2016 International Solid Freeform Fabrication Symposium

Permanent URI for this collectionhttps://hdl.handle.net/2152/89344

Proceedings for the 2016 International Solid Freeform Fabrication Symposium. For more information about the symposium, please see the Solid Freeform Fabrication website.

The Twenty-Seventh Annual International Solid Freeform Fabrication (SFF) Symposium – An Additive Manufacturing Conference, held at The University of Texas in Austin on August 8-10, 2016, was attended by 544 researchers from 19 countries. The number of oral and poster presentations increased to 424 this year. The meeting was held on the campus of The University of Texas at Austin in the AT&T Executive Education and Conference Center. The meeting consisted of a Monday morning plenary, 40 parallel technical sessions and a poster session.

The conference attendance is growing rapidly, clearly reflective of the interest at large in the area.

The recipient of the International Outstanding Young Researcher in Freeform and Additive Manufacturing Award was Dr. Li Yang from The University of Louisville. Dr. Brent Stucker from 3DSIM, LLC won the International Freeform and Additive Manufacturing Excellence (FAME) Award.

There are 197 papers in this conference proceedings volume. Papers marked “REVIEWED” on the first page heading were peer reviewed by two external reviewers. Papers have been placed in topical order and numbered sequentially to facilitate citation. Manuscripts for this and all preceding SFF Symposia are available for free download below and at the conference website: http://sffsymposium.engr.utexas.edu/archive.

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 (N00014-16-1-3004) and the National Science Foundation (CMMI-1639406) 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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Now showing 1 - 20 of 197

