, the fabrication technologies will be required to enhance the structures with additional features such as electromechanical content. In the last decade, several research groups have reported embedding electronic components and electrical interconnect into 3D printed structures during process interruptions. However, to date there appears to be an absence of fabricated devices with electromechanical functionality in which moving parts with electronic control have been created within a single Additive Manufacturing (AM) build sequence. Moreover, previously reported 3D printed electronics were limited by the use of conductive inks, which serve as electrical interconnect and are commonly known for inadequate conductivity. This paper describes the fabrication of a high current (>1 amp) electromechanical device through a single hybrid AM build sequence using a uPrint Plus, a relatively low cost 3D. Additionally, a novel integrated process for embedding high performance conductors directly into the thermoplastic FDM substrate is demonstrated. By avoiding low conductivity inks, high power electromechanical applications are enabled such as 3D printed robotics, UAVs and biomedical devices.
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    Manufacture of Functionally Gradient Materials using Weld-Deposition
    (University of Texas at Austin, 2013) Suryakumar, S.; Somashekara, A.
    When the inherent inhomogeneity of Additive Manufacturing techniques is carefully exploited, the anisotropy transforms into the desired distribution of the properties paving the way for manufacture of Functionally Gradient Materials. The present work focuses on using weld-deposition based Additive Manufacturing techniques to realize the same. Mechanical properties like hardness and tensile strength can be controlled by a smaller degree through control of process parameters like current, layer thickness etc. A wider control of material properties can be obtained with the help of tandem weld-deposition setup like twin-wire. In tandem twin-wire weld-deposition, two filler wires (electrodes) are guided separately and it is possible to control each filler wire separately. The investigations done on these two approaches are presented in paper.
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    Design of Auxetic Sandwich Panels for Structural Applications
    (University of Texas at Austin, 2013) Yang, Li; Harrysson, Ola; Cormier, Denis; West, Harvey; Park, Chun; Peters, Kara
    Based on an analytical modeling analysis, a sandwich structure with a 3D re-entrant auxetic core was designed. Auxetic samples were produced by electron beam melting (EBM) and selective laser sintering (SLS), and compared to other regular cellular sandwich structures through various experiments. It was shown that sandwich structures with pre-designed auxetic cores could exhibit significantly improved mechanical properties such as bending compliance and energy absorption, which are critical to many structural applications. This work demonstrated an alternative of effectively designing 3D cellular structures, and also showed the potential of this type of auxetic structure in applications via careful design.
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    An Investigation of the Material Properties of Laser Sintered Parts Incorporating Conformal Lattice Structures (CLS™) Technology
    (University of Texas at Austin, 2013) Cooke, A.L.; Folgar, C.E.; Folgar, L.N.; Williams, J.; Park, S.; Rosen, D.W.
    Cellular materials, including foams, honeycombs, lattices, and similar constructions, offer the key advantages of high strength-to-weight ratios and favorable energy absorption characteristics. The concept of designed cellular materials enables customized material placement to best suit the demands of specific applications or achieve particular performance targets. The design, generation, and fabrication of conformal lattice structures via laser sintering are at the center of the disruptive manufacturing technologies proposed by 3D Systems Corporation. The primary work reported here is the maturation and mechanical testing of the conformal lattice structure technology developed between 3D Systems Corporation and the Georgia Institute of Technology.
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    Experimental Investigation of Different Cellular Lattice Structures Manufactured by Fused Deposition Modeling
    (University of Texas at Austin, 2013) Iyibilgin, Osman; Yigit, Cemil
    Experimental tests were conducted to evaluate the compressive properties (yield strength and compressive modulus) and build time for five different cellular lattice structures fabricated by the Fused Deposition Modeling (FDM) process. The lattice structures had repeating unit cells, and the shapes of the unit cell under study included honeycomb, square, diamond, triangle, and circle. Test specimens were manufactured by a Stratasys Fortus 400mc machine using ABS (Acrylonitrile Butadiene Styrene) as the part material. The five different lattice structures were compared with each other and also with the sparse and sparse-double dense build styles that are directly available from the Fortus machine. Honeycomb structure was found to have the best compression properties for the same porosity, although the differences among the different lattice structures were small (<7%). All of these lattice structures were found to have much higher strength than the specimens with the same porosity built using the sparse and sparse-double dense styles. However, the various lattice structures required significantly longer build times than the sparse and sparse-double dense builds. For the honeycomb structure, our investigation also included the effects of porosity and cell size. Higher porosity led to lower compression strength but shorted build time. For the same porosity, the yield strength could be increased and the build time shortened simultaneously by having a certain cell size.
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    Utilizing Additive Manufacturing Techniques to Fabricate Weight Optimized Components Designed using Structural Optimization Methods
    (University of Texas at Austin, 2013) Smith, C.J.; Todd, I.; Gilbert, M.
    This paper describes a preliminary study of the application of structural optimization techniques to the design of additively manufactured components, using load testing to failure to establish true load carrying capacity. The cantilever component specimens fabricated were designed to resist a tip load and comprised one conventional benchmark design and two designs developed using layout optimization (LO) techniques. The designs were fabricated from Titanium Ti-6Al-4V and then scanned for internal defects using X-Ray Computed Tomography (XCT). All three specimens failed below the design load during testing. Several issues were identified in both the design optimization and fabrication phases of the work, contributing to the premature failure of the specimens. Various recommendations to improve the optimization phase are presented in the paper.
