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
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.
Browsing 2009 International Solid Freeform Fabrication Symposium by Title
(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.
(University of Texas at Austin, 2009-09) Petrzelka, Joseph E.; Frank, Matthew C.
This paper presents process planning methods for Subtractive Rapid Prototyping, which deals with
multiple setup operations and the related issues of stock material management. Subtractive Rapid
Prototyping (SRP) borrows from additive rapid prototyping technologies by using 2½D layer based
toolpath processing; however, it is limited by tool accessibility. To counter the accessibility problem,
SRP systems (such as desktop milling machines) employ a rotary fourth axis to provide more complete
surface coverage. However, layer-based removal processing from different rotary positions can be
inefficient due to double-coverage of certain volumes. This paper presents a method that employs STL
models of the in-process stock material generated from slices of the part along the rotation axis. The
developed algorithms intend to improve the efficiency and reliability of these multiple layer-based
removal steps for rapid manufacturing.
(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.
(University of Texas at Austin, 2009-09-15) Zhou, Chi; Chen, Yong
Solid freeform fabrication (SFF) processes based on mask image projection such as digital
micro-mirror devices (DMD) have the potential to be fast and inexpensive. More and more research
and commercial systems have been developed based on such digital devices. However, a digital light
processing (DLP) projector based on DMD has limited resolution and certain image blurring. In order
to use a DLP projector in the large-area mask projection stereolithography, it is critical to plan mask
images in order to achieve high accuracy and resolution. Based on our previous work on optimized
pixel blending, we present a calibration method for capturing the non-uniformity of a projection image
by a low cost off-the-shelf DLP projector. Our method is based on two calibration systems, a
geometric calibration system that can calibrate the position, shape, size, and orientation of a pixel and
an energy calibration system that can calibrate the light intensity of a pixel. Based on both results, the
light intensity at various grayscale levels can be approximated for each pixel. Developing a library of
such approximation functions is critical for the optimized pixel blending to generate a better mask
image plan. Experimental results verify our calibration results.
(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.
(University of Texas at Austin, 2009-09) Weiss, C.M.; Aindow, M.; Marcus, H.
The method of Selective Area Laser Deposition (SALD) and Vapor Infiltration
(SALDVI) has been successfully used to fabricate small three-dimensional SiC/SiC and
SiC/metal powder parts. Ceramic joints made by this technique have been limited by the
throwing power of the laser resulting in incomplete joint penetration. Studies were performed to
show the effectiveness of a fiber laser, with a wavelength of 1070 nm, for a joining process. The
ability of the laser to penetrate a powder bed was utilized in the joint fabrication. The
combination of powder fill, and deep laser penetration into the powder bed shows potential in the
field of ceramic joining.
(University of Texas at Austin, 2009-09) Kambly, Kiran; Yuan, Dajun; Shao, Peng; Das, Suman
Large Area Maskless Photopolymerization (LAMP) is a high throughput direct digital
manufacturing technology being developed for producing ceramic investment casting molds.
Polymerization shrinkage and accompanying stresses developed during photopolymerization of
ceramic particle-loaded resins in LAMP can cause deviations from the desired geometry. The
extent of deviations depends on photoinitiator concentration, filler loading, degree of monomer
conversion and operating parameters such as energy dose. An understanding of shrinkage and
stresses built up in the part can assist in developing source geometry compensation algorithms
and exposure strategies to alleviate these effects. Real-time Fourier Transform Infrared
Spectroscopy (RTFTIR) operated in Attenuated Total Reflectance (ATR) mode is used to
characterize the three-dimensional shrinkage stresses. This work is sponsored by DARPA Grant
(University of Texas at Austin, 2009-09-15) Spierings, A.B.; Levy, G.
Selective Laser Melting is a powder based additive manufacturing process where the metallic
powder particles are fused to 3D parts using a high energy laser beam. Much work has already
been conducted to investigate the details of the process, suitable materials and process parameters
and further more. As metallic powders are the raw material for this process, there are still a lot of
open questions relating to suitable grain size distributions for dense parts with regard to
productivity, surface quality, mechanical strength and ductility. The present work shows the
results of density measurements of parts, produced using three different particle size distributions
and different energy densities of the laser beam. Two layer thicknesses of 30μm and 45μm were
It is shown that without a minimal amount of fine grains, which are able to fill the voids between
the coarse grains, lower scan speeds are needed in order to produce dense parts. Furthermore, the
differences in the relation of the powders to the densities, the layer thicknesses and laser scan
speeds indicate, that the powder grain size distribution plays an important role and that should be
taken into account for optimal results. This work is a contribution to the ASTM initiative F42 for
(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.