2015 International Solid Freeform Fabrication Symposium

Permanent URI for this collectionhttps://hdl.handle.net/2152/88478

Proceedings for the 2015 International Solid Freeform Fabrication Symposium. For more information about the symposium, please see the Solid Freeform Fabrication website.

The Twenty-Sixth Annual International Solid Freeform Fabrication (SFF) Symposium – An Additive Manufacturing Conference, held at The University of Texas in Austin on August 10-12, 2015, was attended by 388 researchers from 19 countries. The organizers are pleased that 175 of the attendees were students, representing 45% of the audience. The number of oral and poster presentations increased to 289 this year, an increase of almost 50% over 2014. The meeting was held on the camps of The University of Texas at Austin in the AT&T Executive Education and Conference Center.

The meeting consisted of a Monday morning plenary, 25 parallel technical sessions and a poster session. This year’s best oral presentation was entitled, “Thermographic Measurements of the Commercial Laser Powder Bed Fusion Process at NIST”, authored by B. Lane, S. Moylan, E. Whitenton and L. Ma from the National Institute of Standards and 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 256 oral presentations, the associated manuscript appears on Page 575. The best poster presentation selected from 33 posters was given by L.B. Bass, N.A. Meisel and C.B. Williams from Virginia Polytechnic Institute and State University. Titled, “Exploring Variability in Material Properties of Multi-Material Jetting Parts”, the paper is included in the Proceedings on Page 993. Posters are judged based on the quality and organization of the poster as well as the discussion of the poster by the author during the poster session.

The recipient of the International Outstanding Young Researcher in Freeform and Additive Manufacturing Award was Dr. Ibrahim T. Ozbolat from The Pennsylvania State University. Dr. Richard J.M. Hague from the University of Nottingham won the International Freeform and Additive Manufacturing Excellence (FAME) Award.

The editors 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 (N00014-15-1-0071) and the National Science Foundation (CMMI-1536671) for supporting this meeting financially. The meeting was co-organized by The University of Connecticut at Storrs, and the Mechanical Engineering Department/Lab for Freeform Fabrication under the aegis of the Advanced Manufacturing and Design Center at The University of Texas at Austin.


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    2015 International Solid Freeform Fabrication Symposium Table of Contents
    (2015) Laboratory for Freeform Fabrication and University of Texas at Austin
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    Experimental Study of Snap-Fits Using Additive Manufacturing
    (University of Texas at Austin, 2015) Torossian, Kevin; Bourell, David
    A snap-fit is a mechanical joint system whose mating parts exert a cam action, flexing until one part slips past a raised lip on the other part, preventing their separation. The use of snaps in additive manufacturing (AM) is an approach for assembling components of parts too large to build in one piece in AM. There are broadly two types of snap-fits possible to encounter, permanent and non-permanent, depending on the design geometry. An experimental study was carried out to evaluate the mating/dismounting force for snap-fits regarding several geometrical parameters for additive manufacturing. The design chosen for this study has been established from the start to work on only one design. The parameters chosen for experimental investigation were the mating angle, the separation angle and the inner diameter of the mating part. All in all, fifteen pairs were designed and additive manufactured for evaluation. The force required to insert and separate the snap components was recorded and compared to the value based on a derived equation.
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    Capillary-Driven Flow in Open Microchannels Printed with Fused Deposition Modeling
    (University of Texas at Austin, 2015) Lade, Robert K. Jr; Hippchen, Erik J.; Rodgers, Luke; Macosko, Christopher; Francis, Lorraine F.
    The fundamentals of fluid flow in 3D printed, open microchannels created using fused deposition modeling (FDM) are explored. Printed microchannels are used in microfluidic devices and have potential applications in embedding electronics in plastic substrates. However, FDM parts possess rough surfaces, and in this study, surface topography is shown to have an important impact on flow behavior, causing the liquid to travel down the channel with a characteristic ‘pulsing’ movement. We also analyze the influence of print orientation on capillary flow, where microchannels printed in specific orientations are shown to exhibit different flow dynamics.
