ccm/sff-papers · Datasets at Hugging Face

['Shrestha, Rakish', 'Simsiriwong, Jutima', 'Shamsaei, Nima']

2021-11-18T00:22:18Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90368', 'http://dx.doi.org/10.26153/tsw/17289']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['stress gradient', 'fatigue', '316L stainless steel', 'surface roughness']

Comparison of Rotating-Bending and Axial Fatigue Behaviors of LB-PBF 316L Stainless Steel

Conference paper

https://repositories.lib.utexas.edu//bitstreams/e72c83ca-00c4-46bd-a799-e67d70adf8ca/download

University of Texas at Austin

Additive manufactured (AM) materials are prone to internal defects such as entrapped gas pores and lack of fusions along with having a rough surface. There are different types of fatigue tests that are used to characterize the effects of such defects on the structural integrity of AM parts. The present study aims to investigate the effect of stress gradient on the fatigue behavior of 316L stainless steel (SS), fabricated using a laser beam powder bed fusion (LB-PBF) process. Axial fatigue tests are performed on as-built (non-machined) LB-PBF 316LSS round specimens with uniform gage section, while rotating bending fatigue tests are conducted on hourglass specimens (i.e. reduced gage section). Fatigue tests revealed that the specimens subjected to the axial loading exhibited lower fatigue resistance compared to the specimens failed under rotating bending test. Such differences in the fatigue life was attributed to the variation in the stress distribution resulting from different loading types and its effect on the fatigue crack propagation. Fractography analysis conducted to determine the failure mechanism showed that all of the cracks initiated from the surface of the specimen irrespective to the loading conditions. Furthermore, fracture surface observed for LB-PBF 316L SS specimens resembled a typical fracture surface of notched specimens, which supports the fact that for the as-built specimens cracks initiates from the micro-notches as a result of layer wise fabrication in AM process.

null

['Roach, Michael', 'Williamson, R. Scott', 'Pegues, Jonathan', 'Shamsaei, Nima']

2021-11-11T15:19:10Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90217', 'http://dx.doi.org/10.26153/tsw/17138']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['stress corrosion cracking', 'environmentally assisted cracking', 'titanium alloy', 'tensile properties']

A Comparison of Stress Corrosion Cracking Susceptibility in Additively-Manufactured and Wrought Materials for Aerospace and Biomedical Applications

Conference paper

https://repositories.lib.utexas.edu//bitstreams/b28ef43d-a78a-4bb3-bba1-3cbd7d0914c4/download

University of Texas at Austin

Additive manufacturing (AM) is becoming an increasingly popular method in both aerospace and biomedical industries. Titanium alloys are increasingly common in additive manufactured applications due to their excellent strength to weight ratio and biocompatibility. Traditional wrought Ti-6Al-4V alloys show little sensitivity to stress corrosion cracking (SCC) when subjected to in-vitro conditions. In AM applications the alloy powder is often sifted and reused multiple times which often results in a degradation of the powder’s shape. Recent studies have also shown that the oxygen content of additive powders increases with repeated powder use which may increase the susceptibility of the resulting parts to SCC. This research compares the microstructural characteristics and tensile SCC behavior of AM Ti-6Al-4V parts fabricated from new and recycled powder in distilled H2O, salt water, and Ringers solution. Additionally, the effect of surface finish is investigated for each microstructure comparing the as-built surfaces to machined and polished surfaces.

null

['De La Cruz, Alex', 'Medina, Francisco', 'Arrieta, Edel', 'Weston, Luke', 'Benedict, Mark', 'Gibson, Theo']

2024-03-27T03:42:25Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124472', 'https://doi.org/10.26153/tsw/51080']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'laser powder bed fusion', 'Ti6Al4V', 'surface texture', 'surface morphology']

Comparison of Surface Texture from Various Surface Morphology Techniques for Evaluating As-Built Ti6Al4V Laser Powder Bed Fusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d8669a2c-7452-4046-8cb6-dd9be6890d39/download

University of Texas at Austin

Additive manufacturing (AM) is capable of creating unique and complex geometries that conventional methods cannot achieve. The applications for AM have been rapidly increasing across a variety of sectors, particularly for biomedical and aerospace components, the relatively low production volumes and high demand for customizability in both sectors are especially amiable to AM. However, without post-processing, AM components contain a variety of flaws, such as surface roughness and porosity, that can partially be mitigated by process parameters like scan speed and laser power. Surface roughness is a flaw present for every as-built AM surface that serves as an array of sites for every mode of material failure to occur. Common surface roughness measurements involve the use of optical and contact stylus profilometry. However, xray Computed Tomography (xCT) is already the most widely used method of analyzing AM parts for porosity, inclusions, and various other flaws. In terms of resolution, xCT should be fully capable of analyzing surface roughness and is the only method of the three investigated that can inspect interior geometries. Therefore, evaluating xCT as a fully inclusive analysis method for AM parts is advantageous. In this study, we compared three surface characterization technologies, xCT, optical profilometry, and contact stylus profilometry. The comparison of these technologies is being done on as-built Laser Powder Bed Fusion (L-BPF) Ti6AI4V fourpoint bending fatigue samples. Further understanding the difference among each of the technologies will aid ongoing research on developing a standard for xCT surface characterization while also providing more knowledge and insight into each technique and what can be expected. Each of the samples was produced by varying scanning speed and laser power, resulting in different surface textures. Preliminary results show deviations of Sa _%, Sz _%, Sv _%, and Sku _% between the xCT and optical microscopy methods are comparable between these two methods.

null

['Chu, Jane', 'Engelbrecht, Sarah', 'Graf, Greg', 'Rosen, David W.']

