ccm/sff-papers · Datasets at Hugging Face

['Ahmadi, Zabihollah', 'Lee, Seungjong', 'Shamsaei, Nima', 'Mahjouri-Samani, Masoud']

2021-11-18T00:55:47Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90380', 'http://dx.doi.org/10.26153/tsw/17301']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['laser surface processing', 'surface defects', 'surface roughness', 'pores', 'fatigue behavior', 'titanium', 'additive manufacturing']

Laser-Assisted Surface Defects and Pore Reduction of Additive Manufactured Titanium Parts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f1ae62e2-edac-4e62-9d2d-38ddd553381c/download

University of Texas at Austin

Laser surface treatment of additively manufactured parts has attracted considerable interest in the past few years due to its flexibility, operation speed, and capability for polishing complex surfaces as compared to conventional mechanical based methods. This study presents the role of laser surface processing in minimizing the surface roughness and pores that have detrimental effects on the fatigue behavior of additively manufactured specimens. This study is performed by a precise laser melting and recrystallization process to close the pores within 70 μm of the surface in order to enhance the fatigue life of these specimens. A continuous-wave fiber laser is employed to investigate the effect of various processing parameters for controlled laser surface treatments in this study.

null

['Li, Xiaochun', 'Choi, Hongseok', 'Yang, Yong']

2019-10-24T18:31:49Z

2002

Mechanical Engineering

null

['https://hdl.handle.net/2152/77422', 'http://dx.doi.org/10.26153/tsw/4511']

eng

2002 International Solid Freeform Fabrication Symposium

Open

Rapid Manufacturing

Laser-Based Meso/Micro Rapid Manufacturing System

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5cd4264a-7483-49bf-932b-57e0a5adad39/download

null

The meso/micro layered manufacturing technologies have significant implications for the design and fabrication of complex miniature structures. A laser-based additive/subtractive Rapid Manufacturing system is thus developed to build meso/micro structures. By incorporating laser microdeposition and micromachining with a pulsed Nd:YAG laser that has four harmonic wavelengths, this manufacturing system takes computer-aided design (CAD) output to reproduce meso/micro components in a wide selection of materials. To precisely deposit micro/nano powders and to control composition in-situ, an ultrasonic-based micro powder-feeding mechanism is developed. This additive/subtractive micro/meso manufacturing technology provides a platform for a solid integration from CAD to the realization of complex 3D miniature parts.

The authors are grateful to the support from Wisconsin Alumni Research Foundation and National Science Foundation.

null

Zhou, Wenchao

2021-10-21T18:12:38Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89415

eng

2015 International Solid Freeform Fabrication Symposium

Open

['Lattice Boltzmann Method', 'multiple droplet interaction', 'inkjet deposition', 'contact angle', 'non-ideal surfaces']

Lattice Boltzmann Simulation of Multiple Droplet Interaction on Non-ideal Surfaces for Inkjet Deposition

Conference paper

https://repositories.lib.utexas.edu//bitstreams/e151d9f7-3f91-418b-b23e-1af85d9029a5/download

University of Texas at Austin

Inkjet deposition enables a more efficient, economic, scalable manufacturing process for a wider variety of materials than other traditional additive techniques. The interaction dynamics of inkjettted droplets on surfaces are crucial for controlling the formation of the printed patterns, the accuracy of which is critical to the functionalities of the printed device (e.g., electronics). However, little research has been reported on this front due to the prohibitive computational cost of simulating the dynamics of multiple droplet interaction on surfaces. Recently, Zhou et al. [1] reported an efficient numerical solver based on Lattice Boltzmann Method (LBM) that enabled the simulation of multiple droplet interaction dynamics on an ideal surface (i.e., smooth and homogeneous). In this model, the final shape of the droplets always relax back to the equilibrium shape (i.e., spherical cap) prescribed by the static contact angle of the idea surface, which does not provide any useful information on the final printed pattern. In order to simulate the printed pattern in real world, it is necessary to take into consideration of the contact angle hysteresis phenomenon on a non-ideal surface, which is caused by the surface roughness and chemical inhomogeneity of the surface. In this paper, a dynamic contact angle boundary condition is developed to take into account the contact angle hysteresis effect based on the previously reported LBM model. The improved LBM model was validated with experimental data from literature. The influence of the printing conditions, droplet spacing, and surface conditions on the two-droplet interaction dynamics were investigated with the validated LBM model. Interesting phenomena were observed and discussed. The interaction of a line of six droplets on a non-ideal surface was simulated to demonstrate the powerful capability of the developed numerical solver in simulating real-world inkjet printing process.

null

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

2021-10-11T21:35:28Z

2013

Mechanical Engineering

null

['https://hdl.handle.net/2152/88651', 'http://dx.doi.org/10.26153/tsw/15585']

eng

2013 International Solid Freeform Fabrication Symposium

Open

['droplet interactions', 'inkjet deposition', 'Lattice Boltzmann Method', 'COMSOL', 'droplet impingement', 'inkjet manufacturing']

Lattice Boltzmann Simulations of Multiple Droplet Interactions During Impingement on the Substrate

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f2ce02da-0804-4984-8e52-6db732e9880a/download

University of Texas at Austin

Studying material interface evolution in the course of multiple droplet interactions is critical for understanding the material additive process in inkjet deposition. In this paper, we have developed a novel numerical model based on the Lattice Boltzmann Method (LBM) to simulate the interface dynamics during impingement and interaction of multiple droplets. A lattice Boltzmann formulation is proposed to solve the governing equations of the continuous phasefield model that are used in commercial software COMSOL. The LBM inter-particle force is derived by comparing the recovered macroscopic equations from LBM equations with the governing equations of the phase-field model. In addition, a new set of boundary conditions for the LBM formulation is proposed based on conservation of mass and momentum to ensure correct evolution of contact line dynamics. The results of LBM simulations are compared with those of COMSOL and experimental data from literature. The comparison shows the proposed LBM model not only yields a significant improvement in computational speed, but also results in better accuracy than COMSOL as validated against the experiments. We have also demonstrated the capability of the developed LBM numerical solver for simulating interactions between multiple droplets impinging on the substrate, which is critical for development and optimization of inkjet manufacturing.

null

Bhate, Dhruv

2021-11-08T23:30:52Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90076', 'http://dx.doi.org/10.26153/tsw/16997']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['lattice design', 'design optimization', 'crowdsourcing', 'classroom', 'students', 'design for additive manufacturing']

Lattice Design Optimization: Crowdsourcing Ideas in the Classroom

Conference paper

https://repositories.lib.utexas.edu//bitstreams/998cd9fb-a351-40b1-92ba-c28e0b2a0475/download

University of Texas at Austin

Crowdsourcing is a powerful method of generating ideas, particularly when there are many possible solutions to a particular problem with no obvious process towards arriving at the optimum one. In this paper, results of a crowdsourcing exercise conducted in a 30-student classroom are reported. Students were tasked with using lattice design concepts to minimize the weight of a beam under bending, tension and torsion. Using the nTopology software, they approached the problem in three steps: (1) Selection/design of a unit cell, (2) Distribution of cell size, and (3) Optimization of the thickness of individual members. The first two steps were design decisions made by the students, the last step used nTopology's native solver. This work shares insights gained both in lattice design itself, as well as on the use of crowdsourcing in the classroom, particularly in the context of the rapidly evolving field of Design for Additive Manufacturing.

null

['Tang, Y.', 'Zhao, Y.F.']

2021-10-21T19:11:16Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89425

eng

2015 International Solid Freeform Fabrication Symposium

Open

['lattice-skin structures', 'lattice orientation', 'orientation optimization', 'additive manufacturing']

Lattice-skin Structures Design with Orientation Optimization

Conference paper

https://repositories.lib.utexas.edu//bitstreams/eebcca65-ec7e-4314-961e-80c2352d5909/download

University of Texas at Austin

Parts with complex geometry can be produced by an additive manufacturing process without a significant increase of fabrication time and cost. One application of AM technologies is to fabricate customized lattice structures to enhance products’ performance with less material and less weight. Thus, design methods of customized lattice structures have recently attracted great research interests. Most existing design methods only consider the distribution of lattice struts’ thickness as a primary design variable for customized lattice structures. Few of them notice the importance of lattice orientation with regard to its structural performance. In this paper, a design method for customized lattice-skin structures is proposed to optimize the distribution of lattice orientations inside the design domain. In this design method, an initial Functional Volume (FV) is divided into several sub-FVs and connected with additional Functional Surfaces (FSs). The orientation of uniform lattice in each sub-FV is regarded as the design variable. To optimize the design variables, an equivalent analysis model based on the effective orthotropic properties of lattice structures is built. On the basis of this model, genetic algorithm is applied to obtain the optimized distribution of lattice orientations. Two case studies are provided at the end of this paper to validate the proposed design method.

null

['Conner, Timothy Glen', 'Loerwald, Matthew', 'Hayasi, Mohammad', 'Asiabanpour, Bahram']

2021-10-04T20:47:18Z

8/17/11

Mechanical Engineering

null

['https://hdl.handle.net/2152/88344', 'http://dx.doi.org/10.26153/tsw/15283']

eng

2011 International Solid Freeform Fabrication Symposium

Open

['Fully Dense Freeform Fabrication', 'FDFF', 'layer alignment', 'layer bonding']

Layer Alignment and Lamination for the Fully Dense Freeform Fabrication (FDFF) Process

Conference paper

https://repositories.lib.utexas.edu//bitstreams/09693bd8-4681-4aa8-93ad-d240026ac8e8/download

University of Texas at Austin

Fully Dense Freeform Fabrication uses an adaptive layering method for predefined sheets and uses slices cut by a water cutter or laser cutter machine for manufacturing functional parts through smart layer alignment, adjustable compression system, and compatible bonding materials. Under pressure and heat, layers are attached and form a 3D prototype. This paper presents an automated alignment mechanism and compression bonding method that is functional for a variety of complex parts. The alignment system makes a nest setting by using five linear actuators and the compression system is using an array of uneven pins that are locked by sliding surfaces.

null

['Zeng, Kai', 'Patil, Nachiket', 'Gu, Hengfeng', 'Gong, Haijun', 'Pal, Deepankar']

2021-10-07T15:28:32Z

2013

Mechanical Engineering

null

['https://hdl.handle.net/2152/88481', 'http://dx.doi.org/10.26153/tsw/15415']

eng

2013 International Solid Freeform Fabrication Symposium

Open

['geometrical accuracy', 'Additive Manufacturing', 'Common Layer Interface', 'StereoLithography Interface', 'layer-bylayer', 'part quality']

Layer by Layer Validation of Geometrical Accuracy in Additive Manufacturing Processes

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a3014d69-f562-4386-9a03-8c722eb4aa63/download

University of Texas at Austin

Geometrical inaccuracy from shrinkage and residual stress-induced deformations are key sources of defects in Additive Manufacturing (AM). In most AM processes the CAD model is represented by an STL file which is sliced into layers. The Common Layer Interface (CLI) and StereoLithography Interface (SLI) files are two layer file formats which store this slice information and can be data mined to analyze sources of error. By comparing the original STL file against a ‘stacked’ model based upon SLI and CLI files, a “theoretical" part accuracy can be created. In addition, these SLI/CLI files can be combined with detailed process parameter knowledge such as scan pattern, laser power, scan speed, etc., to enable a numerical prediction of part accuracy and deformations on a layer-by-layer basis. This paper introduces a research project which is developing software and hardware tools to enable prediction and measurement of part dimensions on a layer-by-layer basis with the goal of real-time part quality validation and closed loop control.

null

['Badrossamay, M.', 'Childs, T. H. C.']

2020-02-28T16:25:31Z

2006

Mechanical Engineering

null

['https://hdl.handle.net/2152/80115', 'http://dx.doi.org/10.26153/tsw/7136']

eng

2006 International Solid Freeform Fabrication Symposium

Open

Selective Laser Melting

Layer Formation Studies in Selective Laser Melting of Steel Powders

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3b1d5e9e-2ec0-46e3-a000-984e609828d9/download

null

This paper advances the findings of the selective laser melting (SLM) of tool steel and stainless steel powders. The distinguishing feature is the melting of single layers in deep powder beds by a continuous CO2 laser. First, effect of process parameters on the surface roughness for each material is investigated. Based on these results combined with visual observation of the solidified tracks, the question is then discussed as how the processability of various type of steels is changed. The results show that surface morphology of layers is affected strongly by scan spacing, thereby giving a lower average roughness at reduced scan spacing. The effect of scan speed is also remarkable. In addition, other roughness parameters such as the peak height and skewness are found to be useful tools for evaluation of laser melted surfaces.

null

['Kahnert, M.', 'Lutzmann, S.', 'Zaeh, M.F.']

2020-03-09T13:41:26Z

2007

Mechanical Engineering

null

['https://hdl.handle.net/2152/80177', 'http://dx.doi.org/10.26153/tsw/7196']

eng

2007 International Solid Freeform Fabrication Symposium

Open

Electron Beam Sintering

Layer Formations in Electron Beam Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/fce7815f-3b52-4f95-afde-cecd93ef6cc8/download

null

Among direct metal processing manufacturing technologies (Rapid Manufacturing), Electron Beam Sintering (EBS) exhibits a high application potential. Especially, the fast beam deflection provided by electromagnetic lenses allows the realization of considerable building speeds and minor residual stresses. Therefore, this paper aims to examine and utilize the given potential for additive layer manufacturing. In this context, the deployed scanning strategy is a very important aspect. By means of an increasing computer power, innovative and flexible patterns for the solidification of the powder can be implemented. Thus, different patterns are being examined and evaluated. Finally, occurring effects in the exposed zone are introduced.

null

['Bocking, Chris', 'Jacobson, David', 'Bennett, Graham']

2019-09-23T16:22:24Z

2000

Mechanical Engineering

null

['https://hdl.handle.net/2152/75955', 'http://dx.doi.org/10.26153/tsw/3054']

eng

2000 International Solid Freeform Fabrication Symposium

Open

Photochemical

Layer Manufacturing of Heat Exchange Elements using Photochemical Machining with Diffusion Brazing 325

Conference paper

https://repositories.lib.utexas.edu//bitstreams/4d716d78-6c2d-4768-b713-6c9030b7a1f2/download

null

A number of heat exchanger elements for a Stirling engine were designed but found to be very difficult to manufacture using conventional technology. Each element required 1800 <1mm oval holes through a 70 mm length of the cooler. The elements were produced by repeated photochemical machining of 185 copper sheets of 0.455 mm thickness and joining them using a process known as diffusion brazing. This paper describes the science and process of manufacturing these components. The procedure was complicated by the need to integrate spigots at each end of the cooler, which meant that some layers required selective diffusion soldering.

null

['Tang, Lie', 'Ruan, Jianzhoung', 'Sparks, Todd E.', 'Landers, Robert G.', 'Liou, Frank']

2021-09-23T22:12:44Z

9/10/08

Mechanical Engineering

null

['https://hdl.handle.net/2152/88036', 'http://dx.doi.org/10.26153/tsw/14977']

eng

2008 International Solid Freeform Fabrication Symposium

Open

['Laser Metal Deposition', 'Particle Swarm Optimization', 'layer-to-layer height control', 'mechanical engineering']

Layer-to-Layer Height Control for Laser Metal Deposition

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d2bc1c1d-7e34-48f0-95ed-3b136d4e3c08/download

null

A Laser Metal Deposition (LMD) height controller design methodology is presented in this paper. The height controller utilizes the Particle Swarm Optimization (PSO) algorithm to estimate model parameters between layers using measured temperature and track height profiles. The process model parameters for the next layer are then predicted using Exponentially Weighted Moving Average (EWMA). Using the predicted model, the powder flow rate reference profile, which will produce the desired layer height reference, is then generated using Iterative Learning Control (ILC). The model parameter estimation capability is tested using a four-layer deposition. The results demonstrate the simulation based upon estimated process parameters matches the experimental results quite well. Simulation study also shows that the methodology described above works well in producing the reference layer height.

null

['Ikeshoji, T.-T.', 'Yonehara, M.', 'Aoyagi, K.', 'Yamanaka, K.', 'Chiba, A.', 'Kyogoku, H.', 'Hashitani, M.']

