2009 International Solid Freeform Fabrication Symposium

Permanent URI for this collectionhttps://hdl.handle.net/2152/88017

Proceedings for the 2009 International Solid Freeform Fabrication Symposium. For more information about the symposium, please see the Solid Freeform Fabrication website.

The Twentieth Annual International Solid Freeform Fabrication (SFF) Symposium, held at The University of Texas in Austin on August 3-5, 2009, was attended by 123 national and international researchers from 9 countries. Papers addressed SFF issues in computer software, machine design, materials synthesis and processing, and integrated manufacturing. The diverse domestic and foreign attendees included industrial users, SFF machine manufacturers, university researchers and representatives from the government. The Symposium organizers look forward to its being a continuing forum for technical exchange among the expanding body of researchers involved in SFF.

The Symposium was again organized in a manner to allow the multi-disciplinary nature of the SFF research to be presented coherently, with various sessions emphasizing process development, design tools, modeling and control, process parameter optimization, applications and materials. We believe that documenting the changing state of SFF art as represented by these Proceedings will serve both those presently involved in this fruitful technical area as well as new researchers and users entering the field.

New this year was recognizing outstanding research by a senior and junior researcher. The recipient of the first Freeform and Additive Manufacturing Excellence (FAME) Award was Phill Dickens of Loughborough University. The junior award, the International Outstanding Young Researcher in Freeform and Additive Manufacturing Award, went to Carolyn Seepersad of The University of Texas at Austin. These awards include a framed certificate, a small honorarium and a freeformed trophy.

The awards were presented at a conference banquet Monday evening, August 3. As part of the celebration of the twentieth anniversary of the International Solid Freeform Fabrication Symposium, several special presentations were given. Tom Mueller of Express Pattern described the manufacture of the FAME trophies which were donated by his company. The trophy art was designed by digital artist, Sheba Grossman. She described the artwork and some of the details of its development. Finally, Harris Marcus, the founder of the SFF Symposium, made some remarks about the circumstances surrounding the first SFF Symposium held in 1990.

This year’s best oral presentation was given by Christopher Williams of Virginia Tech University. 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. The paper title was, “Design and Manufacture of Formula SAE Intake System Using Fused Deposition Modeling and Fiber-Reinforced Composite Materials” by Ryan Ilardo and Christopher B. Williams. Selected from 84 oral presentations, his presentation appears on Page 770 of this Proceedings. The best poster presentation selected from 15 posters was given by David Espalin of The University of Texas at El Paso (co-authored by K. Arcaute, D. Rodriguez, F. Medina, M. Posner, R. Wicker). The paper title was, “Fused Deposition Modeling of Polymethylmethacrylate for Use in Patient-Specific Reconstructive Surgery”, and the paper starts on Page 569.

The editors would like to extend a warm “Thank You” to Rosalie Foster for her detailed handling of the logistics of the meeting and the Proceedings, as well as her excellent performance as registrar and problem solver during the meeting. We would like to thank the Organizing Committee, the session chairs, the attendees for their enthusiastic contributions, 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 SFF community in organizing the Symposium. We also want to thank the Office of Naval Research (N00014-09-1-0940) and the National Science Foundation (CMMI-0905636) for supporting this meeting financially. The meeting was co-organized by the University of Connecticut at Storrs, and the Mechanical Engineering Department, Advanced Manufacturing Center, and Laboratory for Freeform Fabrication at The University of Texas at Austin.

