2017 International Solid Freeform Fabrication Symposium

Permanent URI for this collectionhttps://hdl.handle.net/2152/89792

Proceedings for the 2017 International Solid Freeform Fabrication Symposium. For more information about the symposium, please see the Solid Freeform Fabrication website.>

The Twenty-Eighth Annual International Solid Freeform Fabrication (SFF) Symposium – An Additive Manufacturing Conference, held at The University of Texas in Austin on August 7-9, 2017, was attended by 654 researchers from 20 countries. The number of oral and poster presentations increased to 473 this year. The meeting was held on the Hilton Austin in the downtown area. The meeting consisted of a Monday morning plenary, 50 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. Allison Beese from Penn State University. Dr. Ian Gibson form Deakin University in Australia won the International Freeform and Additive Manufacturing Excellence (FAME) Award.

There are 231 papers in the conference proceedings. Papers marked “REVIEWED” in the title area were peer reviewed by two external reviewers. We have sequentially numbered the pages of the papers 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 (N00014-17-1-2471) and the National Science Foundation (CMMI-1639406) for supporting this meeting financially. The meeting was co-organized by 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. The 2018 SFF Symposium is set for August 13-15, 2018 in Austin, Texas USA.

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2017 International Solid Freeform Fabrication Symposium Table of Contents
(2017) Laboratory for Freeform Fabrication and University of Texas at Austin
Comparative Costs of Additive Manufacturing vs. Machining: The Case Study of the Production of Forming Dies for Tube Bending
(University of Texas at Austin, 2017) Previtali, B.; Demir, A.G.; Bucconi, M.; Crosato, A.; Penasa, M.
Additive manufacturing processes for metallic components become economically viable when they substitute conventional processes that make use of moulds and dies to produce casting or semi-finished parts with high added value. Common examples are: i) components in aerospace or energy sectors obtained by investment casting in high-temperature alloys; ii) personalized prostheses and implants in biocompatible metals in the biomedical sector. In both cases, the annual batch size is low and often limited to a single or few pieces. However, for many other sectors decision making for process substitution from conventional to AM processes requires a correct economic analysis. The cost of AM processes depends also on the use of technological advantages. The paper explores the economic feasibility of selective laser melting (SLM) process when producing tube-forming tools. The analysed industrial case addresses the whole annual production of bending tools, traditionally made by milling from a solid block. The aim of this work is to identify the levers of the process that make additive production advantageous, even in more traditional sectors like tooling when different tool materials are used (namely a tool steel and a bronze alloy) and when hybrid manufacturing (subtractive plus additive) is carried out.
Design and Preliminary Evaluation of a Deployable Mobile Makerspace for Informal Additive Manufacturing Education
(University of Texas at Austin, 2017) Sinha, Swapnil; Rieger, Kelsey; Knochel, Aaron D.; Meisel, Nicholas A.
Additive Manufacturing (AM) has played an integral part in the growth of makerspaces as democratization of manufacturing continues to evolve. AM has also shown potential in enabling the successful amalgamation of art (A) with science, technology, engineering, and math (STEM) disciplines, giving new possibilities to STEAM subjects and its implementation. This paper presents the conceptual design and development of a deployable, mobile makerspace curriculum focused on AM education for a diverse range of participant backgrounds, ages, and locations. The aim is to identify effective means of informal learning to broaden participation and increase engagement with STEAM subjects through the context of AM. The curriculum is envisioned as “material-to-form,” offering separate modules that present opportunities for self-directed learning through all the stages of design, material use, and manufacturing associated with AM. Pilot studies of the curriculum were performed to identify potential changes to improve the effectiveness of the mobile makerspace.