2024-03-26T21:23:23Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124415', 'https://doi.org/10.26153/tsw/51023']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['PBF-LB', 'lack-of-fusion', 'Inconel 718', 'machine learning', 'additive manufacturing']

LAYER-WISE IN-PROCESS MONITORING-AND-FEEDBACK SYSTEM BASED ON SURFACE CHARACTERISTICS EVALUATED BY MACHINE-LEARNING-GENERATED CRITERIA

Conference paper

https://repositories.lib.utexas.edu//bitstreams/70b66940-86bd-4147-a73b-2b453d23feb9/download

University of Texas at Austin

In the laser powder bed fusion (PBF-LB) process, a set of parameters that are considered optimal are selected. Still, a set of parameters cannot accommodate complex model geometries, model placement in the build chamber, and unforeseen circumstances, leading to internal defects. Therefore, a new in-situ monitoring and feedback system has been developed to suppress the occurrence of lack-of-fusion (LOF) defects in the PBF-LB process. This system measures surface properties after each laser irradiation to predict whether LOF defects occur. Then, if necessary, a feedback process is performed to re-melt the same surface. Evaluation thresholds are defined by a combination of aerial surface texture parameters created in advance by machine learning of surface properties and defect occurrence. For example, a square pillar of Inconel 718 alloy built with feedback had a higher relative density than one without feedback.

null

['Seifi, Seyyed Hadi', 'Tian, Wenmeng', 'Doude, Haley', 'Tschopp, Mark A.', 'Bian, Linkan']

2021-11-09T15:24:48Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90093', 'http://dx.doi.org/10.26153/tsw/17014']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['layer-wise process', 'profile monitoring', 'thermal-microstructure', 'laser-based additive manufacturing']

Layer-Wise Profile Monitoring of Laser-Based Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3c6f8129-b15b-42a3-a30d-91690a47eb7d/download

University of Texas at Austin

Additive manufacturing (AM) is a novel fabrication technique capable of producing highly complex parts. Nevertheless, a major challenge is improving the quality of fabricated parts. While there are a number of ways of approaching this problem, developing data-driven methods that use AM process signatures to identify these part anomalies can be rapidly applied to improve overall part quality during build. The objective of this study is to build a new layer-wise process signature model to create the thermal-microstructure relationship. In this study, we derive novel key process signatures for each layer (from melt pool thermal images), which are reduced using multilinear principal component analysis (MPCA) and are directly correlated with layer-wise quality of the part. Using these key process signatures, a Gaussian SVM classifier model is trained to detect the existence of anomalies inside a layer. The proposed models are validated through a case study of real-world direct laser deposition experiment where the layer-wise quality of the part is predicted on the fly. The accuracy of the predictions is calculated using three measures (recall, precision, and f-score), showing reasonable success of the proposed methodology in predicting layer-wise quality. The ability to predict layer-wise quality enables process correction to eliminate anomalies and to ultimately improve the quality of the fabricated part.

null

['Starly, B.', 'Nam, J.', 'Lau, W.', 'Sun, W.']

2019-10-22T17:39:05Z

2002

Mechanical Engineering

null

['https://hdl.handle.net/2152/76323', 'http://dx.doi.org/10.26153/tsw/3412']

eng

2002 International Solid Freeform Fabrication Symposium

Open

Fabrication

Layered Composite Model for Design and Fabrication of Bone Replacement

Conference paper

https://repositories.lib.utexas.edu//bitstreams/bf66be92-91d5-4c91-97f6-7682917eda34/download

null

Biological tissues are inherently heterogeneous. The design of 3D tissue scaffolds for tissue engineering application should, if possible, biomimic the complex hierarchy and structural heterogeneity of the replaced tissues. This is particularly true for design of bone scaffolds with structural properties compatible with the spatial heterogeneity and mechanical properties of the replaced tissue. The paper presents an image-based computer modeling approach for reconstruction, characterization, and biomimetic modeling and design of three-dimensional heterogeneous tissue structure. The presented work will cover: 1) overview of biomimetic modeling and design of bone structures and reverse engineering for CAD-based constructive solid geometry; 2) design of bone scaffold; and 3) slicing and process planning for solid freeform fabrication

We gratefully acknowledge support from NSF CRCD-9980298 and support from Therics, Inc.

null

['Yasar, O.', 'Martin, M.', 'Harris, C.', 'Sun, S.', 'Starly, B.']

2020-03-10T16:13:44Z

2007

Mechanical Engineering

null

['https://hdl.handle.net/2152/80222', 'http://dx.doi.org/10.26153/tsw/7241']

eng

2007 International Solid Freeform Fabrication Symposium

Open

Hydrogel Patterning

Layered Fabrication of Branched Networks Using Lindenmayer Systems

Conference paper

https://repositories.lib.utexas.edu//bitstreams/4184ec42-16e7-45ee-9845-553d14497b2f/download

null

A current challenge impeding the growth of bone tissue engineering is the lack of functional scaffolds of geometric sizes greater than 10mm due to the inability of cells to survive deep within the scaffold. It is hypothesized that these scaffolds must have an inbuilt nutrient distribution network to sustain the uniform growth of cells. In this paper, we seek to enhance the design and layered fabrication of scaffold internal architecture through the development of Lindenmayer systems, a graphical language based theory to create nutrient delivery networks. The scaffolds are fabricated using the Texas Instruments DLP™ system through UV‐photopolymerization to produce polyethylene glycol hydrogels with internal branch structures. The paper will discuss the Lindenmayer system, process planning algorithms, layered fabrication of samples, challenges and future tasks.

null

['Kietzman, J. W.', 'Cooper, A. G.', 'Weiss, L. E.', 'Schultz, L.', 'Lombardi, J. L.', 'Prinz, F. B.']

2018-11-28T21:27:45Z

1997

Mechanical Engineering

doi:10.15781/T22805J53

http://hdl.handle.net/2152/70333

eng

1997 International Solid Freeform Fabrication Symposium

Open

['SDM', 'Shape Deposition Manufacturing']

Layered Manufacturing Material Issues for SDM of Polymers and Ceramics

Conference paper

https://repositories.lib.utexas.edu//bitstreams/14761699-eca2-44b7-8a87-36ecf0b037f1/download

null

Shape Deposition Manufacturing (SDM) is a solid freeform fabrication process which enables the manufacture of structural parts from engineering materials. This paper discusses the requirements and constraints for SDM part and sacrificial support materials, including chemical and physical compatibility, mutual adhesion, low shrinkage, machinability, and support material removability. Polymers and ceramics processed by SDM include polyurethanes, epoxies, polyurethane foams, photocurable acrylics, and green alumina ceramics. SDM compatible support materials include waxes, water-soluble polyacrylate soldermasks, and water-soluble thermoplastics. This paper details the selection of SDM part and support material combinations for the fabrication of polymer prototypes and polymer molds for ceramic prototyPes.

null

['Messia, David', 'Pegna, Joseph', 'Lee, Woo Ho']

2018-11-29T21:08:44Z

1997

Mechanical Engineering

doi:10.15781/T2G737Q08

http://hdl.handle.net/2152/70346

eng

1997 International Solid Freeform Fabrication Symposium

Open

['3-D LCVD', 'SALD']

Layered Micro-Wall Structures from the Gas Phase

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f48a57f9-6b72-4022-9b4b-402a90231448/download

null

The use of3-D LCVD with volumetric rate feedback was investigated in the fabrication ofmicromechanical wall structures. These were constructed by recursive laser scanning and resulted in layered wall composed ofrecursive line deposition. Experiments were designed to uncover the relationship between scan rate, volumetric deposition rate, pressure and laser powerfor pyrolytic graphite from an ethylene precursor. Results point to a conduction dominated heat transfer which greatly limits the volumetric deposition rate at the wall. This also results in a highly unstable deposition process, since volumetric deposition increases by orders ofmagnitude as soon as rod growth is initiated. An unexpected results ofthis work is the ability to grow rods at an angle to the laser axis, with good control ofthe linear growth rate. This is achieved by adaptive laser scanning during rod growth.

null

['Zak, G.', 'Sela, M.N.', 'Park, C.B.', 'Benhabib, B.']

2018-11-28T16:43:33Z

1997

Mechanical Engineering

doi:10.15781/T2M61C89K

http://hdl.handle.net/2152/70321

eng

1997 International Solid Freeform Fabrication Symposium

Open

['UV Laser Based System', 'Composite Liquid', 'liquid leveling subsystems']

A Layered-Manufacturing Process For the Fabrication of Glass-Fiber-Reinforced Composites

Conference paper

https://repositories.lib.utexas.edu//bitstreams/0221f42e-87cc-4f7b-b7fd-51b6a1ee92b1/download

null

In this paper, we present a rapid manufacturing process for the layered fabrication of polymer-based composite parts using short discontinuous fibers as reinforcements. In the recent past, numerous research efforts, similar to ours, have been made to produce fiber-reinforced plastic parts via layered manufacturing methods. However, most of these attempts have not resulted in the development of an effective commercially-viable manufacturing process. Our proposed fabrication process on the other hand has been experimentally verified to yield composite parts comparable in quality to pure polymer parts manufactured on a commercial stereolithography system.

null

['Abdelrahman, Mostafa', 'Starr, Thomas L.']

2021-10-12T21:38:54Z

2014

Mechanical Engineering

null

['https://hdl.handle.net/2152/88747', 'http://dx.doi.org/10.26153/tsw/15681']

eng

2014 International Solid Freeform Fabrication Symposium

Open

['Polymer Laser Sintering', 'end-use parts', 'high resolution infrared thermal imaging', 'thermal imaging']

Layerwise Monitoring of Polymer Laser Sintering Using Thermal Imaging

Conference paper

https://repositories.lib.utexas.edu//bitstreams/7bbf5350-7846-496f-89f3-17f249c230db/download

University of Texas at Austin

Polymer Laser Sintering (LS) is used increasingly for manufacture of end-use parts. Improved methods of monitoring the process are needed to certify the quality of these parts. This paper describes the use of high resolution infrared thermal imaging to monitor the temperature of individual layers before, during and after laser scanning. The time-temperature history of each point in a layer depends on process parameters and part geometry. This history also controls the sintering and crystallization process for a single volume element of the part and its mechanical properties. Proposed new process control schemes may use this monitoring data to ensure that all volume elements achieve full density. The proposed framework includes creating a 3D template of the input model. This template simulates the part fabrication in the SLS machine. Registration of this template to the monitor data creates a 3D quality certificate for the part.

null

['Gill, David D.', 'Griffith, Michelle L.', 'Reckaway, Daryl E.', 'Briner, Clifton F.', 'Abrams, Douglas G.']

2019-11-20T16:49:13Z

2003

Mechanical Engineering

null

['https://hdl.handle.net/2152/78482', 'http://dx.doi.org/10.26153/tsw/5567']

eng

2003 International Solid Freeform Fabrication Symposium

Open

Geometries

LENS Deposition of Complex Geometries

Conference paper

https://repositories.lib.utexas.edu//bitstreams/2f2d900e-30bd-4daf-84ca-fde204695386/download

null

The Laser Engineered Net Shaping (LENS®) system at Sandia National Laboratories, a laser-based direct metal deposition process, was recently used for the fabrication of a complex prototype. The LENS process involved the challenges of adjacent areas of thick and thin cross section, overhanging unsupported features, high aspect ratios, and a hemispherical substrate. These challenges were overcome through the use of closed-loop weld pool control, height monitoring, a strong understanding of build parameters, and unique process planning strategies. The near-net shape LENS part was completed with annealing and conventional machining to produce the complex components in a reduced timeframe.

null

['Gill, D. D.', 'Atwood, C. J.', 'Voth, T. E.', 'Robbins, J.', 'Dewhurst, P.', 'Taggart, D. G.']

2020-03-10T14:30:37Z

2007

Mechanical Engineering

null

['https://hdl.handle.net/2152/80210', 'http://dx.doi.org/10.26153/tsw/7229']

eng

2007 International Solid Freeform Fabrication Symposium

Open

solid freeform fabrication

LENS® and SFF: Enabling Technologies for Optimized Structures

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f1d9de28-6146-4de2-acd6-2284351e6dba/download

null

Optimized, lightweight, high-strength structures are needed in many applications from aerospace to automotive. In pursuit of such structures, there have been proposed analytical solutions and some specialized FEA solutions for specific structures such as automobile frames. However, generalized 3D optimization methods have been unavailable for use by most designers. Moreover, in the cases where optimized structural solutions are available, they are often hollow, curving, thin wall structures that cannot be fabricated by conventional manufacturing methods. Researchers at Sandia National Laboratories and the University of Rhode Island teamed to solve these problems. The team has been pursuing two methods of optimizing models for generalized loading conditions, and also has been investigating the methods needed to fabricate these structures using Laser Engineered Net Shaping™ (LENS®) and other rapid prototyping methods. These solid freeform fabrication (SFF) methods offer the unique ability to make hollow, high aspect ratio features out of many materials. The manufacturing development required for LENS to make these complex structures has included the addition of rotational axes to Sandia’s LENS machine bringing the total to 5 controlled axes. The additional axes have required new efforts in process planning. Several of the unique structures that are only now possible through the use of SFF technology are shown as part of the discussion of this exciting new application for SFF.

null

['White, Liam', 'Quaife, Bryan', 'Borish, Michael', 'Adkins, Cameron', 'Roschli, Alex']

2024-03-26T17:10:56Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124379', 'https://doi.org/10.26153/tsw/50987']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['hybrid manufacturing', 'additive manufacturing', 'subtractive manufacturing', 'OpenVDB', 'sparse volumetric grid', 'voxel grid', 'level set function', 'signed distance function', 'marching squares']

Level Set Grids for Hybrid Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/014c22ba-300f-4422-9191-7be9ebbd4264/download

University of Texas at Austin

We propose a novel hybrid model, the Level Set Grid, to facilitate parallel additive and subtractive processes in hybrid manufacturing. The Level Set Grid combines the strengths of explicit and implicit representations, offering precise modeling of evolving geometries and fast and efficient collision detection. This research focuses on integrating Level Set Grids into the additive slicing and subtractive pathing generation processes, laying the groundwork for future advancements in the parallelization of hybrid manufacturing.

null

['Chung, Haseung', 'Das, Suman']

2019-11-20T16:27:48Z

2003

Mechanical Engineering

null

['https://hdl.handle.net/2152/78473', 'http://dx.doi.org/10.26153/tsw/5558']

eng

2003 International Solid Freeform Fabrication Symposium

Open

Laser Melting

Level Set Methods for Modeling Laser Melting of Metals

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f58a319b-8495-478d-9774-ee937a38a11c/download

null

The physical model describing heat transfer and melting taking place during and after the interaction of a laser beam with a semi-infinite metal surface is based on the classical Stefan problem with appropriately chosen boundary conditions to reflect direct selective laser sintering of metals. A level set method for solving this problem is presented in this paper. From the results of these computations, we obtain time evolution of solid-liquid interface and temperature distribution.

null

['Rodriguez, Carlos', 'Barraza, Sol', 'Diaz, Julio', 'Arrieta, Edel', 'Hernandez, Alejandro', 'Hicks, Adam', 'Wicker, Ryan B.', 'Medina, Francisco']