2021-09-23T22:08:07Z

9/10/08

Mechanical Engineering

null

['https://hdl.handle.net/2152/88035', 'http://dx.doi.org/10.26153/tsw/14976']

eng

2008 International Solid Freeform Fabrication Symposium

Open

['cellular materials', 'lattice structures', 'design synthesis', 'particle swarm optimization', 'least square minimization', 'additive manufacturing']

A Comparison of Synthesis Methods for Cellular Structures with Application to Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c5e7d7b2-681e-4db7-87ac-fdda3c82826a/download

null

Cellular material structures, such as honeycombs and lattice structures, have been engineered at the mesoscale for high performance and multifunctional capabilities. We desire efficient algorithms for searching the large, complex design spaces associated with cellular structures. In this paper, we present a comparison of two synthesis methods, Particle Swarm Optimization (PSO) and least-squares minimization (LSM), for the design of components comprised of cellular structures. Computational characteristics of the algorithms are reported for design problems with hundreds of variables. Constraints from SLS and direct-metal manufacturing processes are incorporated to ensure that resulting designs are realizable. Two 2- dimensional examples are used to study the characteristics of the proposed synthesis methods.

null

['Zeng, Kai', 'Teng, Chong', 'Xu, Sally', 'Sublette, Tim', 'Patil, Nachiket', 'Pala, Deepankar', 'Stucker, Brent']

2021-10-18T21:56:44Z

2014

Mechanical Engineering

null

https://hdl.handle.net/2152/89265

eng

2014 International Solid Freeform Fabrication Symposium

Open

['simulation infrastructure', 'simulation code', 'computational speed', 'metal-based additive manufacturing', '3DSIM', 'ANSYS', 'University of Louisville']

A Comparison of the Computational Speed of 3DSIM Versus ANSYS Finite Element Analyses for Simulation of Thermal History in Metal Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/e7297114-1d98-4428-b025-cd28a7cc0f22/download

University of Texas at Austin

A new simulation infrastructure for predicting the effects of changes in process parameters on mechanical properties, residual stress/strain, crystal structure, and other micro & macro features of components made using metal-based AM techniques has been developed at the University of Louisville (UofL) and is being commercialized by 3DSIM, LLC. Based upon its MatLab and Fortran code, UofL personnel predicted their multi-scale, multi-physics finite element solvers should solve for thermal history and residual stress evolution many orders of magnitude faster than competing tools while achieving better solution accuracy. In order to test this contention, a series of computational experiments were designed to benchmark the performance of the code being commercialized by 3DSIM against a well-respected simulation tool, ANSYS. The results of these initial studies indicate the 3DSIM architecture is significantly faster than ANSYS for simulating metal-based AM processes.

null

['Yang, Yu', 'Obahor, Omoghene Osaze', 'Bao, Yaxin', 'Sparks, Todd E.', 'Ruan, Jianzhong', 'Stroble, Jacquelyn Kay', 'Landers, Robert', 'Newkirk, Joseph', 'Liou, Frank']

2020-03-02T15:20:25Z

9/14/06

Mechanical Engineering

null

['https://hdl.handle.net/2152/80131', 'http://dx.doi.org/10.26153/tsw/7152']

eng

2006 International Solid Freeform Fabrication Symposium

Open

Laser Flash

Comparison of Thermal Properties of Laser Deposition and Traditional Welding Process via Thermal Diffusivity Measurement

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f388914f-ad1f-4766-bfa3-ecee9ac4f4eb/download

null

Laser deposition is an effective process for mold and die repair. In order to improve the part repair qualityˈthe process impact on thermal diffusivity and thermal conductivity needs to be understood for laser deposited, welded and virgin H13. In this paper, H13 tool steel samples were made by laser deposition, welding and virgin H13 and then cut into pieces. Experiments were conducted to investigate the thermal diffusivity and conductivity. A laser flash method is used to test these samples. The future work and opportunities are also summarized.

null

['Loeber, L.', 'Biamino, S.', 'Ackelid, U.', 'Sabbadini, S.', 'Epicoco, P.', 'Fino, P.', 'Eckert, J.']

2021-10-05T14:24:15Z

2011

Mechanical Engineering

null

['https://hdl.handle.net/2152/88377', 'http://dx.doi.org/10.26153/tsw/15316']

eng

2011 International Solid Freeform Fabrication Symposium

Open

['selective laser melting', 'electron beam melting', 'titanium aluminides']

Comparison off Selective Laser and Electron Beam Melted Titanium Aluminides

Conference paper

https://repositories.lib.utexas.edu//bitstreams/03ec721a-a0bf-48bf-afb6-d0f66135474e/download

University of Texas at Austin

In the following paper we present the investigation of microstructure and mechanical properties produced by selective laser melting (SLM) and electron beam melting (EBM). The chosen alloy is a Ti-(46- 48)Al-2Cr-2Nb alloy which has a great potential in replacing heavy weight Ni-base superalloys in turbine blades. Cylindrical specimens were produced and characterized by optical microscopy (OM), scanning electron microscopy (SEM) and chemical analysis to determine the microstructure and composition. In addition compression tests at room and elevated temperatures (700-800 °C) were carried out to identify the mechanical properties of the alloy.

null

['Dai, Kun', 'Li, Xiaoxuan', 'Shaw, Leon L.']

