ccm/sff-papers · Datasets at Hugging Face

['Johanson, Roy', 'Kikuchi, Noboru', 'Papalambros, Panos']

2018-05-03T18:42:28Z

1993

Mechanical Engineering

doi:10.15781/T2FB4X41H

http://hdl.handle.net/2152/65057

eng

1993 International Solid Freeform Fabrication Symposium

Open

['Department of Mechanical Engineering and Applied Mechanics', 'MAXWELL', 'Topology', 'Recursive Mask and Deposit']

Homogenization Design and Layered Manufacturing of a Lower Control Arm in Project MAXWELL

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ad2234cb-d3db-4370-b4d5-68260c30340c/download

null

We briefly describe a new methodology for the design and manufacture of mechanical components and demonstrate the process for the design of an automobile suspension component. The methodology is a unique coupling between advanced technologies for product design and manufacture, which leads to the rapid realization of superior products. The concurrent design and analysis strategy yields information about the optimal structural layout, as well as details about the material composition. The fabrication of such designs requires unconventional manufacturing processes, such as layered manufacturing. Project MAXWELL, therefore, offers the possibility for the integration of layered manufacturing into the mainstream product development and fabrication process.

null

['Buls, S.', 'Clijsters, S.', 'Kruth, J.-P.']

2021-10-12T19:40:11Z

2014

Mechanical Engineering

null

['https://hdl.handle.net/2152/88725', 'http://dx.doi.org/10.26153/tsw/15659']

eng

2014 International Solid Freeform Fabrication Symposium

Open

['Selective Laser Melting', 'PID feedback controller', 'homogenous melt pool intensity distribution', '2D intensity maps', 'laser scanning', 'melt pool intensity distribution']

Homogenizing the Melt Pool Intensity Distribution in the SLM Process through System Identification and Feedback Control

Conference paper

https://repositories.lib.utexas.edu//bitstreams/b39a4667-f62e-4a86-a332-464f859dcd50/download

University of Texas at Austin

The common scanning strategies in Selective Laser Melting lead to an inhomogeneous melt pool intensity distribution throughout the different layers and scan tracks. This results in various defects such as porosity at the edges, residual stresses, or even excessive warping and delamination. In this research, this issue is resolved by the implementation of an on-line and real-time PID feedback controller. The PID feedback controller will alter the laser power based upon the melt pool intensity resulting in a homogeneous intensity distribution throughout the different scan tracks and layers. 2D intensity maps can be generated from the on-line monitoring system during the production of a benchmark part and will serve as validation for the PID feedback controller.

null

['Baumers, M.', 'Tuck, C.', 'Dickens, P.', 'Hague, R.']

2021-10-12T21:03:59Z

2014

Mechanical Engineering

null

['https://hdl.handle.net/2152/88741', 'http://dx.doi.org/10.26153/tsw/15675']

eng

2014 International Solid Freeform Fabrication Symposium

Open

['multi-material Additive Manufacturing', 'Additive Manufacturing', 'material jetting', 'build-time', 'energy consumption', 'production cost', 'photopolymers']

How Can Material Jetting Systems Be Upgraded for More Efficient Multi-Material Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3a294c41-d03e-4fd7-82da-676986ba3cd4/download

University of Texas at Austin

Multi-material Additive Manufacturing (AM) platforms are able to build up components from multiple materials in a single layer-by-layer process. It is expected that this capability will enable the manufacturing of functional structures within products, such as conductive tracks or optical pathways, resulting in radically novel products with unprecedented degrees of functional density. An important variant of commercially available multi-material AM technology is material jetting, which is currently in commercial use for the manufacture of prototypes and design studies. This paper presents a detailed process model of build-time, energy consumption and production cost for the Stratasys Objet 260 Connex system, analyzing the contemporaneous deposition of two different types of photopolymers (Veroclear RGD810 and Tangoblack FLX973). By using this process model to anticipate the effects of various upgrades to the investigated system, such as a larger build volume and a higher deposition speed, this forward-looking paper explores pathways to enhancing the value proposition of such multi-material systems through incremental technology improvement.

null

['Stevenson, A.', 'Baumers, M.', 'Segal, J.', 'Macdonell, Sarah']

2021-11-08T21:59:32Z

2017

Mechanical Engineering

null

['https://hdl.handle.net/2152/90053', 'http://dx.doi.org/10.26153/tsw/16974']

eng

2017 International Solid Freeform Fabrication Symposium

Open

['cost impact', 'cost analysis', 'part consolidation', 'additive manufacturing', 'PC', 'AM']

How Significant is the Cost Impact of Part Consolidation Within AM Adoption?

Conference paper

https://repositories.lib.utexas.edu//bitstreams/52d0b8f1-cf14-4a39-9085-4e48785bec54/download

University of Texas at Austin

Successful implementation of advanced manufacturing technologies requires a robust pre-installation phase involving evaluation and justification of potential benefits. However, despite part consolidation (PC) being described as one of the major benefits of additive manufacturing (AM), there has been very little quantification of its potential impact on costs. This makes it difficult for organisations to consider all the benefits of AM adoption. A case study research approach has been used to develop an empirical cost model based on PC for the development and production stages of a product, which can be adapted by organisations during their own pre-installation stage. The case studies involve re-design of existing sub-assemblies within a laboratory instrument producer, and the resulting cost model has been trialed using empirical data. The results show that AM has the potential to considerably reduce part count by up to 93% and associated costs by up to 85%. The significant cost saving occurs where PC results in the consolidation of numerous components thereby eliminating considerable cost elements.

null

['Weflen, E.D.', 'Peters, F.E.', 'Frank, M.C.']

2023-04-05T13:42:42Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117773', 'http://dx.doi.org/10.26153/tsw/44652']

eng

2022 International Solid Freeform Fabrication Symposium

Open

Additive manufacturing

Hybrid Additive and Subtractive Manufacturing of Direct-Heated Tooling

Conference paper

https://repositories.lib.utexas.edu//bitstreams/47308ae5-19dc-44ff-b237-e3650cc74c0a/download

null

Pre-heating is a common requirement for production tooling in applications such as compression and injection molding. While the carbon fiber reinforcements commonly used in large-area additive manufacturing improve the thermal conductivity of polymers, they are still far below that of metal tooling. This study presents a method for direct, local Joule heating of tooling without the need for additional heating elements. A current is induced in the composite tooling, resulting in resistance heating of the substrate. High conductivity material is locally embedded to achieve local control over the heating characteristics. Embedding of the conductive material is accomplished by selectively switching material compositions during the printing process. Demonstration tooling is produced using hybrid additive and subtractive manufacturing using an AMBIT XTRUDE in a HAAS machining center and evaluated with thermal imaging. Direct heating of tooling expands the potential applications of additive manufacturing by overcoming the challenges of low thermal conductivity materials.

null

['Aremu, A.', 'Ashcroft, I.', 'Wildman, R.', 'Hague, R.', 'Tuck, C.', 'Brackett, D.']

2021-10-04T21:38:32Z

8/17/11

Mechanical Engineering

null

['https://hdl.handle.net/2152/88356', 'http://dx.doi.org/10.26153/tsw/15295']

eng

2011 International Solid Freeform Fabrication Symposium

Open

['topology optimization', 'additive manufacturing', 'adaptive meshing strategy', 'bidirectional evolutionary structural optimization']

A Hybrid Algorithm for Topology Optimization of Additive Manufactured Structures

Conference paper

https://repositories.lib.utexas.edu//bitstreams/913c9e8b-9f84-4df0-ba63-2b73b06004c7/download

University of Texas at Austin

Most topology (TO) algorithms involve the penalization of intricate structural features to eliminate manufacturing difficulties. Since additive manufacturing is less dependent on manufacturing constraints, it becomes necessary to adapt these algorithms for AM. We propose a hybrid algorithm consisting of an adaptive meshing strategy (AMS) and a modified form of the bidirectional evolutionary structural optimization (BESO) method. By solving a standard cantilever problem, we show that the hybrid method offers improved performance over the standard BESO method. It is proposed that the new method is more suitable for optimizing structures for AM in a computational efficient manner.

null

Boudreaux, J.C.

2021-10-19T15:12:40Z

2014

Mechanical Engineering

null

https://hdl.handle.net/2152/89293

eng

2014 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'hybrid automata', 'operational features', 'technical issues']

Hybrid Automata in the Context of Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/99d4d6b8-934d-4480-8feb-1d5d746760f1/download

University of Texas at Austin

To maintain the forward momentum of additive manufacturing technology, it is necessary to thoroughly evaluate new and potentially useful technological developments in this field. One such development is the intense interest being directed to the field of hybrid automata (HA). Hybrid automata combine both the discrete processing behavior of finite automata as well as the continuous, or flow, behavior of dynamical systems. At this point, some important results on hybrid automata have been obtained, but many open questions remain, including those concerning the decidability of HS operational procedures. (Recall that decidability is directed to a decision problem, that is, a definite true-or-false response given by an effective procedure.) Some important decidability results for HAs have been obtained. For example, in [Henzinger et al.1998] the reachability problem for timed automata (an HA class) has been convincingly shown to be decidable. However, it should also be noted that subtle and difficult issues have been identified, e.g., [Fraenzle 1999], [Asarin, Collins, 2005]. This paper will provide a summary review of the operational features of HAs as they might pertain to additive manufacturing, and then briefly consider the following technical issues: (i) are the classical models of the real numbers best suited to deal with the necessarily approximate measures of physical systems or would non-standard analysis of [Robinson 1996] be a better fit; and (ii) would the introduction of “noisy semantics” and finite arithmetic precision, following [Freidlin, Wentzell 1984], be a better work around?

null

['Wade, Charles', 'Borish, Michael']

2023-01-26T14:39:54Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117308', 'http://dx.doi.org/10.26153/tsw/44189']

eng

2022 International Solid Freeform Fabrication Symposium

Open

hybrid curve fitting

Hybrid Curve Fitting for Reducing Motion Commands in Object Construction

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6748fff8-633b-4d95-9ee8-7f087e7499c5/download

null

Existing slicing software for additive manufacturing typically requires a triangulated mesh as its input. Triangulated meshes are approximate representations of exact CAD models. Despite the loss in dimensional accuracy, triangulated meshes are used because they are computationally easier to cross-section and offset than the exact geometry in CAD format. When a triangulated object is prepared, the resulting machine instructions include only linear motion commands. Numerous modern motion controllers can move in arc and spline motions; however, the absence of slicing software that supports curvature prevents these commands from being leveraged. To address this limitation, this paper presents a method for the hybrid reconstruction of arcs and splines as a post-processing step to traditional slicing. This method can greatly reduce the number of motion commands required to construct an object by printing smooth curved surfaces. This concise representation of tool-pathing allows for more even extrusion and is computed without a major impact on slicing time.

null

['Zhang, Haiou', 'Xie, Yang', 'Rui, Daoman', 'Wang, Guilan']

2021-10-07T18:13:22Z

8/16/13

Mechanical Engineering

null

['https://hdl.handle.net/2152/88497', 'http://dx.doi.org/10.26153/tsw/15431']

eng

2013 International Solid Freeform Fabrication Symposium

Open

['new AM method', 'hybrid deposition and micro rolling', 'HDMR', 'metallic parts', 'high performance', 'efficiency and low cost']

Hybrid Deposition and Micro Rolling Manufacturing Method of Metallic Parts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d192824d-b46f-490d-a7bd-f1adb3b41af3/download

University of Texas at Austin

To conquer the bottleneck problems of cracking, deformation, low accuracy and performance in existing additive manufacturing (AM) process, a new hybrid direct manufacturing method of metallic parts which integrates freeform deposition with micro rolling is proposed in this paper. The principle, devices and simulations are introduced and the comparison with Freeform Deposition Fabrication method are made through experiments, showing that hybrid manufactured parts has distinctive features of higher accuracy and better microstructures. The tensile strength is increased by 33% for stainless steel while the elongation percentage is improved more than 2 times. By using the Φ1.6mm wire in a feed rate of 1060mm/min, the deposition rate can get to 10kg/h. This method is appropriate for fabricating large-scale metal parts with outstanding quality, efficiency and low cost.

null

['Baldwin, Martha', 'Meisel, Nicholas A.', 'McComb, Christopher']

2024-03-27T15:42:27Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124486', 'https://doi.org/10.26153/tsw/51094']

en

2023 International Solid Freeform Fabrication Symposium

Open

['multi-lattice transition', 'geometry autoencoder', 'property autoencoder', 'additive manufacturing']

Hybrid Geometry/Property Autoencoders for Multi-Lattice Transitions

Conference paper

https://repositories.lib.utexas.edu//bitstreams/cc4e6968-ba6f-4da4-adca-75bd2a43917f/download

University of Texas at Austin

Additive manufacturing has revolutionized structural optimization by enhancing component strength and reducing material requirements. One approach used to achieve these improvements is the application of multi-lattice structures. The performance of these structures heavily relies on the detailed design of mesostructural elements. Many current approaches use data-driven design to generate multi-lattice transition regions, making use of models that jointly address the geometry and properties of the mesostructures. However, it remains unclear whether the integration of mechanical properties into the data set for generating multi-lattice interpolations is beneficial beyond geometry alone. To address this issue, this work implements and evaluates a hybrid geometry/property machine learning model for generating multi-lattice transition regions. We compare the results of this hybrid model to results obtained using a geometry-only model. Our research determined that incorporating physical properties decreased the number of variables to address in the latent space, and therefore improves the ability of generative models for developing transition regions of multi-lattice structures.

null

['Coronel, Jose L. Jr', 'Billah, Kazi Md Masum', 'Acosta Carrasco, Carlos F.', 'Barraza, Sol A.', 'Wicker, Ryan B.', 'Espalin, David']

2021-11-09T15:53:34Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90102', 'http://dx.doi.org/10.26153/tsw/17023']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['hybrid manufacturing', 'fused deposition modeling', 'power electronics', 'kapton coated wire', 'polycarbonate']

Hybrid Manufacturing with FDM Technology for Enabling Power Electronics Component Fabrication

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6e882235-e6b9-45cd-bc7c-ed49f9d1624a/download

University of Texas at Austin

The introduction of Kapton coated wires within a printed substrate presents the opportunity to design and fabricate power electronics components. Preventing dielectric breakdown of the printed substrate, the ultrasonic embedding approach enables complex geometrical embedding through customized software. This work presents the effective embedding of large diameter (14 AWG) kapton coated litz wire into polycarbonate (PC) substrate. Custom software allowed for generation of embedding toolpaths directly from the CAD model of the designed coupon. Results showed the most successful embedding paths were circular pre-formed cavities. Through characterization of a myriad of printed samples, an approach was developed for embedding large diameter wire. Through the use of the Foundry Multi3D System, the increased complexity of embedded electronic parts can further impulse the implementation of hybrid additive manufacturing in large scale applications.

null

['Medina, Frank', 'Lopes, Amit', 'Inamdar, Asim', 'Hennessey, Robert', 'Palmer, Jeremy', 'Chavez, Bart', 'Davis, Don', 'Gallegos, Phil', 'Wicker, Ryan']

2020-02-20T19:42:21Z

8/23/05

Mechanical Engineering

null

https://hdl.handle.net/2152/80043

eng

2005 International Solid Freeform Fabrication Symposium

Open

['commercial stereolithography machine', 'rapid prototyping', 'direct-write']

Hybrid Manufacturing: Integrating Direct Write and Stereolithography

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9b154873-8548-4daf-b188-ea5d3804ac59/download

null

A commercial stereolithography (SL) machine was modified to integrate fluid dispensing or direct-write (DW) technology with SL in an integrated manufacturing environment for automated and efficient hybrid manufacturing of complex electrical devices, combining threedimensional (3D) electrical circuitry with SL-manufactured parts. The modified SL system operates similarly to a commercially available machine, although build interrupts were used to stop and start the SL build while depositing fluid using the DW system. An additional linear encoder was attached to the SL platform z-stage and used to maintain accurate part registration during the SL and DW build processes. Individual STL files were required as part of the manufacturing process plan. The DW system employed a three-axis translation mechanism that was integrated with the commercial SL machine. Registration between the SL part, SL laser and the DW nozzle was maintained through the use of 0.025-inch diameter cylindrical reference holes manufactured in the part during SL. After depositing conductive ink using DW, the SL laser was commanded to trace the profile until the ink was cured. The current system allows for easy exchange between SL and DW in order to manufacture fully functional 3D electrical circuits and structures in a semi-automated environment. To demonstrate the manufacturing capabilities, the hybrid SL/DW setup was used to make a simple multi-layer SL part with embedded circuitry. This hybrid system is not intended to function as a commercial system, it is intended for experimental demonstration only. This hybrid SL/DW system has the potential for manufacturing fully functional electromechanical devices that are more compact, less expensive, and more reliable than their conventional predecessors, and work is ongoing in order to fully automate the current system.

null

['Liravi, Farzad', 'Jacob-John, Varun', 'Toyserkani, Ali', 'Vlasea, Mihaela']

2021-11-04T18:12:42Z

2017

Mechanical Engineering

null

['https://hdl.handle.net/2152/89993', 'http://dx.doi.org/10.26153/16914']

eng

2017 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'binder jetting', 'micro-deposition', 'hybrid printing', 'binder distribution', 'silicone materials']

A Hybrid Method for Additive Manufacturing of Silicone Structures

Conference paper

https://repositories.lib.utexas.edu//bitstreams/adcc6344-6bb7-48d8-ab3e-2ca671f2bab2/download

University of Texas at Austin

Developing an additive manufacturing (AM) technique for fabrication of complex-shaped silicone structures is a challenging task due to difficulties in layer-wise dispensing and stacking of such non-Newtonian viscous materials. The need for such a technique becomes apparent when surveying the ever-increasing applications of the silicone polymer in the biomedical sector. In this research, a hybrid powder-bed binder-jetting (PBBJ) and material micro-dispensing method (hybrid-PBBJ) is employed for the production of structures from silicone powder for the first time. The conventional PBBJ technique is coupled with a micro-syringe dispensing mechanism to make the layer-by-layer infiltration of fluidic silicone rubber into the silicone powder possible. Standard cylindrical (5 mm (D) ´ 3 mm (H)) and thin walled (10 mm (L) ´ 1.8 mm (H)) artefacts were manufactured as part of a design of experiment (DOE) and as a proof of concept. The AM parts were characterized in terms of geometry, porosity and mechanical performance. The DOE results will be deployed to subsequent manufacturing of complex structures.

null

['Ferreira, J. C.', 'Madureira, H.', 'Beira, R.']