2023-02-09T18:56:35Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117440', 'http://dx.doi.org/10.26153/tsw/44321']

eng

2022 International Solid Freeform Fabrication Symposium

Open

bell crank

Lightweight Additively Manufactured Bell Crank

Conference paper

https://repositories.lib.utexas.edu//bitstreams/2adbc897-d45c-4847-83fe-3c7bec49607e/download

null

Due to the long service life of Air Force Legacy aircrafts, some companies that used to manufacture their components and spares are no longer able to do so. In this case, Additive Man- ufacturing (AM) poses as a viable option to manufacture those spares when needed and even im- prove their cost, weight, and performance. This project focuses on designing, building and testing of a bell crank, a largely needed spare part in these aircrafts, in order to achieve weight reduction and increased strength. The designing process was done using Fusion 360’s Generative Design, which can be tailored to produce different outcomes which satisfy the user’s needs. Fused Depo- sition Modeling (FDM) was chosen for the manufacturing method with ABS chosen as the testing material. The components were tested using an adapted Instron 5900 Series. The initial testing phase served to show that a horizontal build proved to be the most optimal out of three orientations tested, while the second phase showed that the Bk_fpx design, which focused on strength, was the best performing due to its strength-to-weight ratio (29.7) and cost ($160). It is recommended that all this work is continued by the metal AM method laser powder bed fusion (LPBF) with compa- nies such as Selective Laser Melting (SLM) using Aluminum since this method is capable of rapid prototyping and this material would help minimize the weight in the aircraft.

null

['Meisel, Nicholas A.', 'Williams, Christopher B.', 'Druschitz, Alan']

2021-10-05T18:35:24Z

8/16/12

Mechanical Engineering

null

['https://hdl.handle.net/2152/88401', 'http://dx.doi.org/10.26153/tsw/15340']

eng

2012 International Solid Freeform Fabrication Symposium

Open

['indirect 3D printing', 'cellular structures', 'metal casting']

Lightweight Metal Cellular Structures via Indirect 3D Printing and Casting

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5b7fd9be-0631-47d2-8f14-16985aa834b4/download

University of Texas at Austin

Cellular materials offer high strength accompanied by low-density and can offer high stiffness, good impact-absorption, and thermal and acoustic insulation. In this paper, the authors describe their progress towards exploring the use of metal casting into 3D printed sand molds for creating cellular materials and sandwich panels. The use of 3D printing allows for the fabrication of sand molds without the need for a pattern, and thus enables the creation of cellular structures with designed mesostructure from a bevy of metal alloys. The quality-of-fill results for several cast aluminum cellular parts of varying geometry are presented in this paper, along with a discussion of overall truss diameter variation.

null

['Roe, Matthew', 'Yang, Li']

2023-02-24T14:53:53Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117526', 'http://dx.doi.org/10.26153/tsw/44406']

eng

2022 International Solid Freeform Fabrication Symposium

Open

['Interpenetrating design', 'cellular structure', 'design', 'experimentation investigation']

A Limited -Scale Expeirmental Invstigation of the Unit Cell Topology Effects on Interpenetrating Cellular Structures

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1136dab8-c16b-4b88-8621-ee75e871d8d0/download

null

The interpenetrating cellular structure is a novel recent design concept that has been subjected to some preliminary research efforts in recent years. As there still exist relatively limited understanding of such design concept, the current work aimed to provide additional insights via experimental-based study. Several baseline cellular unit cell structures that follow multiple cellular unit cell topology design rules were included in the study, in order to investigate whether there exist significant design relationships between the cellular topology pairing and the resulting performance of the interpenetrating structures. In general, the interpenetrating designs did not result in synergetic performance reinforcement with elastic modulus, ultimate strength or energy absorption, except for specific cases. In most cases, the local strut interaction between the two component cellular structures appear to exert negative effects on the properties of the interpenetrating structures. The results tentatively suggest the need of additional research with such concept.

null

Bolvie, Klas

2019-10-18T14:59:54Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76230', 'http://dx.doi.org/10.26153/tsw/3319']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Sinterstation

Limits of Loose Metal Powder Density in the Sinterstation

Conference paper

https://repositories.lib.utexas.edu//bitstreams/705a41d3-b331-4e46-bc5f-268dd046baa7/download

null

The possibility to increase the density of applied metal powder in the Sinterstation has been investigated by successive addition of smaller sized particle fractions to a base powder. The optimal composition for each blend was determined experimentally, and their apparent densities were compared to the densities after Sinterstation application. The principal limiting factors for the density of metal powder in the Sinterstation were found to be the interparticle friction and the small sized particles’ tendency to form a suspension in the air. Finally, based on the evaluation of the different powder compositions’ behavior, a practical upper limit of loose metal powder density was estimated to 86%, when applied by a Sinterstation. The highest applied powder density in this investigation was a binary blend with 68.60% relative density.

null

['Poudel, Arun', 'Shamsaei, Nima', 'Shao, Shuai']

2021-12-06T22:17:48Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90695', 'http://dx.doi.org/10.26153/tsw/17614']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['linear elastic finite element analysis', 'stress intensity factor', 'three-dimensional defects', 'effect of defect shape']

Linear Elastic Finite Element Calculations of Short Cracks Initiated from the Defects: Effect of Defect Shape and Size

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d4a56c56-4a01-463e-9e51-643ece00f52b/download

University of Texas at Austin

The defects present in an additively manufactured component deteriorate its mechanical, especially fatigue performance. During loading, these defects influence the stress concentration, promote the fatigue crack initiation and thus, lead to a lower fatigue performance. In this study, the effect of defect shape and size on the Mode-I stress intensity factor (KI) of the short cracks initiating from both 2D and 3D internal defects was investigated using linear elastic finite element analysis (FEA). The shape of the defect was varied by altering the aspect ratio (width/height) from 0 to 1. Later, the dimensionless results from FEA were utilized to calculate the SIF in defects with half-span width of range 10-100 µm. As a result, the influence of defect shape on the SIF was only observed in the short crack length regimes and the measure of SIF was observed to increase with decreasing aspect ratio for a given crack length.

null

['Ullett, Jill S.', 'Rodrigues, Stanley J.', 'Chartoff, Richard P.']

2018-11-02T15:11:22Z

1995

Mechanical Engineering

doi:10.15781/T25H7CD0C

http://hdl.handle.net/2152/69333

eng

1995 International Solid Freeform Fabrication Symposium

Open

['stereolithography', 'laser cured polymer', 'photo-polymer cure']

Linear Shrinkage of Stereolithography Resins

Conference paper

https://repositories.lib.utexas.edu//bitstreams/82f4e828-c093-465a-8e41-ca892ca869a4/download

null

The linear shrinkage of an acrylate and an epoxy based stereolithography resin was measured during cure. A helium-cadmium (He-Cd) laser cured strands of resin as is done in the stereolithography process using two exposures. The exposure time was held constant while the delay time between exposures was varied. It was found for both resins that the final cure depth and linear shrinkage were a function of delay time

null

['Cesarano TI, Joseph', 'Baer, Thomas A.', 'Calvert, Paul']

2018-11-16T17:09:14Z

1997

Mechanical Engineering

doi:10.15781/T2NG4HB9B

http://hdl.handle.net/2152/70299

eng

1997 International Solid Freeform Fabrication Symposium

Open

['freeform fabrication', 'dense ceramics', 'structural ceramics']

Liquid Metal Jetting for Printing Metal Parts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c71be89c-c5d4-4c74-9f6b-68c1657f7c4c/download

null

Liquid Metal Jetting (LMJ) is solid freeform fabrication process for producing metal mechanical parts and electronic interconnects. It is a technology similar to ink jet printing where individual molten droplets are accurately printed. LMJ will produce metal parts on demand from a CAD database with functional performance parameters similar to metal parts produced by machining or casting. By controlling solidification rates and metal alloy composition, LMJ is able to produce parts with unique properties such as metal matrices and functionally graded materials. This paper will review the current status of LMJ and future applications for this technology.

null

['Kirchebner, Benedikt', 'Weidner, Christoph', 'Ploetz, Maximilian', 'Rehekampff, Christoph', 'Volk, Wolfram', 'Lechner, Philipp']

2024-03-26T21:25:41Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124416', 'https://doi.org/10.26153/tsw/51024']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['liquid metal jetting', 'liquid salt jetting', 'support structures', 'additive manufacturing']

LIQUID METAL JETTING OF ALUMINUM PARTS WITH SALT SUPPORT STRUCTURES

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a0f2ab6f-7f9d-46ba-9858-5c332ad9584c/download

University of Texas at Austin

Liquid metal jetting (LMJ) bears the potential of being a fast part manufacturing technology while using a cheap raw material. LMJ is a subtype of material jetting (MJT) and the parts are built by successively depositing droplets of molten metal onto a build platform. For full 3D capability, support structures are necessary, which must be removed in subsequent processes. In previous investigations, we proposed the usage of water-soluble salt as a support material, selected a suitable salt, and analyzed the influence of this material on aluminum parts made in LMJ. The present work shows a duplex MJT print head for processing aluminum alloys and KClNaCl salt. Various printing sequences and support structure strategies are compared. The results show that the sequence of printing aluminum and salt is crucial. Furthermore, using thin layers of the support material as a release layer appears promising.

null

Crockett, R.S.

2018-11-14T17:06:06Z

1996

Mechanical Engineering

doi:10.15781/T2RJ49F1Z

http://hdl.handle.net/2152/70242

eng

1996 International Solid Freeform Fabrication Symposium

Open

['stereodeposition', 'FDC', 'Advanced ceramics Research']

The Liquid-to-Solid Transition in Stereodeposition Techniques

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c715f069-efa3-4965-af2f-fc89d1bfebc7/download

null

['Maxwell, James', 'Borse, Sandesh']

2018-12-06T21:05:50Z

1997

Mechanical Engineering

doi:10.15781/T29W09K05

http://hdl.handle.net/2152/71428

eng

1997 International Solid Freeform Fabrication Symposium

Open

['micromachining', 'excimer lasers']

The LMP Process: Layered Metal Prototyping of Titanium from Condensed Thin-Films for Microelectromechanical Devices

Conference paper

https://repositories.lib.utexas.edu//bitstreams/cf8328db-417c-495f-b198-3d7b033ce461/download

null

Layered prototyping of three-dimensional titanium micromechanical components was demonstrated using selected area laser photolysis of liquid-phase organo-metallic and metal halide thin films. Scanning KrF and XeF excimer lasers were employed at 248 and 351 nm, respectively, generating solid titanium traces from condensed precursor films. Multiple layers were patterned to produce high-aspect ratio titanium lines. Laser pulse repetition rate, scan rate, pulse energy, and layer thickness were related to the resulting layer topography. This process is a first step toward layered metal rapid prototyping ofelectronic packaging microstructures and microelectromechanical systems.

null

['Simmons, Jacob', 'Daeumer, Matthias', 'Azizi, Arad']

2021-11-11T16:36:46Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90240', 'http://dx.doi.org/10.26153/tsw/17161']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['laser powder-bed fusion', 'additive manufacturing', 'thermal conductivity', 'thermal transport', 'stainless steel', '316L', 'metal 3D printing']

Local Thermal Conductivity Mapping of Selective Laser Melted 316L Stainless Steel

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6f12fe49-486a-45c7-a47e-9db29b2beb66/download

University of Texas at Austin

The variation in thermal conductivity of 316L stainless steel samples produced with selective laser melting with a varying process parameters is investigated in the bulk and in the microscale. A critical scan rate was observed, while holding all other process parameters constant, above which the porosity started to rapidly increase. For the lowest-porosity sample, a local thermal conductivity map was produced using frequency-domain thermoreflectance. The local stainless steel thermal conductivity varied between 10.4 and 19.8 W/m-K. The average thermal conductivity of the thermal conductivity map agrees within measurement uncertainty with flash diffusivity measurements. The reduction in thermal conductivity with increasing scan rate is not fully explained by the porosity. The average measured values are less than conventionally produced bulk 316L due to the unique processing conditions of laser powder bed fusion, which modifies the crystallographic texture and microstructure.

null

['Raja, Sandeep', 'Court, Nadia', 'Sidhu, Jagjit', 'Tuck, Chris', 'Hague, Richard']

2021-09-30T14:23:43Z

9/23/10

Mechanical Engineering

null

['https://hdl.handle.net/2152/88255', 'http://dx.doi.org/10.26153/tsw/15196']

eng

2010 International Solid Freeform Fabrication Symposium

Open

['Direct Write', 'Additive Manufacturing', 'polymer thick film inks', 'inkjet inks', 'curing kinetics']

Localised Broadband Curing of Directly Written Inks for the Production of Electrical Devices for Aerospace Applications

Conference paper

https://repositories.lib.utexas.edu//bitstreams/7ad59c9b-166f-431b-b220-5d3227c45c64/download

University of Texas at Austin

Direct Write (DW) technologies afford the possibility of printing electronics and sensors directly onto structural components. This allows advantageous weight saving by making good use of available space through conformal printing whilst adding functionality. To enable DW fabrication of devices onto large aerospace structures a localised processing method is required. This paper investigates the feasibility of using a broadband thermal spot curing system for processing DW Inkjet and Polymer Thick Film (PTF) materials onto composite structures. The characteristics of spot cured tracks were compared to conventional oven cured tracks and were shown to exhibit equivalent resistances.

null

['Paudel, Basil J.', 'Thompson, Scott M.']

2021-11-18T17:05:25Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90430', 'http://dx.doi.org/10.26153/tsw/17351']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['laser-powder bed fusion', 'heat transfer', 'simulation', 'multi-pass', 'numerical methods']

Localized Effect of Overhangs on Heat Transfer During Laser Powder Bed Fusion Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5c6a9a3b-2c2a-4dde-b416-2e419d5a1db2/download

University of Texas at Austin

The current study concentrates on the effect of local part topology on heat transfer during the laser-powder bed fusion (L-PBF) additive manufacturing (AM) process. The high heat flux diffusion (i.e. thermal spreading) is numerically modeled and investigated for the L-PBF of a thin-walled part with various negative draft angles (overhangs) and a thin wall of variable cross-sectional area. Scan-wise and layer-wise manufacturing effects on heat transfer are quantified via peak melt pool temperature and resulting melt pool morphology. These thermal metrics are used to understand the effect of overhang angles on the melt pool mand the surface roughness traits of stainless steel 316L, Inconel 625 and Ti-6Al-4V parts. Both powder effects and phase change within the melt pool are considered using approximate, reduced-complexity techniques. The employed numerical model has been validated using data available in the literature. Results demonstrate that the melt pool morphology and temperature distribution along build geometries with negative draft angles are significantly different than those with positive draft angles.

null

['Aggarangsi, Pruk', 'Beuth, Jack L.']