Design for Additively Manufactured Lightweight Structure: A Perspective
(University of Texas at Austin, 2016) Yang, L.; Harrysson, O.L.A.; Cormier, D.; West, H.; Zhang, S.; Gong, H.; Stucker, B.
The design of lightweight structures realized via additive manufacturing has been drawing considerable amount of attentions in academia and industries for a wide range of applications. However, various challenges remain for AM lightweight structures to be reliably used for these applications. For example, despite extensive advancement with geometric design, there still lacks adequate understanding with the process-material property relationship of AM lightweight structures. In addition, a more integrated design approach must also be adopted in order to take non-uniform material design into consideration. In our works, a design approach based on unit cell cellular structure was taken in the attempt to establish a comprehensive design methodology for lightweight structures. Analytical cellular models were established to provide computationally efficient property estimation, and various design factors such as size effect, stress concentration and joint angle effect were also investigated in order to provide additional design guidelines. In addition, it was also found that the geometry and microstructure of the cellular structures are dependent on both the process setup and the feature dimensions, which strongly support the argument to establish a multi-scale hierarchical cellular design tool.
Additive Manufacturing of High Performance Semicrystalline Thermoplastics and Their Composites
(University of Texas at Austin, 2016) Kishore, Vidya; Chen, Xun; Ajinjeru, Christine; Hassen, Ahmed Arabi; Lindahl, John; Failla, Jordan; Kunc, Vlastimil; Duty, Chad
This work investigates the use of two semi-crystalline high performance thermoplastics, polyphenylene sulfide (PPS) and poly (ether ketone ketone) (PEKK), as feedstock for fused filament fabrication process. Composites of PPS and PEKK are emerging as viable candidates for several components in aerospace and tooling industries and additive manufacturing of these materials can be extremely beneficial to lower manufacturing costs and lead times. However, these materials pose several challenges for extrusion and deposition due to some of their inherent properties as well as thermal and oxidative responses. To better understand the properties of such systems specific to 3D printing and determine the critical parameters that make them “printable”, various rheological and thermal properties have been studied for neat as well as short fiber reinforced PPS and PEKK systems. Attempts were also made to print these materials in a customized high temperature fused filament fabrication system.
In-Process Monitoring of Cross Contamination in Laser Powder Bed Fusion (L-PBF) Additive Manufacturing (AM)
(University of Texas at Austin, 2016) Jamshidinia, M.; Boulware, P.; Marchal, J.; Mendoza, H.; Cronley, L.; Kelly, S.; Newhouse, S.
Cross contamination in laser powder bed fusion (L-PBF) Additive Manufacturing (AM) could locally change the chemical composition and stress distribution in a component. It also could result in the formation of flaws, and consequently lower the mechanical performance of a component. In this study, the in-process monitoring and detection of cross contamination was investigated in L-PBF process, also known as direct metal laser sintering (DMLS). A setup was designed and fabricated at EWI, where contaminant materials could be introduced on the powder bed without interrupting the fabrication process or breaking the chamber environment. Tungsten particles were used as the contaminant material, in the matrix of Inconel 625. Six levels of contamination were calibrated, and were introduced in two static and dynamic modes. Photodetector, spectrometer, and optical camera were used for the data acquisition. One of the sensors showed the most promising results. X-ray computed tomography (CT) and optical microscopy were used to validate data collected by the sensors.
A Reconfigurable System to Enhance the Work Envelope of a Solid Freeform Fabrication System
(University of Texas at Austin, 2016) Dwivedi, Rajeev; Sinha, Ayush; Ebburu, Pranav; Saxena, Yash; Haque, Shabab; Kulkarni, Shaunak
Size and aspect ratio of parts created by Solid freeform fabrication systems is limited by the configuration of equipment. Also referred to as Axes, the maximum reach of material deposition end effector determines the maximum size of the part that can be built. Inherent to most the SFF system is the drive configuration that limits the extent of the reach of the end effector. This paper proposes an alternate architecture that overcomes the drive limitations and hence provides an ability to enhance the work envelope. Two systems proposed include – (1) Cartesian axis stacking and (2) Common Vehicle arrangement. The system drive may be built such that multiple units can be combined and reconfigured to expand the total work envelope.
Large Scale Metal Additive Techniques Review
(University of Texas at Austin, 2016) Nycz, A.; Adediran, A.I.; Noakes, M.W.; Love, L.J.
In recent years additive manufacturing has made long strides toward becoming a main stream production technology. Particularly strong progress has been made in large-scale polymer deposition. However, large scale metal additive has not yet reached parity with large scale polymer. This paper is a survey of the metal additive techniques in the context of building large structures. Current commercial devices are capable of printing metal parts on the order of several cubic feet compared to hundreds of cubic feet for the polymer side. In order to follow the polymer progress path many factors must be considered—potential to scale, economy, environment friendliness, material properties, feedstock availability, robustness of the process, quality and accuracy, potential for defects, and post processing as well as potential applications. This paper focuses on current state of art of large scale metal additive technology with a focus on expanding the geometric limits.
Saving Weight with Metallic Lattice Structures: Design Challenges with a Real-World Example
(University of Texas at Austin, 2016) Kantareddy, S.N.R.; Roh, B.M.; Simpson, T.W.; Joshi, S.; Dickman, C.; Lehtihet, E.A.