Applied Solvent-Based Slurry Stereolithography Process to Fabricate High-Performance Ceramic Earrings with Exquisite Details
(University of Texas at Austin, 2017) Wang, Jia-Chang; Dommati, Hitesh
This paper discusses the application of Slurry based Stereolithography additive manufacturing process in the fabrication of complex earring models without any support structures requirement, using High-Performance Ceramic (HPC) materials. The earring model chosen in this study is a Rose flower with blossomed petals. The petals have edge thickness in microns and extreme overhangs with a custom text and logo on the bottom. Using any other ceramic additive manufacturing process, it requires support structures to build this model. The support removal in such minute structures is not easy and not always successful. Using Solvent based Slurry Stereolithography (3S) process, models with the micron details and overhangs can be easily built. This is enabling the neat and clean post-processing procedure to maintain the exquisite details and also gain high surface quality. The ceramic material used in this application is alumina. With some additives, it will show in different colors like sapphire. The resultant flowers are vividly shown in white, pink, green, and blue. In this study, it is also discussed about the slurry process, Stereolithography system, and proven applications of the 3S process.
New Filament Deposition Technique for High Strength, Ductile 3D Printed Parts
(University of Texas at Austin, 2017) Rodriguez, Nicholas; Crawford, Richard
This paper proposes a method to use an off-the-shelf commercial Fused Deposition Modeling (FDM) 3D printer with minimal modifications to manufacture higher strength parts that fail in a ductile rather than brittle manner. A novel scan pattern designed to increase interlayer adhesion in FDM parts is modeled and tested to determine its effect on mechanical properties of printed ABS parts. Results from three-point bend testing indicate a significant increase in part strength and elongation at break when using the proposed scan pattern compared to parts manufactured using a traditional scan pattern.
Geometrical Accuracy of Holes and Cylinders Manufactured with Fused Deposition Modeling
(University of Texas at Austin, 2017) Knoop, F.; Schoeppner, V.
A widely used Additive Manufacturing (AM) technology is Fused Deposition Modeling (FDM) to create prototypes and end-use parts with close-to-production thermoplastics. For their use as a final product, it is necessary that additively manufactured parts strictly adhere to the geometrical requirements of the technical drawing. In this paper, the holes and cylinders of the cylindrical elements are investigated in terms of achievable geometrical accuracy. For this purpose, different test specimens that allow a measurement of inner and outer diameters from 3 to 80 mm were designed. All specimens were measured with a coordinate measuring machine (CMM) to evaluate deviations from the nominal dimension and form deviations. The measuring method includes a scanning of the surface to record the course of dimensional deviations over the diameter. Thus, it was possible to visualize how deviations on cylindrical elements manufactured in FDM occur. In order to counteract these deviations and to improve the dimensional accuracy, different shrink factors and filling patterns were investigated. Consequently, an improvement of the dimensional accuracy was achieved.
Powder Bed Fusion Metrology for Additive Manufacturing Design Guidance
(University of Texas at Austin, 2017) Allison, Jared; Sharpe, Conner; Seepersad, Carolyn Conner; Kubiak, Steven
Design for additive manufacturing (DFAM) guidelines are important for helping designers avoid iterations and fully leverage the design freedoms afforded by additive manufacturing (AM). Guidelines can be generated via metrology studies that use test parts to characterize statistically the geometric capabilities of specific AM processes. Towards that end, a test part is designed for polymer selective laser sintering (SLS) that incorporates an array of geometric features in an extremely compact volume, such that it can be easily inserted into existing builds. The part is then built in multiple materials, build orientations, and locations within the build chamber in a factorial-style study to assess the variation attributed to each processing parameter. Both part resolution and accuracy are investigated. Upon measurement of the test parts, tolerances and design allowables are established and compiled into a set of design guidelines for SLS. The guidelines are then made publicly accessible through an online web tool to be used by designers creating parts for polymer SLS.
Investigation of Optical Coherence Tomography Imaging in Nylon 12 Powder
(University of Texas at Austin, 2017) Lewis, Adam; Katta, Nitesh; McElroy, Austin; Milner, Thomas; Fish, Scott; Beaman, Joseph
Optical Coherence Tomography (OCT) has shown promise as a new process sensor in selective laser sintering (SLS) which can yield depth resolved data not attainable with conventional sensors. However, OCT images of nylon 12 SLS parts and powder contain artifacts, which have not been previously investigated in literature. These artifacts along with the highly scattering nature of the SLS parts and powder limit the imaging depth, which decreases the usefulness of OCT imaging. This study seeks to study the causes of the imaging artifacts and proposes and investigates methods to improve OCT imaging depth in nylon 12 powder.