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    Creating Embedded Radiofrequency Structures Using PolyJet Material Jetting
    (University of Texas at Austin, 2015) Dumene, Richard L.; Kennedy, Paul; Williams, Christopher B.; Sweeney, Dennis; Earle, Greg
    Embedding of integrated systems via Additive Manufacturing (AM) offers the potential to save weight, space, and time in the production of electronics and vehicles. Of specific interest are embedded electrical systems that operate in the radiofrequency (RF) range as they have great potential utility in communication systems and aircraft avionics including navigation. However, systems in this frequency range pose unique manufacturing challenges such as the need to minimize impedance discontinuities in the system. In this work, the authors explore various techniques for embedding RF structures such as antennas and filters via a multi-material jetting AM process. Specifically, the dielectric constants and loss tangents of Vero White and Tango Black polymers were determined to facilitate the design of RF structures with these materials. It is shown that measurements of S-parameters of the resultant embedded RF structures approach or match the performance of non-embedded electronics.
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    Construction by Contour Crafting Using Sulfur Concrete with Planetary Applications
    (University of Texas at Austin, 2015) Khoshnevis, Behrokh; Yuan, Xiao; Zahiri, Behnam; Xia, Bin
    This paper reports on the experiments with the Contour Crafting Automated Construction process using sulfur concrete as the choice of construction material. Sulfur concrete has numerous terrestrial applications and is potentially an ideal construction material for planetary construction. On Mars, sulfur can be found in abundance and the range of temperature variation on the planet is within the safe zone for the structures to be built and survive over reasonable length of time with sulfur concrete. Several experiments have been performed at centimeter and meter scales. A FEA simulation model for the behavior of sulfur concrete based structures has been developed. Experimental results were compared with the results of simulation.
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    Direct Selective Laser Sintering of Reaction Bonded Silicon Carbide
    (University of Texas at Austin, 2015) Meyers, Sebastian; Kruth, Jean-Pierre; Vleugels, Jef
    Three-dimensional reaction bonded silicon carbide (SiSiC or RBSC) parts have been produced by direct selective laser sintering (SLS). Unlike previously investigated processing routes, which make use of a sacrificial polymer binder to form green parts, the parts in this work are built by scanning subsequent layers composed of a mixture of silicon and silicon carbide powders. A fibre laser is used to selectively melt the silicon under an inert argon atmosphere, resulting in porous preforms of sufficient strength for further handling and processing. After impregnation with a graphite suspension and infiltration with liquid Si at 1450°C, highly dense reaction bonded silicon carbide parts are obtained.
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    Thermal Aspects of Selective Laser Sintering of PMMA+β-TCP Composites
    (University of Texas at Austin, 2015) Velu, Rajkumar; Singamneni, Sarat
    Biocompatible and osteoconductive characteristics expected of materials used for bone grafting applications identified Polymethyl methacrylate (PMMA) and β-Tri Calcium Phosphate (βTCP) combinations to be potential biopolymer composite options. Together with additive manufacturing methods such as selective laser sintering (SLS), these materials options would also bring about the benefits of free from fabrication. While earlier research laser sintering PMMA+β-TCP composites experimentally proved the combination to be promising, the resulting microstructures are indicative of varied coalescence and consolidation with varying amounts of β-TCP. Considering the differential thermal properties, it becomes necessary and interesting to evaluate the possible role of the filler material in altering the nature of the thermal fields. This paper presents results of numerical and experimental work carried out investigating the thermal fields of laser sintered PMMA+β-TCP composites.
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    Further Study of the Electropolishing of Ti6Al4V Parts Made via Electron Beam Melting
    (University of Texas at Austin, 2015) Yang, Li; Lassell, Austin; Perez Vilhena Paiva, Gustavo
    In this study, the effect of various parameters including the voltage, current, polishing time, temperature and electrode spacing on the electropolishing quality of Ti6Al4V samples made via electron beam melting was investigated using specialty designed research setups. The relationships between these process parameters and the surface roughness of the parts were established experimentally.
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    Thermal Performance and Surface Characterization of a Selective Laser Melted Flat-Plate Oscillating Heat Pipe
    (University of Texas at Austin, 2015) Monroe, J.G.; Ibrahim, O.T.; Thompson, S.M.; Shamsaei, N.; Bian, L.; Elwany, A.