2020-02-27T19:28:24Z

2006

Mechanical Engineering

null

['https://hdl.handle.net/2152/80094', 'http://dx.doi.org/10.26153/tsw/7115']

eng

2006 International Solid Freeform Fabrication Symposium

Open

rapid product development

Hybrid Prototypes to Assist Modeling Automotive Seats

Conference paper

https://repositories.lib.utexas.edu//bitstreams/b2388b2e-fc44-4613-b0af-34a3cb2f6d85/download

null

The development of new modular seats is an important issue in the automotive industry. However, is very time consuming and costly. Virtual models and hybrid prototypes could accelerate the car seats development process. The hybrid prototypes are mainly manufactured by rapid prototyping with multi materials. The objective of this paper is to establish a methodology to develop innovative lightweight multi-functional, modular car seats to be used in Multi-Purpose Vehicles (MPV), by means of FEA simulation and rapid prototyping additive/subtractive technologies utilizing multi materials. A case study is presented to validate the developed methodology. The manufactured hybrid prototype’s reproduces the main functionalities of the MPV modular seat, namely its three key positions: normal, stored and table.

null

['Frank, Matthew C.', 'Peters, Frank E.', 'Luo, Xiaoming', 'Meng, Fanqi', 'Petrzelka, Joseph']

2021-09-28T18:21:40Z

2009-09

Mechanical Engineering

null

['https://hdl.handle.net/2152/88145', 'http://dx.doi.org/10.26153/tsw/15086']

eng

2009 International Solid Freeform Fabrication Symposium

Open

['sand castings', 'Rapid Pattern Manufacturing']

A Hybrid Rapid Pattern Manufacturing System for Sand Castings

Conference paper

https://repositories.lib.utexas.edu//bitstreams/b71f75c4-f260-4fdb-aabb-c253c312cfc7/download

University of Texas at Austin

This paper presents a Rapid Pattern Manufacturing system developed for the sand casting process. It involves both additive and subtractive techniques whereby slabs are sequentially bonded and milled using layered toolpaths. As such, patterns are grown in a bottom-up fashion, both eliminating the need for multi-axis operations and allowing small features in deep cavities. Similar approaches exist in the literature; however, this system is specifically targeted at large wood and urethane sand casting patterns. This method introduces a novel support structure approach by integrating a flask into the pattern build process. We also present adaptive slicing algorithms that optimally place layer transitions to avoid thin sections near flats, peaks, and valleys or where interaction with chemically bonded sand could be problematic. The system has been implemented in an automated machine capable of producing patterns in excess of several thousand pounds. Preliminary testing of the system in the development of next generation military equipment is presented in a case study.

null

['Cohen, Daniel L.', 'Lipton, Jeffrey I.', 'Cutler, Meredith', 'Coulter, Deborah', 'Vesco, Anthony', 'Lipson, Hod']

2021-09-29T20:23:03Z

9/18/09

Mechanical Engineering

null

['https://hdl.handle.net/2152/88213', 'http://dx.doi.org/10.26153/tsw/15154']

eng

2009 International Solid Freeform Fabrication Symposium

Open

['Solid Freeform Fabrication', 'food', 'food production', 'culinary field', 'hydrocolloids', 'flavor agents', 'molecular gastronomy']

Hydrocolloid Printing: A Novel Platform for Customized Food Production

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ac256b22-d43d-434c-9162-05fefb14aa00/download

University of Texas at Austin

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.

null

['Arcaute, Karina', 'Ochoa, Luis', 'Mann, Brenda', 'Wicker, Ryan']

2020-02-24T15:17:24Z

8/23/05

Mechanical Engineering

null

['https://hdl.handle.net/2152/80080', 'http://dx.doi.org/10.26153/tsw/7101']

eng

2005 International Solid Freeform Fabrication Symposium

Open

stereolithography

Hydrogels in Stereolithography

Conference paper

https://repositories.lib.utexas.edu//bitstreams/298949ad-1be9-4f0f-8451-742243587600/download

null

The use of stereolithography (SL) for fabricating complex three-dimensional (3D) tissue engineered scaffolds of aqueous poly(ethylene glycol) (PEG) hydrogel solutions is described. The primary polymer used in the study was PEG-dimethacrylate (PEG-dma) with an average molecular weight (MW) of 1000 in distilled water with the photoinitiator Irgacure 2959 (I-2959). Successful layered manufacturing (LM) with embedded channel architecture required investigation of the photopolymerization characteristics of the PEG solution (measured as hydrogel thickness or cure depth) as a function of photoinitiator concentration and laser energy dosage for a specific photoinitiator type and polymer concentration in solution. Hydrogel thickness was a strong function of PI concentration and energy dosage. Curves of hydrogel thickness were utilized to successfully plan, perform, and demonstrate layered manufacturing of highly complex hydrogel scaffold structures, including structures with internal channels of various orientations. Successful fabrication of 3D, multi-layered bioactive PEG scaffolds containing cells was accomplished using a slightly modified commercial SL system (with 325 nm wavelength laser) and procedure. Human dermal fibroblast (HDF) cells were encapsulated in PEG hydrogels using small concentrations (~ 5 mg/ml) of acryloyl-PEG-RGDS (MW 3400) added to the photopolymerizable PEG solution to promote cell attachment. HDF cells were combined with the PEG solution, photocrosslinked using SL, and successfully shown to survive the fabrication process. The combined use of SL and photocrosslinkable biomaterials such as PEG makes it possible to fabricate complex 3D scaffolds that provide site-specific and tailored mechanical properties (i.e., multiple polymer materials) with a polymer matrix that allows transport of nutrients and waste at the macroscale and facilitates cellular processes at the microscale through precisely placed bioactive agents.

null

['French, M.R.', 'Yarberry, W.A. III', 'Pawlowski, A.E.', 'Shyam, A.', 'Splitter, D.A.', 'Elliott, A.M.', 'Carver, J.K.', 'Cordero, Z.C.']

2021-11-04T20:53:53Z

2017

Mechanical Engineering

null

['https://hdl.handle.net/2152/90025', 'http://dx.doi.org/10.26153/16946']

eng

2017 International Solid Freeform Fabrication Symposium

Open

['A356', '316L', 'stainless steel', 'hypervelocity impact', 'interpenetrating phase composite', 'additive manufacture']

Hypervelocity Impact of Additively Manufactured A356/316L Interpenetrating Phase Composites

Conference paper

https://repositories.lib.utexas.edu//bitstreams/91024cb5-e794-4a65-a696-43035c7c9600/download

University of Texas at Austin

We have examined the hypervelocity impact response of targets made from monolithic A356 and 316L stainless steel, as well as an additively manufactured A356/316L interpenetrating phase composite. 1.9 mm diameter spherical projectiles made from 2017 aluminum were fired at velocities of 5.9-6.1 km/s, allowing for the observation of multiple types of macro- and microstructural damage within each target. The macroscopic cratering damage to the A356/316L composite resembles that of the A356, but observations of both the cross section and the microstructural damage suggest that the A356/316L composite may be more resistant to spalling than A356 shielding with the same areal density.

null

['Seltzer, D.', 'Schiano, J.L.', 'Nassar, A.R.', 'Reutzel, E.W.']

2021-10-28T20:02:49Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89687

eng

2016 International Solid Freeform Fabrication Symposium

Open

['optical illumination', 'image processing', 'melt-pool width', 'build height', 'real-time control', 'melt pool geometry', 'directed energy deposition', 'additive manufacturing']

Illumination and Image Processing for Real-Time Control of Directed Energy Deposition Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/4e81070b-0b19-4bdd-aadf-2295e92a3b74/download

University of Texas at Austin

This paper describes the optical setup and image processing required to estimate melt-pool width and build height for real-time control of melt-pool geometry in directed energy deposition additive manufacturing. To overcome optical interference from plasma emissions and laser interactions, the melt-zone is imaged using laser illumination. A single camera, fixed to the processing laser, views the laser interaction zone and provides images for estimating melt-zone width and build height. Using a bandpass filter and a single aspheric lens, the camera system provides sufficient magnification and depth of field to achieve a 1-mil (25.4 µm) resolution. Maintaining melt-zone geometry within desired tolerances requires an image acquisition and processing rate on the order of 100 frames per second. This bandwidth is achieved by a Camera Link camera and field-programmable gate array that implements algorithms for estimating melt-pool width and build height. The design and experimental verification of the camera, illumination, and processing systems are discussed.

null

['Lang, Andrew', 'Ortiz Rios, Cesar', 'Newkirk, Joseph', 'Landers, Robert G.', 'Castle, James', 'Bristow, Douglas A.']

2021-12-07T18:01:22Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90739', 'http://dx.doi.org/10.26153/tsw/17658']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['image registration', 'matching error', '2D image', '3D image', '301L', 'stainless steel', 'laser powder bed fusion']

Image Registration and Matching Error in 2D and 3D for Laser Powder Bed Fusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/941818e2-4d10-43d0-857a-c3dbf8b019fb/download

University of Texas at Austin

This work outlines a method to register 2D and 3D images taken post-process and in situ from 301L stainless steel parts printed by Laser Powder Bed Fusion. The process uses DREAM.3D, an open-source software that provides for data transport in a non-proprietary format. The Robust Automatic Threshold selection technique is used to create a boundary point cloud of the part from each image. The Iterative Closest Point technique is applied to the point clouds for both 2D images and 3D image stacks to create an affine transformation matrix for registration. Multiple 2D SEM images of the same sampled layer are taken under different settings and imaging conditions and registered to a common target. Images from post-process X-ray Computed Tomography and an in situ short-wave infrared camera create 3D image stacks, which are directly registered in 3D space. Registration accuracy is validated by creating a correspondence list of the closest point in the registered point clouds and the matching error is calculated using mean average error. Mean average error is computed using point-to-point and point-to-plane methods; the pointto-plane method is shown to be more reliable. Finally, the registered 3D images are down sampled to the lower resolution image dimensions creating arrays of in situ and post-process data at the same resolution.

null

['Hauser, C.', 'Lewis, D. M.', 'Dunschen, M.', 'Egan, M.', 'Sutcliffe, C.']

2020-03-09T14:21:11Z

2007

Mechanical Engineering

null

['https://hdl.handle.net/2152/80182', 'http://dx.doi.org/10.26153/tsw/7201']

eng

2007 International Solid Freeform Fabrication Symposium

Open

Spiral growth manufacturing

Image Transformations and Printing of Plaster Layers in Spiral Growth Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a74fed63-7f95-40d7-9876-2f26b1876fce/download

null

Spiral growth manufacturing (SGM) is a high speed rapid manufacturing technique in which objects are built up, layer by layer, by simultaneously depositing, levelling and selectively consolidating thin powder layers onto a rotating build platform. The size and position of the jetted droplets are mapped by the position and greyscale level of pixels within an 8 bit greyscale bitmap image. This paper reports on the development of software in which mathematical algorithms apply geometric transformations to images in preparation for printing onto a rotating substrate. In support of this work, dimensional accuracy measurements of printed images and methods to correct radial print density variations are reported. The accuracy of printed images were found to be within ±0.2mm of their predicted size. The experimental work is briefly extended to the direct printing of plaster layers, formed by mixing two reactive ink solutions.

null

['He, Li', 'Fei, Fan', 'Wang, Wenbo', 'Song, Xuan']

2021-11-15T22:16:35Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90291', 'http://dx.doi.org/10.26153/tsw/17212']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['immiscible interface', 'direct metal drawing', 'colloidal suspension', 'self-stabilization', 'heat treatment']

Immiscible-Interface Assisted Direct Metal Drawing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/2093d106-c698-4742-9240-a8ee0d13e77d/download

University of Texas at Austin

State-of-the-art metal additive manufacturing (AM) techniques construct a three-dimensional (3D) structure through sintering or melting dry metal powders in a layer-by-layer fashion, which consequently results in some typical manufacturing defects in the final structure, such as residual stress and highly-orientated microstructures. To overcome these defects, we present a new low-cost metal AM process, named Immiscible-interface assisted Direct Metal Drawing (II-DMD), which fabricates self-supported and isotropic 3D metal structures by continuously extruding a metal colloidal suspension within a second immiscible matrix colloidal suspension. The shape of the metal colloidal suspension is stabilized due to the presence of an immiscible interface between the two colloidal suspension systems. Dense metal structures can be achieved via post-consolidation of the self-stabilized metal-matrix systems, including liquid-phase drying and metal-phase sintering. In this article, the immiscible-interface-assisted self-stabilization mechanism is studied. The post-consolidation processes are discussed. Several test cases were fabricated and characterized.

null

['Brennan-Craddock, J. P. J.', 'Bingham, G. A.', 'Hague, R. J. M.', 'Wildman, R. D.']

2020-03-11T15:26:53Z

2008

Mechanical Engineering

null

['https://hdl.handle.net/2152/80251', 'http://dx.doi.org/10.26153/tsw/7270']

eng

2008 International Solid Freeform Fabrication Symposium

Open

Rapid Manufacturing

Impact Absorbent Rapid Manufactured Structures (IARMS)

Conference paper

https://repositories.lib.utexas.edu//bitstreams/0301e9fe-4d31-4cc1-936c-2e1cecdba437/download

null

Rapid Manufacturing (RM) is increasingly becoming a viable manufacturing process due to dramatic advantages that it facilitates in the area of design complexity. Through the exploration of the design freedom afforded by RM, this paper introduces the concept and initial research surrounding Impact Absorbent Rapid Manufactured Structures (IARMS), with an application in sports personal protective equipment (PPE). Designs are based on the cellular structure of foams; the inherent advantages of the cellular structure are used as a basis to create IARMS that have the potential to be optimised for a specific impact absorbent response. The paper provides some initial results from compression testing

null

['Lindemann, C.', 'Jahnke, U.', 'Moi, M.', 'Koch, R.']