Material Selection on Laser Sintered Stab Resistance Body Armor
(University of Texas at Austin, 2017) Yuan, Mengqi; Liu, Yu; Qian, Xinming
Stab resistant body armor (SRBA) is essential defensive equipment to protect the human body from injury due to stabbing. The conventional SRBAs are heavy and inflexible. Therefore a new type of SRBA has been recently developed using Laser Sintering (LS), which has resulted in a substantial improvement to SRBA in terms of structure and material design. In this development, carbon fiber was employed in the polyamide matrix to obtain the optimal stab resistant performances. Four kinds of materials were used and showed that the polyamide/carbon fiber (PA/CF) composite improved the stab resistance property compared to pure polyamide (PA). The stab resistance performances of flat plates were weaker than structured plates. The penetration depth of the PA/CF structured plate was 2 mm less than the pure PA structured plate. SEM observations of the products confirmed experimental conclusions that the addition of the CF largely improved the plate stab resistance. Moreover, using the PA/CF structured plate to produce SRBA would reduce the weight of the product by 30-40% comparing to the conventional SRBA, which would greatly reduce the physical burden to the wearer and largely improve the chance that the armor would be used.
Qualification Challenges with Additive Manufacturing in Space Applications
(University of Texas at Austin, 2017) Dordlofva, Christo; Törlind, Peter
Additive Manufacturing (AM) has the potential to remove boundaries that traditional manufacturing processes impose on engineering design work. The space industry pushes product development and technology to its edge, and there can be a lot to gain by introducing AM. However, the lack of established qualification procedures for AM parts has been highlighted, especially for critical components. While the space industry sees an advantage in AM due to expensive products in low volumes and long lead-times for traditional manufacturing processes (e.g. casting), it also acknowledges the issue of qualifying mission critical parts within its strict regulations. This paper focuses on the challenges with the qualification of AM in space applications. A qualitative study is presented where conclusions have been drawn from interviews within the aerospace industry. The results highlight important gaps that need to be understood before AM can be introduced in critical components, and gives insight into conventional component qualification.
Technological Challenges for Automotive Series Production in Laser Beam Melting
(University of Texas at Austin, 2017) Haeckel, Felix; Meixlsperger, Maximilian; Burkert, Torsten
Compared to traditional production methods, Additive Manufacturing enables a tool free production leading to higher flexibility, freedom of design and lightweight potential. For these reasons the BMW Group is proceeding from the production of prototypes to the direct series production of parts. For metal components, the process of selective Laser Beam Melting is able to realize these potentials. Aside from the economic issues, technological challenges also have to be met. Among them is achieving consistent part quality in the production of same parts. To achieve technical specifications compliant in series production, a defined process stability and reproducibility of the part properties is needed. This reproducibility is investigated for the process of selective Laser Beam Melting. Also variables which have the biggest impact on the part quality throughout a simulated series production are being examined. Thus the reproducibility of the process can be quantified. To guarantee a high and stable part quality in the future, approaches are being developed to monitor or systematically prevent influences, which are found to have a negative effect on the process quality.
A Mobile Robot Gripper for Cooperative 3D Printing
(University of Texas at Austin, 2017) Steck, Jason; Morales-Ortega, Rolando; Currence, Jacob; Zhou, Wenchao
Cooperative 3D printing is an emerging technology that aims to overcome several limitations of contemporary 3D printing (e.g., print size, cost, complexity) by allowing multiple mobile 3D printers (or printhead-carrying mobile robots) to work simultaneously on a single print job. In particular, one challenge of 3D printing is the inability to incorporate pre-manufactured components in a structure without human intervention. In this paper, we present a mobile robot gripper that can work with other mobile 3D printers to pick and place pre-manufactured components into a 3D printed structure during the printing process. First, we designed a simple gripper using a rack and pinion actuator that can be driven by a single stepper motor like a regular extrusion printhead. Next, a mobile robot gripper is developed with the designed gripper mechanism. Finally, we tested the mobile robot gripper for picking and placing objects using G-code commands. Results show the mobile robot gripper can successfully pick and place pre-manufactured components into a 3D printed structure. This development will potentially enable autonomous hybrid manufacturing that combines 3D printing and traditional manufacturing to improve the quality and capability for manufacturing complex products.