    A titanium alloy (Ti-6Al-4V) flat-plate oscillating heat pipe (FP-OHP) was fabricated using Selective Laser Melting (SLM). The 50.8 x 38.1 x 15.75 mm3 FP-OHP consisted of four integral layers of capillary-sized, circular mini-channels (1.52 mm in diameter). The post-SLM prototype was de-powdered using pressurized air and a novel layer-by-layer, plug-and-pressurize design/approach. A vacuum-grade port was threaded into the FP-OHP, and the heat pipe was charged with acetone (~70% by volume) then hermetically sealed. Experiments were conducted to characterize the thermal performance and functionality of the multi-layered FP-OHP. Results indicate that the acetone-filled FP-OHP operates and can provide for an 800% increase in effective thermal conductivity relative to pure Ti-6Al-4V. The build integrity of the FP-OHP was investigated by shearing along its width to inspect the channel-area surface using field emission scanning electron microscopy (SEM) and laser triangulation for channel topography. The mean surface roughness was found to be approximately 45 micrometers and characterized by partiallymelted, abraded particles. This study demonstrates the appeal of additive manufacturing for fabrication of customized heat transfer media traditionally challenging to realize.
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    Study of Vapourised Solvent Attack on Additive Manufacturing Part Surface
    (University of Texas at Austin, 2015) Cunico, Marlon Wesley Machado; Cunico, Miriam Machado; de Carvalho, Jonas
    The additive manufacturing technologies has been facing an extraordinary growth during that last years, mainly as consequence of the increase of low cost FDM technologies into the marketing. In contrast with that, one of the main disadvantages of this sort of equipment is the final object finishing. For that reason, the main goal of this work is to present and characterise the post-processing which was introduced in the marketing as smoothing. In addition, a concise overview about the theory beneath this process is presented besides an experimental study that evaluates the impact of this process for the main mechanical properties of object.
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    Improving Energy Efficiency of Car Climate Control with SLS
    (University of Texas at Austin, 2015) Vetterli, M.; Schmid, R.; Schmid, M.; Harke, S.; Durand, T.; Wegener, K.
    In Europe, passenger cars are responsible for 12% of CO2 emissions. The European Commission established new regulations to drastically reduce the emissions from 130g to 95g CO2 per km between 2015 and 2021. While the automobile industry is looking at different ways to meet those criteria, the presented industry-driven project aims at reducing energy consumption by up to 30% of air-conditioning (AC) in passenger cars with the introduction of a novel system. The current systems reduce the fuel economy to up to 20% for gas motors and even more for electric cars. Through Selective Laser Sintering (SLS) design freedom and short production cycles; the design of the AC casing was drastically optimized to increase its contact area with incoming air. To further increase the heat exchange throughout the system, the thermal conductivity of SLS material was improved by incorporation of mineral fillers. The successful implementation of both optimizations led to a CO2 emission reduction of around 50% for the climate control of passenger cars.
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    Freeform Extrusion Fabrication of Titanium Fiber Reinforced Bioactive Glass Scaffolds
    (University of Texas at Austin, 2015) Thomas, Albin; Kolan, Krishna C.R.; Leu, Ming C.; Hilmas, Gregory E.
    Although implants made with bioactive glass have shown promising results for bone repair, their application in repairing load-bearing long bones is limited due to their low fracture toughness and fairly fast degradation response in vivo. In this paper, we describe our investigation of freeform extrusion fabrication of silicate based 13-93 bioactive glass scaffolds reinforced with titanium fibers. A composite paste was prepared with 13-93 bioactive glass filled with titanium fibers (~16 µm in diameter and aspect ratio of ~250) having a volume fraction of 0.4 vol. %. This paste was then extruded to fabricate scaffolds with an extrudate diameter of about ~0.8 mm. The sintered scaffolds, with and without titanium fibers, had measured pore sizes ranging from 400 to 800 µm and a porosity of ~50%. Scaffolds produced with 0.4 vol. % titanium fibers were measured to have a fracture toughness of ~0.8 MPa•m1/2 and a flexural strength of ~15 MPa. Bioactive glass scaffolds without titanium fibers had a toughness of ~ 0.5 MPa•m1/2 and strength of ~10 MPa. The addition of titanium fibers increased the fracture toughness of the scaffolds by ~70% and flexural strength by ~40%. The scaffolds’ biocompatibility and their degradation in mechanical properties, in vitro were assessed by immersing the scaffolds in a simulated body fluid over a period of one to four weeks.