2021-10-12T18:50:56Z

8/16/13

Mechanical Engineering

null

['https://hdl.handle.net/2152/88718', 'http://dx.doi.org/10.26153/tsw/15652']

eng

2013 International Solid Freeform Fabrication Symposium

Open

['Additive Manufacturing', 'lifecycle costs', 'costing model', 'product lifecycle']

Impact and Influence Factors of Additive Manufacturing on Product Lifecycle Costs

Conference paper

https://repositories.lib.utexas.edu//bitstreams/fbdf45f1-2dcf-46e8-839e-e1c41aec40f1/download

University of Texas at Austin

At first sight the direct costs of Additive Manufacturing (AM) seem too high in comparison to traditional manufacturing. Considering the whole lifecycle costs of parts changes the point of view. Due to the modification of the new production process and new supply chains during a parts lifecycle, producing companies can strongly benefit from AM. Therefore, a costing model for assessing lifecycle costs with regard to specific applications and branches has been developed. The costing model represents the advantages of AM monetary. For the evaluation of this model and the influence factors, different case studies have been performed including different approaches in part redesign. Deeper research is and will be carried out with respect to the AM building rates and the comparability of various AM machines, as these facts are hardly comparable for end users. This paper will present the methodology as well as the results of the case studies conducted over the whole product lifecycle.

null

['Wu, Y.', 'Hermes, J.', 'Verbelen, L.', 'Yang, L.']

2021-11-30T21:35:04Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90556', 'http://dx.doi.org/10.26153/tsw/17475']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['cellular structures', 'thermoplastic polyurethane', 'TPU', 'impact energy absorption', 'powder bed fusion']

Impact Energy Absorption Ability of Thermoplastic Polyurethane (TPU) Cellular Structures Fabricated via Powder Bed Fusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6e961562-add5-4f53-a2ec-8b3f9e63bacc/download

University of Texas at Austin

In this study, experimental based investigation was carried out with various cellular structure designs realized using a developmental thermoplastic polyurethane (TPU) fabricated by powder bed fusion process, in the attempt to evaluate the effectiveness of impact energy absorption design with cellular structures when combined with favorable materials. Various cellular designs including the re-entrant auxetic, double-arrow auxetic, octet-truss, BCC, octahedral, diamond and double bow-tie were designed and evaluated. Pendulum-rebound resilience testing and drop-weight impact testing were carried out with each designs, and the effective energy absorption capabilities of these designs were compared. The results from this study provide some initial insights into the design of TPU-based cellular structures for energy absorption applications that could benefit the establishment of more comprehensive knowledge base in this area.

null

['Corbin, David J.', 'Nassar, Abdalla R.', 'Reutzel, Edward W.', 'Kistler, Nathan A.', 'Beese, Allison M.', 'Michaleris, Pan']

2021-10-27T21:27:58Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89620

eng

2016 International Solid Freeform Fabrication Symposium

Open

['directed energy deposition', 'laser cladding', 'Ti-6Al-4V', 'additive manufacturing', 'distortion', 'in situ measurements']

Impact of Directed Energy Deposition Parameters on Mechanical Distortion of Laser Deposited Ti-6Al-4V

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ebc74849-3b3b-4596-b054-fc57782a5f49/download

University of Texas at Austin

The effects of laser-based powder-fed directed energy deposition processing parameters on the distortion of deposited Ti-6Al-4V parts are assessed through in situ monitoring. Experiments were conducted wherein substrate thickness, deposition thickness, and initial substrate temperature were varied in order to investigate their effects on distortion. Correlations of process parameters to the mechanical characteristic were also developed, uncovering some of the driving mechanisms of the measured characteristic. This work highlights the impact of substrate preheating on distortion. Most notably, the effect of initial substrate temperature on distortion depended on the size of the substrate. On thin substrates, preheating reduced the total amount of distortion. However on thick substrates, preheating increased the amount of distortion. Techniques to mitigate the unwanted mechanical defect are discussed.

null

['Sinha, Swapnil', 'Meisel, Nicholas A.']

2021-11-30T19:13:48Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90517', 'http://dx.doi.org/10.26153/tsw/17436']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['material extrusion additive manufacturing', 'cavity design', 'toolpath design', 'thermal history']

Impact of Embedding Cavity Design on Thermal History between Layers in Polymer Material Extrusion Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9250ec57-7fb1-40ed-a3ec-e7c8bb97802f/download

University of Texas at Austin

By pausing an additive manufacturing process in mid-print, it is possible to create multifunctional structures through strategic insertion of foreign components. However, in polymer material extrusion, previous research has shown that pausing the build decreases the eventual strength of the final part, due to cooling between layers. To better predict this part weakness, this paper seeks to quantify how the toolpath affects the thermal history of a cross-section, thus impacting the formation of weld strength between printed layers. This is pertinent to in-situ embedding as different embedded geometries will require different cavity designs, which, in turn, will affect toolpath design. In-situ thermal measurements are experimentally collected with a thermocouple at the layer interface of structures with different cavity designs. The weld strength between layers is then obtained through tensile tests and theoretically evaluated using polymer weld theory. Results show more accurate predictions of load at failure with this method.

null

['Kleijnen, R.G.', 'Schmid, M.', 'Wegener, K.']

2021-11-18T01:39:36Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90396', 'http://dx.doi.org/10.26153/tsw/17317']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['flow aid', 'flowability', 'coalescence', 'polybutylene terephthalate', 'PBT', 'selective laser sintering']

Impact of Flow Aid on the Flowability and Coalescence of Polymer Laser Sintering Powder

Conference paper

https://repositories.lib.utexas.edu//bitstreams/8d0b11d9-72ba-4f3e-9ab6-f3e4297cbc89/download

University of Texas at Austin

Small amounts of nanometer-sized flow aids are typically added to polymer powders for selective laser sintering to increase flowability. These additives reduce friction between particles by electrostatic repulsion, leading to better bed density and part properties. The same repulsion however can hinder particle coalescence in the melt, reducing part density. This study investigates the effect of different amounts of flow aid on flowability and coalescence. A polybutylene terephthalate (PBT) powder with spherical morphology, specially designed for selective laser sintering, is used as a base and ideal model material. The coalescence is monitored by hot-stage optical microscopy. It was found that with increasing amounts of flow aid, the flowability could be characterized by three regions; one of low flowability where the powder contained insufficient flow aid, followed by a sharp transition region towards a high flowability region, where the flow aid was most effective. Addition of flow aid impacted the coalescence, which was marked by an increase of the temperature at which the particles started to melt and flow. At the maximum concentration of 0.5 wt.-% flow aid, the melting of some particles was delayed, and they remained solid for longer time at temperatures beyond the melting temperature. The optimum amount of flow aid therefore lies in the plateau region of high flowability, but before the occurrence of delayed melting.

null

['Campbell, R.I.', 'Hodgson, A.R.']

2019-11-20T15:47:50Z

2003

Mechanical Engineering

null

['https://hdl.handle.net/2152/78461', 'http://dx.doi.org/10.26153/tsw/5546']

eng

2003 International Solid Freeform Fabrication Symposium

Open

Industrial

The Impact of In-House RP Upon Final Year Industrial Design Student Projects

Conference paper

https://repositories.lib.utexas.edu//bitstreams/b09c1056-0b50-4d87-b4b2-e0f1bf7e6499/download

null

A vital part of the Industrial Design and Technology degree course at Loughborough University is the development of appearance and functional prototypes. Previously, the use of rapid prototyping (RP) has been fairly limited because of the high cost and problematic timing issues of using external facilities. However, during 2003, the availability of an in-house FDM 2000 machine has greatly increased the use of RP models. This paper identifies the impact this has had upon a) the design approach, b) the characteristics of the models produced and c) the use of the models with user evaluation trials. Conclusions drawn show that RP has brought major benefits but that there are some pitfalls that must be avoided.

null

['Praniewicz, M.', 'Fox, J.C.', 'Saldana, C.']

2023-03-30T16:16:26Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117700', 'http://dx.doi.org/10.26153/tsw/44579']

eng

2022 International Solid Freeform Fabrication Symposium

Open

Additive manufacturing

The Impact of Measurement Methodology on the Diameter Measurement of Simple Additively Manufactured Features

Conference paper

https://repositories.lib.utexas.edu//bitstreams/7b2d0484-25d4-4a55-8e0f-29061c4607b3/download

null

Dimensional qualification of additive manufacturing (AM) components is a continuing research problem. Different measurement techniques implemented on the same feature can yield different measurement results. While this can also be true for components made from more traditional manufacturing processes, the deviations between measurement techniques are often increased by an order of magnitude due to greater form and surface texture variations that occur on AM components. Understanding the origins of deviations and comparability of measurement processes is crucial to the measurement of AM components. In this work, identically designed components are produced using a laser powder-bed fusion process. The components are then measured using manual gaging and a coordinate measurement machine. The measurement of diameter is executed using various association criteria. A statistical analysis is performed to determine the comparability between the measurement techniques. Results indicate that the selection of different association criteria can provide statistically significant differences in the measurement result.

null

['Gong, Haijun', 'Runzi, Michael', 'Wang, Zezheng', 'Wu, Lianjun']

2023-01-19T17:45:21Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117250', 'http://dx.doi.org/10.26153/tsw/44131']

eng

2022 International Solid Freeform Fabrication Symposium

Open

3d printing

Impact of Moisture Absorption on 3D Printing Nylon Filament

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9e197366-3c07-474f-9597-88407a15f783/download

null

Nylon is a commonly used thermoplastic material featured for its high resistance to heat, chemical, and impact. Nylon filaments that facilitate complex part manufacturing through the extrusion-based 3D printing process are widely used in industry and can be easily acquired from various vendors or suppliers. However, as a hygroscopic material, nylon directly absorbs moisture from the surrounding air at a fast rate. This study concentrates on evaluating the moisture absorption of nylon filament in a humid environment. Experiments are conducted to correlate the moisture content of nylon filament with its dwelling time in a humidity chamber. Test artifacts are printed to demonstrate the influence of moisture on nylon part quality. Mechanical testing is also carried out for analyzing the material property degradation due to increased moisture content. Suggestions on nylon filament usage and storage are discussed.

null

['Heinrich, Lauren', 'Fletcher, Joseph', 'Feldhausen, Thomas', 'Kurfess, Thomas', 'Saldaña, Christopher']

2023-01-27T14:05:35Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117334', 'http://dx.doi.org/10.26153/tsw/44215']

eng

2022 International Solid Freeform Fabrication Symposium

Open

['Hybrid manufacturing', 'Blown-powder DED', 'Catchment efficiency']

Impact of Nozzle Condition on Powder Catchment Efficiency for Coaxial Powder Direct Energy Deposition

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1c4fd24e-22f3-4860-aeaa-27280ebaeca4/download

null

Blown powder directed energy deposition is well-designed for fine resolution additive manufacturing processing. Coaxial powder deposition heads use an outer layer of shielding gas directed by an outer nozzle to prevent oxidation occurring during the powder melting process. Powder blown feedstock catchment efficiency can be as low as 50-80% whereas wire deposition systems are closer to 98% efficient. The present study evaluates the impact of directed energy deposition nozzle condition on catchment efficiency. Changes in the overall outer shielding gas nozzle length has been found to increase material usage efficiency by 10% through convergence of the powder flow. The results of this experiment show that for coaxial powder deposition head design, if the standoff distance can safely be decreased, powder catchment efficiency can be increased as the outer shielding gas nozzle is increased in length, or the standoff distance is decreased.

null

['Zhou, Wenchao', 'Loney, Drew', 'Fedorov, Andrei G.', 'Degertekin, F. Levent', 'Rosen, David W.']

2021-09-30T18:47:31Z

2010

Mechanical Engineering

null

['https://hdl.handle.net/2152/88276', 'http://dx.doi.org/10.26153/tsw/15217']

eng

2010 International Solid Freeform Fabrication Symposium

Open

['ink-jet printing', 'droplet deposition', 'droplet impact behavior']

Impact Of Polyurethane Droplets on a Rigid Surface for Ink-Jet Printing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/0fa5669f-b76f-462f-9bd8-1f1ae18fb3bc/download

University of Texas at Austin

Ink-jet printing enables a more efficient, economic, scalable manufacturing process for a wider variety of materials than other traditional additive techniques. Understanding droplet impact onto a substrate is critical for accuracy control and optimization of the droplet deposition process. This paper reviews fundamentals of droplet impact behavior from literature, followed by our CFD simulations of droplet impact on a substrate. A numerical model is developed to simulate the transient flow dynamics during impact and spreading of an impinging droplet on a wetting rigid wall. The phase-field surface tracking technique is employed within a fixed (Eulerian) structured mesh. Simulation results are critically compared and validated with predictions of analytical models and experiments from literature. Droplet impact and spreading of a thermoplastic polyurethane material are investigated for SFF applications.

null

['Ramachandra, S.', 'Ravichander, B.B.', 'Farhang, B.', 'Ganesh-Ram, A.', 'Hanumantha, M.', 'Marquez, J.', 'Humphrey, G.', 'Swails, N.', 'Amerinatanzi, A.']

2021-12-06T22:45:43Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90703', 'http://dx.doi.org/10.26153/tsw/17622']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['laser powder bed fusion', 'porous structures', 'mechanical properties', 'IN718', 'microstructure', 'Vickers hardness']

Impact of Porosity Type on Microstructure and Mechanical Properties in Selectively Laser Melted IN718 Lattice Structures

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ddcc866c-c0b1-4fb9-99bf-2a5a22da52ad/download

University of Texas at Austin

Laser Powder Bed Fusion (LPBF), one of the most employed additive manufacturing techniques for metals, has opened new dimensions in realizing strong and weight reducing structures. In this study, Inconel 718 (IN718) unit cell designs, were fabricated through the LPBF technique and analyzed. Among the plethora of lattice structures in existence, BCC, BCC-Z, FCC, FCC-Z, Gyroid, Diamond and Schwarz structures have been selected to focus on. A relationship between the mechanical properties including yield strength, failure stress and strain, and hardness with each type of unit cell was established. Also, the effect of the possible defects on the hardness value was examined using microstructural analysis on samples. Scanning Electron Microscopy (SEM) analysis was also performed to examine the possible defects and its effect on the hardness of the as-built part. The SEM images of the grain structures indicated higher levels of isotropy in Gyroid, and Diamond samples compared to the rest of the samples which relates to the load bearing capacities of each unit cell structure. A similar trend was observed in terms of the uniformity of meltpool which can be linked with the consistency in yield characteristics. Further, Diamond and BCC-Z structures displayed high values of hardness in comparison with rest of the samples.

null

['Khajavi, S.H.', 'Deng, G.', 'Holmström, J.', 'Puukko, P.']

2021-10-28T15:51:37Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89669

eng

2016 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'raw material commoditization', 'supply chain']

Impact of Raw Material Commoditization on Supply Chains

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ef033abb-18a7-4987-8286-60f5ebc9199e/download

University of Texas at Austin

In this research we analyze the impact of a less cost intensive raw material supply chain on the utilization of additive manufacturing (AM) and its implications for the whole production supply chain. Utilizing the case data and scenario modeling we compared the competitiveness of additive manufacturing in comparison to conventional methods such as machining and casting. Results illustrated the increased production competitiveness with regard to both conventional methods. Moreover, we found simplicity and swiftness of supply chain as the two significant changes that occur as the result of a new raw material supply. One of the major limitations of this research was due to the secrecy of the companies which are currently utilizing the technology and their reluctance to share their perceived competitive advantage for the analysis. Therefore, the data extracted from our own case simulations which then were analyzed to compare the supply chains. Future research should expand the number of cases and utilize more suitable AM machines.

null

['Dwivedi, R.', 'Bhupathiraj, Ravi', 'Bhupathiraju, Rohit', 'Agarwal, Anvita', 'Dwivedi, Indira', 'Dwivedi, Bharat', 'Nadella, Saketh']

2021-12-01T21:55:55Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90628', 'http://dx.doi.org/10.26153/tsw/17547']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['competitive robotics', 'solid freeform fabrication', 'design', 'prototyping']

Impact of Solid Freeform Fabrication in Enabling Design and Prototyping Capabilities for Competitive Robotics such as World Robotics League, FTC, FRC, WRO etc.

Conference paper

https://repositories.lib.utexas.edu//bitstreams/75f1b694-4cad-480e-9ca9-c33d8587f27e/download

University of Texas at Austin

Competitive Robotics such as World Robotics League (WRL), World Robotics Olympiad (WRO), BEST, FIRST programs such as FTC and FRC, etc. have recently evolved as an avenue for learning, innovation and providing real life perspective to classroom learning. Given the short duration for Robot Development and diverse range of challenges, innovation, and product development has to happen at fast pace. Typical challenges include stow, configure, launch, traverse 3D environment, sorting, assembly etc. Many challenges include underwater and aerial spaces. Participants typically use reconfigurable “Robotics Kits”. However, "Robotics Kits" are limited in many ways and do not go beyond mobile platform and simple mechanisms. Many participants are turning to quicker alternatives such as Solid Freeform Fabrication. This paper provides a current state of the Competitive Robotics, the existing solutions, and examples of how Solid Freeform Fabrication is accelerating innovation in competitive robotics.

null

['Obeidat, Suleiman', 'Nervis, Joe Jr.', 'Ma, Junkun']

2023-02-10T14:14:26Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117451', 'http://dx.doi.org/10.26153/tsw/44332']

eng

2022 International Solid Freeform Fabrication Symposium

Open

['Additive manufacturing', 'FFF/ FDM', '316L stainless steel']

The Impact of the Printed Part Geometry on the Shrinkage and the Density of 316L Stainless Steel Parts Printed by FFF/FDM Technology

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d43fd2e9-f43d-46b4-aa8a-54ea48a34c58/download

null

['Neff, Clayton', 'Trapuzzano, Matthew', 'Crane, Nathan B.']

