2009 International Solid Freeform Fabrication Symposium

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https://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.

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