2020-03-05T20:01:06Z

2006

Mechanical Engineering

null

['https://hdl.handle.net/2152/80153', 'http://dx.doi.org/10.26153/tsw/7174']

eng

2006 International Solid Freeform Fabrication Symposium

Open

Additive Manufacturing

Localized Preheating Approaches for Reducing Residual Stress in Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/12a209fc-325d-4e69-a4b8-0b0dee085179/download

null

Uniform preheating can be used to limit residual stress in the solid freeform fabrication of relatively small parts. However, in additive manufacturing processes, where a feature is deposited onto a much larger part, uniform preheating of the entire assembly is typically not practical. This paper considers localized preheating to reduce residual stresses, building on previous work using a defined thermal gradient through the part depth as a metric for predicting maximum final residual stress. The building of thinwalled structures is considered. Two types of localized preheating approaches are compared, appropriate for use in laser- or electron beam-based additive manufacturing processes. In evaluating the effectiveness of each approach, a simplified thermomechanical model is used that can be related directly to analytical thermomechanical models for thermal stresses in unconstrained thin plates. Results are presented showing that one of the methods yields temperature profiles likely to yield reduced residual stresses at room temperature. Mechanical model results confirm this, showing a significant reduction in maximum stress values. A more complete thermomechanical simulation of thin wall fabrication is used to verify the trends seen in the simplified model results.

null

['Abolmaali, Saina', 'Vinel, Alexander', 'Fox, Jason', 'Liu, Jia', 'Silva, Daniel', 'Shamsaei, Nima']

2021-12-01T23:10:48Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90650', 'http://dx.doi.org/10.26153/tsw/17569']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'surface roughness', 'ANOVA test', 'extreme value theory']

Location and Orientation Dependency in Surface Roughness of Nickel Super Alloy 625 Parts: Statistical and Distributional Analysis

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f1d21574-fc24-4d93-9f95-b7641f326e9c/download

University of Texas at Austin

Surface roughness is an important characteristic of additively manufactured parts, since it can impact various mechanical properties, such as friction or fatigue life. Further, surface roughness can change significantly depending on a number of factors: part geometry, location on the build platform, process parameters, or powder characteristics. Generally, it has been previously established that printing angle has a significant effect on surface roughness. In this study we reanalyze a dataset constructed based on Laser-Beam Powder Bed Fusion manufactured Nickel super alloy 625 parts. The goal is to evaluate the effect of location and print orientation on the variability of surface roughness, particularly relative to printing angle. Different combinations of location orientation-angles factors are tested using analysis of variance (ANOVA), with some significant findings. In addition, we further consider the question of characterizing surface roughness measures as applied to additive manufacturing and explore distributional analysis (particularly extreme value theory) as a way to qualify these measures.

null

['Lee, Seungjong', 'Muhammad, Muztahid', 'Zheng, Jingyi', 'Shao, Shuai', 'Shamsaei, Nima']

2021-12-01T23:13:52Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90651', 'http://dx.doi.org/10.26153/tsw/17570']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'AM', 'laser beam powder bed fusion', 'LB-PBF', 'surface roughness', 'stainless steel', 'fatigue']

Locational Dependency of Additively Manufactured Parts: Effects of Surface Roughness on Fatigue Behavior

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d0df7228-778e-449c-9df9-55d2d8361b50/download

University of Texas at Austin

Surface roughness (SR) can vary significantly among parts manufactured at different locations on the same build platform because of the gas flow and powder recoating process in current laser beam powder bed fusion (LB-PBF) technique. In this study, intra-build SR variation across locations was investigated for LB-PBF 316L stainless steel. The build platform was divided into 4 quadrants to assess the location-dependent variation of SR. Uniaxial stress-controlled fatigue tests were conducted using a servo-hydraulic system. The SR from the four quadrants was analyzed using the one-way Analysis of Variance (ANOVA) method and further verified SR's location dependency. Kruskal-Wallis test was also employed since Box-Cox transformed data failed to meet the requirements of the ANOVA test. Kruskal-Wallis test revealed that there are statistically significant differences in SR values across different locations. The results were validated using fatigue test results and gas flow simulation results reported in literature.

null

['Lang, Andrew', 'Castle, James', 'Bristow, Douglas A.', 'Landers, Robert G.', 'Siddhardh Nadendla, Venkata Sriram']

2023-02-09T18:53:45Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117439', 'http://dx.doi.org/10.26153/tsw/44320']

eng

2022 International Solid Freeform Fabrication Symposium

Open

regression analysis

Logistic regression classification to predict regional anomalies in nominally printed volume of separate test pieces

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c61eeb2e-df34-4f18-ab2a-e99ed4285855/download

null

Supervised machine learning techniques have struggled to accurately predict voxel-wise occurrence of anomalies in metal powder bed parts printed with optimal processing parameters. This work discusses a method to visualize machine learning model predictions in 3D to interrogate patterns in the predictions. A simple logistic regression classifier, with cross validation and an optimized classification threshold, is trained using synthetic in situ features, a machine parameter, and post-process output labels. The developed classifier is shown to outperform deep learning and boosted classifiers on the datasets used. Voxel-wise prediction performance is very low, but 3D representation of model predictions shows the developed model can predict anomalies in the correct region of the printed part. The practical use of the developed method is demonstrated by predicting the occurrence of anomalies in nominally printed volume using a model that had been trained on a dataset printed with induced defects.

null

['Bagsik, A.', 'Schöppner, V.', 'Klemp, E.']

2021-10-06T20:50:05Z

8/22/12

Mechanical Engineering

null

['https://hdl.handle.net/2152/88441', 'http://dx.doi.org/10.26153/tsw/15378']

eng

2012 International Solid Freeform Fabrication Symposium

Open

['Fused Deposition Modeling', 'long-term ageing', 'tensile specimes', 'Ultem*9085']

Long-Term Ageing Effects on Fused Deposition Modeling Parts Manufactured with Ultem*9085

Conference paper

https://repositories.lib.utexas.edu//bitstreams/af65892f-a70e-40b9-948e-edba4bacaea4/download

University of Texas at Austin

Relating to the direct manufacturing of end-use parts the knowledge about the effect of the long-term ageing of Fused Deposition Modeling (FDM) parts is of particular importance. For this, tensile specimens were stored for time periods of up to 52 weeks in two different conditions and the testing was conducted at different temperatures within a temperature range of -60°C to +160°C. Further tests were made after the exposure in multiple media. The parts were built up with the system “Fortus 400mc” from Stratasys with the material Ultem*9085 in two different build directions, the strongest direction X (on its side) and the weakest build direction Z (upright) and with the standard toolpath parameters of the Insight software version 7.0.

null

['Schmid, M.', 'Woellecke, F.', 'Levy, G.N.']

2021-10-05T19:04:08Z

8/15/12

Mechanical Engineering

null

['https://hdl.handle.net/2152/88410', 'http://dx.doi.org/10.26153/tsw/15349']

eng

2012 International Solid Freeform Fabrication Symposium

Open

['Selective Laser Sintering', 'automotive application', 'Duraform® DF', 'Duraform® HST SLS', 'sealants']

Long-Term Durability of SLS Polymer Components Under Automotive Application Environment

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f38e519d-a3f8-4098-bde3-95893b088f17/download

University of Texas at Austin

Selective Laser Sintering (SLS) is close to be accepted as a genuine production technique (Additive Manufacturing). However, one problem restricting a more frequent specific use of SLS-parts is the limited or unknown long-term or functional behaviour under particular environmental conditions. In our specific case, for automotive applications, plastic materials can get in contact with brake fluid and coolant. The behaviour of commercial SLS materials in contact with these liquids must be qualified in advance for a successful implementation. This contribution investigates the resistance of Duraform® DF and Duraform® HST SLS made parts in contact with the cited automotive media. The testes were carried out for parts as of the machine and in a post processed coated state. Distinctive Epoxy-, Silicon- and PVC-based sealant was used. Gravimetric analyses and results of mechanical behaviour are presented with respect to material, type of coating and immersion time.

null

['Ali, Mohammad Alshaikh', 'Huseynov, Orkhan', 'Fidan, Ismail', 'Vondra, Fred']

2024-03-26T21:28:38Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124417', 'https://doi.org/10.26153/tsw/51025']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'metal casting', 'fused filament fabrication', 'material extrusion', 'investment casting']

Lost-PLA Casting Process Development Using Material Extrusion with Low-Weight PLA

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5a7abb66-3ce7-4f9c-a1e9-12e4ac9b2d7c/download

University of Texas at Austin

The goal of this research is to develop a baseline procedure for lost-PLA casting process of aluminum. Traditional Manufacturing techniques and Smart Manufacturing techniques have their advantages and disadvantages. Integrating the traditional and modern aspects of manufacturing enhances the capabilities of manufacturing. In this study, low-weight PLA is used in a Material Extrusion (MEX) machine to fabricate sacrificial patterns for an aluminum lost-casting process. Different process parameters, after a calibration process, are tested for the MEX process The MEX process parameters tested are: infill pattern, and top/bottom solid layers. The MEX process parameter investigation allows to draw conclusions to establish a standard for which parameters are ideal for the casting process. For this research, casting process parameters are set constant. The preliminary studies show that the lost-PLA casting process is successful in producing dimensionally accurate aluminum parts by a direct-pour casting process using the suggested MEX process parameters.

null

['Hume, Chad A.', 'Rosen, David W.']

2021-11-15T20:42:36Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90264', 'http://dx.doi.org/10.26153/tsw/17185']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['numerical modeling', 'methodology', 'predictive models', 'material jetting', 'material jetting-based additive manufacturing']

Low Cost Numerical Modeling of Material Jetting-Based Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/dd39aae1-82b9-4150-b3e7-67b3fa5cdcf5/download

University of Texas at Austin

Material jetting-based additive manufacturing is a promising manufacturing approach with increasing interest in mesoscale applications such as microfluidics, membranes, and microelectronics. At these size scales, significant edge deformation is observed limiting the resolvable feature size. Currently, predicting and controlling such deformations would require extensive experimentation or computationally prohibitive simulations. The objective of this work is to develop a computationally low cost material jetting model that enables the simulation and prediction of mesoscale feature fabrication. To this end, a quasi-static boundary-based method is proposed and demonstrated as a simplified and accurate means of predicting the line-by-line, layer-by-layer feature development. The method is validated through comparison with the known analytical solution for a single droplet; then the method’s application to AM is demonstrated through modeling of representative mesoscale features. The benefits and limitations of each are discussed.

null

['Barrett, Christopher', 'Carradero, Carolyn', 'Harris, Evan', 'McKnight, Jeremy', 'Walker, Jason', 'MacDonald, Eric', 'Conner, Brett']

2021-11-15T21:59:26Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90285', 'http://dx.doi.org/10.26153/tsw/17206']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['spatter tracking', 'stereovision', 'low cost', 'high speed', 'cameras', 'laser powder bed fusion']

Low Cost, High Speed Stereovision for Spatter Tracking in Laser Powder Bed Fusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/8661556e-585e-4687-a941-86d0cdc81190/download

University of Texas at Austin

Powder Bed Fusion Additive Manufacturing affords new design freedoms for metallic structures with complex geometries in high performance materials. The aerospace industry has identified the inherent benefits of AM not just in terms of shape creation but also with regard to producing replacement parts for an aging fleet of aircraft. However, for these parts to be deployed in flight-critical applications, the quality must be well established given the lack of flight heritage for the manufacturing process. As additive manufacturing is executed layerwise, opportunities exist to non-destructively verify the fabrication in situ with a qualify-as-you-go methodology. In this study, a pair of low cost, high speed cameras are integrated and synchronized together to provide stereovision in order to identify the size, speed, direction and age of spatter ejected from the laser melt pool. The driving hypothesis of the effort is that behavior of spatter can be reliably measured in order to determine the health of the laser process and ensure that spatter is not contaminating the build. Feasibility demonstrations are shown that describe how the measurements are made and characteristics calculated from the image data and how the data were verified with alternative measurements. Opportunities, future work and challenges are discussed.

null

['Ullett, J. S.', 'Chartoff, R. P.', 'Schultz, J. W.', 'Bhatt, J. C.', 'Dotrong, M.', 'Pogue, R. T.']

2018-11-15T20:52:32Z

1996

Mechanical Engineering

doi:10.15781/T27D2QT2J

http://hdl.handle.net/2152/70279

eng

1996 International Solid Freeform Fabrication Symposium

Open

['high performance resins', 'dimensional accuracy', 'stereolithography']

Low Shrinkage, High T Liquid Crystal Resins For Sterelithography

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5f6def77-ca29-4aaf-a1f3-915b07c26efc/download

null

['Yamauchi, Yuki', 'Kigure, Takashi', 'Niino, Toshiki']

2021-11-01T21:45:00Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89765

eng

2016 International Solid Freeform Fabrication Symposium

Open

['PA powder', 'fiber laser', 'low temperature laser sintering']

Low Temperature Laser Sintering of PA Powder Using Fiber Laser

Conference paper

https://repositories.lib.utexas.edu//bitstreams/2c821765-8de5-4f29-9937-107ca2643969/download

University of Texas at Austin

Low temperature process is a novel plastic laser sintering process having potential for improving powder recyclability dramatically. Although fiber laser has been rarely used for plastic laser sintering in commercial base, its ability of being focused in a very small spot suits it to improve precision of plastic laser sintering. In this research, low temperature laser sintering using fiber laser was tested. The highest part density of 99% was obtained while standard high temperature process can provide only 81%. Although generation of fume, which is a major problem in low temperature process using CO2 laser, is not suppressed, it did not affect quality of parts. Part density was strongly affected by slice size of parts and improved when the size is reduced.

null

['Menge, D.', 'Schmid, H.-J.']

2021-12-01T23:46:40Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90662', 'http://dx.doi.org/10.26153/tsw/17581']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['low temperature laser sintering', 'laser sintering system', 'laser sintering', 'PA12']

Low Temperature Laser Sintering on a Standard System: First Attempts and Results with PA12

Conference paper

https://repositories.lib.utexas.edu//bitstreams/15054e14-1008-4385-8325-98893b2a9b31/download

University of Texas at Austin

The laser sintering process has been a well-established AM process for many years. Disadvantages of LS are the low material variety and the thermal damage of the unprocessed material. The low temperature laser sintering attacks at this point and processes powder material at a build chamber temperature lower than the recrystallization temperature. This drastic reduction in temperature results in significantly less thermal damage to the material. This work deals with the low temperature laser sintering of Polyamide 12 (PA12) on a commercial, unmodified laser sintering system to compare it to standard laser sintered PA12 and to create the basis for low temperature laser sintering of high temperature materials on such a system. First results by changing the exposure parameters and by fixing parts on a building platform show a processing of PA12 on an EOS P396 at a build chamber temperature less than 100 °C instead of standard approx. 175 °C.

null

['Niino, Toshiki', 'Uehara, Takashi']

2021-10-21T14:55:22Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89385

eng

2015 International Solid Freeform Fabrication Symposium

Open

['plastic laser sintering', 'warpage', 'PEEK', 'temperature', 'powder bed']

Low Temperature Selective Laser Melting of High Temperature Plastic Powder

Conference paper

https://repositories.lib.utexas.edu//bitstreams/97895c28-4025-4ca4-99ee-55274f5d75ee/download

University of Texas at Austin

In a typical plastic laser sintering or melting system, powder bed temperature is maintained above the recrystallization temperature of the powder material to prevent the parts under process from warping until the whole layers are processed. Although this countermeasure can elegantly suppress the part warpage, heating the powder bed to such a high temperature causes many problems. In case of high temperature plastic such as polyetheretherketone (PEEK), bed temperature should be more than 300°C. Due to this requirement, machine cost is extremely high and powder recyclability is very low. The authors had introduced another countermeasure for the part warpage that anchors the in-process parts to a rigid base plate instead of heating the powder bed above the recrystallization temperature. In the current research, application of this method to PEEK powder is tested, and a simple test piece of which relative density is more than 90% was successfully obtained with preheating temperature of 200°C. In this paper, mechanical performances of obtained parts are presented, and several problems with the process of PEEK powder are discussed as well.

null

['Chen, Jingdong', 'Smith, Douglas E.']

2021-11-18T19:13:13Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90474', 'http://dx.doi.org/10.26153/tsw/17395']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['melt flow', 'polymer filaments', 'low-cost', 'fused filament fabrication', 'additive manufacturing']

A Low-Cost Approach for Characterizing Melt Flow Properties of Filaments Used in Fused Filament Fabrication Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a74c07bd-06f9-4d96-8856-16b204b8539b/download

University of Texas at Austin

Users of Fused Filament Fabrication (FFF) can choose from a wide variety of new materials as filament producers continue to introduce new polymer and polymer composite filament into the marketplace. This paper describes a low-cost device capable of measuring the rheological properties of off-the-shelf polymer filament. In this approach, measurements are taken during filament extrusion which are combined with a pressure drop model based on simple shear flow within the FFF nozzle to perform inverse analysis that computes parameters for the power law generalized Newtonian fluid (GNF) model. The applicability of our FFF-filament rheometer is demonstrated with four commercially available polymer filaments by comparing the results to those obtained from a commercial rotational rheometer. A filament characterization approach similar to Melt Flow Index (MFI) is also proposed to assess the extrusion characteristics of materials specific to FFF.

null

['Gibson, Ian', 'Ming, Ling Wai']

2018-11-28T19:25:58Z

1997

Mechanical Engineering

doi:10.15781/T2ZG6GS99

http://hdl.handle.net/2152/70326

eng

1997 International Solid Freeform Fabrication Symposium

Open

['Selective Laser Sintering', 'Process control']

Low-cost Machine Vision Monitoring of the SLS Process

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d6d815a1-9dd1-41e4-b50f-919bd1b575aa/download

null

During the building of a part using SLS, it is common practice to adjust the temperature parameters. It is important to control these parameters because ifthey are too high then part breakout is difficult. Ifthey are too low then parts have poor material properties. One method of controlling these parameters is by observation through the process chamber window. Any adjustment can be determined by examining the colour ofthe cross-section in process. By using a machine vision system to determine colour variation, it is possible to calculate temperature or laser power adjustments necessary to maintain consistent part quality.

null

['Mathewson, Brian B.', 'Hebbar, Ravi', 'Choi, Sangeun', 'Newman, Wyatt S.', 'Cawley, James D.', 'Heuer, Arthur H.']