2021-11-01T22:09:08Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89775

eng

2016 International Solid Freeform Fabrication Symposium

Open

['surface roughness', 'surface finish', 'strength', 'ductility', 'vapor polishing', 'ABS', '3D printing']

Impact of Vapor Polishing on Surface Roughness and Mechanical Properties for 3D Printed ABS

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1d06b5f3-5641-4114-afae-ed6299547bbe/download

University of Texas at Austin

Additive manufacturing (AM) is useful when creating complex geometric models and prototypes. However, a well-known drawback is the fact that parts produced by AM methods typically have lower strength and higher surface roughness than traditionally-formed parts. To compensate for this, the surface finish is commonly improved by mechanical finishing or some type of coating. Another widely used surface treatment for ABS components is vapor polishing. In this process, the part is exposed to a solvent vapor that partially dissolves a surface layer and enables smoothing through surface tension-driven flow; it is known to decrease the surface roughness. However, little work has been reported quantifying the surface roughness change or on the mechanical impacts of this processing method. This work compares the strength, ductility and surface finish of vapor-polished ABS tensile specimens of varying thicknesses (1 mm, 2mm, and 4 mm). Results show that elongation at break is improved, while the modulus of elasticity is reduced in thin specimens. The tensile strength is largely unchanged. The power spectral density for roughness features larger than 20 µm were reduced 10X.

null

['Sperry, McKay', 'Bates, Jakob', 'Davis, Taylor', 'Nelson, Tracy W.', 'Crane, Nathan B.']

2023-01-27T14:45:13Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117341', 'http://dx.doi.org/10.26153/tsw/44222']

eng

2022 International Solid Freeform Fabrication Symposium

Open

['Laser Powder Bed Fusion', 'Stainless Steel 316L', 'Zirconia']

Impact of Zirconia Slurry Doping on 316L Stainless Steel Prepared by Laser Powder Bed Fusion for Biological/High Corrosion Applications

Conference paper

https://repositories.lib.utexas.edu//bitstreams/54f9820f-ca89-4956-a9e1-cd239c54302c/download

null

Laser Powder Bed Fusion (LPBF) is a versatile additive manufacturing (AM) method used primarily for processing plastics and metals. Stainless steel (type 316L) is a biocompatible metal used extensively for LPBF and commonly for medical applications. Zirconium Dioxide (zirconia) is a common engineering material used in applications ranging from dental implants to oxide dispersion strengthening of metals. This paper presents the process development and results of in- situ deposition of small quantities of zirconia nanoparticles in a stainless steel (316L) powder bed prior to fusion in the LPBF process. The zirconia slurry was deposited as an atomized mist. The deposition process may be adapted to selectively dope a powder bed to form parts with spatially varying properties for use in complex parts. In this work, the added zirconia was shown to be partially distributed in the matrix, but a large portion segregated to grain boundaries and surfaces. Porosity increased in multi-layer parts with the zirconia agglomerated on the porous surfaces. This is undesirable for many applications but may be useful for creating porous surfaces for heat exchanger or bio-integration applications. The deposition of zirconia limits the anisotropic crystal growth throughout the entire doped region.

null

['Gong, Haijun', 'Xing, Xiaodong', 'Nel, Jan']

2021-11-18T01:16:32Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90388', 'http://dx.doi.org/10.26153/tsw/17309']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['PEEK', 'impact strength', '3D printing']

Impact Strength of 3D Printed Polyether-ether-ketone (PEEK)

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6404e40e-78ab-4500-81e1-bec5333eb9b3/download

University of Texas at Austin

Polyether-ether-ketone (PEEK) is a high-performance thermoplastic with high heat-, high chemical-, high water-, and high wear-resistance. Its strength and durability also make it highly accepted for a range of industrial applications. 3D printing of PEEK filaments offers a unique quality and flexibility in making PEEK parts for low-volume production or special designs. This study investigates the impact strength of 3D printed PEEK materials. The specimens are fabricated using a fused deposition modeling (FDM) based 3D printer and tested by a pendulum impact tester in compliance with ASTM standard. The testing result is discussed with respect to the processing parameters and the annealing treatment. Impact strength comparison of PEEK materials manufactured by 3D printing and by conventional production is also conducted.

null

['Scrocco, Mackenzie', 'Chamberlain, Timothy', 'Chow, Chloe', 'Weinreber, Logan', 'Elks, Edward', 'Halford, Connor', 'Cortes, Pedro', 'Conner, Brett P.']

2021-11-10T22:22:28Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90191', 'http://dx.doi.org/10.26153/tsw/17112']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['impact testing', 'kevlar', 'markforged', 'projectile']

Impact Testing of 3D Printed Kevlar-Reinforced Onyx Material

Conference paper

https://repositories.lib.utexas.edu//bitstreams/b8abe53c-d787-4305-9d8c-09c513eed9c0/download

University of Texas at Austin

Kevlar is a common reinforcement used in composites for applications requiring impact resistance. This research evaluated the impact performance of 3D printed continuously reinforced Kevlar fiber on 3D printed nylon composites containing chopped carbon fiber (CCF). The 3D printer used was a Markforged Mark Two material extrusion system, and Onyx is the trade name of Markforged’s nylon/CCF material. In this work, a diverse number of composite architecture designs including type of infill pattern, number of Kevlar layers, and location of Kevlar layers were investigated. The printed specimens were characterized using a Charpy impact testing and gas gun ballistic testing. Results were compared on the basis of weight and estimated part cost.

null

['Wasser, Tobias', 'Jayal, Anshu Dhar', 'Pistor, Christoph']

2019-03-11T16:33:42Z

1999

Mechanical Engineering

null

['https://hdl.handle.net/2152/73580', 'http://dx.doi.org/10.26153/tsw/722']

eng

1999 International Solid Freeform Fabrication Symposium

Open

['FDM', 'Construction Procedures']

Implementation and Evaluation of Novel Buildstyles in Fused Deposition Modeling (FDM)

Conference paper

https://repositories.lib.utexas.edu//bitstreams/0c571c76-5ee2-46cf-8ff5-cee452bf2392/download

null

Previous investigations have shown that the optimization of extrusion dynamics in .conjunction with the buildstyle pattern is of paramount importance to increase part quality in Fused Deposition Modeling (FDM). Recently domain decomposition and space filling curves have been introduced for slice generation in FDM [1]. The current work focuses on the implementations of fractal-like buildstyle .patterns using. Simulated Annealing [2, 3], Lin-Kernighan algorithms [4] and Construction Procedures based on Nearest Neighbor Heuristics [5]. These computational optimization procedures are able to generate filling patterns that allow the continuous deposition of a single road to fill arbitrary shaped domains. The necessary software modules to produce arbitrary threedimensional artifacts have been developed and are evaluated with respect to part quality and build time.

null

Silwal, B.

2021-11-16T15:42:13Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90318', 'http://dx.doi.org/10.26153/tsw/17239']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['material processing', 'hands-on', '3D printer', 'engineering course', 'engineering education']

Implementation of 3D Printer in the Hands-On Material Processing Course: An Educational Paper

Conference paper

https://repositories.lib.utexas.edu//bitstreams/aafd3f6d-d836-4f3d-b215-b14336ddbcb3/download

University of Texas at Austin

Manufacturing equipment and technology will continue to be an integral part of engineering education. Using advanced and modern equipment and technology not only emphasizes hands-on activity-based teaching and learning, but it also makes the educator and the program competitive. There are many advantages to implementing 3-d printers in engineering education; however, there are also some challenges. In this paper, a two-year implementation of 3-d printers in a traditional material processing undergraduate engineering course has been presented and discussed.

null

['Pratap, Aparajit', 'Crawford, Richard H.']

2019-11-20T15:56:40Z

2003

Mechanical Engineering

null

['https://hdl.handle.net/2152/78463', 'http://dx.doi.org/10.26153/tsw/5548']

eng

2003 International Solid Freeform Fabrication Symposium

Open

Material Modeling

Implementation of a Functionally Gradient Material Modeling and Design System

Conference paper

https://repositories.lib.utexas.edu//bitstreams/fa34ffad-2701-414a-a788-9d8017fa7ed8/download

null

New advancements in Solid Freeform Fabrication (SFF) processes promise the capability to produce Functionally Gradient Material (FGM) parts, in which the material compositions vary spatially. To realize this potential there is a need for CAD methods and design software to model, design, represent and exchange material information and instructions to the manufacturing process. However, currently available commercial CAD systems are limited to representing and storing only geometric information, which is not adequate for material design purposes. This work presents an extension of a theoretical approach based on Volumetric MultiTexturing (VMT) and hypertexturing schemes to make the material design process intuitive and user controllable. Inverse distance weighted interpolation is used in conjunction with procedural material functions to accomplish axial or linear material gradient directions from surface to surface across a solid. This offers the capability of specifying fixed material composition values to the faces in the solid and blending them across the interior of the solid. The extension of the proposed approach to the modeling of discrete material domains is also discussed. These material regions can be combined using special sets of operators depending on the form of the material functions. Finally, a design environment has been developed, which allows users to systematically apply material information to geometry and captures design intent.

null

['Ito, Fumio', 'Niino, Toshiki']

2021-11-01T21:42:30Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89764

eng

2016 International Solid Freeform Fabrication Symposium

Open

['poly phenylene sulfide', 'low temperature', 'tophat profile laser', 'laser sintering']

Implementation of Tophat Profile Laser into Low Temperature of Poly Phenylene Sulfide

Conference paper

https://repositories.lib.utexas.edu//bitstreams/bc29a658-e184-4cd7-9075-f0140e35bf04/download

University of Texas at Austin

Poly Phenylene Sulfide is a high performance plastics that is used in high-value parts. The most commercially available plastic laser sintering machines employ Gaussian profile CO2 laser. In this research, low temperature process of the material with tophat profile laser is tested. By using tophat profile, a tensile strength of 64.5 MPa was obtained. The value is equivalent to 75% of those from injection molding and 140% of standard laser sintered polyamide. Tophat profile effectively suppressed sparkling and fuming and improved surface finish decreasing surplus sintering or sticking powder.

null

Frank, Matthew C.

2020-03-09T13:51:46Z

2007

Mechanical Engineering

null

['https://hdl.handle.net/2152/80179', 'http://dx.doi.org/10.26153/tsw/7198']

eng

2007 International Solid Freeform Fabrication Symposium

Open

Rapid Prototyping

Implementing Rapid Prototyping Using CNC Machining (CNC-RP) Through a CAD/CAM Interface

Conference paper

https://repositories.lib.utexas.edu//bitstreams/8f5ea8c0-dc7e-4f62-94a3-4a8b3a5096db/download

null

This paper presents the methodology and implementation of a rapid machining system using a CAD/CAM interface. Rapid Prototyping using CNC Machining (CNC-RP) is a method that has been developed which enables automatic generation of process plans for a machined component. The challenge with CNC-RP is not the technical problems of material removal, but with all of the required setup, fixture and toolpath planning, which has previously required a skilled machinist. Through the use of advanced geometric algorithms, we have implemented an interface with a CAD/CAM system that allows true automatic NC code generation directly from a CAD model with no human interaction; a capability necessary for a practical rapid prototyping system.

null

['Adams, D.W.', 'Turner, C.J.']

2021-11-02T20:14:52Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89885

eng

2017 International Solid Freeform Fabrication Symposium

Open

['implicit slicing method', 'infill pattern', 'GCode', 'fused deposition modeling']

Implicit Slicing Method for Additive Manufacturing Processes

Conference paper

https://repositories.lib.utexas.edu//bitstreams/37b860f2-8bd6-41ed-837a-c8c4443a4e50/download

University of Texas at Austin

All additive manufacturing processes involve a distinct preprocessing stage in which a set of instructions, or GCode, that control the process specific manufacturing tool are generated, otherwise known as slicing. In regards to fused deposition modeling, the GCode defines many crucial parameters which are needed to produce a part, including tool path, infill density, layer height, feed rate, tool head and plate temperature. The majority of current commercial slicing programs generate tool paths explicitly, and do not consider particular geometric properties of parts, such as thin walls, small corners and round profiles that can result in critical voids leading to part failure. This work replicates an implicit slicing algorithm in which functionally derived infill patterns are overlaid onto each layer of a part, reducing the possibility of undesired voids and flaws. This work also further investigates the effects that varying implicitly derived infill patterns have on a part’s mechanical properties through tensile testing dog bone specimens with three different infill patterns and comparing ultimate stress and elastic modulus properties.

null

['Deckard, Carl', 'Miller, David']

2018-10-05T18:30:41Z

1995

Mechanical Engineering

doi:10.15781/T26W96V1G

http://hdl.handle.net/2152/68722

eng

1995 International Solid Freeform Fabrication Symposium

Open

['SLS', 'SFF', 'CAD']

Improved Energy Delivery For Selective Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/489cdc5e-801b-4982-8d3f-45da71ae25e6/download

null

Selective Laser Sintering (SLS) is a leadingtechnology in the important new area of Solid Freeform Fabrication (also ca1ledR.apid Prototyping). Selective Laser Sintering produces freeform parts directly from a CAD model by building the parts up in layers from a powder. A laser is used to selectively melt each layer of powder to form the part. The laser beam is scanned across the powder using two galvanometer scanners. The energy delivery system (laser, optics, scanner and controls) is a critical component technology of SLS. Projects with the objective of improving the energy delivery system are underway at Clemson University

null

['Martina, Filomeno', 'Williams, Stewart W.', 'Colegrove, Paul']

2021-10-11T20:44:49Z

2013

Mechanical Engineering

null

['https://hdl.handle.net/2152/88640', 'http://dx.doi.org/10.26153/tsw/15574']

eng

2013 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'Ti-6Al-4V', 'interpass rolling', 'microstructure', 'distortion', 'residual stress', 'ansiotropy']

Improved Microstructure and Increased Mechanical Properties of Additive Manufacture Produced Ti-6Al-4V By Interpass Cold Rolling

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6069348b-a63d-4fae-b51f-f6211b000329/download

University of Texas at Austin

Distortion, residual stress and mechanical property anisotropy are current challenges in additive manufacturing (AM) of Ti–6Al–4V. High-pressure, interpass rolling was applied to linear AM parts and resulted in a change from large columnar prior β grains to a completely equiaxed microstructure with grains as small as 89 µm. Moreover, α laths thickness was also reduced to 0.62 µm. The change in material microstructure resulted in a substantial improvement of all mechanical properties tested, which were also totally isotropic. In rolled specimens, maximum measured strength and elongation were 1078 MPa and 14% respectively, both superior to the wrought material. Distortion was reduced to less than half. Rolling proved to be a relatively easy method to overcome some of the critical issues which keep AM from full industrial implementation.

null

['Cohen, Daniel L.', 'Tsavaris, Andrew M.', 'Lo, Winifred M.', 'Bonassar, Lawrence J.', 'Lipson, Hod']

2021-09-28T17:53:19Z

9/10/08

Mechanical Engineering

null

['https://hdl.handle.net/2152/88137', 'http://dx.doi.org/10.26153/tsw/15078']

eng

2008 International Solid Freeform Fabrication Symposium

Open

['alginate hydrogels', 'Solid Freeform Fabrication', 'cell-seeded tissue engineering scaffolds']

Improved Quality of 3D-Printed Tissue Constructs Through Enhanced Mixing of Alginate Hydrogels

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f74acc54-df40-4480-8199-1c1f46bd3c11/download

University of Texas at Austin

While alginate hydrogel is a desirable material platform for Solid Freeform Fabrication (SFF) of cell-seeded tissue engineering scaffolds, achieving consistently high-quality results can be challenging. Local variations in the material properties cause inconsistent material deposition behavior and consequently decrease the resultant geometric fidelity of the construct. The effects of gel mixing on material property consistency, geometric fidelity, and cell viability were characterized in an attempt to improve the formulation’s compatibility with SFF processing. Material homogeneity was quantified through a novel experimental setup composed of an EnduraTEC mechanical test-frame and custom syringe-extrusion jig. Cell viability and geometric fidelity were assessed using standard protocol. The baseline mechanical stiffness of the printed samples was 16±3 kPa (n=6). We found that increasing mixing reduced material inconsistency and improved geometric fidelity, without adversely affecting cell viability: the printed construct quality was drastically improved by increasing mixing well beyond previously established limits.

null

['Emami, Mohammad Mahdi', 'Rosen, David W.']