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2009 International Solid Freeform Fabrication Symposium Table of Contents
(2009) Laboratory for Freeform Fabrication and University of Texas at Austin
Design, Fabrication and Evaluation of Negative Stiffness Elements
(University of Texas at Austin, 2009-09) Kashdan, Lia; Seepersad, Carolyn; Haberman, Michael; Wilson, Preston S.
Recent research has shown that constrained bistable structures can display negative stiffness behavior and provide extremal vibrational and acoustical absorptive capacity. These bistable structures are therefore compelling candidates for constructing new metamaterials for noise reduction, anechoic coatings, and backing materials for broadband imaging transducers. To date, demonstrations of these capabilities have been primarily theoretical, because the geometry of bistable elements is difficult to construct and refine with conventional manufacturing methods and materials. The objective of this research is to exploit the geometric design freedoms provided by selective laser sintering (SLS) technology to design and construct constrained bistable structures with negative stiffness behavior. The static and dynamic behaviors of resulting bistable structures are experimentally investigated. Initial bistable designs and test results are presented in this paper.
Scaffold Fabrication for Drug Delivery System Using Layered Manufacturing Methods
(University of Texas at Austin, 2009-09-15) Chu, W.S.; Jung, B.S.; Ahn, H.
To fabricate functional shape of drug delivery system (DDS), various processes are used. In this research, based on layered manufacturing, two different processes of 1) replication and 2) direct deposition were used to fabricate scaffold type implantable DDS. For replication process, hot embossing process for fabrication of patterned layers and bonding for construction of three-dimensional shape were used. As a direct deposition process, nano composite deposition system (NCDS) was used. Various scaffolds were fabricated with different filament size, pore size, and shape. It is observed that the scaffold type of implantable DDS is more stable than non-porous DDS through the in vivo test.
Experimental Characterization of High Viscosity Droplet Ejection
(University of Texas at Austin, 2009-09) Meachum, J. Mark; O'Rourke, Amanda; Yang, Yong; Fedorov, Andrei G.; Degertekin, F. Levent; Rosen, David W.
Additive Manufacturing via Microarray Deposition (AMMD) expands the allowable range of physical properties of printed fluids to include important, high-viscosity production materials (e.g., polyurethane resins). This technique relies on a piezoelectrically-driven ultrasonic printhead that generates continuous streams of droplets from 45 mm orifices while operating in the 0.5 to 3.0 MHz frequency range. Unique to this new printing technique are the high frequency of operation, use of fluid cavity resonances to assist ejection and acoustic wave focusing to generate the pressure gradient required to form and eject droplets. Specifically, we found that peaks in the ejection quality corresponded to predicted device resonances. Our results indicate that the micromachined ultrasonic print-head is able to print fluids up to 3000 mN-s/m2, far above the typical printable range.
Cellular Structures for Optimal Performance
(University of Texas at Austin, 2009-09) Engelbrecht, Sarah; Folgar, Luis; Rosen, David W.; Schulberger, Gary; Williams, Jim
Cellular material structures, such as honeycombs and lattice structures, enable unprecedented stiffness and strength characteristics, for a given weight. New design and CAD technologies to construct cellular materials are presented in this paper. Such materials have very complex geometries, hence the need for additive manufacturing processes to produce them. A series of experiments was performed to build and test parts fabricated using Selective Laser Sintering. Variations in mechanical properties were quantified and related to processing conditions. Examples help illustrate the variety of applications of cellular materials in the aerospace, automotive, motorsports, energy, electronics, and related industries. A software tool is being developed to enable users to design and construct parts with cellular structures.
Customised Layer Deposition for Chemical Reactor Applications
(University of Texas at Austin, 2009-09) Singh, J.; Hauser, C.; Chalker, P.R.; Sutcliffe, C.J.