2019-02-22T19:55:34Z

1998

Mechanical Engineering

null

['https://hdl.handle.net/2152/73467', 'http://dx.doi.org/10.26153/tsw/617']

eng

1998 International Solid Freeform Fabrication Symposium

Open

['CAM-LEM', 'layer-to-Iayer']

Machine Design, Control and Performance of Automated Computer-Aided Manufacturing of Laminated Engineering Materials

Conference paper

https://repositories.lib.utexas.edu//bitstreams/efab630e-29ca-4906-841e-40a8b4109944/download

null

This paper describes machine design and control aspects of automating a viable CAM-LEM layered manufacturing process. The cut-then-stack sheet-based approach permits using sheet materials of different thicknesses, enabling optimization of build speed. Further, this cut-then-stack approach offers the possibility of assembling parts with multiple materials interleaved both layer-to-Iayer as well as within each layer. The key to realizing these prospective advantages is precise and reliable extraction and assembly of laser-cut regions from sheet feedstock. This paper presents our design approach and examples created on an automated CAM-LEM machine. It will be shown that the use of fugitive materials, automatically assembled interleaved with engineering materials, is feasible, allowing fabrication of laminated components with internal cusps and voids and improving the dimensional stability of components during post-processing. Results of this work are presented and applications of the technology are reviewed. Extensions to tangent-cut thick-sheet interleaved assemblies are described.

null

['Hilton, Z.T.', 'Gray, Jamee']

2023-04-03T15:35:23Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117716', 'http://dx.doi.org/10.26153/tsw/44595']

eng

2022 International Solid Freeform Fabrication Symposium

Open

Laser powder bed fusion

Machine Health Verification Process for Laser Powder Bed Fusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/8e5a24ce-6396-4287-9a45-1073e1bd9635/download

null

Laser powder bed fusion (LPBF) machines are complex systems comprised of a number of interconnected subsystems which work in concert during the laser powder bed fusion process. The health, i.e. consistency in performance, of these complex systems must be monitored and verified to ensure consistency in the process during long-term production. If a system is 'unhealthy' the process becomes less controlled and can lead to decreased, unknown, or unverifiable part quality. To monitor and validate whether a machine is healthy, a number of tests were developed, which consist of: power monitoring, multi-laser alignment, laser position, laser caustic, gas flow, elevator accuracy, and machine condition. The methodology and efficacy of each test are discussed along with additional potential tests and next steps.

null

Beaman, Joseph J.

2018-04-19T18:42:12Z

1992

Mechanical Engineering

doi:10.15781/T2FX74F7X

http://hdl.handle.net/2152/64413

eng

1992 International Solid Freeform Fabrication Symposium

Open

['Department of Mechanical Engineering', 'CAD representation', 'Selective Laser Sintering', 'SLS']

Machine Issues Associated with Solid Freeform Fabrication

Conference paper

https://repositories.lib.utexas.edu//bitstreams/7b752b4c-0bbe-40d5-87a7-e3803639884c/download

null

Before we begin a discussion of machine issues it is important that we categorize exactly what we mean. There are differences between the design of a research piece of equipment as compared to a commercial piece of equipment. A research piece of equipment has to have the flexibility to demonstrate a success pattern. A commercial piece of equipment, on the other hand, assumes that you have a stable platform and you are now trying to assess how broad a success path you have (Figure 1). In fact, you are trying to make that path as broad as possible so that the machine will not fail and will always work the same way. This particular talk, and my expertise, is much more along the lines of design of a research piece of equipment. What I will be talking about today are machine issues associated with developing a success path in Solid Freeform Fabrication. The machines we will be talking about have to have the flexibility to operate in a wide variety of ways with a wide variety of experiments.

null

['Wang, Jier', 'Panesar, Ajit']

2024-03-27T15:47:15Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124489', 'https://doi.org/10.26153/tsw/51097']

en

2023 International Solid Freeform Fabrication Symposium

Open

['metamaterial', 'machine learning', 'additive manufacturing']

Machine Learning Assisted Mechanical Metamaterial Design for Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f30fe5c2-03cf-4945-914e-9bec268a4692/download

University of Texas at Austin

Metamaterials, widely studied for its counterintuitive property such as negative Poisson’s ratio, negative refraction, negative thermal expansion, and employed in various fields, are recognised to provide foundation for superior multiscale structural designs. However, current mechanical metamaterial design methods usually relay on performing sizing optimisations on predefined topology or implementing time-consuming inverse homogenisation methods. Machine Learning (ML), as a powerful self-learning tool, is considered to have the potential of discovering metamaterial topology and extending its property bounds. This work considers the use of Neural Networks (NNs), (De-Convolutional Neural Networks) DCNNs and Generative Adversarial Networks (GANs) to speed up the generation of new topologies for metamaterials. NNs and DCNNs are trained to inversely generate metamaterial designs based on the input target effective macroscale properties, whilst the generator in GANs is expected to output diverse metamaterial microstructures with random noise inputs. This work highlights the potential of data-driven approaches in Design for Additive Manufacturing (DfAM) as an alternative to the time-consuming, conventional methods.

null

['Wang, J.', 'Panesar, A.']

2021-12-01T21:14:26Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90614', 'http://dx.doi.org/10.26153/tsw/17533']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['lattice structures', 'machine learning', 'neural network', 'finite element']

Machine Learning Derived Graded Lattice Structures

Conference paper

https://repositories.lib.utexas.edu//bitstreams/44e74772-3b48-4e18-a066-42d6dcd6486b/download

University of Texas at Austin

Herein, we propose a new lattice generation strategy that is computationally cheaper and produces high-quality geometric definition based on Machine Learning (ML) when compared to traditional methods. To achieve the design of high-performance unit cells, firstly, the optimal mechanical property for each cell region is derived according to the loading condition and the reference density obtained utilising a conventional topology optimisation result. Next, a Neural Network (NN) is employed as an inverse generator which is responsible for predicting the cell pattern for the optimal mechanical property. Training data (~ 500) were collected from Finite Element (FE) analysis with varied cell parameters and then fed to the NN. With the help of ML, the time spent in building the inverse generator is significantly reduced. Furthermore, the ML-based inverse generator can handle different cell types rather than one specific type which facilitates the diversity and optimality of lattices.

null

['Zhang, Wentai', 'Mehta, Akash', 'Desai, Prathamesh S.', 'Higgs, C. Fred III']

2021-11-03T21:43:39Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89941

eng

2017 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing (AM)', 'powder spreading process map', 'discrete element method', 'machine learning']

Machine Learning Enabled Powder Spreading Process Map for Metal Additive Manufacturing (AM)

Conference paper

https://repositories.lib.utexas.edu//bitstreams/dfc8b05c-4978-4ad7-b992-60178e92f62a/download

University of Texas at Austin

The metal powder-bed AM process involves two main steps: the spreading of powder layer and selective fusing or binding the spread layer. Most AM research is focused on powder fusion. Powder spreading is more rarely studied but is of significant importance for considering the quality of the final part and total build time. It is thus essential to understand how to modify the spread parameters such as spreader speed, to generate layers with desirable roughness and porosity. A computational modeling framework employing Discrete Element Method (DEM) is applied to simulate the spreading process, which is difficult to study experimentally, of Ti-6Al-4V powder onto smooth substrates. Since the DEM simulations are computationally expensive, machine learning was employed to interpolate between the highly non-linear results obtained by the running a few DEM simulations. Eventually, a spreading process map is generated to determine which spreader parameters can achieve the desired surface roughness and spread speed. This eventually saves the total time for printing and reduces the cost of build.

null

['Petrich, Jan', 'Gobert, Christian', 'Phoha, Shashi', 'Nassar, Abdalla R.', 'Reutzel, Edward W.']

2021-11-03T22:29:31Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89950

eng

2017 International Solid Freeform Fabrication Symposium

Open

['machine learning', 'defect detection', 'high resolution layerwise imaging', 'post-build CT scans', 'powder bed fusion additive manufacturing']

Machine Learning for Defect Detection for PBFAM Using High Resolution Layerwise Imaging Coupled with Post-Build CT Scans

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3d372929-9f3b-4aab-ae88-80276de95582/download

University of Texas at Austin

This paper develops a methodology based on machine learning to detect defects during Powder Bed Fusion Additive Manufacturing (PBFAM) processes using data from high resolution images. The methodology is validated experimentally using both a support vector machine (SVM) and a neural network (NN) for binary classification. High resolution images are collected each layer of the build, and the ground truth labels necessary for supervised machine learning are obtained from a 3D computed tomography (CT) scan. CT data is processed using image processing tools—extended to 3D—in order to extract xyz position of voids within the component. Anomaly locations are subsequently transferred from the CT domain into the image domain using an affine transformation. Multi-dimensional features are extracted from the images using data surrounding both anomaly and nominal locations. Using cross-validation strategies for machine learning and testing, accuracies of close to 90% could be achieved when using a neural network for in-situ anomaly detection.

null

['He, Haiyang', 'Yang, Yang', 'Pan, Yayue']

2021-11-09T14:56:58Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90088', 'http://dx.doi.org/10.26153/tsw/17009']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['continuous projection stereolithography', 'CLIP', 'machine learning', 'deep neural network', 'siamese network', 'continuous printing speed']

Machine Learning for Modeling of Printing Speed in Continuous Projection Stereolithography

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a159aa64-d973-44a0-ad63-79f6a61eac96/download

University of Texas at Austin

Continuous projection stereolithography technologies, also known as the Continuous Liquid Interface Production (CLIP), can achieve build speeds an order of magnitude faster than conventional layer-by-layer stereolithography process. However, identification of the proper continuous printing speed remains a grand challenge in the process planning. To successfully print a part continuously, the printing speed needs to be carefully adjusted and calibrated for the given geometry. In this paper, we investigate machine learning techniques for modeling and predicting the proper printing speed in the continuous projection stereolithography process. The synthetic dataset is generated by physics-based simulations. Experimental dataset is constructed for training the machine learning models to find the appropriate speed range and the optimum speed. Conventional machine learning techniques including Decision Tree, Naïve Bayes, Nearest Neighbors, and Support Vector Machine (SVM), ensemble methods including Random Forest, Gradient Boosting, and Adaboosting, and the deep learning approach Siamese Network are tested and compared. Experimental results validate the effectiveness of these machine learning models and show that the Siamese Network model gives the highest accuracy.

null

['Pike, J.A.', 'Klett, J.', 'Kunc, V.', 'Duty, C.E.']

2023-04-03T17:49:25Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117731', 'http://dx.doi.org/10.26153/tsw/44610']

eng

2022 International Solid Freeform Fabrication Symposium

Open

Additive manufacturing

Machine Learning in Additive Manufacturing: A Review of Learning Techniques and Tasks

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9a21c73e-897f-4f63-8c5e-3b411f49bc7a/download

null

Due to recent advances, Machine Learning (ML) has gained attention in the Additive Manufacturing (AM) community as a new way to improve parts and processes. The capability of ML to produce insights from large amounts of data by solving tasks such as classification, regression, and clustering provide possibilities to impact every step of the AM process. In the design phase, ML can optimize part design with respect to geometry, material selection, and part count. Prior to printing, process simulations can offer understanding into the how the part will be printed, and energy, time, and cost estimates of a print can be made to assist with resource planning. During printing, AM can benefit from in-situ printing optimization and quality monitoring. Lastly, ML can characterize printed parts from in-situ or ex-situ data. This article describes some of the ML learning techniques and tasks commonly employed in AM and provides examples of their use in previous works.

null

['Rajeshirke, Mithila', 'Alkunte, Suhas', 'Huseynov, Orkhan', 'Fidan, Ismail']

2024-03-25T22:43:47Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124327', 'https://doi.org/10.26153/tsw/50935']

en_US

1990 International Solid Freeform Fabrication Symposium

open

['material extrusion', 'fatigue prediction', 'composites', 'machine learning', 'additive manufacturing']

Machine Learning-Assisted Prediction of Fatigue Behaviour in Fiber-Reinforced Composites Manufactured via Material Extrusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5fb9e9b1-9db1-404a-80c7-31667917f322/download

University of Texas at Austin

The recent advancements in material extrusion (MEX) have expanded the potential use of polymeric and composite structures in a wide range of structural and load-bearing applications. However, cyclic loads can induce fatigue, resulting in the development of structural damage and potentially leading to catastrophic failure at lower stress levels compared to normal mechanical loading. Therefore, it is crucial to thoroughly investigate and understand the fatigue behavior of composite parts manufactured using MEX. Predicting the fatigue life of polymeric composite components poses a significant challenge due to the complex nature of the materials involved. In this research, the aim is to utilize Machine Learning (ML) techniques to predict the fatigue life of fiber-reinforced composites produced through the MEX process. ML focuses on developing models that can learn from data, recognize underlying patterns within the data, and use those patterns to make accurate predictions or decisions.

null

['Mondal, Sudeepta', 'Menon, Nandana', 'Ray, Asok', 'Basak, Amrita']

2023-01-26T15:37:49Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117319', 'http://dx.doi.org/10.26153/tsw/44200']

eng

2022 International Solid Freeform Fabrication Symposium

Open

nickel-base alloys

Machine Learning-Assisted Prediction of Thermophysical Properties of Nickel-Base Alloys over a Temperature Range

Conference paper

https://repositories.lib.utexas.edu//bitstreams/58f3b0a2-3b84-4391-9b45-fd2f6a40b382/download

null

Calculation of thermophysical properties of complex metallic alloys as functions of composition and temperature is essential to design new alloy systems that are suitable for advanced manufacturing processes such as additive manufacturing. Once the properties are obtained, they are typically integrated with a meso-scale simulation framework to understand the impact of composition on different properties. While the forward problem is straight forward, the inverse problem necessitates the integration of the thermodynamic and meso-scale modeling with an optimization framework. The usage of machine learning (ML) tools is, therefore, deemed to be conducive to the development of a digital twin framework for both thermodynamic as well as meso-scale modeling. This paper implements a Gaussian Process (GP) framework to predict thermophysical properties (e.g., bulk density, solidus/liquidus temperatures) of a nickel-base metallic alloy system, nickel-chromium-aluminum (Ni-Cr-Al), over a temperature range. The results show that the proposed GP-based framework is conducive to predicting thermophysical properties with good accuracy and, thus, can be implemented as a surrogate in the digital twin development of additive manufacturing processes.

null

['Hayasi, Mohammad T.', 'Asiabanpour, Bahram']

2021-09-23T20:44:48Z

9/10/08

Mechanical Engineering

null

['https://hdl.handle.net/2152/88023', 'http://dx.doi.org/10.26153/tsw/14964']

eng

2008 International Solid Freeform Fabrication Symposium

Open

['machine path generation', 'direct slicing', 'design-by-feature', 'feature recognition']

Machine Path Generation Using Direct Slicing from Design-by-Feature Solid Model for Rapid Prototyping

Conference paper

https://repositories.lib.utexas.edu//bitstreams/be4ff441-f196-41d3-8300-e45bc7df5c9a/download

null

Because of the differences in the rapid prototyping (RP) processes, there is no standard machine path code for them. For each RP process, based on its characteristics and requirements, the required data are extracted from the CAD model and converted into proper format for the RP machine. Slicing a CAD model through intersecting the model with the XY-plane at each Z increment is a well-known method of path generation. Slicing a CAD model is currently conducted through Stereolithography (STL) file slicing, direct slicing, and additive direct slicing. In this paper, a direct slicing approach inside a design-by-feature solid modeler is proposed. Autodesk Inventor solid modeler, as a design-by-feature solid modeler is used for 3D solid modeling. The proposed system is implemented by Visual Basic codes inside Inventor. In this approach, first protrusion and subtractive features that form a model are extracted. Then, the intersection of each feature and the XY plane is identified. Then, internal and external loops are found. Finally a continuous path in required format is generated. Depending on the specific RP process requirements, additional features such as internal or external hatch can be added to the machine path.

null

['Kmecko, I.S.', 'Kovacevic, R.', 'Jandric, Z.']