Lattice structures are structurally efficient yet complex designs that enable high stiffness and reduce weight. While lattice structures are traditionally difficult to manufacture in metal with conventional fabrication processes, AM is a viable solution to manufacture such complex geometries to achieve lightweight designs. However, there is relatively little information available in the literature about designing large-scale lattice structures, particularly concerning computer-aided design tools, structural analysis, and post-processing for functional metallic components. In this study, we investigate and discuss these aspects in the context of a real-world problem for an oil and gas application. The lattice structure is designed and fabricated with IN 718 powder using an EOS M280 laser-based powder bed fusion system. A weight reduction of 42.4% is achieved while obtaining the desired mechanical performance. Results and challenges, particularly with the design workflow, are discussed along with future research directions.
Microstructural and Mechanical Performance of Al2O3 Nanoparticle Reinforced 17-4 PH Stainless Steel Bulk Composite Parts Fabricated by Laser Engineered Net Shaping Process
(University of Texas at Austin, 2016) Ning, Fuda; Hu, Yingbin; Liu, Zhichao; Wang, Hui; Cong, Weilong; Li, Yuzhou
Alloy 17-4 PH (AISI 630) is a precipitation-hardening martensitic stainless steel that has been extensively employed in the industries of aerospace, marine, and chemical. In this study, bulk parts of both 17-4 PH and Al2O3 reinforced 17-4 PH composites were fabricated on a steel substrate by laser engineered net shaping (LENS) process to investigate the effects of Al2O3 reinforcements on the part performance. The 17-4 PH powders were pre-mixed with Al2O3 nanoparticles by ball milling. The microstructures of both parts were observed using scanning electron microscopy and mechanical properties including microhardness and compressive properties were evaluated by means of a Vickers microhardness tester and a universal tester, respectively. The results indicate that Al2O3 reinforced 17-4 PH composite parts fabricated by LENS process exhibited superior microhardness and compressive properties as compared to pure 17-4 PH parts.
Design of a Micro-scale Selective Laser Sintering System
(University of Texas at Austin, 2016) Roy, Nilabh K.; Foong, Chee S.; Cullinan, Michael A.
Micro and nanoscale additive manufacturing methods employing metals and ceramics have many promising applications in the aerospace, medical device, and electronics industries. However, the present state of art metal additive manufacturing tools have feature-size resolutions of greater than 100 µm, which is too large to precisely control the geometrical and dimensional aspects of the parts they produce. The weakness is particularly profound in application of additive manufacturing to the fabrication of fine pitch interconnects in the packaging and assembly of integrated circuits. A new microscale selective laser sintering (µ-SLS) is being developed in this research to improve the minimum feature-size resolution of metal additively manufactured parts by up to two orders of magnitude, while still maintaining the throughput of traditional additive manufacturing processes. This paper presents a detailed design of the sub-assemblies of the µ-SLS system including innovative design features such as the use of (1) ultra-fast lasers, (2) a micro-mirror based optical system, (3) nanoscale particles, (4) a precision spreader mechanism, (5) long-range precision XY nano-positioner and (6) a global positioner.
Cotton Fibers in 3D Printing
(University of Texas at Austin, 2016) Kearns, Alexa; Farahbakhsh, Nasim; Venditti, Richard; Jur, Jesse
This work explores the materials challenges of cotton-loaded with polymer composites toward sustainable solutions in 3D printed free forms. A key step toward composite filament development is the reduction in size of the original cotton fibers. Mechanical processing of the cotton is introduced as a means of reducing the size of cotton fibers to form a material of an ultra-high aspect ratio (>250) structure that is nanometers in diameter and micrometers in length. Mechanical advantages are low density polyethylene loaded with the high aspect ratio cotton and is observed to maintain a mechanically robust material at loading up to 40 wt%. In addition, attempts to print with 25 wt% cotton fillers (~10-15 aspect ratio) in LDPE is demonstrated. Finally, considerations to processing challenges from a sustainable and practical viewpoint are provided.
A High-Performance Material for Aerospace Applications: Development of Carbon Fiber Filled PEKK for Laser Sintering
(University of Texas at Austin, 2016) Fischer, S.; Pfister, A.; Galitz, V.; Lyons, B.; Robinson, C.; Rupel, K.; Booth, R.; Kubiak, S.
In a time where rapid prototyping successively transforms to additive manufacturing (AM), nylon 11 and 12 and their composite powders, which have evolved to be the most commonly used materials in laser sintering (LS) due to their easy processability, cannot fulfil all challenging requirements of industrial applications any more. Especially in the aerospace industry, there is a high demand for stiff and lightweight parts for interiors, which currently are fabricated from glass fiber reinforced phenolic and epoxy resins by a lamination process. Due to the strong diversity of the parts, this traditional manufacturing is quite labor-intensive and expensive, which makes it very attractive to manufacture these parts with additive manufacturing, especially laser sintering. Additional part design requirements, such as greater chemical and UV resistance, an elevated softening temperature, higher mechanical strength and better performance in flammability and heat release tests generate opportunities for the use of high performance AM polymers. Promising candidates that have the potential of satisfying these demands can be found among the different Polyaryletherketone thermoplastics. In this work we present the development of a carbon fiber filled PEKK composite material for laser sintering, optimized especially for the production of interiors, such as air ducts for cabin ventilation in aerospace application. Based on process tests, powder characterization and test builds, the material and its manufacturing procedure were optimized towards isotropic properties and refreshability. Simulations of building cycles helped to understand the extent of powder ageing, which is directly connected to the ability to recycle the material. Furthermore the laser sintering hardware of an EOSINT P800 and the building processes were adapted to ensure a stable building process and fulfill the requirements of parts on mechanical properties in x, y and z directions, dimensional stability and surface quality.