2021-11-15T21:12:52Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90274', 'http://dx.doi.org/10.26153/tsw/17195']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['photopolymerization', 'photobleaching', 'grayscale stereolithography', 'volumetric intensity']

An Improved Vat Photopolymerization Cure Model Demonstrates Photobleaching Effects

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9da46d83-a04d-4e1d-a079-200b4758189b/download

University of Texas at Austin

An improved high-fidelity simulation model for a grayscale projection micro-stereolithography process has been developed. The modeling purpose is to accurately predict cured part shapes and dimensions, given a radiation intensity distribution. The model employs COMSOL to solve a series of chemical reaction differential equations that model the evolution of chemical species (photoinitiator, monomer, and polymer) concentrations. Additionally, the model incorporates the effects of oxygen inhibition and species diffusion. This research offers two primary contributions to the cure model: the consideration of volumetric intensity to model variations in photoinitiator absorbance as a function of depth into the resin and a change to the rate model for photoinitiator to free radical conversion. The effects of these changes demonstrate observed photobleaching effects. Simulated cured part profiles are compared to experiments and demonstrate good agreement. Additionally, initial results are presented on the usage of the simulation model in a new process planning method.

null

['Niino, Toshiki', 'Morita, Keisuke']

2021-09-30T13:48:21Z

9/23/10

Mechanical Engineering

null

['https://hdl.handle.net/2152/88251', 'http://dx.doi.org/10.26153/tsw/15192']

eng

2010 International Solid Freeform Fabrication Symposium

Open

['plastic laser sintering', 'additive manufacturing', 'spot sized CO2 laser beams', 'micro-plastic-laser-sintering', 'fine geometries', 'complex geometries']

Improvement in Geometrical Resolution of Plastic Laser Sintering by using Reduced Spot Sized Laser

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1f5fe2ab-8b0b-4ff9-9452-b65743a78234/download

University of Texas at Austin

Plastic laser sintering is one of the most promising processes for rapid manufacturing among various additive manufacturing (AM) technologies. Though the process tends to be applied to fabrication of larger parts in comparison to stereolithography, its ability of creating complex structure as an advantage of additive manufacturing technologies should be demonstrated in production of smaller parts and parts including fine and complex geometries as well. In this research, narrow CO2 laser beams with spot diameters of 130µm and 150µm were tested while the commercially available machines are equipped with those around 500µm. Relationship between resolution (available wall thickness) and spot diameter is proportional when the diameter is greater than 150µm, but effect of reducing the spot size further is not significant. The minimum wall thickness of 180µm was obtained, but this part was so fragile that skill in breakout treatment is critical. To discuss the mechanical strength of micro-plastic-laser-sintering, packing rate of obtained parts was introduced as an index of the strength. Build parameter that minimizes the wall thickness without decreasing the tensile strength below 30MPa was searched, and a set of parameters that provides minimal thickness of 0.6mm was obtained. Reducing laser spot size inevitably leads to shrinkage of scanning range of galvanometer mirrors. To overcome this problem, the whole laser scanning system was set on an X-Y positioner which are driven by stepper motors. The whole exposure area is divided into some regions each of which is smaller than range of galvanometer mirror system, and it is exposed by repeating fast scanning by galvanometer mirrors and slow sliding by the X-Y positioner. Problems occurring at the region boundary were investigated. As counter measures, overlapping of exposure areas and switching of region boundary are introduced and successfully eliminate the problem.

null

['Chen, Ssuwei', 'Bourell, David L.', 'Wood, Kristin L.']

2020-02-24T15:26:22Z

8/3/05

Mechanical Engineering

null

['https://hdl.handle.net/2152/80082', 'http://dx.doi.org/10.26153/tsw/7103']

eng

2005 International Solid Freeform Fabrication Symposium

Open

proton exchange membrane

Improvement of Electrical Conductivity of SLS PEM Fuel Cell Bipolar Plates

Conference paper

https://repositories.lib.utexas.edu//bitstreams/fb6acb34-1e6e-47a3-8345-5774df03de88/download

null

Previous work in this research demonstrated the feasibility of fabrication of proton exchange membrane (PEM) fuel cell bipolar plates by an indirect selective laser sintering (SLS) route. Properties of the SLS bipolar plate, such as flexural strength, corrosion resistance and gas impermeability, etc. are quite promising and satisfactory. However, initial results showed that there was still room for the improvement in electrical conductivity. This paper summaries the strategies investigated in an effort to increase the electrical conductivity, among which are: (1) infiltration of brown parts with conductive polymer (2) addition of a liquid phenolic infiltration/re-curing step prior to final sealing and (3) reduction of glassy carbon resistivity by curing process parameter control. Results show that the electrical conductivity value may be improved from 80 S/cm to around 108 S/cm, which is equivalent to a 35% jump, when the phenolic infiltration/re-curing step is applied before final epoxy sealing.

null

['Kigure, T.', 'Niino, T.']

2021-11-02T18:32:08Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89862

eng

2017 International Solid Freeform Fabrication Symposium

Open

['recycle rate', 'low temperature', 'processing', 'laser sintering']

Improvement of Recycle Rate in Laser Sintering by Low Temperature Process

Conference paper

https://repositories.lib.utexas.edu//bitstreams/00f44607-95f9-43bf-846a-139e555173e9/download

University of Texas at Austin

Laser sintering process selectively solidifies its powder bed to obtain designated parts and leaves the rest unsolidified. When the remained powder is recycled, a certain amount of fresh powder is added to moderate the effect of deterioration by preheating in the previous batch. In terms of economy, improvement of the recycle rate of used powder is one of the big challenges. The authors are developing a novel laser sintering process that prevents part being processed from warping not by preheating the powder bed but by anchoring the parts to a rigid base plate. Since the new process, namely low temperature process, can lower the bed temperature than normal high temperature process, it is expected to reduce deterioration of the used powder. In present research, processablity of recycled powder is evaluated by its MFR, and it is shown that operation at a high recycle rate more than 90% is possible.

null

['Nelson, Christian', 'McAlea, Kevin', 'Gray, Damien']

2018-10-10T15:29:47Z

1995

Mechanical Engineering

doi:10.15781/T2222RR22

http://hdl.handle.net/2152/68754

eng

1995 International Solid Freeform Fabrication Symposium

Open

['SLS', 'material shrinkage', 'laser beam']

Improvements in SLS Part Accuracy

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6297e24b-7f12-437b-9c3b-f958da9ea5c8/download

null

SLS® part accuracy is influenced by a number ofmachine and material characteristics. Some of the most significant sources of error are associated with laser beam positioning (static and dynamic) on the part bed surface and uncertainty in the calibration factors used to compensate for material shrinkage and growth as well as the finite width ofthe laser beam. Another source of error is the minimum resolution of the process, which is a dependent on the particle size and shape ofthe material. In this presentation, technical background on these issues will be provided. In addition, part data obtained with a number of SLS materials demonstrating improved accuracy obtained through machine modifications and improved calibration methods will be described.

null

['Crane, N. B.', 'Wilkes, J.', 'Sachs, E.', 'Allen, S. M.']

2020-02-21T15:28:32Z

8/26/05

Mechanical Engineering

null

['https://hdl.handle.net/2152/80063', 'http://dx.doi.org/10.26153/tsw/7085']

eng

2005 International Solid Freeform Fabrication Symposium

Open

Solid freeform fabrication

Improving Accuracy of Powder Sintering-based SFF Processes by Metal Deposition from Nanoparticle Dispersion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/7ad1dadf-d16e-4971-8c49-e733f4579364/download

null

Solid Freeform Fabrication processes such as three-dimensional printing (3DP) and selective laser sintering (SLS) produce porous parts that must be densified. New steel infiltration methods can produce parts of standard alloy compositions with properties comparable to wrought materials. However, the infiltration process introduces dimensional errors due to both shrinkage and creep—particularly at the high temperatures required for steel infiltration. A post-processing method has been developed to reduce creep and shrinkage of porous metal skeletons. Tests have achieved over 90% reduction in creep and 50% reduction in shrinkage. In this method, metal is deposited into the porous part from a suspension of metallic nanoparticles. These particles densify at low temperatures to reinforce the bonds and reduce stress concentrations that amplify creep deformation in untreated parts. After treatment, the reinforced parts can be densified by infiltration.

null

['Vetterli, M.', 'Schmid, R.', 'Schmid, M.', 'Harke, S.', 'Durand, T.', 'Wegener, K.']

2021-10-21T21:08:22Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89449

eng

2015 International Solid Freeform Fabrication Symposium

Open

['selective laser sintering', 'energy efficiency', 'energy consumption', 'climate control', 'air-conditioning', 'passenger cars']

Improving Energy Efficiency of Car Climate Control with SLS

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a3361936-2ef6-4b90-8b79-9475308503d8/download

University of Texas at Austin

In Europe, passenger cars are responsible for 12% of CO2 emissions. The European Commission established new regulations to drastically reduce the emissions from 130g to 95g CO2 per km between 2015 and 2021. While the automobile industry is looking at different ways to meet those criteria, the presented industry-driven project aims at reducing energy consumption by up to 30% of air-conditioning (AC) in passenger cars with the introduction of a novel system. The current systems reduce the fuel economy to up to 20% for gas motors and even more for electric cars. Through Selective Laser Sintering (SLS) design freedom and short production cycles; the design of the AC casing was drastically optimized to increase its contact area with incoming air. To further increase the heat exchange throughout the system, the thermal conductivity of SLS material was improved by incorporation of mineral fillers. The successful implementation of both optimizations led to a CO2 emission reduction of around 50% for the climate control of passenger cars.

null

['Ram, G. D. Janaki', 'Yang, Y.', 'George, J.', 'Robinson, C.', 'Stucker, B. E.']

2020-03-05T19:57:38Z

9/14/06

Mechanical Engineering

null

['https://hdl.handle.net/2152/80152', 'http://dx.doi.org/10.26153/tsw/7173']

eng

2006 International Solid Freeform Fabrication Symposium

Open

Ultrasonic Consolidation

Improving Linear Weld Density in Ultrasonically Consolidated Parts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/720f9191-d5de-4029-ad79-f5ea934587af/download

null

Ultrasonic consolidation is a novel additive manufacturing process with immense potential for fabrication of complex shaped three-dimensional metallic objects from metal foils. The proportion of bonded area to unbonded area along the layer interface, termed linear weld density (LWD), is perhaps the most important quality attribute of ultrasonically consolidated parts. Part mechanical properties largely depend on LWD and a high level of LWD must be ensured in parts intended for load-bearing structural applications. It is therefore necessary to understand what factors influence LWD or defect formation and devise methods to enhance bond formation during ultrasonic consolidation. The current work examines these issues and proposes strategies to ensure near 100% LWD in ultrasonically consolidated aluminum alloy 3003 parts. The work elucidates the effects of various process parameters on LWD and a qualitative understanding of the effects of process parameters on bond formation during ultrasonic consolidation is presented. The beneficial effects of using elevated substrate temperatures and its implications on overall manufacturing flexibility are discussed. A preliminary understanding of defect morphologies and defect formation is presented, based on which a method (involving surface machining) for minimizing defect incidence during ultrasonic consolidation is proposed and demonstrated. Finally, trade-offs between part quality and build time are discussed.

null

['Shojib Hossain, Mohammad', 'Ramos, Jorge', 'Espalin, David', 'Perez, Mireya', 'Wicker, Ryan']

2021-10-07T19:01:06Z

8/16/13

Mechanical Engineering

null

['https://hdl.handle.net/2152/88505', 'http://dx.doi.org/10.26153/tsw/15439']

eng

2013 International Solid Freeform Fabrication Symposium

Open

['FDM-manufactured parts', 'tensile mechanical properties', 'processing parameters', 'Insight']

Improving Tensile Mechanical Properties of FDM-Manufactured Specimens via Modifying Build Parameters

Conference paper

https://repositories.lib.utexas.edu//bitstreams/0cfb10ff-e7ba-47bc-842c-007a1e2841b9/download

University of Texas at Austin

In this paper, the focus was on improving tensile mechanical properties of FDMmanufactured parts by adjusting FDM processing parameters and analyzing stress concentration features between adjacent roads of material. FDM processing parameters are specified by the user via Insight – the file preparation software for most FDM machines. Even though Insight gives the impression that adjacent roads are to be deposited and connected throughout, an optical imaging observation of the deposited material revealed that adjacent roads are not consistently connected forming voids that reduce mechanical performance. Therefore, this work reports the tensile mechanical properties of specimens built using three sets of parameters: standard/default parameters, an Insight revision method, and a visual feedback method. When compared to the default build parameters, the experimentally determined, visual feedback approach produced specimens, in some cases, exhibiting as high as 19% improvement in ultimate tensile strength.

null

['Fisher, Joseph W.', 'Miller, Simon W.', 'Bartolai, Joseph', 'Simpson, Timothy W.']

2024-03-27T15:44:08Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124487', 'https://doi.org/10.26153/tsw/51095']

en

2023 International Solid Freeform Fabrication Symposium

Open

['lattice structures', 'triply periodic minimal surface', 'shape optimization']

Improving the Mechanical Response of the IWP Exo-skeletal Lattice Through Shape Optimization

Conference paper

https://repositories.lib.utexas.edu//bitstreams/dd9b91ff-c95c-48b3-8b7d-5b1cf6f0c5e1/download

University of Texas at Austin

Triply Periodic Minimal Surfaces have been identified as good candidates for the generation of lattice structures produced with additive manufacturing. These TPMS-based lattice structures avoid sharp features that are characteristic of strut-based lattice structures because of their constant zero mean curvature. Although studies have explored part-scale optimization using TPMS-based lattice structures, they have only varied the volume fraction by changing the level set in the approximate surface equations. By defining new parameterizations in the approximate surface equation, we can redistribute volume within the lattice structure at any volume fraction. In this paper, we introduce an approach for optimization of this new parameterization of TPMS equations using the Borg multi-objective evolutionary algorithm. We demonstrate this framework on the IWP exo-skeletal lattice under uniaxial compression. A relationship between the new parameters and the level set is derived for designs on the Pareto frontier of the optimized IWP TPxS. The performance of the Pareto optimal designs and the efficacy of the optimization approach are shown by comparing to the standard IWP lattice and four other lattices that share the same topology. The optimized designs are implemented and shared in custom nTopology blocks.

null

['Jayanthi, Suresh', 'Hokuf, Bronson', 'Lawton, John']

2018-11-14T20:28:13Z

1996

Mechanical Engineering

doi:10.15781/T2HT2GX71

http://hdl.handle.net/2152/70262

eng

1996 International Solid Freeform Fabrication Symposium

Open

['stereolithographic', 'photopolymers', 'prototyping techniques']

Improving the Thermal Stability of Somos™ 6110 Photopolymer Patterns

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f9c22c09-cc2f-48c5-924b-3fe5f1e4188f/download

null

With the increased emphasis on functional testing and tooling applications using stereolithographic rapid prototyping (RP) techniques, the need for RP materials with improved thermal stability is becoming more pronounced. Glass transition temperature and Heat deflection temperature are two commonly used measures to determine the thermal stability of a polymeric material. This paper shows the effect of different postcuring techniques on the heat deflection temperature (HDT) of DuPont Somos™ 6110 photopolymer. In addition, the benefits of using heat transfer mediums which provide neutral buoyancy and thus minimize thermal distortions are discussed.

null

['Malyala, Santosh Kumar', 'Manmadhachary, A.', 'Kumar, Yennam Ravi']

2021-10-21T15:45:20Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89401

eng

2015 International Solid Freeform Fabrication Symposium

Open

['Additive Manufacturing', 'volumetric accuracy', 'octree structure', 'STL file', 'adaptive slicing']

Improving Volumetric Accuracy of AM Part Using Adaptive Slicing of Octree Based Structure

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1bdd98db-fb97-46d9-ab68-7663508c321b/download

University of Texas at Austin

In Additive Manufacturing (AM) processes, the layer-by-layer fabrication of complex geometries may lead to stair casing and thus error resulting in volumetric inaccuracies in the model. Using thinner slices reduces the staircase error and improves part accuracy but there is a tradeoff between number of layers and the build time for manufacturing part. This paper presents a octree based structure to improve the accuracy as well as reduces the build time. In the current work, firstly converting STL file into a modified boundary octree data structure (MBODS) and then calculating the non-uniform slice thicknesses (adaptive slicing) from the octree representation. This slice thickness at any height is computed from the AM machine parameters and the smallest octree size at that available height. After the computation of the variable slice thicknesses has been completed, the part is virtually manufactured and the part errors are calculated. The virtually manufactured part and physical models are inspected to evaluate the volumetric errors. This algorithm uses an octree approach to improve the volumetric accuracy. And build time for the two different case studies are also done.

null

['Alberts, D.', 'Schwarze, D.', 'Witt, G.']