2019-09-23T17:29:42Z

2000

Mechanical Engineering

null

['https://hdl.handle.net/2152/75985', 'http://dx.doi.org/10.26153/tsw/3084']

eng

2000 International Solid Freeform Fabrication Symposium

Open

Prototyping

Machine Vision Based Control of Gas Tungsten Arc Welding for Rapid Prototyping 578

Conference paper

https://repositories.lib.utexas.edu//bitstreams/0750d482-2891-4f3d-9d83-4481d221902e/download

null

A machine vision system, based on CCD camera, is used to control the molten pool size during the gas tungsten arc welding (GTAW) process. The technique is tested by making a metallic part with a complex 3-D network of conformal channels on a hybrid rapid prototyping machine based on welding and milling. The test part demonstrated manufacturing flexibility and new technological opportunities required for prototyping injection mold tools. The real metallic part made in a layered fashion had good surface quality, dimensional accuracy, and high density.

This work was financially supported by THECB’s Grants No. 0036133-0005-1997 and 003613- 0022-1999, NSF’s Grants No DMI-9732848 and DMI-9809198, and by the U.S. Department of Education Grant No. P200A80806-98.

null

['Koivunen, V.', 'Bajcsy, R.']

2018-05-03T19:43:14Z

1993

Mechanical Engineering

doi:10.15781/T2154F62N

http://hdl.handle.net/2152/65068

eng

1993 International Solid Freeform Fabrication Symposium

Open

['CAD systems', 'CAD model', 'NURBS']

Machine Vision for Rapid Geometric Modeling

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c74cf0ac-162a-423a-aa7a-b2a4606b0967/download

null

['Arigbabowo, Oluwasola K.', 'Tate, Yash', 'Geerts, Wilhelmus J']

2024-03-25T22:26:42Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124321', 'https://doi.org/10.26153/tsw/50929']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['magnetic fillers', 'Polyamide 4.6', 'Twin Screw Extrusion', 'additive manufacturing']

MAGNETIC CHARACTERIZATION OF 3D PRINTED HIGHPERFORMANCE POLYAMIDE MAGNETIC COMPOSITE

Conference paper

https://repositories.lib.utexas.edu//bitstreams/11f6abd5-317c-4dbd-877b-da1df4282107/download

University of Texas at Austin

Polyamide 4.6 is classified as a high-temperature thermoplastic because of its service temperatures of up to 175°C, bringing it close to high-temperature plastics like PPS or PEEK. Due to its high-temperature capability and price/performance ratio, Polyamide 4.6 is considered viable in developing high-performance bonded magnets by serving as a binder/matrix to magnetic powders/fillers to form multifunctional magneto polymeric composites that offer superior properties to conventional materials. In this research, 10 wt.% and 30 wt.% strontium ferrite magnetic powders were compounded with polyamide 4.6 using a co-rotating twin screw extruder to fabricate monofilament bonded magnets for 3D printing. Morphological and magnetic characterization was performed on the 3D printing monofilament samples using Scanning Electron Microscopy, and Vibrating Sample Magnetometer, respectively. The morphological observations showed an even dispersion of the strontium ferrite fillers in the magnetic composite. The magnetic hysteresis results obtained via the VSM measurement at elevated temperatures indicate that the polyamide 4.6 binder was durable enough to keep the magnetic particles from moving in the bonded magnets. This suggests that the strontium ferrite bonded with Polyamide 4.6 binder is a much better composite and can be used in high-temperature applications up to 150 °C.

null

['Sukhotskiy, V.', 'Karampelas, I.H.', 'Garg, G.', 'Verma, A.', 'Tong, M.', 'Vader, S.', 'Vader, Z.', 'Furlani, E.P.']

2021-11-04T15:14:26Z

2017

Mechanical Engineering

null

['https://hdl.handle.net/2152/89984', 'http://dx.doi.org/10.26153/tsw/16905']

eng

2017 International Solid Freeform Fabrication Symposium

Open

['magnetohydrodynamics', 'droplet ejection', 'drop on demand printing', '3D printing', 'additive manufacturing', 'thermo-fluidics', 'molten aluminum']

Magnetohydrodynamic Drop-on-Demand Liquid Metal 3D Printing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ad6bcde5-c808-4a51-bac1-dde0ea1699e0/download

University of Texas at Austin

We present a novel method for liquid metal drop-on-demand (DOD) additive manufacturing of three-dimensional (3D) solid metal structures. This method relies on magnetohydrodynamic (MHD)-based droplet generation. Specifically, a pulsed magnetic field, supplied by an external coil, induces a Lorentz force density within a liquid metal filled ejection chamber, which causes a droplet to be ejected through a nozzle. Three-dimensional solid metal structures of arbitrary shape can be printed via layer-by-layer patterned deposition of droplets with drop-wise coalescence and solidification. We introduce this prototype MHD printing system along with sample printed structures. We also discuss the underlying physics governing drop generation and introduce computational models for predicting device performance.

null

['Wang, W. L.', 'Fuh, J. Y. H.', 'Wong, Y. S.', 'Miyazawa, T.']

2018-11-14T17:41:15Z

1996

Mechanical Engineering

doi:10.15781/T23R0QD14

http://hdl.handle.net/2152/70247

eng

1996 International Solid Freeform Fabrication Symposium

Open

['SLA process', 'rapid prototyping', 'manufacturing processes']

Make-up Fabrication of Big or Complex Parts Using the SLA Process

Conference paper

https://repositories.lib.utexas.edu//bitstreams/cc726201-c6b2-4836-9302-9a6a06b59671/download

null

Rapid prototyping is a highly flexible manufacturing technology which can produce big or complex parts without any special fixtures and tools. But it is often a costly and time consuming process to produce big and complex parts. To solve this problem, this paper proposes the makeup fabrication process. The process cuts the CAD models of big or complex parts into several small components. optimizes the building orientation and the layout of the multiple objects and then uses theSLA process to build. The paper discusses the basic process, the discretion rules of the CAD models and the optimization of the layout of multiple objects in the simultaneous building

null

['Malyala, Santosh Kumar', 'Gibson, Ian', 'Y, Ravi Kumar', 'Chakravarthy, Chitra']

2021-11-09T20:59:28Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90164', 'http://dx.doi.org/10.26153/tsw/17085']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'AM', 'mandibular resection', 'reposition appliance', 'complex surgery']

Mandibular Repositioning Appliance Following Resection Crossing the Midline- A3D Printed Guide

Conference paper

https://repositories.lib.utexas.edu//bitstreams/e062236e-b20b-4d8e-8215-bed261915ef3/download

University of Texas at Austin

Additive Manufacturing (AM) is one of the latest manufacturing processes which has evolved dramatically over the past three decades. The benefits of AM have steadily stepped in to almost all modern industries. The medical and dental industries may have benefitted the most in this regard. In the medical industry, every complex surgery has unique requirements in planning or execution, where it needs customized surgical guides or tools. In patients with mandibular tumors where a surgical resection is performed crossing the midline, currently there is no guide or tool available for repositioning the mandible to the patient’s original anatomy. To overcome this, an attempt has been made to develop a customized repositioning appliance, which can be used for pre surgical planning and the same can be transferred to the patient during surgery. The repositioning appliance is developed using the patient's CT data which is then processed with the use of medical translation software. The final patient specific repositioning appliance is fabricated using AM technology. This guide has been used on the models of the jaws requiring resection to check their efficacy and the condylar repositioning has been seen to be close to the pre-surgical position. This appliance is useful for pre-surgical planning, pre-bending and adaptation of the reconstruction plate to the mandible and also to reposition the condyles to their original positions after the resection.

null

['Trautschold, Olivia', 'Dong, Andy']

2021-12-07T17:16:23Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90725', 'http://dx.doi.org/10.26153/tsw/17644']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['crumple-forming', 'additive manufacturing', 'manufacturability analysis', 'complex network theory', 'eigenvalue decomposition']

Manufacturability Analysis of Crumple-Formed Geometries through Reduced Order Models

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f445a359-62ba-435a-bdd2-9d5394606379/download

University of Texas at Austin

Crumple-formed structures have irregular, multiscale geometric complexity. Similar to periodic lattices, crumpled geometries can be tailored to applications requiring a high strength-to-weight ratio. As an alternative to confinement-based crumple forming, additive manufacturing allows for increased geometric control and structural reproducibility to fabricate these structures. The inherently irregular geometries of crumple-formed structures decrease the sensitivity of macroscale properties to microscale manufacturing defects but pose a unique challenge for the analysis of manufacturability using additive processes. Current approaches to manufacturability analysis lack techniques suitable for addressing the multiscale geometric complexity and irregularity of crumpled structures. This paper presents a preliminary study into the manufacturability of crumple-formed structures using a model reduction technique that preserves the robust bulk statistical properties of crumpled structures. Manufacturability predicted by the reduced order model is assessed against an ideal geometry for additive processes.

null

['Tedia, Saish', 'Williams, Christopher B.']

2021-10-26T17:44:32Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89536

eng

2016 International Solid Freeform Fabrication Symposium

Open

['manufacturability', 'voxel-based', 'geometric modeling', 'part geometry', 'additive manufacturing']

Manufacturability Analysis Tool for Additive Manufacturing Using Voxel-Based Geometric Modeling

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d4d3cd71-4b19-4be8-add0-7f1fada8818f/download

University of Texas at Austin

While Additive Manufacturing (AM) processes provide unparalleled design freedom, they still impose some constraints on the geometries that can be successfully fabricated. Thus, there exists a need for predictive analysis of part geometries’ manufacturability. Existing algorithms based on surface representations require several computationally intensive manipulations. In this paper, the authors present a framework for performing manufacturability analysis of parts to be manufactured by AM using a voxel-based representations schema. The input triangular mesh is first converted into a voxel representation using Ray Casting. Through a series of simple computations on a binary three-dimensional array, the tool provides feedback on infeasible features, minimum feature size, support material, orientation and manufacturing time for different build orientations. The tool’s ability to effectively analyze parts for manufacturability is evaluated against several sample geometries.

null

['Josupeit, Stefan', 'Delfs, Patrick', 'Menge, Dennis', 'Schmid, Hans-Joachim']

2021-11-01T21:07:27Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89752

eng

2016 International Solid Freeform Fabrication Symposium

Open

['manufacturability', 'lattice structures', 'polymer laser sintering']

Manufacturability and Mechanical Characterization of Laser Sintered Lattice Structures

Conference paper

https://repositories.lib.utexas.edu//bitstreams/05cd0f41-6e54-41f8-bbb8-ed757eadf102/download

University of Texas at Austin

The implementation of lattice structures into additive manufactured parts is an important method to decrease part weight maintaining a high specific payload. However, the manufacturability of lattice structures and mechanical properties for polymer laser sintering are quite unknown yet. To examine the manufacturability, sandwich structures with different cell types, cell sizes and lattice bar widths were designed, manufactured and evaluated. A decisive criterion is for example a sufficient powder removal. In a second step, manufacturable structures were analyzed using four-point-bending tests. Experimental data is compared to the density of the lattice structures and allows for a direct comparison of different cell types with varied geometrical attributes. The results of this work are guidelines for the design and dimensioning of laser sintered lattice structures.

null

['Stephens, Sean', 'Crawford, Richard H.', 'Rogers, William', 'Gitter, Andrew', 'Bosker, Gorden']

2019-09-23T17:27:46Z

2000

Mechanical Engineering

null

['https://hdl.handle.net/2152/75984', 'http://dx.doi.org/10.26153/tsw/3083']

eng

2000 International Solid Freeform Fabrication Symposium

Open

Prosthesis

Manufacture of Compliant Prosthesis Sockets using Selective Laser Sintering 565

Conference paper

https://repositories.lib.utexas.edu//bitstreams/de3d7aa6-0fd1-4ec1-a6ab-b45a54b30c69/download

null

Solid Freeform Fabrication to date has largely been applied in prototype fabrication or fabrication of patterns for conventional manufacturing methods. However, many opportunities exist for using SFF for manufacturing the actual product. In particular, those applications that require or can be enhanced by custom geometric design seem to be well suited for SFF techniques. In this paper we describe the design of a prosthesis socket for a below-the-knee amputee. This socket is specifically designed to provide compliance in selected areas to enhance the comfort of the wearer. Additionally, the socket contains an integrated pylon fitting that provides a structurally superior connection while also improving the comfort of the wearer. The socket was manufactured using selective laser sintering, mated to a pylon and foot, and fitted to the patient for gait analysis. The results of the analysis indicate an improved fit is possible with manufacture by SLS.

The authors acknowledge the support of the Veterans Administration for partial support of this work.

null

['Suryakumar, S.', 'Somashekara, A.']

2021-10-12T18:25:56Z

2013

Mechanical Engineering

null

['https://hdl.handle.net/2152/88714', 'http://dx.doi.org/10.26153/tsw/15648']

eng

2013 International Solid Freeform Fabrication Symposium

Open

['weld-deposition based additive manufacturing', 'additive manufacturing', 'twin-wire', 'process parameters', 'mechanical properties', 'material properties']

Manufacture of Functionally Gradient Materials using Weld-Deposition

Conference paper

https://repositories.lib.utexas.edu//bitstreams/264d0f6a-b4ce-4ef9-8b8f-7be1a00c2bf8/download

University of Texas at Austin

When the inherent inhomogeneity of Additive Manufacturing techniques is carefully exploited, the anisotropy transforms into the desired distribution of the properties paving the way for manufacture of Functionally Gradient Materials. The present work focuses on using weld-deposition based Additive Manufacturing techniques to realize the same. Mechanical properties like hardness and tensile strength can be controlled by a smaller degree through control of process parameters like current, layer thickness etc. A wider control of material properties can be obtained with the help of tandem weld-deposition setup like twin-wire. In tandem twin-wire weld-deposition, two filler wires (electrodes) are guided separately and it is possible to control each filler wire separately. The investigations done on these two approaches are presented in paper.

null

['Badrinarayan, B.', 'Barlow, J.W.']