Additive Manufacturing of Carbon Fiber and Graphene – Polymer Composites using the technique of Fused Deposition Modelling
(University of Texas at Austin, 2016) Girdis, Jordan; McCaffrey, Matthew; Proust, Gwénaëlle
Adding micro or nano-carbon reinforcements to polymers enhances their mechanical and electrical properties. In this paper, the effects of the addition of short carbon fibres (SCF) and graphene into acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) polymer to create composite filaments for fused deposition modelling (FDM) are investigated. After creating carbon polymer composite filaments, using a commercial 3D printer, samples were printed and tested for mechanical and electrical properties. The measured values for these composites were compared to those obtained for pure ABS and pure PLA. It was found that by using only 2% SCF it was possible to achieve a 22% increase in tensile strength with no significant impact on printability. With addition of graphene, PLA was made to be conductive. These results show the feasibility of developing new materials for 3D printing that will create structurally sound and conductive designs.
In-Situ Non-Destructive Evaluation of Ultrasonic Additive Manufactured Components
(University of Texas at Austin, 2016) Nadimpalli, Venkata Karthik; Na, Jeong K.; Bruner, Darren T.; King, Brenna A.; Yang, Li; Stucker, Brent E.
In-situ monitoring of Ultrasonic Additive Manufacturing (UAM) process is crucial for producing parts suitable for load-bearing structural applications. Due to the nature of UAM process, it is necessary to monitor the entire build as opposed to only the just bonded layer. For this purpose, an ultrasonic transducer is used in this study to perform in-situ nondestructive evaluation (NDE) of the entire build after the addition of each new layer. This has been successfully implemented first on a manually operated research UAM machine and then applied on a fully automated commercial grade UAM machine. The practical applications of such in-situ measurements for ensuring defect-free part fabrication through closed-loop control of the UAM process control is shown to be possible from the results of this work.
Approaches to Geometric Data Analysis on Big Area Additively Manufactured (BAAM) Parts
(University of Texas at Austin, 2016) Dreifus, G.D.; Jin, Y.; Ally, N.; Post, B.K.
The promise of additive manufacturing is that a user can design and print complex geometries that are very difficult, if not impossible, to machine. The capabilities of 3D printing are restricted by a number of factors, including properties of the build material, time constraints, and geometric design restrictions. In this paper, a thorough accounting and study of the geometric restrictions that exist in the current iteration of additive manufacturing (AM) fused deposition modeling (FDM) technologies on a large scale are discussed. Offline and online methodologies for collecting data sets for qualitative analysis of large scale AM, in particular Oak Ridge National Laboratory’s (ORNL) big area additive manufacturing (BAAM) system, are summarized. In doing so, a survey of tools for designers and software developers is provided. In particular, strategies in which geometric data can be used as training sets for smarter AM technologies in the future are explained.
Compressive Property Comparisons Between Laser Engineered Net Shaping of In Situ TiBw-TMCs and Cp-Ti Materials
(University of Texas at Austin, 2016) Hu, Yingbin; Wang, Hui; Ning, Fuda; Cong, Weilong; Li, Yuzhou
Titanium (Ti) and its alloys are widely used in chemical, astronautical, and biomedical industries. However, their poor load endurance properties affect their fields of applications especially under severe loading conditions. To enhance these properties, TiBw reinforcement was synthesized by in situ chemical reaction between elemental Ti and boron. Strong interfacial bonding between TiBw reinforcement and Ti matrix was obtained due to the in situ chemical reaction. Owing to its capability of producing difficult-to-machine bulk composites with uniform properties, laser engineered net shaping (LENS) technique was utilized to fabricate TiBw reinforced Ti matrix bulk composites. Few researches have been reported on these three-dimensional metal based bulk composites by using LENS. In this work, effects of TiBw reinforcement and laser power on compressive properties were investigated. The microstructures of the fabricated parts were observed and analyzed by using scanning electron microscopy.
Investigation the Additive Manufacture of Extra-Terrestrial Materials
(University of Texas at Austin, 2016) Goulas, Athanasios; Southcott-Engstrøm, Daniel; Friel, Ross J.; Harris, Russell A.
The Powder Bed Fusion (PBF) additive manufacturing process category, consists of a group of key enabling technologies allowing the fabrication of both intrinsic and complex structures for a series of applications, including aerospace and astronautics. The purpose of this investigation was to explore the potential application of in-space additive manufacturing/3D printing, for onsite fabrication of structures and parts, using the available extra-terrestrial natural resources as feedstock. This study was carried out by using simulants of terrestrial origin, mimicking the properties of those respective materials found extra-terram (in space). An investigation was conducted through material characterisation, processing and by powder bed fusion, and resultant examination by analytical techniques. The successful realisation of this manufacturing approach in an extra-terrestrial environment could enable a sustainable presence in space by providing the ability to build assets and tools needed for long duration/distance missions in deep space.