Fabrication and Quality Assessment of Thin Fins Built Using Metal Powder Bed Fusion Additive Manufacturing
(University of Texas at Austin, 2017) Dunbar, Alexander J.; Gunderman, Gabrielle J.; Mader, Morgan C.; Reutzel, Edward W.
Powder bed fusion additive manufacturing (PBFAM) is well suited for the fabrication of metallic components with thin features that would be otherwise impractical using other manufacturing methods. As component designs begin to take full advantage of the capabilities of additive manufacturing, so must the capability of measurement techniques used in assessment of quality increase. The characterization of quality may be application specific, requiring different metrics for different uses, e.g. impact on thermal vs. mechanical considerations. Here, thin fins are built with a wide range of processing conditions to test the limits of thin, metallic components using PBFAM. These thin fins are inspected using novel computed tomography (CT) based measurement techniques to assess their build quality. Within the process parameters tested, fins were successfully built thinner than manufacturer-recommended minimum wall thickness using default process parameters. The quality of these fins was assessed utilizing post-build non-destructive evaluation techniques developed herein.
Design and Additive Manufacturing of a Composite Crossflow Heat Exchanger
(University of Texas at Austin, 2017) Mulholland, T.; Felber, R.; Rudolph, N.
Additive manufacturing (AM) with composite materials reveals new possibilities for direct manufacturing of end-use products, breaking the paradigm of 3D printing as only a prototyping or pre-production technique that has been the norm for many AM technologies. A crossflow air-to-water heat exchanger (HX) was designed for manufacturing via fused filament fabrication (FFF). Design iterations improved the manufacturability, considering issues such as geometric fidelity, watertightness, print time, support material, and manufacturing cost. Carbon fiber fillers enhanced the thermal conductivity of the base polyamide resin, allowing for thermal HX performance comparable to conventional aluminum finned tube heat exchangers. The anisotropic thermal conductivity impacts the heat exchanger performance. The design and manufacturing challenges reveal additional routes to continued performance gains as the HX is scaled up to an 8 kilowatt product.
Design and Process Considerations for Effective Additive Manufacturing of Heat Exchangers
(University of Texas at Austin, 2017) Handler, Evan; Sterling, Amanda; Pegues, Jonathan; Ozdes, Huseyin; Masoomi, Mohammad; Shamsaei, Nima; Thompson, Scott M.
This paper provides some insights into using powder bed fusion (PBF) techniques for additively manufacturing heat transfer equipment (HTE), such as heat pipes and heat sinks. Background information is provided on the operating principles of PBF and the subsequent features of parts fabricated via PBF. Examples of heat transfer equipment produced using PBF are discussed. Some benefits and challenges associated in using PBF for generating effective heat transfer equipment are summarized.
Areal Surface Characterization of Laser Sintered Parts for Various Process Parameters
(University of Texas at Austin, 2017) Delfs, P.; Schmid, H.-J.
Laser sintered polymer parts consist of rough surfaces due to the layered manufacturing and adherence of incomplete molten particles. The absolute roughness depend on various process parameters like build angle, spatial position, build temperature, exposure order and layer time. Analyses with the help of several areal roughness values of DIN EN ISO 25178-2 considering these parameters are introduced in this paper. Multiple build jobs with 120 µm layer thickness and PA2200 powder were built on an EOS P396 machine using the same build job design with varying process parameters. An individual sample part was designed to receive lots of surface topography information with optical 3D measurements. The results show roughness dependencies for 0° to 180° build angles in 15° steps and eleven distributed in-plane and three axial direction positions depending on different build temperatures, reversed exposure order and layer times. Limitations of the varied parameters are finally derived for the manufacturing of improved surface qualities.