2018-10-03T18:28:01Z

1994

Mechanical Engineering

doi:10.15781/T2P844F4Z

http://hdl.handle.net/2152/68672

eng

1994 International Solid Freeform Fabrication Symposium

Open

['SLS technology', 'CAD', 'rapid prototyping']

Manufacture Of Injection Molds Using SLS

Conference paper

https://repositories.lib.utexas.edu//bitstreams/28a4a235-8ce6-4c93-af80-cfd62918d6fb/download

null

This paper describes the use of SLS technology for the fabrication of injection mold cavities. Green shapes were made from metal - copolymer powder mixtures by SLS. The copolymer was gradually burnt out and the metal was oxidized in an air furnace. The porous oxidized metal part was subsequently infiltrated with an epoxy resin and cured. Effect of process variables in SLS, effect of oxidation cycle, dimensional changes on oxidation and epoxy infiltration of the oxidized metal part are discussed.

null

['Dechet, Maximilian A.', 'Lanzl, Lydia', 'Werner, Yannick', 'Drummer, Dietmar', 'Bück, Andreas', 'Peukert, Wolfgang', 'Schmidt, Jochen']

2021-11-18T16:30:33Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90417', 'http://dx.doi.org/10.26153/tsw/17338']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['glass fiber composite particles', 'polyamide 11', 'PA11', 'selective laser sintering']

Manufacturing and Application of PA11-Glass Fiber Composite Particles for Selective Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3a9d4a4e-c410-4cb1-9c10-3e0b298df22f/download

University of Texas at Austin

Selective laser sintering (SLS), a powder-based additive manufacturing technology, employs micronsized polymer particles, which are selectively fused by a laser. SLS yields excellent part qualities with good mechanical properties. However, a persistent challenge in this layer-by-layer process is a reduction of mechanical properties in the z-direction. This is often caused by insufficient layer adhesion. One way to strengthen the layer adhesion in z-direction is the incorporation of glass fibers, which exceed from one layer into another. However, most commercially available glass-fiber enhanced materials are dry blends of the polymer powders and the fibers. In order to enhance the isotropic mechanical properties of parts manufactured via selective laser sintering, the manufacturing of glass fiber-filled PA11 particles is shown in this contribution. We present a single-pot approach to produce glass fiber-filled polyamide 11 (PA11) composite particles. The particles are manufactured via liquid-liquid phase separation and precipitation [1] (also known as solution-dissolution process) from ethanol glass fiber dispersions. Bulk polymer material of PA11 is directly converted to composite microparticles in a single process. The produced particles are characterized regarding their size and morphology. The amount of glass fibers in the bulk is assessed via thermogravimetric analysis and the effect of the fibers on the processing window is investigated via differential scanning calorimetry (DSC). As a proof of concept, the powder is employed in the SLS process to produce glass fiber-enhanced test specimens for mechanical testing.

null

Sachs, Emanuel

2019-10-18T17:11:15Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76266', 'http://dx.doi.org/10.26153/tsw/3355']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Fabrication

Manufacturing by Solid Freeform Fabrication

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a149ee04-5569-4fe0-acdc-4e9bc9403af1/download

null

The SFF/RP industry has grown steadily with the most significant gains made in the number of models produced per year – three million in the year 2000. Future growth is most likely to be in manufacturing applications of SFF where even a single application can double the number of models/parts produced annually. There are a number of factors or drivers which can motivate a manufacturing application of SFF either individually or in combination. These drivers include: i. avoid conventional tooling, ii. minimizing hand work, iii. mass customization, iv. geometric flexibility, v. local control of composition. The most intriguing of these drivers is that of mass customization – the manufacture of highly individual products, but on a mass scale. SFF offers the possibility of mass customization of components with complex 3D geometry. A prominent current example is that of Align Technology of Santa Clara, CA which produces unique plastic aligners for orthodontic applications. There already are manufacturing applications where the advantages offered by SFF are so compelling as to overcome any barriers. However, widespread impact of SFF on manufacturing will depend on overcoming several barriers. The essence of these barriers lies in the distinction between prototyping and manufacturing. Manufacturing applications are far more demanding in terms of build rate and associated cost, demands on dimensional control and tolerances, properties of materials, and ease of use and serviceability of equipment.

null

['Kerbrat, O.', 'Mognol, P.', 'Hascoet, J.-Y.']

2021-09-23T22:29:50Z

9/10/08

Mechanical Engineering

null

['https://hdl.handle.net/2152/88039', 'http://dx.doi.org/10.26153/tsw/14980']

eng

2008 International Solid Freeform Fabrication Symposium

Open

['subtractive processes', 'additive processes', 'hybrid modular tooling']

Manufacturing Complexity Evaluation For Additive and Subtractive Processes: Application to Hybrid Modular Tooling

Conference paper

https://repositories.lib.utexas.edu//bitstreams/e7f856b7-75c1-4662-8992-8849d7ca077c/download

null

The aim of this work is to determine how to combine a subtractive process (HSM) and an additive process (SLS) to realize tools (dies or molds). In fact, the design and manufacturing of tools may be optimized with hybrid and modular points of view. Tools are not seen as single pieces but as 3-D puzzles with modules; each module is manufactured by the best process. So a new methodology is proposed: the most complex-to-manufacture areas of a tool are determined (based on a manufacturability analysis from tool CAD model) and a hybrid modular tool CAD model with a reduced manufacturing complexity is proposed.

null

['Beck, James E.', 'Prinz, Fritz B.', 'Siewiorek, Daniel P.', 'Weiss, Lee E.']

2018-04-19T18:32:33Z

1992

Mechanical Engineering

doi:10.15781/T23N20X5T

http://hdl.handle.net/2152/64408

eng

1992 International Solid Freeform Fabrication Symposium

Open

['Mechatronics', 'Thermal Spray', 'shape deposition']

Manufacturing Mechatronics Using Thermal Spray Shape Deposition

Conference paper

https://repositories.lib.utexas.edu//bitstreams/fcd14e93-6df5-4214-8aec-6bd9a4c7ea62/download

null

A new technology for manufacturing mechatronics is described. The technique is based on recursive masking and deposition of thermally sprayed materials. Using these methods, mechanical structures can be created that embed and interconnect electronic components. This results in highly integrated mechatronic devices. A simple, electromechanical artifact was designed and produced to assess the feasibility of these techniques. The details and limitations of this project will be discussed. Areas of future research are identified which are aimed at realizing the full potential of this emerging manufacturing process.

null

['Williams, Christopher B.', 'Rosen, David W.']

2020-03-10T16:23:58Z

9/5/07

Mechanical Engineering

null

['https://hdl.handle.net/2152/80224', 'http://dx.doi.org/10.26153/tsw/7243']

eng

2007 International Solid Freeform Fabrication Symposium

Open

Additive Manufacturing

Manufacturing Metallic Parts with Designed Mesostructure via Three-Dimensional Printing of Metal Oxide Powder

Conference paper

https://repositories.lib.utexas.edu//bitstreams/eb783689-9258-4328-91f8-102dc2509844/download

null

Cellular materials, metallic bodies with gaseous voids, are a promising class of materials that offer high strength accompanied by a relatively low mass. In this paper, the authors investigate the use of ThreeDimensional Printing (3DP) to manufacture metallic cellular materials by selectively printing binder into a bed of metal oxide ceramic powder. The resulting green part undergoes a thermal chemical post-process in order to convert it to metal. As a result of their investigation, the authors are able to create cellular materials made of maraging steel that feature wall sizes as small as 400 µm and angled trusses and channels that are 1 mm in diameter.

null

['Morvan, Stephane', 'Fadel, Georges', 'Love, James', 'Keicher, Dave']

2019-10-18T16:59:04Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76261', 'http://dx.doi.org/10.26153/tsw/3350']

eng

2001 International Solid Freeform Fabrication Symposium

Open

LENS Apparatus

Manufacturing of a Heterogeneous Flywheel on a LENS Apparatus

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1d07107e-c7a9-4d2b-a34f-f10d2d0e4c63/download

null

The design of a 1D gradient component satisfying a particular set of constraints is extended to its manufacturing on a multi-material capable apparatus. The geometry and composition of this flywheel were designed to meet a bi-objective optimum featuring maximum kinetic energy storage and minimal maximum von-Mises stress along its radius. The efforts expanded during the transformation of this design from a computer abstraction into a tangible object are presented. The process-planning step of the manufacturing of this heterogeneous solid, which was dependent on the specifics of a LENS-based Apparatus, required a different approach than that of traditional solids, and proved critical during fabrication.

null

['Hascoet, J.Y.', 'Muller, P.', 'Mognol, P.']

2021-10-05T14:26:55Z

8/17/11

Mechanical Engineering

null

['https://hdl.handle.net/2152/88378', 'http://dx.doi.org/10.26153/tsw/15317']

eng

2011 International Solid Freeform Fabrication Symposium

Open

['functionally graded materials', 'morphologically complex parts', 'bi-materials gradients', 'additive manufacturing']

Manufacturing of Complex Parts with Continuous Functionally Graded Materials (FGM)

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3db9799c-fa1e-4081-9a67-107390b7b5a4/download

University of Texas at Austin

One of major evolutions of the additive manufacturing is the ability to produce parts with functionally graded materials (FGM). However, manufacturing of these parts is limited to discrete or nearly continuous FGM on samples. To achieve this, it is necessary to have a global control of processes and to develop methodologies to help designers and manufacturers. A methodology to produce morphologically complex parts is proposed in this paper. It consists in classifying all typologies of bi-materials gradients with mathematical description. Each typology of gradient is associating with manufacturing strategies in order to choose slicing and path strategies. Afterwards, mathematical data are used to have a global control of a process. This paper presents the principle of this methodology and the mathematical models which are chosen to describe part and manufacturing.

null

['Shimek, Moss', 'Patwardhan, Nachiket', 'Wood, Kristin L.', 'Beaman, Joseph', 'Crawford, Richard']

2019-10-18T15:23:32Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76237', 'http://dx.doi.org/10.26153/tsw/3326']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Instrumented

Manufacturing of Instrumented Prototypes

Conference paper

https://repositories.lib.utexas.edu//bitstreams/15e2a308-2bf5-41f8-85c0-e51c7b2a2174/download

null

The research for the Cybernetic Physical project at UT Austin has the goal of producing instrumented prototypes, using selective laser sintering (SLS) that can be used in concert with similarity methods to update virtual models. The SLS process builds prototypes sintering powder in a 2-D cross-section, layer by layer, with a CO2 laser. Accomplishing this goal could significantly reduce cycle times and costs associated with traditional prototyping methods. Strain gages and thermocouples are chosen as the first sensors to be embedded. Experiments have been carried out to determine the feasibility of embedding sensors both after the manufacturing process as well as during the SLS process. These experiments have yielded data that will serve as a set of design requirements for the embedding process. The results from the post-embedded prototypes closely matched the theoretical results in one case. Hence a design of experiments will be carried out to study the effects of various factors on these sensors. Embedding thermocouples during an SLS build cycle uncovered issues that must be addressed in the design process, such as keeping the sensor and lead wires flat on the cross-section and managing the extra lead wires. A 1-D heat source, pin fin model was used to accurately predict the temperature reading of the thermo couple in the sample. The error was approximately 3.3%.

null

['Dechet, Maximilian A.', 'Lanzl, Lydia', 'Wilden, Alisa', 'Sattes, Maria-Melanie', 'Drummer, Dietmar', 'Peukert, Wolfgang', 'Schmidt, Jochen']

2021-11-18T16:33:11Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90418', 'http://dx.doi.org/10.26153/tsw/17339']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['nanoparticle-filled composite particles', 'polyamide 11', 'PA11', 'selective laser sintering']

Manufacturing of Nanoparticle-Filled PA11 Composite Particles for Selective Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/714236bb-21ea-4f24-95d7-7c7deb6e8e11/download

University of Texas at Austin

Selective laser sintering (SLS) is an Additive Manufacturing (AM) process that yields excellent part qualities with good mechanical properties. The SLS process employs micron-sized polymer particles, which are selectively fused by a laser. While there seem to be hardly any boundaries regarding design, there are quite some restrictions concerning the variety of commercially available SLS materials. With a market share of roughly 90%, polyamide 12 (PA12) is currently the most widely used polymer material for SLS. Concerning particle or fiber enhanced materials, only dry blended, but hardly any composite materials are available. In this contribution, the manufacturing of nanoparticulate alumina-, titania- and silica-filled polyamide 11 (PA11) particles is demonstrated. The particles are manufactured via liquid-liquid phase separation and precipitation (also known as solution-dissolution process) from ethanol dispersions. Bulk polymer material of PA11 is directly converted to composite microparticles in a one-pot approach. The produced particles are characterized regarding their size and morphology. The amount of nanoparticles in the bulk is assessed via thermogravimetric analysis (TGA). Furthermore, the effect of the nanoparticles as nucleating agents is investigated via DSC and correlated with surface energies as determined by inverse gas chromatography (IGC).

null

['Ruvalcaba, Bryan E.', 'Arrieta, Edel', 'Escarcega, Andres H.', 'Medina, Francisco', 'Wicker, Ryan B.']

2021-11-30T20:04:05Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90530', 'http://dx.doi.org/10.26153/tsw/17449']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['selective laser melting', 'manufacturing process', 'parameter development', 'water-atomized zinc powder']

Manufacturing Process and Parameters Development for Water-atomized Zinc Powder for Selective Laser Melting Fabrication

Conference paper

https://repositories.lib.utexas.edu//bitstreams/bafaca19-44c1-4376-99eb-022738b74614/download

University of Texas at Austin

Biodegradability of metals is a desirable characteristic for medical implants. Metals like Fe, Mg, Zn and their alloys are usually preferred for this application, as their degradation rate has been shown to work on medical implants. The fast degradation rate of Mg may early compromise its structural performance for these components; while the slower degradation rate of Fe may also become a disadvantage. This leaves Zinc’s degradation rate more suitable for this application. Vaporization temperatures make zinc a challenging material to use in conventional additive manufacturing systems. In this work, the process of developing parameters to print water atomized zinc powder is presented. This process was performed in a commercial SLM system, implying inconveniences for a powder not optimized for AM. Optical analysis of wateratomized powder was conducted for size and shapes measurement of precursor powder. This work includes density and microstructure analysis, followed up by conclusion and remarks.

null

['Lambert, Philip', 'Chartrain, Nicholas', 'Schultz, Alison', 'Cooke, Shelley', 'Long, Timothy', 'Whittington, Abby', 'Williams, Christopher']

2021-10-18T20:49:00Z

2014

Mechanical Engineering

null

https://hdl.handle.net/2152/89241

eng

2014 International Solid Freeform Fabrication Symposium

Open

['Mask Projection Microstereolithograhy', 'biocompatible polymers', 'biocompatibility']

Mask Projection Microstereolithography of Novel Biocompatible Polymers

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5506e78f-519a-42e2-8937-92353ead999c/download

University of Texas at Austin

Mask Projection Microstereolithography (MPμSL) selectively cures entire layers of photopolymer to create three-dimensional parts with features on the micron scale. The resolution and scale of MPμSL are ideal for fabricating tissue engineering scaffolds with designed mesostructure. While MPμSL have excellent resolution, there are few biocompatible materials that are compatible with the vat photopolymerization processes. A novel diacrylate functionalized Pluronic L-31 block-copolymer and poly(propylene glycol diacrylate) were synthesized and processed with MPμSL. The resulting structures were analyzed for biocompatibility, as well as accuracy and mechanical strength to assess feasibility for use in tissue engineering scaffold fabrication. Preliminary fabricated scaffold geometries are presented to validate experimental results.

null

['Pallari, J. H. P.', 'Dalgarno, K. W.', 'Woodburn, J.']