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    Controlled Multi-Scale Turbulence through the Use of Laser Sintered Sierpinski Pyramids
    (University of Texas at Austin, 2013) Liu, Y.; Beck, S.; Nicolleau, F.; Majewski, C.E.
    The research presented here is the result of a new collaboration between the Centre for Advanced Additive Manufacturing (AdAM) and the Thermofluids group at The University of Sheffield, regarding the use of fractal geometries for the control and influence of fluid flow. It is believed that the use of multiscale objects can be used to introduce many different orders of turbulence into a flow. However, whilst substantial simulations have been carried out in this area, the complexity of the physical geometries means that to date these have not been validated via physical testing. In this work, varying orders of Sierpinski pyramids were produced using Laser Sintered PA2200 and analysed in a wind tunnel with regards to their effects on air flow through the structures. As predicted by theoretical analyses, the coarsest pyramids induced large vortices into the air-stream, whereas the more complex orders induced vortices at a number of different scales, rapidly developing into a standard turbulent flow. Further investigations are planned to isolate the effects of the smaller-scale turbulence in this situation.
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    Analysis of Ferroelectric Ceramic Fabricated by Binder Jetting Technology
    (University of Texas at Austin, 2013-08-16) Gaytan, Sara M.; Cadena, Monica; Aldaz, Mayela; Herderick, Edward; Medina, Francisco; Wicker, Ryan
    The M-Lab system from ExOne was used to fabricate 3D structures of BaTiO3 ceramic with applications that include dielectric capacitors, sensors, and integrated circuits. For this project, layer thicknesses of 15 and 30 μm and various percentages of binder saturation were used to fabricate components from powder. An organic binding agent was utilized during the printing process and later burned out at ~600°C prior to sintering. Multiple building parameters and sintering profiles were analyzed and compared in an attempt to obtain dense parts while examining shrinkage percentage variations.
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    Additive Manufacturing Laser Deposition of Ti-6Al-4V for Aerospace Repair Applications
    (University of Texas at Austin, 2013-08-16) Dey, N.K.; Liou, F.W.; Nedic, C.
    Parts or products from high performance metal are very expensive, partly due to the processing complexities during manufacturing. The purpose of this project is to use additive laser deposition and machining processes to repair titanium parts, thus extending the service life of these parts. The study broadly included preparing the defects, laser deposition, machining, sample preparation and mechanical tests. Comparative study of mechanical properties (UTS, YS, percentage elongation) of the repaired samples to the ideal conditions was undertaken. The research throws up interesting facts where the data from the test sample shows enhancement of properties of the repaired part.
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    Surface Morphology of Selective Laser-Melted Titanium
    (University of Texas at Austin, 2013) Kyogoku, H.; Shimizu, Y.; Yoshikawa, K.
    The surface morphology of biomaterials is one of the most important biocompatibility factors. In this paper, the change in surface morphology of selective laser-melted titanium with process parameters was investigated to control the pore structure and mesh size. First, the process map which shows the relation between the morphology of laser-melted track and the process parameters such as laser power and scan speed was drawn by experiments. The laser-melted layer was fabricated on the basis of the process map. As a result, the surface morphology, especially pore structure and mesh size, of the layer is affected strongly by energy density as well as scan spacing.
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    The Effects on 3D Printed Molds on Metal Castings
    (University of Texas at Austin, 2013) Snelling, Dean; Blount, Heather; Forman, Charles; Ramsburg, Kelly; Wentzel, Andrew; Williams, Christopher; Druschitz, Alan
    Additive manufacture of sand molds via binder jetting enables the casting of complex metal geometries. Various material systems have been created for 3D printing of sand molds; however, a formal study of the materials’ effects on cast products has not yet been conducted. In this paper the authors investigate potential differences in material properties (microstructure, porosity, mechanical strength) of A356 – T6 castings resulting from two different commercially available 3D printing media. In addition, the material properties of cast products from traditional “no-bake” silica sand is used as a basis for comparison of castings produced by the 3D printed molds.
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    Effect of Architecture and Porosity on Mechanical Properties of Borate Glass Scaffolds Made by Selective Laser Sintering
    (University of Texas at Austin, 2013) Kolan, Krishna C.R.; Leu, Ming C.; Hilmas, Gregory E.; Comte, Taylor
    The porosity and architecture of bone scaffolds, intended for use in bone repair or replacement, are two of the most important parameters in the field of bone tissue engineering. The two parameters not only affect the mechanical properties of the scaffolds but also aid in determining the amount of bone regeneration after implantation. Scaffolds with five different architectures and four porosity levels were fabricated using borate bioactive glass (13–93B3) using the selective laser sintering (SLS) process. The pore size of the scaffolds varied from 400 to 1300 µm. The compressive strength of the scaffolds varied from 1.7 to 15.5 MPa for porosities ranging from 60 to 30%, respectively, for the different architectures. Scaffolds were soaked in a simulated body fluid (SBF) for one week to measure the variation in mechanical properties. The formation of the Hydroxyapatite and in-vitro results are provided and discussed.