2021-11-04T13:45:37Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89958

eng

2017 International Solid Freeform Fabrication Symposium

Open

['in situ', 'real time', 'melt pool monitoring', 'selective laser melting', 'part density', 'Inconel 718']

In Situ Melt Pool Monitoring and the Correlation to Part Density of Inconel® 718 for Quality Assurance in Selective Laser Melting

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f92f4ca0-63f8-49cd-9a3c-20c2bc5dcaba/download

University of Texas at Austin

Additive Manufacturing looks back on a history of about two decades and today SLM® technology keeps moving as an integral element in industrial production environments. Sensitive markets such as energy, medical or aerospace have the highest quality standards for complex, safety-related and highly stressed components which are to be met at competitive costs for each build job and single part. In this context process monitoring is necessary for documentation, qualification and at the same time it is expected to be able to detect process anomalies during the process. In addition to surface roughness, part density which mostly depends on volume energy, changing with laser power, scan velocity etc., is a distinctive quality feature of every component. This paper presents a method for a real time melt pool monitoring system based on photodiodes and the correlation between thermal emission and part density of Inconel® 718 with respect to volume energy deviation.

null

['Liu, W.', 'Sun, W.']

2021-10-21T20:51:02Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89444

eng

2015 International Solid Freeform Fabrication Symposium

Open

['solid freeform fabrication', 'in situ printing']

In Situ Printing - An Alternative Three Dimensional Laden Structure Fabrication Method

Conference paper

https://repositories.lib.utexas.edu//bitstreams/be476475-d15a-4b6a-815f-862f5afd55f1/download

University of Texas at Austin

Recapitulating a structure that mimics the anatomic geometries and intratissue cell distribution as in live organism is a major challenge of tissue engineering nowadays. Solid freeform fabrication (SFF) has been demonstrated as an efficient tool for this purpose. In this paper we presented a SFF based in situ printing method that is free of fabrication time frame and fabrication environment constrains. The fabrication parameters on strut formability, fabricated structural stability against gentle fluidic disturbance, and the integrity of the fabricated structure in cell culture environment were studied to assess the potential of the fabrication method on biomedical application. Based on the results, controlled strut formability can be achieved in an appropriate cross-linking deposition range. Alginate composition is the main parameter that dominates the stability and integrity of the fabricated structure. A parameter set that can produce a stable scaffold with the ability to maintain its structure in cell culture environment for at least 15 days was optimized.

null

['Kolan, Krishna C.R.', 'Thomas, Albin', 'Leu, Ming C.', 'Hilmas, Gregory E.']

2021-10-18T21:13:43Z

2014

Mechanical Engineering

null

https://hdl.handle.net/2152/89246

eng

2014 International Solid Freeform Fabrication Symposium

Open

['pore geometry', 'bioactive glass scaffolds', 'laser sintering', 'bone repair', 'bone replacement']

In Vitro Assessment of Laser Sintered Bioactive Glass Scaffolds with Different Pore Geometries

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9a513389-d831-4870-887d-17f38ebbfa11/download

University of Texas at Austin

The pore geometry of bioactive glass scaffolds intended for use in bone repair or replacement is one of the most important parameters that could determine the rate of bone regeneration. The pore geometry would also affect the mechanical properties of the scaffolds and their rate of degradation. Scaffolds with five different architectures, having ~50% porosity, were fabricated with silicate (13–93) and borate (13–93B3) based bioactive glasses using a laser sintering process. An established, late-osteoblasts/early-osteocytes cell line was used to perform cell proliferation tests on the scaffolds. The results indicated that the cells proliferate significantly more on the scaffolds which mimic the trabecular bone architecture compared to traditional lattice structures.

null

['Conway, K.M.', 'Kulkarni, S.S.', 'Smith, B.A.', 'Pataky, G.J.', 'Mocko, G.M.', 'Summers, J.D.']

2021-11-30T21:53:23Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90562', 'http://dx.doi.org/10.26153/tsw/17481']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['shear strength', 'shear deformation', 'grips', 'cellular materials', 'in-plane']

In-Plane Pure Shear Deformation of Cellular Materials with Novel Grip Design

Conference paper

https://repositories.lib.utexas.edu//bitstreams/fb6fdd5b-ae62-4394-ad20-8c35aa36dd2d/download

University of Texas at Austin

Cellular materials are popular due to their high specific strength, but their in-plane shear behavior is not well understood. Current experimental methods are limited due to the lack of pure shear loading as common arcan-style grips have not been adjusted for cellular materials. A significant concern is a mixture of shear loading with grip induced tension. While in bulk materials the tensile force can be assumed negligible, it has a significant impact on the deformation behavior of cellular materials. In this study, finite element modeling simulations were used to demonstrate that using a new sliding grip design reduced grip induced tension on cellular materials. Experimental studies were performed on honeycomb cellular materials with traditional and newlydeveloped grips to calculate and compare the shear strength and ductility of honeycomb cellular materials. The study concluded that traditional grips overestimate the shear strength of honeycomb cellular materials and honeycomb cellular materials in pure shear with limited grip induced tension has significantly lower strength and ductility due to the early formation of plastic hinges.

null

['Montazeri, Mohammad', 'Rao, Prahalada']

2021-11-03T21:50:25Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89943

eng

2017 International Solid Freeform Fabrication Symposium

Open

['laser powder bed fusion', 'LPBF', 'heterogeneous sensing', 'in-situ monitoring', 'meltpool thermal imaging', 'high-speed imaging', 'photodetection', 'spectral graph theory', 'manifold learning', 'laplacian eigenvectors']

In-Process Condition Monitoring in Laser Powder Bed Fusion (LPBF)

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f3483fbb-f83e-401d-82d9-8812427f198e/download

University of Texas at Austin

The goal of this work is to monitor the laser powder bed fusion (LPBF) process using an array of heterogeneous sensors. This goal is termed as build status monitoring. The overarching aim is to usher a qualify-as-you-build quality assurance paradigm in LPBF whereby incipient build defects are detected through analysis of data acquired from in-process sensors. This will allow opportune preventive action to avert propagation of build defects across multiple layers. In pursuit of this goal, a commercial LPBF machine at the National Institute of Standards and Technology (NIST) was integrated with three types of sensors, namely, a photodetector, high-speed video camera, and SWIR thermal camera with the following objective: to develop and apply a spectral graph theoretic approach to monitor the LPBF build status from the data acquired by the three sensors. This objective will lead to early identification of incipient defects that afflict LPBF despite extensive process automation. The proposed approach is illustrated with experimental sensor data acquired during LPBF of a part having a steep overhang feature of ~ 40.5o . Parts with such steep overhang features may exacerbate deleterious consequences such as poor surface finish, porosity, and distortion. Hence, close monitoring of the signal patterns during scanning of overhang areas is consequential for early detection of build defects. The proposed approach detected differences between overhang and non-overhang build status for different sensors with the statistical fidelity (F-score) of 95% from thermal camera signatures to 79% with the photodetector. In comparison, conventional signal analysis techniques - e.g., neural networks, support vector machines, linear discriminant analysis, etc., are evaluated with F-score in the range of 40% to 60%. As part of our forthcoming work, this study will be further expanded to include more build defects, e.g., due to material contamination.

null

['Jamshidinia, M.', 'Boulware, P.', 'Marchal, J.', 'Mendoza, H.', 'Cronley, L.', 'Kelly, S.', 'Newhouse, S.']

2021-10-28T19:40:52Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89680

eng

2016 International Solid Freeform Fabrication Symposium

Open

['cross contamination', 'in-process monitoring', 'spectrometer', 'photodetector', 'laser powder bed fusion (L-PBF)']

In-Process Monitoring of Cross Contamination in Laser Powder Bed Fusion (L-PBF) Additive Manufacturing (AM)

Conference paper

https://repositories.lib.utexas.edu//bitstreams/b65f1a5a-1aeb-4f8f-b1d7-342b3b53ea7c/download

University of Texas at Austin

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.

null

['Mischliwski, Stefan', 'Weigold, Matthias']

2021-11-18T19:07:28Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90471', 'http://dx.doi.org/10.26153/tsw/17392']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['pasty ceramic composite', 'ceramics', 'UV-curing', 'in-process', 'extrusion-based additive manufacturing', 'additive manufacturing']

In-Process UV-Curing of Pasty Ceramic Composite

Conference paper

https://repositories.lib.utexas.edu//bitstreams/05a15cbe-43df-4da0-bf46-15dafe63f884/download

University of Texas at Austin

Within recent years,a wide range of additive manufacturing processes have been developed. While powder bed based fusion processes like selective laser melting and melting processes like fused layer modelling are being increasingly used in industrial applications, prototyping other processes are in the initial stage. This paper develops a new method for an extrusion-based process of pasty UV-curing ceramic composite material. The method proposes an approach to continuously cure the material while it is deployed to reduce process time and generate complete cured parts. A milling machine has been modified with a syringe and a UV-light source to accommodate the process. Experimental studies have been carried out to examine the influence of the process parameters on the curing process. As a result, a parameter set has been found to make fully dense and cured ceramic composite parts.

null

['Breese, P.P.', 'Becker, T.', 'Oster, S.', 'Metz, C.', 'Altenburg, S.J.']

2024-03-27T15:45:53Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124488', 'https://doi.org/10.26153/tsw/51096']

en

2023 International Solid Freeform Fabrication Symposium

Open

['laser thermography', 'defect detection', 'laser powder bed fusion', 'in-situ', 'additive manufacturing']

IN-SITU DEFECT DETECTION FOR LASER POWDER BED FUSION WITH ACTIVE LASER THERMOGRAPHY

Conference paper

https://repositories.lib.utexas.edu//bitstreams/28193a5f-e96a-4da0-b9e2-3ce5d8a79fa7/download

University of Texas at Austin

Defects are still common in metal components built with Additive Manufacturing (AM). Process monitoring methods for laser powder bed fusion (PBF-LB/M) are used in industry, but relationships between monitoring data and defect formation are not fully understood yet. Additionally, defects and deformations may develop with a time delay to the laser energy input. Thus, currently, the component quality is only determinable after the finished process. Here, active laser thermography, a nondestructive testing method, is adapted to PBF-LB/M, using the defocused process laser as heat source. The testing can be performed layer by layer throughout the manufacturing process. We study our proposed testing method along experiments carried out on a custom research PBF-LB/M machine using infrared (IR) cameras. Our work enables a shift from post-process testing of components towards in-situ testing during the AM process. The actual component quality is evaluated in the process chamber and defects can be detected between layers.

null

['Sturm, Logan', 'Albakri, Mohammed', 'Williams, Christopher B.', 'Tarazaga, Pablo']

2021-10-28T19:59:23Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89686

eng

2016 International Solid Freeform Fabrication Symposium

Open

['impedance-based monitoring', 'in-situ detection', 'build defects', 'additive manufacturing']

In-situ Detection of Build Defects in Additive Manufacturing via Impedance-Based Monitoring

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f53c097e-3860-4ebf-b7c5-fd207bd3915b/download

University of Texas at Austin

In this paper, the authors explore the use of impedance-based monitoring techniques for the in-situ detection of additive manufacturing build defects. By physically coupling a piezoceramic (PZT) sensor to the part being fabricated, the measured electrical impedance of the PZT can be directly linked to the mechanical impedance of the part. It is hypothesized that one can detect in-situ defects of part mass and stiffness by comparing the signatures collected during printing of parts with that of a defect-free control sample. In this paper, the authors explore the layer-to-layer sensitivity of this technique. A control sample is created using Material Jetting and the change in signatures between various layer intervals is measured. To evaluate the technique’s ability to perform in-situ detection, several parts containing designed defects (e.g., internal voids) are fabricated and their layer-to-layer signatures are compared to a control sample. Using this technique, the authors demonstrate an ability to track print progress and detect defects as they occur.

null

['Pustinger, Alexander P.', 'Corral, Joselin', 'Villegas, Arianna', 'Espalin, David']

2024-03-26T20:56:41Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124409', 'https://doi.org/10.26153/tsw/51017']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['hybrid AM', '4-wire resistance measurements', 'encapsulation', 'laser soldering']

In-situ Electrical Resistance Measurements for Soldering Studies in Hybrid AM

Conference paper

https://repositories.lib.utexas.edu//bitstreams/acb58f4a-95aa-43a4-90b9-1233901d5c2b/download

University of Texas at Austin

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof: The views and opinions of-authors expressed herein do not necessarily state or reflect those of the-United States Government or any agency thereof.

null

['Liu, Tao', 'Kinzel, Edward C.', 'Leu, Ming C.']

2023-01-27T17:46:09Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117345', 'http://dx.doi.org/10.26153/tsw/44226']

null

2022 International Solid Freeform Fabrication Symposium

Open

Laser powder bed fusion (L-PBF)

In-situ Infrared Thermographic Measurement of Powder Properties in Laser Powder Bed Fusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c782c1e4-b67c-4899-ba1e-20e0235060e3/download

null

The laser powder-bed fusion (LPBF) process is strongly influenced by the characteristics of the powder layer, including its thickness and thermal transport properties. This paper presents an investigation of in-situ characterization of the powder layer using active infrared thermography. The printing laser beam is diffused and illuminates onto the powder bed’s top surface in various frequencies. A long-wavelength thermal camera monitors the surface temperature history. Insight is provided by a one-dimensional thermal model of the process, which shows the frequency dependence of the surface temperature amplitude and phase on the powder layer thickness and thermal properties. An experiment demonstrates the validity of this model and shows its potential for measuring local powder properties in-situ.

null

['Binder, Maximilian', 'Machnik, Andreas', 'Bosch, Maximilian', 'Kreitz, Katharina', 'Schlick, Georg', 'Seidel, Christian']

2023-02-10T14:19:04Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117452', 'http://dx.doi.org/10.26153/tsw/44333']

eng

2022 International Solid Freeform Fabrication Symposium

Open

['Laser-Based Powder Bed Fusion', 'Metal Additive Manufacturing', 'Strain Gauges', 'Smart Parts', 'Inconel']

In-situ Integration of Weldable Strain Gauges in Components Manufactured by Laser-Based Powder Bed Fusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/50bf2a7c-7ecd-47de-80bf-46bd093ea70a/download

null

The integration of sensors in components made by PBF-LB/M facilitates promising new possibilities for component monitoring. It enables the collection of relevant measurement data at previously inaccessible component regions, which are needed for the determination of maintenance strategies. Therefore, the following research deals with the development of a concept, with which weldable strain gauges (WSG) can be weld-on by the laser-scanner-system of a PBF-LB/M system to the manufactured component. The examinations show that the arrangement of so-called weld seams has a decisive influence on a correct metal carrier connection of the WSG. It can be deduced from the study that WSGs can be integrated within components manufactured by PBF-LB/M and completely welded to it with the laser-scanning-system. Following measurement validations demonstrate that the WSG provides complete and correct measurement data and can therefore be considered as successfully connected to the component.

null

['Phillips, Tim', 'McElroy, Austin', 'Fish, Scott', 'Beaman, Joseph']

2021-10-28T19:43:05Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89681

eng

2016 International Solid Freeform Fabrication Symposium

Open

['in-situ laser control', 'selective laser sintering', 'even melting']

In-Situ Laser Control Method for Polymer Selective Laser Sintering (SLS)

Conference paper

https://repositories.lib.utexas.edu//bitstreams/0867cd12-72f6-464b-a706-bc894a175bcf/download

University of Texas at Austin

Selective laser sintering (SLS) of Nylon is a significant portion of the Additive Manufacturing (AM) market for structurally sensitive applications. To achieve high performance in these laser melted parts, one would like to see consistent melting of the powder over the part region in each layer of the build. Current research methods into improving this consistency focus on the use of IR sensing to adjust heating elements in attempt to gain even temperature distributions over the pre-laser melted powder layer with the expectation that the laser at constant power, speed, spot size, and spacing will deliver constant melting properties. In this paper we examine a complimentary method of gaining even melted properties by sensing the pre-lased powder along the laser track, and adjusting the laser power to achieve a common post melted temperature everywhere on the part. We describe the feedback based laser control method that varies the laser power in to account for the pre-sintering temperature profile across the part bed. Various tests have been performed, and a method for employing this strategy throughout a build is presented.

null

['Esfahani, Mehrnaz Noroozi', 'Bian, Linkan', 'Tian, Wenmeng']

2021-11-16T16:15:04Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90330', 'http://dx.doi.org/10.26153/tsw/17251']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['image series analysis', 'quality monitoring', 'in-situ', 'layer-wise', 'laser-based additive manufacturing']

In-Situ Layer-Wise Quality Monitoring for Laser-Based Additive Manufacturing Using Image Series Analysis

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5c3092d6-2b0d-43b3-b20b-998826a5ac52/download

University of Texas at Austin

Quality assurance has been one of the major challenges in laser-based additive manufacturing (AM) processes. This study proposes a novel process modeling methodology for layer-wise in-situ quality monitoring based on image series analysis. An image-based autoregressive (AR) model has been proposed based on the image registration function between consecutively observed thermal images. Image registration is used to extract melt pool location and orientation change between consecutive images, which contains sensing stability information. Subsequently, a Gaussian process model is used to characterize the spatial correlation within the error matrix. Finally, the extracted features from the aforementioned processes are jointly used for layer-wise quality monitoring. A case study of a thin wall fabrication by a Directed Laser Deposition (DLD) process is used to demonstrate the effectiveness of the proposed methodology.

null

['Lough, Cody S.', 'Wang, Xin', 'Landers, Robert G.', 'Bristow, Douglas A.', 'Drallmeier, James A.', 'Kinzel, Edward C.']