2020-02-27T20:39:32Z

2006

Mechanical Engineering

null

['https://hdl.handle.net/2152/80103', 'http://dx.doi.org/10.26153/tsw/7124']

eng

2006 International Solid Freeform Fabrication Symposium

Open

Rheumatoid arthritis

Mass Customization of Foot Orthosis for Rheumatoid Arthritis

Conference paper

https://repositories.lib.utexas.edu//bitstreams/2dac7d96-b85a-4530-b9be-e1881b8b99e8/download

null

Rheumatoid arthritis (RA) is an inflammatory disease, which can cause pain, stiffness, and swelling in the joints of hands and feet. The foot is a major site for RA involvement and a major source of disability resulting from this disease. This paper introduces research which aims to create a mass customisation process for customised orthoses for patients with RA. 3D laser scanning, and gait analysis will be used to generate the orthosis geometry and rapid manufacturing, namely the selective laser sintering (SLS) process, will be used to produce the orthoses. The SLS process enables the incorporation of compositional functional elements, such as locally adjusted stiffness or flexibility, into the orthosis design. The process involved two central elements. The first was a literature survey to identify orthotic design rules for foot impairments in RA. This survey will form a platform for the design rule development and will be complemented by data obtained from two patient trials. The second is a virtual three-segment foot model, created in Anybody dynamics modelling software which can be motivated by data measured from patients using 3D motion capture and force plate systems. Once the measured data has been applied to the model, a virtual insole can be used to simulate the effects of various features in the orthosis. Considerable variation was noted in the literature for types of material, design and methods of orthotic construction. Pressure redistribution using cushioning materials was consistently mapped to painful deformed joints. Orthoses with contoured surfaces, either custom- or mass produced in thermoplastic materials of varying stiffness and density were mapped to joint motion control and deformity prevention. The paper will also describe applying patient gait data to the Anybody model, and then altering the gait pattern by applying the insole model. Future work will also be discussed.

null

['Ye, Hang', 'Zhou, Chi', 'Xu, Wenyao']

2021-10-26T17:53:21Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89539

eng

2016 International Solid Freeform Fabrication Symposium

Open

['mass customization', 'additive manufacturing', 'topology', 'slicing', 'CLIP']

Mass Customization: Reuse of Topology Information to Accelerate Slicing Process for Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/7e4256f4-aeef-4bbf-8795-7e1dcf5b1b50/download

University of Texas at Austin

Additive manufacturing (AM) can build objects with complex features with little extra effort, opening up potentials to realize mass customization. Continuous Liquid Interface Production (CLIP) prints object in a continuous fashion, leading to extremely high productivity and consequently enabling mass customization. CLIP adopts a large number of images as input, which poses a fundamental challenge in layer generation. The slicing procedure for a single customized model can take tens of minutes or even hours to complete, and the time consumption becomes more prominent in mass customization context. Motivated by the similarities among the customized products, we proposed a new slicing paradigm. It reuses topology information obtained from the template model for other customized products from the same category. The idea of topology information reuse is implemented at three levels, including self reuse, intra-model reuse, and inter-model reuse. Experimental results show that the proposed slicing paradigm can significantly reduce the time consumption on pre-fabrication computation, and ultimately fulfill mass customization enabled by AM.

null

['Delfs, P.', 'Li, Z.', 'Schmid, H.-J.']

2021-10-20T20:30:07Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89355

eng

2015 International Solid Freeform Fabrication Symposium

Open

['selective laser sintering', 'mass finishing', 'disc finishing']

Mass Finishing of Laser Sintered Parts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/cf5566ee-2122-4282-8378-b1692567b564/download

University of Texas at Austin

Selective laser sintered (SLS) part surfaces are quite rough textured by the layered structure and adherence of incomplete molten powder particles. Different post-treatments can help to smooth these surfaces. In this work we investigated the mass finishing method with a disc finishing machine. The aim was to quantify the influences of different process parameters on roughness values and rounding of edges. Therefore different geometries and material of abrasive media were used. Further the intensity was varied by changing the rotational speed and duration of the finishing process. Analysis was done with a 3D optical microscope to get profile and areal roughness parameters as well as radii of edges. SLS part surfaces with build angles from 0° to 180° in 15° steps were evaluated. The results show that depending on the used abrasive media roughness values can be reduced to about 15 % of its initial value in a few hours of finishing.

null

['Chartoff, Richard P.', 'Flach, Lawrance', 'Weissman, Peter']

2018-05-03T19:26:47Z

1993

Mechanical Engineering

doi:10.15781/T2J679D77

http://hdl.handle.net/2152/65064

eng

1993 International Solid Freeform Fabrication Symposium

Open

['SLA', 'rapid prototyping', 'stereolithography']

Material and Process Parameters that Affect Accuracy in Stereolithography

Conference paper

https://repositories.lib.utexas.edu//bitstreams/4f26f401-e99d-4e70-903a-f9bd1f6124fe/download

null

Experimental real time linear shrinkage rate measurements simulating stereolithography are used in an analysis of shrinkage during line drawing in stereolithography. While the amount of shrinkage depends on the polymerization kinetics, shrinkage kinetics and overall degree of cure, it also depends on the length of time to draw a line of plastic. A line drawn slowly will exhibit less apparent shrinkage than one drawn very quickly because much of the shrinkage is compensated for as the line is drawn. The data also indicates that a typical stereolithography resin in the green state may shrink to only 65% of its maximum, thus retaining considerable potential for shrinkage during post-cure. This infonnation can be used to predict the amount of shrinkage to be expected under certain exposure conditions and to fonnulate overall strategies to reduce shrinkage and subsequent warpage that causes shape distortion.

null

['Dobson, Sean', 'Wu, Yan', 'Yang, Li']

2021-11-09T18:39:54Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90113', 'http://dx.doi.org/10.26153/tsw/17034']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['thin wall structures', 'lightweight structures', 'material characteristics', 'Ti-6Al-4V', 'EOS M270', 'laser melting powder bed fusion', 'LM-PBF', 'additive manufacturing']

Material Characterization for Lightweight Thin Wall Structures Using Laser Powder Bed Fusion Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d25a63f6-7047-4887-844e-a3e541f5d53e/download

null

In this study the geometry-process-material characteristics of the Ti6Al4V thin wall features fabricated by the EOS M270 laser melting powder bed fusion (LM-PBF) additive manufacturing (AM) was investigated. Samples with varying wall thickness, orientation, scanning speeds and laser power were fabricated and analyzed. The dimensional accuracies, microstructural characteristics and mechanical properties of the samples were evaluated experimentally. The results clearly indicated the significant coupling effects between the geometry design of these thin wall features and their material properties, which is critical to the design and manufacturing of many AM lightweight structures. By identifying significant design and process parameters for the thin wall structures, this study will enable further investigations of the integrated design theories for the AM lightweight structures.

null

['Nodehi, Mehrab', 'Asiabanpour, Bahram', 'Omer, Liam', 'Ozbakkaloglu, Togay']

2021-12-07T18:24:10Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90748', 'http://dx.doi.org/10.26153/tsw/17667']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', '3D printing cementitious materials', '3D concrete printing']

Material Characterization of Diversity Aggregated Cementitious Materials Produced with a Modular Lightweight Additive Manufacturing Extrusion System

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c46be270-e943-4d38-b6b0-19ab0ec52f18/download

University of Texas at Austin

Applications of additive manufacturing in the construction industry started three decades ago with the first patent and prototype of the contour crafting process. Since then, its obvious benefits in reducing labor cost, construction waste while improving efficiency and flexibility have led to the development of several large-scale commercial machines in this field. However, proper lab-scale machines for training experts in automated construction and research-based activities such as material optimizations for civil and structural engineers are not available. The only available small-scale apparatus in AM-based construction is limited to a minimal list of materials and properties. Those machines are not capable of fabricating samples from cementitious materials with a variety of aggregate sizes. This paper compares two low-cost, modular AM-based construction systems capable of extruding a wide variety of cementitious materials with diverse aggregate sizes. The systems are capable of controlled extrusion with a variety of cross-section forms. The system can be attached to a robotic arm, CNC machine, or other programmable machines. As a proof-of-concept, the developed system is utilized to fabricate cement mortar with larger aggregate sizes with different materials mixture ratios. Mechanical performance of the resulting additively manufactured cementitious parts is examined and compared.

null

['Amon, Christina', 'Beuth, Jack', 'Kirchner, Helmut', 'Merz, Robert', 'Prinz, Fritz', 'Schmaltz, Kevin', 'Weiss, Lee']

2018-05-03T16:20:53Z

1993

Mechanical Engineering

doi:10.15781/T2P26QM6W

http://hdl.handle.net/2152/65032

eng

1993 International Solid Freeform Fabrication Symposium

Open

['layered manufacturing', 'sintering', 'melting', 'thermal modeling', 'residual stress', 'multi material', 'structures', 'stress cracking']

Material Issues in Layered Forming

Conference paper

https://repositories.lib.utexas.edu//bitstreams/047d947b-98c6-4729-9a86-8996a5afcca4/download

null

A brief overview of key issues in layered thermal processing is given. Incremental sintering and layered fusion ofpowder and molten droplets are discussed. The criteria for remelting the solid substrate are derivedfrom a one dimensional heat transfer model. Temperature gradients which occur during solidification and subsequent cooling. are responsible for the build up of internal stresses which can be estimated through establishing an elastic beam model. The difficulties as well as opportunities regarding the generation of multi-layer multi-material structures are also described in this article.

null

['Boivie, K.', 'Karlsen, R.', 'Van der Eijk, C.']

2020-02-28T15:07:59Z

2006

Mechanical Engineering

null

['https://hdl.handle.net/2152/80109', 'http://dx.doi.org/10.26153/tsw/7130']

eng

2006 International Solid Freeform Fabrication Symposium

Open

metal printing process

Material Issues of the Metal Printing Process, MPP

Conference paper

https://repositories.lib.utexas.edu//bitstreams/214a2d4c-d87b-4409-a13c-91b058767bc3/download

null

The metal printing process, MPP; is a novel Rapid Manufacturing process under development at SINTEF and NTNU in Trondheim, Norway. The process, which aims at the manufacturing of end-use products for demanding applications in metallic and CerMet materials, consists of two separate parts; The layer fabrication, based on electrostatic attraction of powder materials, and the consolidation, consisting of the compression and sintering of each layer in a heated die. This approach leads to a number of issues regarding the interaction between the process solutions and the materials. This paper addresses some of the most critical material issues at the current development stage of MPP, and the present solutions to these.

null

Lipton, Jeffrey I.

2024-03-27T15:48:34Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124490', 'https://doi.org/10.26153/tsw/51098']

en

2023 International Solid Freeform Fabrication Symposium

Open

['material jetting', 'suspension system', 'additive manufacturing']

Material Jetting of Suspension System Components.

Conference paper

https://repositories.lib.utexas.edu//bitstreams/e93401fe-b03a-4b49-93cf-511b19742ce8/download

University of Texas at Austin

Material Jetting has demonstrated great promise in being able to produce complex functionalities using multi-material printing. Despite this potential material jetting has struggled to find applications in direct part production. Here we show how material jetting can be used to produce viscoelastic energy absorbers for large displacement applications in harsh environments. We generate printed components to act as the core of a suspension system on a recumbent trike. The 3D printed dampers allowed for improvements of the ride experienced. Through long term exposure studies, we demonstrate that techniques and methods previously applied to the absorption of vibration in indoor power tool applications can be extended to outdoor environments.

null

['Sekmen, K.', 'Rehbein, T.', 'Johlitz, M.', 'Lion, A.', 'Constantinescu, A.']

2023-03-29T16:20:25Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117677', 'http://dx.doi.org/10.26153/tsw/44556']

eng

2022 International Solid Freeform Fabrication Symposium

Open

['Additive manufacturing', 'UV curing', 'photopolymer', 'reaction kinetics', 'viscoelastic modelling']

Material Modelling of the Photopolymers for Additive Manufacturing Processes

Conference paper

https://repositories.lib.utexas.edu//bitstreams/8103589b-ef51-4986-aca5-aa5579c2ae11/download

null

Ultraviolet (UV) curing of polymers is a key phenomenon for several additive manufacturing technologies. This contribution presents a model relating the process parameters of UV light intensity and temperature to the thermal and mechanical properties of the polymer and the experimental results used to calibrate the model. Moreover, photo-differential scanning calorimetry (photo-DSC) measurements are performed to investigate the crosslinking reaction and to model the degree of cure as a function of the light intensity and temperature. The viscoelastic properties are measured by UV rheometry and it is shown that the classical time-cure superposition principle can equally be applied to the experimental results. Complete curing and mechanical model equations are provided to describe the material behavior as a result of our experimental findings.

null

['Guo, C.', 'Ge, W.J.', 'Lin, F.']

2021-10-18T21:39:13Z

2014

Mechanical Engineering

null

https://hdl.handle.net/2152/89256

eng

2014 International Solid Freeform Fabrication Symposium

Open

['Electron Beam Selective Melting', 'material molten time', 'material deposition']

Material Molten Time and its Effect on Material Deposition during Electron Beam Selective Melting

Conference paper

https://repositories.lib.utexas.edu//bitstreams/97239d58-f96a-4a58-b7ef-5677d66f45dd/download

University of Texas at Austin

Electron Beam Selective Melting (EBSM) is an additive manufacturing technology that directly fabricates parts from metal powders in a layer-by-layer fashion. The material molten time, which equals the total time that material keeps molten during scanning, is selected as an indicator for evaluating the effects of process parameters on material deposition. A finite elements model was established to simulate the molten time distribution within the scanning area for various parameters. Samples were fabricated using the same parameters in simulation. It’s found that there is a strong relation between the molten time and material deposition behavior. Appropriate material molten time results in a dense and flat surface. Too little material molten time leads to a non-dense surface and internal pores, and too much material molten time leads to a distorted surface and coarsened microstructures. The material molten time increases with the increase of beam current and with the decrease of scanning velocity and length of scanning line. An optimized process which aims to obtain appropriate and homogeneous molten time within the scanning area is also developed to improve the deposition quality.

null

['Fan, K.M.', 'Cheung, W.L.', 'Gibson, L.']

2019-10-09T16:29:46Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76158', 'http://dx.doi.org/10.26153/tsw/3247']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Trueform

Material Movement and Fusion Behavior of TrueForm and TrueForm/SiO2 during Selective Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c0d20892-823c-4460-8e49-78aee023a779/download

null

Different material systems, TrueForm and TrueForm/SiO2 composites, were sintered under similar conditions. A microscope equipped with a CCD camera was utilized to examine the material movement near the laser beam. Powder movement of the blends was found to start at different ranges ahead of the line of scan. For TrueForm, the polymer particles were found to undergo fusion ahead of the laser beam and form a band, 0.5-0.7mm wide, which then moved as a single block towards the sintered area. The dry mixed TrueForm/SiO2 composites (dry blends) exhibited a short-range material movement in the form of small agglomerates. Meanwhile, the TrueForm/SiO2 composite powder prepared by melt extrusion (melt blend) showed a range of material movement between those of TrueForm and the dry blends. The discrepancy is believed to arise from changes in heat transfer properties and fusion behavior after blending. The surface temperature of the powder bed was monitored during sintering. Generally, the dry blends exhibited a higher surface temperature. Apparently, both the particle size of SiO2 and the blending method had an effect on the temperature and material movement, and hence on the final morphology of the sintered components.

null

['Raju, Nandhini', 'Warren, Peter', 'Subramanian, Ramesh', 'Ghosh, Ranajay', 'Raghavan, Seetha', 'Fernandez, Erik', 'Kapat, Jayanta']

2021-12-06T22:12:19Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90693', 'http://dx.doi.org/10.26153/tsw/17612']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['17-4 PH stainless steel', 'material properties', 'atomic diffusion additive manufacturing', 'ADAM']

Material Properties of 17-4PH Stainless Steel Fabricated by Atomic Diffusion Additive Manufacturing (ADAM)

Conference paper

https://repositories.lib.utexas.edu//bitstreams/4d15f0d0-baeb-4b10-b1c9-b0ea47a808ce/download

University of Texas at Austin

The objective of this paper is to investigate the material properties of 17-4PH stainless steel printed by the Atomic Diffusion Additive manufacturing technique. Samples with film cooling holes in different orientations were manufactured in a Markforged Metal-X machine. The presence of the holes in these samples helps to understand the printability and accuracy of internal cooling holes, as manufactured by the Metal-X machine. Manufactured samples were first washed to remove the plastic binder. These pre-sintered samples were tested, before sintering, for density, microstructure analysis, CT (Computerized Tomography) scan, roughness, and XRF (X-ray Fluorescence Spectrometer) to understand the material properties. The printed holes, their anomalies, and selection of standards of testing will be discussed along with the material behavior of 17-4PH stainless steel.

null