This paper discusses the development and application of an adaptive slicing algorithm for use with Digital Light Processing (DLP) for the manufacture of micro chemical reactors. Micro reactors have highly complex constructions and DLP has a proven ability to deliver features at the micro level with high accuracy. However, DLP fails to provide a truly smooth profiled surface finish which could influence fluid flow through entrance and exit apertures and along snaking micro channels. Ensuring smooth surfaces will minimise energy losses in the fluid flow path. Generally, layer based manufacturing techniques incur a trade off between build time and resolution. The algorithms used in this study attempt to mitigate this to some degree by calculating locations where high resolution is required through surface profiling techniques and adjusts the layer thickness accordingly. It is proposed that this adaptive layering technique may improve surface roughness and reduce friction related energy losses along micro channels within chemical reactor applications.
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, Hod
Solid 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.
Recent Progress on Scanning Laser Epitaxy: A New Technique for Growing Single Crystal Superalloys
(University of Texas at Austin, 2009-09) Kirka, Michael; Bansal, Rohan; Das, Suman
This paper presents recent progress on scanning laser epitaxy, a laser manufacturing technique being developed for achieving single crystal growth in nickel‐based superalloys. Investigations have been performed for creating monolithic deposits on like chemistry single‐crystal nickel superalloy substrates. Progress in the areas of microstructure development and process control will be discussed in the context of repairing high‐value single‐crystal turbine engine components. This work is funded by the Office of Naval Research contract #N00173‐07‐1‐G012.
High Therma
(University of Texas at Austin, 2009-09-15) España, Félix A.; Balla, Vamsi Krishna; Bose, Susmita; Bandyopadhyay, Amit
Surface modification has been used to improve wear resistance, corrosion resistance and thermal barrier properties of metals. However, no significant attempts have been made to improve thermal conductivity by surface modification. In this work, we have examined the feasibility of enhancing thermal conductivity (TC) of stainless steel by depositing brass using Laser Engineered Net Shaping (LENS). The coating increased the TC of the substrate by 65% at 100 C°. Significantly low thermal contact resistance was observed between the coating and the substrate due to minimal dilution and defect free sound interface. Our results indicate that laser processing can be used on low coefficient of thermal expansion metal matrix composites to create feature based coatings to enhance their heat transfer capability.
Multiple Material Microstereolithography
(University of Texas at Austin, 2009-09) Choi, Jae-Won; MacDonald, Eric; Wicker, Ryan
We have previously described the development of a µSL system using a Digital Micromirror Device (DMDTM) for dynamic pattern generation and an ultraviolet (UV) lamp filtered at 365 nm for crosslinking the photoreactive polymer solution. The µSL system was designed with x-y resolution of ~2 µm and a vertical (z) resolution of ~1 µm (with practical limitations on vertical resolution of ~30 µm resulting from the current laboratory setup). This µSL system is capable of producing real three-dimensional (3D) microstructures, which can be used in micro-fluidics, tissue engineering, and various functional micro-systems. As has been explored and described in µSL, many benefits will potentially be derived from producing multiple material microstructures in µSL. One particular application area of interest is in producing multiple material micro-scaffolds for tissue engineering. In this work, a method for multiple material µSL fabrication was developed using a syringe pump system to add material to a small, removable vat designed for the µSL system. Multiple material fabrication was accomplished by manually removing the vat and draining the current material, rinsing the vat, placing the vat back into the system, and dispensing a prescribed volume in the vat using the syringe pump. Layer thicknesses less than ~30 µm were achieved using this process. To demonstrate this system, several multiple material microstructures were produced, and we believe multi-material µSL represents a promising technology for producing functional microstructures with composite materials.
Design and Manufacture of a Formula SAE Intake System Using Fused Deposition Modeling and Fiber-Reinforced Composite Materials
(University of Texas at Austin, 2009-09) Ilardo, Ryan; Williams, Christopher B.
In this paper, the authors discuss the design and manufacture of an intake system for a 600cc Formula SAE engine. Specifically, Fused Deposition Modeling is used to create an intake system (consisting of a plenum, plenum elbow, and cylinder runners) that is then later covered in layers of carbon fiber composite fabric through vacuum bagging. As a result of this approach, the geometry of the intake system has been redesigned to result in reduced weight (due to lower material density and lack of welds, hose clamps, and silicon couples), improved charge distribution, and increased torque through a wide RPM range when compared to its traditionally-manufactured aluminum counterpart.