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    Polymer Particle Formation Using Inkjet Printing
    (University of Texas at Austin, 2015) Hüsler, A.; Wildman, R.D.; Alexander, M.R.
    Exciting advances have been made in biomaterials research, through both relating material properties to cell response and discovery of new materials via high throughput screening. This area of research is still hindered though by the paucity of information on the physicochemical parameters governing the response of cells to a broad range of materials. Herein, a combinatorial library of biodegradable, photocrosslinkable and microparticle-forming polymers is generated by transforming a macro-performed pipetting experiment into a micro-sized piezoelectric inkjet printing. Physiochemical properties such as density, polymerization rate, surface tension, viscosity and solubility have been shown to be critical for successful single and multiple polymer structured microparticles. The vision is to mature this effort for applications that require biocompatibility such as drug delivery and cell carriers in regenerative medicine strategies to engineer cell functions.
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    Optimal Process Parameters for 3D Printing of Dental Porcelain Structures
    (University of Texas at Austin, 2015) Miyanaji, Hadi; Zhang, Shanshan; Lassell, Austin; Zandinejad, Amir Ali; Yang, Li
    Dental porcelain material is a typical glass ceramic material that is widely used in dental restoration applications. However, there still exists limited knowledge about the fabrication of this type of materials using binder jetting additive manufacturing process. There are several important factors such as saturation level, power level, drying time as well as spread speed, which would potentially affect the accuracy and strength of the printed parts before and after sintering. Therefore, in this research an extensive experimental study was performed to obtain the optimal process parameters for the dental porcelain materials fabricated via ExOne binder jetting system. The results also provide general printing guidelines for the fabrication of glass ceramic materials.
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    Inkjet Printing of Materials with Resistance to Bacterial Attachment
    (University of Texas at Austin, 2015) Begines, B.; Hook, A.L.; Wildman, R.D.; Tuck, C.J.; Alexander, M.R.
    Biofilm formation on the surface of medical devices is a major source of health-care associated infections. The discovery of new materials that inherently avoid formation of such biofilms on their surface points the way to the fabrication of biofilm resistant devices, with the consequent reduction in the incidence rate of device centred infections and therefore a reduction in suffering and costs for health-care systems. Drop on Demand (DOD) Three Dimensional (3D) Inkjet Printing presents higher versatility than common techniques for printing biomaterials. One of the main representations of this enhanced versatility is polymerisation post-jetting, which provides a great range of printable polymers. The combination of such materials with inkjet printing could revolutionise the biomedical industry. In this paper, the printability of four acrylates with resistance to bacterial attachment was assessed using the printability indicator or Z parameter. Three of the materials showed a value of Z within the printability range. The remainder displayed a Z value higher than the maximum suggested. However, this material was ejected with stability using a complex waveform designed for low viscosity inks. Drop spacing was optimised for each ink using PET and glass as substrates. The combination of printability optimisation together with ideal drop spacing allowed the construction of 3D structures of three of the four inks that were tested.
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    In Situ Printing - An Alternative Three Dimensional Laden Structure Fabrication Method
    (University of Texas at Austin, 2015) Liu, W.; Sun, W.
    Recapitulating a structure that mimics the anatomic geometries and intratissue cell distribution as in live organism is a major challenge of tissue engineering nowadays. Solid freeform fabrication (SFF) has been demonstrated as an efficient tool for this purpose. In this paper we presented a SFF based in situ printing method that is free of fabrication time frame and fabrication environment constrains. The fabrication parameters on strut formability, fabricated structural stability against gentle fluidic disturbance, and the integrity of the fabricated structure in cell culture environment were studied to assess the potential of the fabrication method on biomedical application. Based on the results, controlled strut formability can be achieved in an appropriate cross-linking deposition range. Alginate composition is the main parameter that dominates the stability and integrity of the fabricated structure. A parameter set that can produce a stable scaffold with the ability to maintain its structure in cell culture environment for at least 15 days was optimized.