Dimensional Accuracy of Titanium Direct Metal Laser Sintered Parts
(University of Texas at Austin, 2016) Mitchell, W.F.; Lang, D.C.; Merdes, T.A.; Reutzel, E.W.; Welsh, G.S.
To address concerns regarding quality of production parts created using the Additive Manufacturing (AM) process, a study was conducted to quantify the dimensional accuracy of said parts. Fourteen AM builds were manufactured in Ti-6Al-4V material across two EOS DMLS machines (EOSINT M 280 and EOS M 290). In addition to studying the impact of machine-to-machine variability, other factors potentially impacting final dimensional accuracy were studied, including: powder state (virgin or reused); post-processing steps (heat treatment and part removal from substrate); location of part on substrate; and nominal part size. The results of the dimensional analysis showed that the individual machine itself was the dominant factor impacting dimensional accuracy. Also, a non-linear relationship between dimensional accuracy and nominal part size was identified, which would require a more complex machine calibration technique to correct.
In-Situ Quality Inspection of Laser Powder-Bed Fusion Using High-Resolution Visual Camera Images
(University of Texas at Austin, 2016) Aminzadeh, Masoumeh; Kurfess, Thomas
Issues of part quality in terms of quality of fusion and formed porosity are widely known and stated as some of the important challenges with laser powder-bed fusion (LPBF) process. This paper addresses the in-situ inspection of layer-wise part quality using visual camera images. High-resolution visual images are captured from each layer of the part during LPBF process. The imaging and illumination setups are developed such that the produced images visualize detailed surface characteristics of each layer of the build such as fused seams, as well as the individual formed pores. To enable automated inspection of these images, appropriate image processing algorithms are developed to detect individual pores formed in each layer. In addition to detection of individual pores, intelligent pattern matching algorithms are developed, trained, and implemented to identify porous regions from non-porous layers. The surface characteristics of the layers as visualized in camera images can also provide a measure of quality of fusion and the energy of the layer, and an estimated level of porosity. Discussion on characterization of the surface quality in terms of roughness, quality of fusion, and the energy of the build will be made. The results of the automated image analyses provide useful feedback for in-situ process modification as well as part quality assessment.
Contoured 3D Printing of Fiber Reinforced Polymers
(University of Texas at Austin, 2016) Tse, L.Y.L.; Kapila, S.; Barton, K.
Additive manufacturing (AM) is a cost effective approach for small-scale production, providing higher design flexibility and less material waste than traditional manufacturing techniques. Polymers constitute one of the most popular AM materials, yielding lightweight but inherently weak components that cannot hold up against high tension and bending stresses. A need for improved tensile strength has driven a recent interest in AM of fiber reinforced polymers (FRPs). AM-FRPs reinforced with short fibers have demonstrated increased mechanical strength, but with limited design and structural flexibility. AM-FRPs reinforced with continuous fibers provide structural reinforcement within plane; as such, the fibers cannot be extruded along a contoured profile, significantly minimizing the application space for these AM-FRP devices. In this article, we address this current gap through the development of a new FRP additive manufacturing process that is capable of continuous fiber deposition along contoured trajectories. Experimental demonstrations validate the proposed process.
3D Inkjetting Droplet Formation of Bacterial Cellulosic Exopolysaccharide Gel
(University of Texas at Austin, 2016) Aguiar, Daniel; Albuquerque, Amanda; Li, Bingbing
On-demand 3D printing of scaffolds and cell-laden structures has shown promising results that can significantly impact human welfare. The objective is to fully understand the behavior of bacterial cellulosic exopolysaccharide gel (BCEG) as a new bioink with low toxicity and high biocompatibility for regenerative medicine. Its possible application is to construct scaffolds that can be used for several biomedical applications, especially tissue engineering and treatment of critical bone defects. By using a MicroFab inkjet micro dispenser, BCEG was dispersed to create drops on demand that can be used to fabricate scaffolds. In order to fully understand the material’s behavior and droplet formation, we analyzed the physical and mechanical properties of the BCEG in different concentrations (0.1% 0.5% and 1%) and characterized it by its macroscopy, microscopy, rheology and particle size distribution.
Powders for Additive Manufacturing Process: Characterization Techniques and Effects on Part Properties
(University of Texas at Austin, 2016) Sutton, Austin T.; Kriewall, Caitlin S.; Leu, Ming C.; Newkirk, Joseph W.
Powder-bed based Additive Manufacturing is a class of Additive Manufacturing (AM) processes that bond successive layers of powder by laser melting to facilitate the creation of parts with complex geometries. As AM technology transitions from the fabrication of prototypes to end-use parts, the understanding of the powder properties needed to reliably produce parts of acceptable quality becomes critical. Consequently, this has led to the use of powder characterization techniques such as scanning electron microscopy (SEM), laser light diffraction, x-ray photoelectron spectroscopy (XPS), and differential thermal analysis (DTA) to both qualitatively and quantitatively study the effect of powder characteristics on part properties. Utilization of these powder characterization methods to study particle size and morphology, chemical composition, and microstructure of powder has resulted in significant strides being made towards the optimization of powder properties for powder-bed based AM processes. This paper reviews methods commonly used in characterizing metallic AM powders, and the effects of powder characteristics on the part properties in these AM processes.

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