2019-11-20T16:30:55Z

2003

Mechanical Engineering

null

['https://hdl.handle.net/2152/78474', 'http://dx.doi.org/10.26153/tsw/5559']

eng

2003 International Solid Freeform Fabrication Symposium

Open

Thermal Modeling

Comparisons Between Thermal Modeling and Experiments in Laser-Densified Dental Powder Bodies

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ec597b85-4168-4b5c-a8b3-b8da0ab63b0e/download

null

A three-dimensional thermal finite element model including the effect of the powder-tosolid transition has been developed to investigate the transient temperature distribution during laser densification of dental powder bed for the layer-by-layer fabrication. The model encompasses the effects of the temperature- and porosity-dependent thermal conduction and radiation as well as the temperature-dependent natural convection. The simulation result is compared with the experiments which establish the temperature dependence of the dental porcelain microstructure and utilize this dependence to construct the temperature distribution profile. It is found that the trend of the simulation result matches the experiments very well.

The authors gratefully acknowledge financial support provided by the National Science Foundation under Grant Nos: DMI-9908249 and DMI-0218169.

null

['Fearon, E.', 'Watkins, K. G.']

2020-02-14T15:50:03Z

8/31/04

Mechanical Engineering

null

['https://hdl.handle.net/2152/79988', 'http://dx.doi.org/10.26153/tsw/7013']

eng

2004 International Solid Freeform Fabrication Symposium

Open

Direct Laser Deposition

Compensation for Uneven Surfaces When Building Laser Deposited Structures

Conference paper

https://repositories.lib.utexas.edu//bitstreams/46187ee2-951e-413e-82ee-d634d4837d3b/download

null

Direct Laser Deposition (DLD) is a blown-powder laser deposition process that can be used to quickly produce, modify or repair fully-dense metallic parts by a layered manufacturing method. However, uneven substrate surfaces often cause variation in the deposited layer which is magnified by succeeding layers. Research carried out at the University of Liverpool has resulted in a non-feedback layer height controlling process based on controlling the shape of the powder streams emitted from a four-port side feed nozzle. This method limits deposited layer height by causing a sharp reduction of catchment efficiency in the vertical plane at a fixed distance from the powder feed nozzle, and is therefore capable of depositing a consistent layer height in spite of power, powder flow or process velocity variation. This paper demonstrates how this method of layer height control can compensate for irregular substrate surfaces in the production of accurate DLD parts.

null

['Manetsberger, K.', 'Shen, J.', 'Muellers, J.']

2019-10-18T15:25:53Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76238', 'http://dx.doi.org/10.26153/tsw/3327']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Polymer

Compensation of Non-Linear Shrinkage of Polymer Materials in Selective Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5f3cc1c7-17b7-4eb4-9cc0-b06ad23cf663/download

null

Inaccuracies in the selective laser sintering (SLS) process using polymer materials are typically caused by inhomogeneous shrinkage due to inhomogeneous temperature distribution in the powder bed of the SLS machine. These shrinking effects lead to stress in the sintered parts, causing the part to distort. The inhomogeneous shrinkage of benchmark parts has been compensated empirically in a former work. The results cannot been transferred to all geometries, because each geometry requires a specific temperature for laser sintering and, thus, has its own related shrinkage distribution. In a new theoretical approach, shrinkage behavior is to be integrated in a thermal simulation of the SLS process and the thermal shrinkage calculated prior to the building process. In the following, experimental data of the temperature- and pressuredependent shrinkage of laser-sintered powder samples is presented. Possible theories for a physical model of thermal shrinkage are discussed. In particular, these models have to consider granular characteristics such as internal friction, particle sliding, and powder compaction.

null

['Limaye, Ameya', 'Rosen, David W.']

2020-02-21T20:56:14Z

8/26/05

Mechanical Engineering

null

['https://hdl.handle.net/2152/80071', 'http://dx.doi.org/10.26153/tsw/7092']

eng

2005 International Solid Freeform Fabrication Symposium

Open

Mask Projection Stereolithography

Compensation Zone Approach to Avoid Z Errors in Mask Projection Stereolithography Builds

Conference paper

https://repositories.lib.utexas.edu//bitstreams/49b18c6d-d459-446a-bf7a-b3b56cb62f95/download

null

Print-through results in unwanted polymerization occurring beneath a part cured using Mask Projection Stereolithography (MPSLA) and thus creates error in its Z dimension. In this paper, the "Compensation zone approach" is proposed to avoid this error. This approach entails modifying the geometry of the part to be cured. A volume (Compensation zone) is subtracted from underneath the CAD model in order to compensate for the increase in the Z dimension that would occur due to Print-through. Three process variables have been identified: Thickness of Compensation zone, Thickness of every layer and Exposure distribution across every image used to cure a layer. Analytical relations have been formulated between these process variables in order to obtain dimensionally accurate parts. The Compensation zone approach is demonstrated on an example problem.

null

['Zhang, Meng', 'Sun, Chen-Nan', 'Zhang, Xiang', 'Chin Goh, Phoi', 'Wei, Jun', 'Li, Hua', 'Hardacre, David']