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    A Glance at the Recent Additive Manufacturing Research and Development in China
    (University of Texas at Austin, 2015) Xing, Xiaodong; Yang, Li
    This paper reviews some of the recent additive manufacturing research and development works in China. A considerable amount of AM research activities in China focuses on directed energy deposition processes, powder bed fusion processes and stereolithography, with much of the effect dedicated to system and application development. Although many of the recent results are not readily available from the literatures published in China, from the available information the areas of focus for research and development could be clearly seen. Despite some speculations, the AM research in China is vibrate and aggressive, with some areas at least several years ahead of the other countries.
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    Protection Measures against Product Piracy and Application by the Use of AM
    (University of Texas at Austin, 2015) Jahnke, U.; Büsching, J.; Reiher, T.; Koch, R.
    Presently the implications Additive Manufacturing (AM) on intellectual properties are discussed in public. Here AM is often mentioned as a driver for product piracy as it allows to produce and to copy objects with any geometries. Imitators need a lot of information to copy an object accurately. As reverse engineering has been identified as the most important information source for product imitators, AM can also help to reduce the threat of product piracy when correctly applied in the product development. Due to the layer wise production process that allows the manufacturing of very complex shapes and geometries, the reverse-engineering process can be complicated by far. By this, quite contrary to the public opinion, AM can increase the needed effort of imitators and strongly reduce the economic efficiency of product piracy. This paper will show different protection measures and a methodological approach of how to apply these measures to a product. Beside the protective effect some measures allow a traceability of parts over the product’s lifecycle and thus support the quality management of AM processes and additively produced parts.
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    Polymer Recycling and Additive Manufacturing in an Open Source Context: Optimization of Processes and Methods
    (University of Texas at Austin, 2015) Cruz, Fabio; Lanza, Silvia; Boudaoud, Hakim; Hoppe, Sandrine; Camargo, Mauricio
    Polymer recycling is a way to reduce environmental impacts of accumulation of polymeric waste materials. However, low recycling rates are often observed in conventional centralized recycling plants mainly to the challenge of collection and transportation for high-volume low-weight-polymers in conventional centralized recycling plants. As the democratization of open-source 3D printers is going forward thanks to initiatives such as FabLab environments, there is a growing interest on how to use this technology to improve the efficiency of use of raw materials. Studies have been proposed in order to recycle waste polymer into open-source 3D printer feedstock. The recycling of high-density polyethylene (HDPE) issued from bottles of used milk jugs through use of an open-source filament fabricator system called RecycleBot has been evaluated. In this study, we propose an evaluation of the mechanical recyclability of Polylactic Acid (PLA), material widely used in the open-source 3D printing context, in order to establish the viability of this recycled material to be used in the open-source 3D printers. The degradation of the material’s mechanical and rheological properties after a number of cycles of multiple extrusion and printing processes is evaluated. The characterization of recycled raw materials for open-source 3D printing has implications not only to reduce the environmental impact of polymers waste, but also it will allow us to understand the technical requirements and challenges for development of open-source filament recycle machine/process. The coupling of open-source 3D printers and filament extruders can offer the bases of a new distributed polymer recycling paradigm, which reverses the traditional paradigm of centralizing recycling of polymers where is often uneconomic and energy intensive due to transportation embodied energy. Moreover, this characterization also will allow the exploration of new source of materials and new composite materials for open-source 3D printing, in order to improve the quality of products made by this technology.
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    Feasibility Study of Small Scale Production Based on Additive Manufacturing Technologies
    (University of Texas at Austin, 2015) Cunico, Marlon Wesley Machado; de Carvalho, Jonas
    Along the last years, the complexity of products has been growing progressively, while the product development life-cycle tended to be reduced. In addition to that, additive manufacturing technologies increased their role in the product development process, resulting in reduction of errors and products release time. In spite of these benefits, the main application of these technologies is still focused on initial phases of projects and results in high costs of parts and low volumes. On the other hand, although conventional productivity processes results in low costs and high volumes, the investment related to these processes are high and the implementation time are long. For that reason, the main goal of this work is to investigate the possibility of application of additive manufacturing technologies for small and medium scale production. Along this work, the main direct and indirect processes which are used for small and medium scale production were studied and a numerical cost model were developed for each one. In order to compare the benefits and disadvantages among the processes, 3 parts were selected and analysed through such models. By the end, the main cost, payback; amortization and takt time were identified and the most suitable process was found in accordance with annual part demand.