2021-11-18T18:47:36Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90464', 'http://dx.doi.org/10.26153/tsw/17385']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['local part qualification', 'local part prediction', 'voxel based processing', 'SWIR imaging', '304L', 'stainless steel', 'selective laser melting']

In-situ Local Part Qualification of SLM 304L Stainless Steel through Voxel Based Processing of SWIR Imaging Data

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c7daaedd-37f9-48eb-89d8-8f363c19dc45/download

University of Texas at Austin

This paper demonstrates the potential for qualification through local part property prediction of 304L stainless steel parts manufactured by Selective Laser Melting (SLM). This is accomplished through voxel based processing of SWIR imaging data measured in-situ. Thermal features are extracted from time-series SWIR imaging data recorded from layer-to-layer to generate 3D point cloud reconstructions of parts. The voxel based data is indexed with localized measurements of SLM part properties (light-to-dark microstructural feature ratio, microhardness, μCT data) to demonstrate the correlations. Various features are extracted from the thermal history for comparison of their respective abilities to predict the resulting local part properties. The correlations and comparisons developed in this paper are then used to discuss the capability of a voxel based framework using information from in-situ measurements of the thermal history to locally qualify parts manufactured by SLM.

This work was funded by the Department of Energy’s Kansas City National Security Campus which is operated and managed by Honeywell Federal Manufacturing Technologies, LLC under contract number DE-NA0002839.

null

['Ritchie, M.', 'Mehraban, S.', 'Brown, S.G.R.', 'Butcher, D.', 'Cullen, J.', 'Calvo-Dahlborg, M.', 'Lavery, N.P.']

2023-03-29T16:43:14Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117685', 'http://dx.doi.org/10.26153/tsw/44564']

eng

2022 International Solid Freeform Fabrication Symposium

Open

['High Entropy Alloy', 'Laser Powder Bed Fusion', 'Pitting Corrosion']

In-situ Modification of a High Entropy Alloy with 2.4% Molybdenum Using LPBF, and Its Effect on Microstructure and Corrosion Resistance

Conference paper

https://repositories.lib.utexas.edu//bitstreams/74c72927-f280-444c-aafc-f0abe26dde2f/download

null

Laser powder bed fusion (LPBF) components display higher porosity compared to parts made by conventional processes and these pores act as preferential initiation sites for pitting corrosion to occur. In stainless steels such as 316L, molybdenum is 3.5X more effective at enhancing the pitting resistance than chromium, without adding unwanted nitrides to the alloy. In this work, the effect on corrosion resistance is reported for an Al-Cr-Mn-Ni-Fe high entropy alloy (HEA) gas atomised specifically for LPBF, as well as the effects of modifying the alloy by blending the HEA with molybdenum. In-situ LPBF processing, even for low levels of additions has made the comparison difficult, as the pitting resistance is so strongly linked to the porosity, which is higher in the in-situ process. Pitting resistance for both the original HEA and the doped HEA will be compared between samples processed by casting and by LPBF.

null

['Roach, M.A.', 'Fowler, B.', 'Thakkar, D.', 'Babbitt, C.', 'Khurana, S.', 'Jared, B.H.']

2023-04-03T15:54:26Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117720', 'http://dx.doi.org/10.26153/tsw/44599']

eng

2022 International Solid Freeform Fabrication Symposium

Open

Laser powder bed fusion

In-situ Monitoring of Laser-Powder-Bed-Fusion Using IR and NIR Emissions to Detect Thermal Anomalies

Conference paper

https://repositories.lib.utexas.edu//bitstreams/08dbecf1-84d9-452b-9575-bb8ff75c6e4c/download

null

Process monitoring of laser-powder-bed-fusion (L-PBF) has advanced significantly since the beginning of this technology. Many methods exist today for in-situ process monitoring; however, these methods can be costly to implement and provide sub-par image resolutions. This research aims to develop a method of low-cost and high-resolution thermal monitoring system using near-infrared (NIR) wavelength band emission monitoring to detect anomalies. This research will compare more expensive infrared (IR) wavelength band monitoring methods to the cheaper NIR method and other drawbacks brought about by monitoring one wavelength band over the other.

null

['Nadimpalli, Venkata Karthik', 'Na, Jeong K.', 'Bruner, Darren T.', 'King, Brenna A.', 'Yang, Li', 'Stucker, Brent E.']

2021-10-28T20:36:38Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89694

eng

2016 International Solid Freeform Fabrication Symposium

Open

['in-situ non-destructive evaluation', 'in-situ monitoring', 'ultrasonic transducer', 'ultrasonic additive manufacturing']

In-Situ Non-Destructive Evaluation of Ultrasonic Additive Manufactured Components

Conference paper

https://repositories.lib.utexas.edu//bitstreams/bde5037a-d2ad-4262-85e7-843b3ceb2395/download

University of Texas at Austin

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.

null

['Lough, Cody S.', 'Escano, Luis I.', 'Qu, Minglei', 'Smith, Christopher C.', 'Landers, Robert G.', 'Bristow, Douglas A.', 'Chen, Lianyi', 'Kinzel, Edward C.']

2021-11-15T22:19:33Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90292', 'http://dx.doi.org/10.26153/tsw/17213']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['optical emission spectroscopy', '304L', 'stainless steel', 'in-situ', 'selective laser melting']

In-Situ Optical Emission Spectroscopy during SLM of 304L Stainless Steel

Conference paper

https://repositories.lib.utexas.edu//bitstreams/367c44d8-7526-4006-acec-651fa4bff5be/download

University of Texas at Austin

This paper demonstrates the potential of in-situ Optical Emission Spectroscopy (OES) to monitor the Selective Laser Melting (SLM) process. A spectrometer is split into the beam path of a home-built SLM system to collect visible light emitted from the melt pool and plume. The inline configuration allows signal collection regardless of the laser scan location. The spectral data can be used to calculate the temperature of the vapor plume and correlated with the melt-pool size. The effects of varying the atmosphere and pressure on the OES signal are also explored. These results demonstrate that OES can provide useful feedback to the SLM process for process monitoring and part validation. The challenges implementing OES in-line on a commercial SLM platform are discussed.

This work was funded by Honeywell Federal Manufacturing & Technologies under Contract No. DE-NA0002839 with the U.S. Department of Energy.

null

['Legesse, Fisseha', 'Kapil, Sajan', 'Chabra, Rimpy', 'Sharma, Arun', 'Karunakaran, K.P.']

2021-10-26T19:33:27Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89566

eng

2016 International Solid Freeform Fabrication Symposium

Open

['in-situ preheating', 'solidification cracking', 'hybrid layered manufacturing', 'metal inert gas', 'tungsten inert gas']

In-Situ Preheating in Hybrid Layered Manufacturing for Tooling Elements

Conference paper

https://repositories.lib.utexas.edu//bitstreams/e530069f-eba9-48ce-ac73-9efc2c20ddc7/download

University of Texas at Austin

Solidification cracking of hard materials such as H13 tool steel is one of the major problems in metal based Additive Manufacturing (AM) processes. Hybrid Layered Manufacturing (HLM) is one of the metal based AM process which uses Metal Inert Gas (MIG) cladding for addition and CNC milling for subtraction of material. In this work, an in-situ induction heating based preheating system has been developed to solve the solidification cracking problem. The Tungsten Inert Gas (TIG) and Induction heating methods are compared and it has been found that the induction based preheating system can produce better microstructure and sound products. In the experimental procedure, before deposition of a layer the prebuild layer is preheated up to 350-5000C. Also the effect of in-situ preheating on the microstructure of the deposited layers have been studied using Scanning Electron Microscope (SEM).

null

['Lewis, Adam', 'Gardner, Michael', 'McElroy, Austin', 'Milner, Thomas', 'Fish, Scott', 'Beaman, Joseph']

2021-10-28T19:46:04Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89682

eng

2016 International Solid Freeform Fabrication Symposium

Open

['optical coherence tomography', 'selective laser sintering', 'in-situ process monitoring', 'ex-situ part quality']

In-Situ Process Monitoring and Ex-Situ Part Quality Assessment of Selective Laser Sintering Using Optical Coherence Tomography

Conference paper

https://repositories.lib.utexas.edu//bitstreams/23881d3c-6d43-4163-a5d1-91b67e365a8e/download

University of Texas at Austin

Widespread commercial adoption of Selective Laser Sintering has been hindered by inadequate quality and consistency of manufactured parts. Improved process monitoring and control have the potential to improve part quality and thus increase adoption of SLS for various applications. In this paper, optical coherence tomography (OCT) is explored as a new process monitoring tool in SLS polymer printing. The basic operating principles behind OCT are reviewed to illustrate the potential monitoring capabilities followed by results for both in-situ process monitoring and ex-situ examinations of built parts comprised of various polymers. Capabilities and limitations of OCT in each application are discussed.

null

['Guess, T.R.', 'Chambers, R.S.']

2018-10-05T17:28:50Z

1995

Mechanical Engineering

doi:10.15781/T2QZ2327H

http://hdl.handle.net/2152/68718

eng

1995 International Solid Freeform Fabrication Symposium

Open

['3D Printing', 'cure shrinkage', 'laser path dependance']

In-Situ Property Measurements On Laser-Drawn Strands Of SL 5170 EPOXY and 5149 Acrylate

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5c0c9b8f-cd63-4552-b1e4-951983350b45/download

null

Material behavior plays a significant role in the mechanics leading to internal stresses and, potentially, to distortion (curling) of parts as they are built by stereolithography processes that utilize photocuring resins. A study is underway to generate material properties that can be used to develop phenomenological material models of epoxy and acrylate resins. Strand tests are performed in situ in a 3D System's SLA-250 machine; strands are drawn by either single or multiple exposures ofthe resin to a laser beam. Linear shrinkage, cross-sectional areas, cure shrinkage forces and stress-strain data are presented. Also, the curl in cantilever beam specimens, built with different draw patterns, are compared.

null

['Aminzadeh, Masoumeh', 'Kurfess, Thomas']

2021-10-28T19:50:33Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89683

eng

2016 International Solid Freeform Fabrication Symposium

Open

['laser powder bed fusion', 'in-situ quality inpsection', 'visual camera images', 'high-resolution imaging']

In-Situ Quality Inspection of Laser Powder-Bed Fusion Using High-Resolution Visual Camera Images

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6047f28b-55dd-4d38-a4ca-8726295fef4d/download

University of Texas at Austin

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.

null

['Ganesh-Ram, A.', 'Tanrikulu, A.A.', 'Valdez Loya, O.', 'Davidson, P.', 'Ameri, A.']

2024-03-26T20:58:59Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124410', 'https://doi.org/10.26153/tsw/51018']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['laser powder bed fusion', 'in-situ strengthening', 'Ti6Al4V']

In-situ Reinforcement Processing for Laser Powder Bed Fused Ti64 Parts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c4cf86b2-e821-41f4-b717-2cf4e7430d08/download

University of Texas at Austin

The objective of this study was to investigate how the microstructure and mechanical properties of Ti-6Al-4V samples, fabricated using laser powder bed fusion (L-PBF), change when a predefined local double melting strategy is employed within each layer of the manufacturing process. The analysis primarily focused on evaluating microstructural aspects, defects, and grain size, along with the mechanical properties, specifically the Vickers hardness at various positions within the samples. The findings indicated that the integration of the predefined locally double melting scan in each layer had a significant influence on the microstructure, resulting in variations in grain size across different locations, as well as hardness values with variations of up to 10% across different areas. Moreover, these discoveries underscore the potential of employing the predefined locally double melting strategy in each layer to create fabricated components with distinctive behaviors, like composites, which could find applications in the aerospace industry.

null

['Wroe, Walker', 'Gladstone, Jessica', 'Phillips, Timothy', 'McElroy, Austin', 'Fish, Scott', 'Beaman, Joseph']

2021-10-20T22:51:55Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89382

eng

2015 International Solid Freeform Fabrication Symposium

Open

['selective laser sintering', 'Nylon-12', 'thermal conditions', 'tensile properties', 'layer-by-layer']

In-Situ Thermal Image Correlation with Mechanical Properties of Nylon-12 in SLS

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1feb92e4-102a-4b93-9594-f619380007d6/download

University of Texas at Austin

Selective laser sintering (SLS) of Nylon is a significant portion of the additive manufacturing market for structurally sensitive applications. Current methods of acceptance for such parts are based on the inclusion of ASTM tensile test specimens within the build volume to assess the overall build quality. Ultimate strength and elongation of these specimens oriented both in-plane and normal to the layer build direction are the primary quality metrics. This paper looks at a more complete method of certifying parts for acceptance based on examination of the build conditions in each layer of the part by comparing layer-by-layer thermal conditions during the part build to the resulting ASTM specimen tensile properties. Through such a comparison, a more complete three-dimensional assessment of part quality during the build process can be constructed. The layer-by-layer assessment used here is derived from infrared thermal imaging; mapping temperature profiles of SLS-built tensile bars with data collected before, during, and after each layer-wise laser melting sequence. Mechanical properties and fracture conditions are then quantified and correlated with the conditions where the fractures occur. Build conditions associated with poor failure conditions may then be used to assess poor SLS bonding throughout the part volume, improving overall part quality assessment and certification. As the method is matured, real time layer-by-layer assessment will be linked to SLS control, to correct for observed defects during the build and improve overall part quality and repeatability.

null

['Liu, T.', 'Lough, C.S.', 'Sehhat, H.', 'Huang, J.', 'Kinzel, E.C.', 'Leu, M.C.']

2021-12-01T22:21:08Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90637', 'http://dx.doi.org/10.26153/tsw/17556']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['laser powder bed fusion', 'long wavelength infrared', 'powder thickness']

In-Situ Thermographic Inspection for Laser Powder Bed Fusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/31f7cc78-0048-4a65-839a-d73c66a39507/download

University of Texas at Austin

Laser powder bed fusion is strongly influenced by the quality of the powder layer including the powder properties as well as the layer thickness. In particular, thermal stresses can produce sufficient part deformation to the point that a part interferes with the wiper. This paper investigates the use of long-wave infrared thermography to monitor the surface temperature of the build. When cold powder is spread by the wiper, heat diffuses from the underlying part through the powder. The surface temperature history is a strong function of the thermal transport properties of the powder as well as the thickness. This correlation is explored and measured experimentally. It is then used to estimate the powder layer thickness above overhanging parts. This approach is shown to capture the part distortion and predicts wiper state prior to catastrophic interaction with the part.

null

['AlMangour, B.', 'Grzesiak, D.', 'Yang, J.M.']