Reprinting the Telegraph: Replicating the Vail Register using Multi-Materials 3D Printing
(University of Texas at Austin, 2009-09) Alonso, Matthew Paul; Malone, Evan; Moon, Francis C.; Lipson, Hod
Solid Freeform Fabrication is a family of manufacturing processes that create three-dimensional objects by depositing material, layer-by-layer. Traditionally, this technology has been used to fabricate passive parts, but recently it has been used for producing active components such as batteries and soft-polymer actuators. In this paper we demonstrate the ability of this process to fabricate a complete, active electromechanical system. Using only SFF processes, we reproduced the 1844 Vail register - a landmark in digital communications history. With the techniques developed in this research, a range of solenoid devices can be fabricated and embedded into freeform fabricated devices. This could enable the realization of novel and otherwise difficult to manufacture electromechanical designs.
Advanced Heat Sinks Enabled by Three-Dimensional Printing
(University of Texas at Austin, 2009-09-15) Lyons, Alan; Krishnan, Shankar; Mullins, John; Hodes, Marc; Hernon, Domhnaill
With the rapid rise in power dissipated by integrated circuits, improved heat sinks designs are needed to decrease the thermal resistance between them and forced air streams. Manufacturing methods such as extrusion, machining and die-casting have been used to fabricate conventional longitudinal fin designs. Although these technologies add relatively little cost, they preclude the fabrication of more complex heat sink designs. We discuss novel heat sink designs which increase surface area and/or modulate air flow streams. Fabrication of these unconventional designs is enabled by using 3D printing technologies with the subsequent conversion of the printed parts into monolithic copper structures by investment casting.
Design of Periodic Cellular Structures for Heat Exchanger Applications
(University of Texas at Austin, 2009-09) Kumar, Vikas; Manogharan, Guhaprasanna; Cormier, Denis R.
Powder based metal additive manufacturing processes generally produce parts with a textured surface. Although surface roughness is undesirable in most cases, it can be advantageous for applications such as heat exchangers or catalyst support structures. While stochastic metal foams have been used for these applications, it is not possible to tailor the foam geometry to the application. SFF techniques permit designers to use different cell geometries and orientations to achieve specific performance objectives. More specifically, the unit cell type and size, ligament size, and cell orientation have a considerable influence on surface area, volume, density and fluid flow behavior of the lattice structure. This paper illustrates the effect of the orientation of hexagonal periodic cellular structures on heat transfer and pressure drop. Finite element analysis of air flowing through the hot hexagonal periodic cellular structures shows the effect of orientation on heat transfer and pressure drop. The analysis indicates that the ideal orientation is dependent on the specific application.
Electronics Integration in Conformal Substrates Fabricated with Additive Layered Manufacturing
(University of Texas at Austin, 2009-09) Castillo, Sylvia; Muse, Dan; Medina, Frank; MacDonald, Eric; Wicker, Ryan
A three-dimensional (3D) accelerometer sensor system with microprocessor control was fabricated using a previously developed integrated layered manufacturing system that combines conductive ink dispensing with stereolithography (SL). The electronics are integrated into a conformal substrate that is press-fit into a helmet for the purpose of detecting Traumatic Head Injury (THI) when an excessive acceleration to the head is measured. Applications include monitoring the health of soldiers or athletes. Traditional fabrication of electronics is implemented with a 2 dimensional printed circuit board (PCB), which are not well suited for rugged installations in curved locations such as the interior of a helmet. The advantage of layered manufacturing for the integration of electronics is the ability to fabricate in a conformal substrate - conforming to the curved, complex, and often flexible shapes dictated by the human body.
Selective Electron Beam Melting: A new Way to Auxetic Cellular Structures
(2009-09-18) Schwerdtfeger, Jan; Heinl, Peter; Singer, Robert F.; Körner, Carolin