Approaching Rectangular Extrudate in 3D Printing for Building and Construction by Experimental Iteration of Nozzle Design
(University of Texas at Austin, 2017) Lao, Wenxin; Li, Mingyang; Masia, Lorenzo; Tan, Ming Jen
In Extrusion based 3D Printing technology, the voids could be reduced and the surface finish of printed parts could be improved with extrudate shape optimization. For large-scale 3D Printing technology like 3D Printing for Building and Construction, reducing printed layer height would increase the fabrication time drastically, while having few effect on voids reduction and surface finish improvement. In this paper, an iterative experimental approach to achieve the optimized nozzle design for rectangular shaped extrudate was proposed. Two nozzle prototypes were manufactured by Fused Deposition Method and implemented for experimental tests, then a new nozzle design was created based on the experimental extrudate shapes. This process iterated until a good rectangular extrudate shape was obtained. Printing tests were conducted with the optimized nozzle, which showed the designed nozzle could help to eliminate the voids among the printed parts and guarantee good surface finish without losing the speed of printing.
Rational Decision-Making for the Beneficial Application of Additive Manufacturing
(University of Texas at Austin, 2017) Deppe, Gereon; Kaesberg, Martin; Koch, Rainer
Additive Manufacturing is a technology that offers a high potential for industrial companies. Nevertheless, companies lack experience with this new technology and face the problem to identify processes where a successful and beneficial application can be achieved. They have to be supported in this analysis with a decision support tool which is capable to compare different manufacturing or repair approaches in order to determine the optimal solution for the correspondent use case. This is not always driven solely by costs but can also be critically affected by further influencing factors. This is why the decision support takes into account also time and quality alongside the costs. For a time-critical spare part supply, for example within aerospace sector, they are substantial for taking a decision. The presented decision support features a multi-attribute decision-making approach for selecting the most appropriate process, either Additive Manufacturing, conventional technologies or an external procurement.
Ramp-Up-Management in Additive Manufacturing – Technology Integration in Existing Business Processes
(University of Texas at Austin, 2017) Büsching, J.; Koch, R.
In conventional manufacturing, ramp-up-management describes the planning and organization of the period between finished product development and the achievement of full production capacity for defined products. This classification has to be adapted and restructured by means of product independent and tool-free production in additive manufacturing. Therefore ramp-up-management already starts with decisions on the extent of the use of additive manufacturing, includes the building of technology-know-how as well as the technology integration into processes and infrastructure of the company and ends with the attainment of a sufficient process reliability for the AM-machine. This paper focuses on technology integration in processes and infrastructure, which is part of the German research project OptiAMix. In this project, new systems for process state analysis adapted to additive manufacturing and methods for the optimal integration of additive manufacturing are developed. Furthermore ways of using the synergies of existing infrastructures and new innovative production technologies are determined.
Integrating AM into Existing Companies - Selection of Existing Parts for Increase of Acceptance
(University of Texas at Austin, 2017) Kruse, A.; Reiher, T.; Koch, R.
In many branches in the design engineer department, product designs are just variations of existing parts. To bring the additive manufacturing technology closer to the Designer, it is necessary to show them which of their existing, conventionally manufactured parts can be produced with this technology. A part selection methodology supports designers in the decision whether a part is suitable for additive manufacturing or not. Due to the potential of the technology, which was especially seen in the aerospace industries, many criteria of the methodology were initially adapted for this industry. Furthermore the methodology is based on a quantified weighting system, which comes to a certain subjectivity. For future use, a development towards a less subjective methodology should be accomplished. Through a more detailed adaption for individual industries and a simplification of the input mode, the objectivity of the criteria can be increased. Likewise, the input time can be reduced by simplifying the questioning. A more efficient part selection will be achieved by a better weighting system. In the BMBF project “OptiAMix” this methodology is supposed to be further developed for highly different branches. By a better weighting system, the part selection will be more efficient. Therefore, the willingness for the use of the improved selection and for the additive manufacturing technology will be increased.

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