2021-10-27T21:04:42Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89613

eng

2016 International Solid Freeform Fabrication Symposium

Open

['mechanical alloying', 'selective laser melting', 'porosity', 'hardness', 'wear']

In-Situ TiC Particle Reinforced 316L Stainless Steel Matrix Nanocomposites: Powder Preparation by Mechanical Alloying and Selective Laser Melting Behavior

Conference paper

https://repositories.lib.utexas.edu//bitstreams/63bab039-4ce4-4d99-998b-99c25275b573/download

University of Texas at Austin

null

Ahlers, Daniel

2021-12-01T22:24:42Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90638', 'http://dx.doi.org/10.26153/tsw/17557']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['printed electronics', 'visual inspection', 'neural network', 'fused filament fabrication']

In-Situ Verification of 3D-Printed Electronics Using Deep Convolutional Neural Networks

Conference paper

https://repositories.lib.utexas.edu//bitstreams/494dd034-3aae-4ee7-a1bc-c27e4f94a495/download

University of Texas at Austin

Printed electronics processes are becoming more stable and evolve into first industrial applications. These industrial applications require proper quality assurance to get a mostly autonomous production process. In this work, we present a new approach to inspect printed electronics and ensure their quality. Our hardware setup extends a fused filament fabrication (FFF) printer with an extruder for direct dispensing of conductive paste, a pick and place unit, and two cameras. The cameras take multiple images during printing. A trained neural network analyzes these pictures to separate the electronic wires from the plastic background. All separated images of a layer are combined to get a full view of the layer. Our algorithms then examine the detected wires to identify printing flaws. The algorithms currently detect connection breaks, shorts, find points that have not been reached, and evaluate the width of the printed wires.

null

['Karnati, Sreekar', 'Hoerchler, Jack', 'Flood, Aaron', 'Liou, Frank']

2021-11-11T15:02:44Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90211', 'http://dx.doi.org/10.26153/tsw/17132']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['automated ball indentation', 'plastic behavior', 'Power Law', '304L', 'stainless steel', 'powder bed fabrication']

Incorporation of Automated Ball Indentation Methodology for Studying Powder Bed Fabricated 304L Stainless Steel

Conference paper

https://repositories.lib.utexas.edu//bitstreams/0f2399ee-df11-476a-baee-ae70bcf10248/download

University of Texas at Austin

Automated Ball Indentation (ABI) is a viable method for estimating the ductility, yield stress, and ultimate stress, among other metrics, in different metallic materials. Currently, ABI data analysis utilizes Holloman’s Power Law to model the plastic region of the true stress-true strain curve. While this formulation is accurate for some materials, its relevance for additively manufactured austenitic stainless steels, such as 304L, needed investigation. The deviation of the material’s plastic behavior from the Power Law was investigated. In order to better model this behavior, both the Voce and Ludwigson formulation were investigated. These formulations were tested for both wrought and additively manufactured 304L stainless steel. Regression analysis was used to choose the appropriate fit. The chosen formulation was then used to generate a material model to simulate the ABI process. These simulations were validated through experimental analysis.

null

['Leu, Ming C.', 'Isanaka, Sriram P.', 'Richards, Von L.']

2021-09-28T19:28:54Z

9/22/09

Mechanical Engineering

null

['https://hdl.handle.net/2152/88161', 'http://dx.doi.org/10.26153/tsw/15102']

eng

2009 International Solid Freeform Fabrication Symposium

Open

['Rapid Freeze Prototyping', 'heat transfer', 'build time reduction']

Increase of Heat Transfer to Reduce Build Time in Rapid Freeze Prototyping

Conference paper

https://repositories.lib.utexas.edu//bitstreams/b7007eb7-8af3-4d38-aa03-b6a345ee5dce/download

University of Texas at Austin

Reduction of part build time in the Rapid Freeze Prototyping (RFP) process, which fabricates a 3D ice part layer-by-layer by depositing and freezing water droplets, has been achieved by increase of heat transfer. Three mechanisms have been experimentally investigated: 1) cooling the substrate, 2) use of forced convection, and 3) use of a chilling plate. Cooling the substrate is effective for parts of small heights but becomes ineffective with increase in part height. Forced convection produced desirable reduction in part build time but with the undesirable formation of frost on the built ice part. The use of chilling plate to increase heat conduction proved to be most effective. To ensure that the frozen ice from the deposited water can be easily removed from the chilling plate, various surface coats were investigated and the most effective surface coat was found to be a thin Teflon film. After incorporating the chilling plate we have successfully achieved 75% reduction in part build time.

null

['Roschli, Alex', 'Duty, Chad', 'Lindahl, John', 'Post, Brian K.', 'Chesser, Phillip C.', 'Love, Lonnie J.', 'Gaul, Katherine T.']

2021-11-09T19:14:35Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90135', 'http://dx.doi.org/10.26153/tsw/17056']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['z-pinning', 'interlaminar strength', 'large scale additive manufacturing', 'big area additive manufacturing', 'BAAM']

Increasing Interlaminar Strength in Large Scale Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/8a660f19-abef-4da5-ad49-fa4f7e2c8390/download

University of Texas at Austin

Interlaminar strength of extrusion-based additively manufactured parts is known to be weaker than the strength seen in the printed directions (X and Y). With Big Area Additive Manufacturing (BAAM), large parts lead to long layer times that are prone to splitting, sometimes referred to as delamination, between the layers. Fiber filled materials, such as carbon fiber reinforced ABS, are used to counteract the effects of thermal expansion by increasing the strength in the X and Y directions. These fibers stay in-plane meaning that no fibers span from layer to layer, which would help counteract the weak interlaminar strength that causes splitting. A solution to this is a patent pending approach called Z-Pinning. The process involves strategically positioning voids across multiple layers that are backfilled with hot extrudate. This paper will explore the benefits and results of using Z-Pinning in large scale additive manufacturing.

null

['Ahlers, D.', 'Koppa, P.', 'Hengsbach, F.', 'Gloetter, P.', 'Altmann, A.', 'Schaper, M.', 'Tröster, T.']

2021-11-04T13:52:37Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89960

eng

2017 International Solid Freeform Fabrication Symposium

Open

['process melting', 'porosity', 'Ti6Al4V', 'hot isostatic pressing', 'selective laser melting']

Increasing Process Speed in the Laser Melting Process of Ti6Al4V and the Reduction of Pores During Hot Isostatic Pressing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d2a0a259-f930-4a05-b6b5-58190214ce4c/download

University of Texas at Austin

Additive manufacturing of titanium alloys has gained intensive attraction from industry and academia. Moreover, for additively fabricated parts consisting of Ti6Al4V, hot isostatic pressing (HIP), is widely used as a post treatment in order to increase the relative density of the built parts. However, one aspect which has rarely been addressed so far, is the increase of process speed, accompanied by a reduced relative density in the as-built condition and a subsequent hot isostatic pressing process to achieve the desired dense material. The approach here is to use the standard process route as described, but intentionally increase the process speed and accept a certain value of porosity. The focal objective of this study is the identification of a parameter-set with the highest potential for an increase of process speed and subsequently reduce the internal defects during the hot isostatic pressing process to achieve completely dense components.

null

['Duty, Chad', 'Smith, Tyler', 'Lambert, Alexander', 'Condon, Justin', 'Lindahl, John', 'Kim, Seokpum', 'Kunc, Vlastimil']

2021-11-18T19:15:18Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90475', 'http://dx.doi.org/10.26153/tsw/17396']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['z-pinning', 'solid cross-section', 'interlayer bond', 'fused filament fabrication']

Increasing the Interlayer Bond of Fused Filament Fabrication Samples with Solid Cross-Sections using Z-Pinning

Conference paper

https://repositories.lib.utexas.edu//bitstreams/56532fac-e5bf-444b-b9c9-8b5b35fac9ac/download

University of Texas at Austin

The mechanical properties of parts made by fused filament fabrication is highly anisotropic, with the strength across layers (z-axis) typically measuring ~50% lower than the strength along the direction of the extruded material (x-axis). A z-pinning method has been developed in which material is extruded in the z-direction to fill intentionally aligned voids in the x-y print pattern. In previous studies that involved a sparse rectilinear grid cross-section (35% infill), the z-pinning approach demonstrated more than a 3.5x increase in strength in the z-direction. The current study expanded these efforts to evaluate the use of z-pins in a printed sample with a solid cross-section. Although a solid cross-section is more common in structural components, it is much less forgiving of instabilities that may occur in the z-pinning approach (such as over-filling). Even though this study utilized a low pin volume (~43% fill factor), the pinning approach demonstrated a 40% increase in z-direction strength for solid samples that had similar printing times.

null

['Mun, Jiwon', 'Ju, Jaehyung', 'Thurman, James']

2021-10-13T20:40:28Z

2014

Mechanical Engineering

null

['https://hdl.handle.net/2152/88781', 'http://dx.doi.org/10.26153/tsw/15715']

eng

2014 International Solid Freeform Fabrication Symposium

Open

['indirect additive manufacturing based casting', 'I AM Casting', 'indirect 3D printing based casting', 'metallic cellular structures', 'PolyJet', 'volume of fluid', 'additive manufacturing']

Indirect Additive Manufacturing of a Cubic Lattice Structure with a Copper Alloy

Conference paper

https://repositories.lib.utexas.edu//bitstreams/97f124e2-765e-4a7d-9ff1-005054fd5771/download

University of Texas at Austin

Direct-metal additive manufacturing (AM) processes such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM) methods are being used to fabricate complex metallic cellular structures with a laser or electron beam over a metal powder bed. Even though their excellent capabilities to fabricate parts with cellular mesostructure, there exist several constraints in the processes and applications; limited selection of materials, high thermal stress by the high local energy source, poor surface finish and anisotropic properties of parts caused by combined effects of one-dimensional (1D) energy based patterning mechanism, the deposition layer thickness, powder size, power and travel speed of laser or electron beam. In addition, manufacturing cost is still high with the Direct-metal AM processes. As an alternative way to manufacture metallic 3D cellular structures, which can overcome the disadvantages of direct-metal AM techniques, polymer AM methods can be combined with metal casting. We may call this “Indirect AM based Casting (I AM casting)”. The objective of the study is to explore the potential of I AM Casting associated with development of a novel manufacturing process - Indirect 3D Printing based casting which is capable of producing metallic cellular structures within a cell size of 3mm and cell thickness of 0.5mm. We will characterize polymers making sacrificial patterns by PolyJet typed 3D printers; e.g., melting and glass transition temperatures and thermal expansion coefficients. A transient flow and heat-transfer analysis of molten metal through 3D cellular network mold will be conducted. Solidification of molten metal through cellular mold during casting will be simulated with temperature dependent properties of molten metal and mold over a range of running temperature. The volume of fluid (VOF) method will be implemented to simulate the solidification of molten metal together with a user defined function (UDF) of ANSYS/FLUENT. Finally, experimental validation will be followed.

null

['Chakravarthy, Kumaran M.', 'Bourell, David L.']

2021-10-05T14:42:58Z

8/17/11

Mechanical Engineering

null

['https://hdl.handle.net/2152/88383', 'http://dx.doi.org/10.26153/tsw/15322']

eng

2011 International Solid Freeform Fabrication Symposium

Open

['direct methanol fuel cells', 'corrugated flow field plates', 'power density', 'laser sintering']

Indirect Laser Sintering of Corrugated Flow Field Plates for Direct Methanol Fuel Cell Applications

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d5db2bd0-d0e1-4d5e-8f4e-f669cc0a48ac/download

University of Texas at Austin

Direct methanol fuel cells (DMFC) hold distinct advantages over traditional hydrogen-based fuel cells. Their commercialization, however, has been bound by many factors – especially their suboptimal efficiency. This work aims at enhancing the performance of DMFC through the use of corrugated flow field plates. Our objectives are two-fold – one, to increase the power density of DMFC by corrugating flow field plates and two, to introduce Laser sintering (LS) as an efficient and robust method for the manufacture of such plates. Corrugated flow field plates with 10% more surface area as compared to a planar design were made by LS & tested in a DMFC environment. Our results show that the particle size of the material used – Graphite – has a significant effect upon the green strength of LS parts. We also report the performance of corrugated flow field plates with 10% higher surface area (as compared to planar plates), channel width and depth of 2mm and an electrode area of 5 cm2. This study is the first experimental approach to the use of indirect LS for making such fuel cell components.

null

['Tobin, James R.', 'Badrinarayan, B.', 'Barlow, J.W.', 'Beaman, J.J.']

2018-05-03T19:52:50Z

1993

Mechanical Engineering

doi:10.15781/T2H708H81

http://hdl.handle.net/2152/65072

null

1993 International Solid Freeform Fabrication Symposium

Open

['Center for Materials Science and Engineering', 'Department of Chemical Engineering', 'Department of Mechanical Engineering', 'Selective Laser Sintering', 'SLS']

Indirect Metal Composite Part Manufacture Using the SLS Process

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ad9fd096-f9c3-4e83-9ad8-2b01b0eab9d3/download

null

As a near term alternative process to direct sintering, an intermediate polymer binder is combined with powder to produce green preforms with the Selective Laser Sintering (SLS) process. To produce parts with desirable strength dimensional control, the binder is gradually removed from the green preform (obtained from the SLS process), and the remaining form is lightly bonded. This porous part then infiltrated. Final part density, shrinkage, and strength data are presented. An injection mold insert was fabricated from this material and used to mold PMMA, polyester, and polycarbonate parts. To date, the mold insert 176 shots at injection to 35,000 and melt temperatures up to 300°C.

null

['Gervasi, Vito R.', 'Shaikh, F. Zafar']

2019-09-23T17:13:27Z

2000

Mechanical Engineering

null

['https://hdl.handle.net/2152/75978', 'http://dx.doi.org/10.26153/tsw/3077']

eng

2000 International Solid Freeform Fabrication Symposium

Open

Prototype

Indirect Rapid Molds for Prototype Lost-Foam Pattern Production 506

Conference paper

https://repositories.lib.utexas.edu//bitstreams/87f984b1-e22e-4902-9796-4a1f30c75633/download

null

Lost-foam (also known as Expendable Pattern Casting, EPC) is an ever-growing metalmcasting technique, capable of producing complex metal components without parting lines. Mold preparation for lost-foam casting is typically accurate, but expensive and slow. The goal of this research was to develop a new approach for producing rapid lost-foam molds. With this new approach, patterns generated by SFF technology are used to form indirect composite lost-foam molds. Ultimately, our objective is to produce these molds quickly, accurately, and inexpensively. This new approach to lost-foam mold-making will be explained as well as the results of one trial.

null

['Vallabhajosyula, Phani', 'Bourell, David L.']

2021-09-29T14:19:20Z

2009-09

Mechanical Engineering

null

['https://hdl.handle.net/2152/88179', 'http://dx.doi.org/10.26153/tsw/15120']

eng

2009 International Solid Freeform Fabrication Symposium

Open

['Selective Laser Sintering', 'ferrous components', 'infiltrant composition']

Indirect Selective Laser Sintered Fully Ferrous Components – Infiltration Modeling, Manufacturing and Evaluation of Mechanical Properties

Conference paper

https://repositories.lib.utexas.edu//bitstreams/207a6988-fb5b-4d29-bc14-0015aac38757/download

University of Texas at Austin

Commercially available Selective Laser Sintered (SLS) ferrous components contain copper-based infiltrant in a ferrous preform. The choice of infiltrant has led to inferior mechanical properties of these components limiting their use in many non-injection-molding structural applications, particularly at elevated temperature. In the present work, an attempt has been made to replace the copper-based infiltrant considering cast iron as potential infiltrant for its fluidity, hardness and stability at comparatively high temperature. A critical issue associated with the infiltration was diffusion of carbon from the cast iron into the steel preform thereby decreasing its melting temperature and distorting the part geometry. A predictive model was developed which defines the degree of success for infiltration based on final part geometry and depending on the relative density of the preform and infiltration temperature. The model may be extended to other ferrous powder and infiltrant compositions in an effort to optimize the properties and utility of the final infiltrated part. Initial studies were carried out to validate the model by infiltrating SLSed Laserformtm A6 tool steel preforms with ASTM Type I A532 cast iron. The parts were analyzed for geometry, microstructure and hardness. This research was sponsored by the National Science Foundation under Grant #DMI-0522176.

null