This paper is concerned with the build up and characterisation of well defined auxetic structures from Titanium alloys through Selective Electron Beam Melting (SEBM).The negative Poisson’s ratio of auxetic structures make them interesting candidates for a wide range of applications (e.g. joining of dissimilar materials). Up to date auxetic cellulars have mainly been produced through volumetric compression of conventional foams. However, by using SEBM we are able to produce structures of any geometry in a well defined manner. This opens an almost limitless field for new cellular auxetics and the tuning of their properties. In the following we will introduce a simple self designed auxetic structure and show first results for the mechanical characterisation of that structure.
Brick Printing: Freeform Fabrication of Modular Architectural Elements with Embedded Systems
(University of Texas at Austin, 2009-09-15) Lipton, Jeffrey I.; Cohen, Daniel; Lipson, Hod
We propose the use of modular, printed bricks to enable the integration of building systems and various processing techniques through the use of scalable printer platforms. This is enabled by a novel material platform comprised of clay, gypsum cement, FabEpoxy™, and SS-26F conductive silicone. On an open-architecture SFF system, a segment of cement wall with embedded electrical and fluidic conduits and various processing techniques was fabricated. Electrical and fluidic tolerances were comparable to traditionally constructed systems.
Design, Fabrication and Testing of Graphite Bipolar Plates for Direct Methanol Fuel Cells
(University of Texas at Austin, 2009-09-15) Alayavalli, Kaushik; Bourell, David L.
Direct Methanol Fuel Cells (DMFCs) are clean energy devices that convert chemical energy into electrical energy. The bipolar plate component of the DMFC is required to be fluid impermeable to prevent fuel leakage and electrically conductive to collect the electrons produced within the cell. Graphite possesses the properties of high electrical conductivity, low weight and resistance to corrosion that make it an attractive material for bipolar plates. However, the poor mechanical properties of graphite lead to prohibitive machining costs. The indirect Selective Laser Sintering (SLS) process, involving the laser sintering of graphite powders mixed with a phenolic resin binder, offers the advantage of complex part production and testing of prototype bipolar plates in short times. The current research deals with the production of bipolar plates for DMFC's by utilizing indirect SLS followed by post processing steps.
Fuel Cell Development using Additive Manufacturing Technologies - A Review
(University of Texas at Austin, 2009-09-15) Kulkarni, N.P.; Tandra, G.; Liou, F.W.; Sparks, T.E.; Ruan, J.
Fuel cells are being perceived as the future clean energy source by many developed countries in the world. The key today for clean power is the reliance of fuel cells not only to power automobiles but also for residential, small commercial, backup power etc. which calls for production on a large scale. Additive manufacturing is perceived as a way to develop cost effective fuel cells. It imparts flexibility to design different kinds of fuel cells along with reduction in material wastage. This paper deals with the review of additive manufacturing processes for research and development of fuel cell components, such as synthesizing and prototyping new materials for fuel cell components, fuel cell system design and prototyping, designing well sealed fuel cells, bridging from fuel cell design to manufacturing tooling, etc.
Customised Rapid Manufactured Parts: Technology and Case Studies from the Custom-Fit Project
(2009-09) Jones, J.; Jones, C.L.; Wimpenny, D.I.
The design and manufacture of individually customised products is generally restricted to bespoke clothing or footwear for very wealthy customers. The aim of the Custom-Fit project was to develop a fast, flexible and economically viable route for the manufacture of individually customised parts. These products not only provide improved comfort levels but also provide better functional performance, including enhanced safety for the user. This 4.5 year, European Commission subsidised €16 million project, supported by the EU, involving 30 partners across the breadth of the Europe finished in early 2009. This paper will showcase the technology developed: CAD packages which automate the design process and three new rapid manufacturing methods. It will also include case studies on a range of customised products, including customised Motorcycles helmets. The case studies not only demonstrate the performance benefits of individual customisation but also show the potential for new approaches to product design. More information at www.Custom-Fit.org.

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