2021-11-02T15:28:25Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89829

eng

2017 International Solid Freeform Fabrication Symposium

Open

['fatigue', 'porosity', 'microstructure', 'powder bed fusion', 'selective laser melting', 'stainless steel 316L']

Competing Influence of Porosity and Microstructure on the Fatigue Property of Laser Powder Bed Fusion Stainless Steel 316L

Conference paper

https://repositories.lib.utexas.edu//bitstreams/48e8051a-eb95-4ff1-9205-12cfdc4be7d2/download

University of Texas at Austin

Crack initiation constitutes a large portion of the total life for parts under high cycle fatigue loading. Materials made by the laser powder bed fusion (L-PBF) process contain unavoidable process-induced porosity whose effect on the mechanical properties needs to be considered for fatigue applications. Results from this work show that not all pores in L-PBF parts promote fatigue crack initiation. The length scale of local microstructure defects, i.e. grain boundary, could be larger than the pores and in such cases they are the primary cause for crack initiation. Samples were produced in this work to demonstrate the critical defect size responsible for the transition between the porosity-driven and microstructure-driven failure modes.

null

['Morris, S.J.', 'Dudman, J.P.R.', 'Körner, L.', 'Melo, P.', 'Newton, L.H.', 'Clare, A.T.']

2021-11-01T22:48:11Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89787

eng

2016 International Solid Freeform Fabrication Symposium

Open

['advanced surfaces', 'complex functional surface', 'additive manufacturing', 'methodology']

Complex Functional Surface Design for Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/cfbd5bdd-88b8-423d-ad13-fdd5d2009341/download

University of Texas at Austin

This paper presents a new methodology for the creation of advanced surfaces which can be produced by Additive Manufacturing (AM) methods. Since there is no cost for enhanced complexity, AM allows for new capabilities in surface design. Micro-scale surface features with varying size, shape and pitch can be manufactured by Two-Photon Polymerisation (2PP). Computer-Aided Design (CAD) tools allowing for this variation to be incorporated into the surface design are only just emerging. With the presented methodology, surfaces are created from a single feature design. Variation is applied to the surface features through algorithmic design tools, allowing for arrays of hundreds of unique features can be created by non-CAD experts. The translation of these algorithmic expressions from CAD to a physical surface is investigated. Using the proposed methodology, 2PP is used to create quasi stochastic surfaces for the purpose of enhancing the biointegration of medical implants against current state-of-the-art.

null

['Li, Longmei', 'Bellehumeur C., Sun', 'Gu, P.']

2019-10-10T17:01:54Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76173', 'http://dx.doi.org/10.26153/tsw/3262']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Modeling

Composite Modeling and Analysis of FDM Prototypes for Design and Fabrication of Functionally Graded Parts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/aad86b09-ab35-4444-8869-707364c683f1/download

null

Solid Freeform Fabrication technologies have potential to manufacture parts with locally controlled properties (LCP), which would allow concurrent design of part’s geometry and desired properties. To a certain extent, Fused Deposition Modelling (FDM) has the ability to fabricate parts with LCP by changing deposition density and deposition orientation. To fully exploit this potential, this paper reports a study on the mechanical properties of FDM prototypes, and related materials and fabrication process issues. Both theoretical and experimental analyses of mechanical properties of FDM parts were carried out. To establish the constitutive models, a set of equations is proposed to determine the elastic constants of FDM prototypes. An example is provided to illustrate the model with LCP using FDM.

The financial support for this research was provided by the National Sciences and Engineering Research Council of Canada (NSERC) through Research Grant OGP0192173.

null

['Gervasi, V.R.', 'Crockett, R.S.']

2019-03-01T17:41:46Z

1998

Mechanical Engineering

null

['https://hdl.handle.net/2152/73520', 'http://dx.doi.org/10.26153/tsw/670']

eng

1998 International Solid Freeform Fabrication Symposium

Open

['gradient materials', 'stereolithography']

Composites with Gradient Properties From Solid Freeform Fabrication

Conference paper

https://repositories.lib.utexas.edu//bitstreams/69a55609-9615-40ad-a3e8-599589580d87/download

null

TetraCast is a build style developed by Milwaukee School ofEngineering involving stereolithography patterns produced with an open cellular structure inside a surface shell. Composites are created using this pattern as a host fora filler material, generally epoxy matrices loaded with various fibers or microspheres. Regions within a singleobjectrrray be separated by thin barriers, allowing filling with different matrix materials.to create regiollsof differing.local properties. The internal structure can also be continually graded in thickness to prodUl::e composites with properties ranging from that ofthe fillermaterial to that ofthe TetraCast material (currently stereolithography epoxy or FDM ABS)

null

['Murphy, D.', 'Fashanu, O.', 'Spratt, M.', 'Newkirk, J.', 'Chandrashekhara, K.']

2021-11-30T21:10:20Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90551', 'http://dx.doi.org/10.26153/tsw/17470']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['selective laser melting', 'AlSi10Mg', 'compression', 'bending', 'tension']

Compressive and Bending Performance of Selectively Laser Melted AlSi10Mg Structures

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a9e08dbc-8f5e-4fd8-8cfd-f8f2c6a2b4e0/download

University of Texas at Austin

Selective laser melting (SLM) is a widely used additive manufacturing technique that effectively manufactures complex geometries such as cellular structures. However, challenges such as anisotropy and mechanical property variation are commonly found due to process parameters. In a bid to utilize this method for the commercial production of cellular structures, it is important to understand the behavior of a material under different loading conditions. In this work, the behavior of additively manufactured AlSi10Mg under compression, bending, and tension loads was investigated. Vertical and horizontal build directions are compared for each type of loading. Specimens were manufactured using the reduced build volume (RBV) chamber of the Renishaw AM 250 SLM machine.

null

['Meng, Liang', 'Wang, Zemin', 'Zeng, Xiaoyan']

2021-11-30T21:48:46Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90561', 'http://dx.doi.org/10.26153/tsw/17480']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['bio-inspired structure', 'selective laser melting', 'NSGA-II', 'multi-layers']

Compressive Properties Optimization of a Bio-Inspired Lightweight Structure Fabricated via Selective Laser Melting

Conference paper

https://repositories.lib.utexas.edu//bitstreams/91484285-2bbc-473c-b8be-32195bf2c4c2/download

University of Texas at Austin

Compressive properties optimization of a bio-inspired lightweight structure is developed by Response Surface Methodology (RSM) and Non-dominated Sorting Genetic Algorithm II (NSGA-II). Multi-layered bio-inspired structures of a Ti6Al4V alloy are designed and fabricated by Selective Laser Melting. The results show that the optimized structure parameters of bio-inspired structures can be obtained by RSM and NSGA-II. The relative error rate of experimental results and response values is less than 10%. Moreover, increasing the number of layers cannot effectively improve energy absorption (EA) and specific energy absorption (SEA) for multi-layered bio-inspired structures. The damage process of bio-inspired structures with different core-arranged configurations fails layer by layer. The load-displacement curves and damage process of FE simulations are consistent with the experimental results.

null

['Hu, Yingbin', 'Wang, Hui', 'Ning, Fuda', 'Cong, Weilong', 'Li, Yuzhou']

2021-10-26T20:12:32Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89573

eng

2016 International Solid Freeform Fabrication Symposium

Open

['laser engineered net shaping (LENS)', 'TiBw reinforcement', 'titanium matrix composites (TMCs)', 'compressive properties']

Compressive Property Comparisons Between Laser Engineered Net Shaping of In Situ TiBw-TMCs and Cp-Ti Materials

Conference paper

https://repositories.lib.utexas.edu//bitstreams/83aa182d-d408-49fa-92d4-8fa8c0786e85/download

University of Texas at Austin

Titanium (Ti) and its alloys are widely used in chemical, astronautical, and biomedical industries. However, their poor load endurance properties affect their fields of applications especially under severe loading conditions. To enhance these properties, TiBw reinforcement was synthesized by in situ chemical reaction between elemental Ti and boron. Strong interfacial bonding between TiBw reinforcement and Ti matrix was obtained due to the in situ chemical reaction. Owing to its capability of producing difficult-to-machine bulk composites with uniform properties, laser engineered net shaping (LENS) technique was utilized to fabricate TiBw reinforced Ti matrix bulk composites. Few researches have been reported on these three-dimensional metal based bulk composites by using LENS. In this work, effects of TiBw reinforcement and laser power on compressive properties were investigated. The microstructures of the fabricated parts were observed and analyzed by using scanning electron microscopy.

null

['Gautam, Rinoj', 'Sridharan, Vijay Shankar', 'Teh, Wee Lee', 'Idapalapati, Sridhar']

2021-11-30T21:22:25Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90552', 'http://dx.doi.org/10.26153/tsw/17471']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['lattice structures', 'strut-reinforced kagome', 'SRK', 'ABS', 'compressive loading', 'fused deposition modeling']

Compressive Response of Strut-Reinforced Kagome with Polyurethane Reinforcement

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5ff1f2d9-5b94-4e42-a99d-213f0083a10e/download

University of Texas at Austin

Lattice structures find immense application in lightweight structures for their high specific strength, modulus, and energy absorption. Strut-reinforced Kagome (SRK) structures provide better compressive performance compared to many existing lattice structures. In this study, the performance of acrylonitrile butadiene styrene (ABS) SRK lattice structures, fabricated by fused deposition modeling, under compression loading is investigated. Further, SRK structures were filled with different polyurethane in the empty space and their effect on the compressive performance was examined. The SRK structure demonstrated abrupt failure at the joints in the vicinity of face sheet, thereby reducing the energy absorption of the structure. The SRK with flexible foam (low-density polyurethane foam) had no significant effect on peak failure load and moduli, whereas energy absorption per unit mass was higher by 16.5%. The SRK with the rigid foam (high-density foam) displayed not only the better energy absorption per unit mass (116%) but also different failure behavior than SRK only.

null

['Sereshk, Mohammad Reza Vaziri', 'Triplett, Kevin', 'St. John, Christopher', 'Martin, Keith', 'Gorin, Shira', 'Avery, Alec', 'Byer, Eric', 'St Pierre, Conner', 'Soltani-Tehrani, Arash', 'Shamsaei, Nima']

2021-11-30T21:26:43Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90553', 'http://dx.doi.org/10.26153/tsw/17472']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['mechanical properties', 'lattice structures', 'finite element method', 'laser beam powder bed fusion']

A Computational and Experimental Investigation into Mechanical Characterizations of Strut-Based Lattice Structures

Conference paper

https://repositories.lib.utexas.edu//bitstreams/61d6f7cd-0fe7-4e50-a9ad-a9d1c57e8185/download

University of Texas at Austin

Strut-based lattices are widely used in structural components for reducing weight. Additive manufacturing has provided a unique opportunity to fabricate such complex geometries. In addition to the unit cell type, the strut size and shape can significantly affect the mechanical properties achieved. Therefore, furnishing a lattice structure library may help in selecting the appropriate combination of lattice types and dimensions for targeted mechanical performance for a specific application. This study presents a method for determination of mechanical properties, including strength and stiffness, for lattice structures. Finite element (FE) simulations are used as the main tool and the results of which are to be verified by mechanical testing of samples fabricated using the laser beam powder bed fusion (LB-PBF) process. Proper lattices with the stiffness matched with associated bone were determined. However, the result indicated that lattices made from 316L SS are not strong enough for bone implants. The proposed procedure can be used for other unit cells of interest due to its generality.

null

['Das, Suman', 'Hollister, Scott J.', 'Flanagan, Colleen', 'Adewunmi, Adebisi', 'Bark, Karlin', 'Chen, Cindy', 'Ramaswamy, Krishnan', 'Rose, Daniel', 'Widjaja, Erwin']

2019-10-22T17:33:44Z

2002

Mechanical Engineering

null

['https://hdl.handle.net/2152/76321', 'http://dx.doi.org/10.26153/tsw/3410']

eng

2002 International Solid Freeform Fabrication Symposium

Open

Scaffolds

Computational Design, Freeform Fabrication and Testing of Nylon-6 Tissue Engineering Scaffolds

Conference paper

https://repositories.lib.utexas.edu//bitstreams/8288f87e-18aa-428c-a074-a7a36d780f22/download

null

Approximately 100,000 people in the US alone suffer from TMJ disease to the extent that surgical reconstruction is needed. In order to reconstruct a whole joint such as the TMJ, advanced, novel fabrication methods are needed to build complex, threedimensional scaffolds incorporating multiple, functionally graded biomaterials and porosity that will enable the simultaneous growth of multiple tissues including blood vessels. The aim of this research is to develop, demonstrate and characterize techniques for fabricating such scaffolds by combining solid freeform fabrication and computational design methods. When fully developed, such techniques are expected to enable the fabrication of tissue engineering scaffolds endowed with functionally graded material composition and porosity exhibiting sharp or smooth gradients. As a first step towards realizing this goal, we have designed and fabricated scaffolds with various architectures in Nylon-6, a biocompatible polymer using selective laser sintering. Results of biocompatibility, mechanical testing and implantation are presented.

The authors gratefully acknowledge Honeywell Plastics for a generous donation of Nylon-6 powder.

null

['Basak, Amrita', 'Acharya, Ranadip', 'Bansal, Rohan', 'Das, Suman']

2021-10-21T18:15:59Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89416

eng

2015 International Solid Freeform Fabrication Symposium

Open

['equiaxed superalloys', 'Scanning Laser Epitaxy', 'optimization', 'gas turbine']

Computational Modeling and Experimental Validation of Melting and Solidification in Equiaxed Superalloys Processed through Scanning Laser Epitaxy

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f0302416-e7a2-403c-9e8d-f173649a69e5/download

University of Texas at Austin

This paper focuses on simulation-based optimization of the Scanning Laser Epitaxy (SLE) process applied to gas turbine hot-section components made of nickel-base superalloys. SLE creates equiaxed, directionally-solidified and single-crystal microstructures from superalloy powders melted onto like-chemistry substrates using a fast scanning, high power laser beam. In this paper, a transient coupled flow-thermal approach is implemented to accurately simulate the melting and solidification process in SLE. The laser movement is modeled as a Gaussian moving heat source, and the thermophysical properties of the alloys are adjusted based on the thermal field. Simulations for different superalloys such as IN100, René 80 and MAR-M247 are performed and the instantaneous melt pool characteristics are recorded. Comparisons of the simulations with experimental results show reasonably good agreement for the melt depth. Feedback control is implemented, and demonstrated to produce superior quality SLE deposits.

This work is sponsored by the ONR through grants N00014-11-1-0670 and N00014-14-1-0658.

null

['Acharya, Ranadip', 'Bansal, Rohan', 'Gambone, Justin J.', 'Cilino, Paul', 'Das, Suman']

2021-10-06T21:38:23Z

8/22/12

Mechanical Engineering

null

['https://hdl.handle.net/2152/88452', 'http://dx.doi.org/10.26153/tsw/15389']

eng

2012 International Solid Freeform Fabrication Symposium

Open

['Scanning Laser Epitaxy', 'nickel-based superalloys', 'single-crystal structures', 'equiaxed, directionally-solidified structures', 'CMSX-4 alloy']

Computational Modeling and Experimental Validation of Microstructural Development in Superalloy CMSx-4 Processed through Scanning Laser Epitaxy

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d9fb5e6f-b2e9-40a4-9785-7d82c9473567/download

University of Texas at Austin

This paper focuses on computational modeling of Scanning Laser Epitaxy (SLE), an additive manufacturing technology being developed at Georgia Tech for the creation of equiaxed, directionally-solidified or single-crystal structures in nickel-based superalloys. The thermal modeling of the system, carried out in a commercial CFD software package, simulates a heat source moving over a powder bed and dynamically adjusts the property values for consolidating CMSX-4 alloy powder. For any given position of the beam, the geometrical parameters of and the temperature gradient in the melt pool are used to estimate the resulting solidification microstructure. Detailed study of the flow field also revealed formation of rotational vortices in the melt pool. Microstructural predictions are shown to be in good agreement with experimental metallography. This work is sponsored by the Office of Naval Research through grant N00014-11-1-0670.

null

['Zhang, Xiaobing', 'Tuffile, Charles', 'Cheng, Bo']

2021-11-18T17:47:05Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90445', 'http://dx.doi.org/10.26153/tsw/17366']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['selective laser melting', 'SLM', 'computational fluid dynamics', 'CFD', 'discrete phase method', 'DPM', 'gas flow', 'spatter']

Computational Modeling of the Inert Gas Flow Behavior on Spatter Distribution in Selective Laser Melting

Conference paper

https://repositories.lib.utexas.edu//bitstreams/74fb6b05-5f1e-4e86-bac6-535f5eb91df3/download

University of Texas at Austin

In the selective laser melting (SLM) process, the spatter, introduced by moving melt pools, can contaminate the build region and potentially reduce the part quality. A well-designed inert gas flow system can help to effectively remove the process emissions. Therefore, it is critical to understand the flow characteristics as well as the interactions between gas flow and spatter. In this study, a Computational Fluid Dynamics (CFD) model for the SLM gas flow system has been developed to simulate the complicated flow behavior in the chamber. The generation of spatter over the build region has been simulated by a discrete phase model (DPM). The Eulerian-Lagrangian modeling technique has been applied to accurately capture the influence of gas flow on ejected spatter. The process variables that can significant affect the gas flow efficiency in the chamber, such as inlet design, volume flow rate and material property, have been numerically investigated.

null

['Rosser, J.', 'Megahed, M.', 'Mindt, H.-W.', 'Brown, S.G.R.', 'Lavery, N.P.']

2021-11-18T17:11:02Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90432', 'http://dx.doi.org/10.26153/tsw/17353']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['line tracks', 'laser tracks', 'IN625', 'laser powder bed fusion']

Computational Modelling and Experimental Validation of Single In625 Line Tracks in Laser Powder Bed Fusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/e41c0b80-19d4-48ac-8ea2-fa6ff662d859/download

University of Texas at Austin

Laser track experiments are performed using INCONEL® nickel-based powder alloy, IN625, in a Powder Bed Fusion (PBF) system. Optical microscopy is used to obtain key track dimensions and morphology for various machine parameters, allowing direct validation of ESI Group’s ICME suite of tools for modelling AM. The high-fidelity powder bed model simulates the melt pool formation based on solution of the Navier-Stokes equations and heat transfer, radiative powder-laser interaction, phase change, surface tension, Marangoni forces and recoil pressure. Models are enhanced by measured thermophysical material properties. Validation of the solidified melt geometry showing that conductive mode melting and instabilities such as balling can be captured with existing models and pave the way for models which capture the onset of keyholing. Examination of the melt track microstructures can also be used to determine local cooling rates, granting insight into the phase evolution differences between the alloys.

null

['Gwynn, Daniel', 'Gundimeda, Sree Samhita', 'Menon, Nandana', 'Basak, Amrita']

2023-01-26T15:02:22Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117314', 'http://dx.doi.org/10.26153/tsw/44195']

deu

2022 International Solid Freeform Fabrication Symposium

Open

Additive manufacturing

A Computational Study Summarizing the Effects of Composition on the Melt Pool Geometry in Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/08d71bf5-38d0-4eea-a9bf-37be567c19f2/download

null

Thermophysical properties play a crucial role in controlling the melt pool dimensions in metal additive manufacturing (AM). It is, therefore, imperative to understand the impact of thermophysical properties on the melt pool dimensions for critical materials such as nickel-based superalloys. In this paper, a three-dimensional analytical model is used to predict the steady-state melt pool dimension over a range of process parameters for several nickel-based superalloys. The effects of composition, in terms of the thermophysical properties, on the melt pool dimensions are also studied. The results show that the melt pool dimensions correlate well with the liquidus temperature, density, and thermal conductivity of the alloy. By exploring the impact of process parameters and compositions on the melt pool dimension evolution, a framework can be established to maintain the desired melt pool dimensions during the fabrication of functionally- graded parts with different alloys belonging to the same material class. 

null

['Kelly, Brett E.', 'Bhattacharya, Indrasen', 'Shusteff, Maxim', 'Taylor, Hayden K.', 'Spaddacini, Christopher M.']

2021-11-02T20:41:27Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89892

eng

2017 International Solid Freeform Fabrication Symposium

Open

['computed axial lithography', '3D parts', 'additive manufacturing']

Computed Axial Lithography for Rapid Volumetric 3D Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/075a1deb-26f8-43ba-ab04-0d6637aa873e/download

University of Texas at Austin

The vast majority of additive manufacturing processes today operate by printing voxels serially point-by-point to build up a 3D part. In some higher throughput techniques, for example optical printing methods such as projection stereolithography [1], [2], parts are printed layer-by-layer by curing full 2D (very thin in one dimension) layers of the 3D part in each print step. In this work, we demonstrate a new technique which prints entire parts all at once and eliminates layering. The approach, termed Computed Axial Lithography (CAL), is based on tomographic reconstruction, with mathematical optimization to generate a set of projections to optically define an arbitrary dose distribution within a target volume and to cure the entire volume simultaneously. Volume-at-once fabrication of complex geometries is achieved using a custom system built from a DLP projector and a rotating resin volume. This technique can be used to expand the range of printable geometries in additive manufacturing and relax constraints on factors such as overhangs in topology optimization. The method also vastly increases print speed for 3D parts. We show complex and overhanging geometries printed in situ without layering.

null

['Isanaka, Sriram Praneeth', 'Sridhar, Amar Bala', 'Liou, Frank', 'Newkirk, Joseph W.']

2021-09-30T18:53:13Z

9/23/10

Mechanical Engineering

null

['https://hdl.handle.net/2152/88278', 'http://dx.doi.org/10.26153/tsw/15219']

eng

2010 International Solid Freeform Fabrication Symposium

Open

['metal deposition', 'deposit contouring', 'coordinate measurement', '3D scanning', 'curve fitting', 'contact angle', 'ripple effect']

Computer Aided Contour Profiling of High Strength Deposits

Conference paper

https://repositories.lib.utexas.edu//bitstreams/183559fd-b5c4-464e-8364-b0ee2217acef/download

University of Texas at Austin

Additive manufacturing processes suffer from the effect of ripples, edge rounding and surface variations. To reduce their effect, ideal process parameters for the laser deposition process were investigated. Also, a new method was identified to analyze deposits by accurately plotting their contours. This was achieved through point cloud data of the deposits generated using coordinate measurement and 3D scanning. Curve fitting was performed on the data in Matlab to generate the contours of the deposit. The intercept values, heights, and contact angle of the curves give an indication of the uniformity of deposits and aid in reducing defects.

null

Crawford, Richard H.

2018-05-03T17:42:34Z

1993

Mechanical Engineering

doi:10.15781/T2VM43F32

http://hdl.handle.net/2152/65046

eng

1993 International Solid Freeform Fabrication Symposium

Open

['Department of Mechanical Engineering', 'SFF', 'Three Dimensional Printing', 'geometric models']

Computer Aspects of Solid Freeform Fabrication: Geometry, Process Control, and Design

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ebff9bda-ddd3-400b-abdd-a807e75c64ee/download

null

Solid Freefonn Fabrication (SFF) is a class of manufacturing technologies aimed at the production of mechanical components without part-specific tooling or process planning. Originally used for creating modelsfor visualization, many industrial users of SFF technologies are realizing the greater potentialofSFF as legitimate manufacturing processes for producing patterns and, in some cases, functional.parts. Thus, SFF is becoming an important aspect of the product realization process in these industries. Solid Freefonn Fabrication arose from the dream of "push-button" prototyping, in which solid reproductions of three-dimensional geometric models are created automatically under computer control. Perhaps more than any other class of manufacturing technologies, computer software development has been an integral part of the emergence of SFF. As SFF technologies evolve toward the ability to create functional parts, computer issues gain more importance. This paper discusses three aspects of software design for SFF: processing of geometric data, global and local control of SFF processes, and computer-based analysis and design for SFF manufacturing. The discussion of geometric processing issues focuses on accuracy and completeness of input models, and the algorithms required to process such models. The interplay between the physics of SFF processing and the desired output geometry is discussed in terms of the development of model-based control algorithms for SFF. These two areas, geometric processing and control, are necessary for the practical implementation of any SFF technology. However, for SFF to realize its potential as an alternative for manufacturing functional parts, engineers must be provided with analysis and design tools for predicting mechanical properties, ensuring dimensional accuracy, choosing appropriate materials, selecting process parameter values, etc. For each of these three different but related areas of software design, the state-of-theart is assessed, contemporary research is summarized, and future needs are outlined.

null

['Mohebi, Masoud M.', 'Yang, Shoufeng', 'Evans, Julian R. G.']

2020-03-02T15:36:48Z

2006

Mechanical Engineering

null

['https://hdl.handle.net/2152/80135', 'http://dx.doi.org/10.26153/tsw/7156']

eng

2006 International Solid Freeform Fabrication Symposium

Open

Solid freeforming

Computer Generation of Metal Components by Simultaneous Deposition of Mould, Cores and Part

Conference paper

https://repositories.lib.utexas.edu//bitstreams/03c936a0-e214-41da-9936-d9976d0a61f7/download

null

A new solid freeforming method based on co-delivery of mould powder materials and part powder materials using vibration-controlled, dry powder valves is presented in this paper. Thin layers of stainless steel powder are delivered to the forming area according to the cross-section of the CAD file to produce the component. Mould powder which has low sinterability is delivered to the non-forming areas of the same layer. All powders are delivered by computer-controlled, acoustic powder valves. The flow rate and switching of the valves provides the composition and shape control during fabrication. The stacked layers of loose powder are then sintered in a conventional furnace. The mould materials are removed after sintering. This method avoids the high thermal stress problem in selective laser sintering, avoids high capitalisation, makes use of conventional furnaces and allows for the incorporation of three dimensional function gradients. Test pieces including step wedge and Spierpinski’s cube were fabricated. Advantages, limitations and problems are discussed.

null

['Wang, Jia-Chang', 'Wang, Jun-Ming', 'Lin, Tsung Te', 'Jeng, Jeng-Ywan']

2019-10-18T16:00:33Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76244', 'http://dx.doi.org/10.26153/tsw/3333']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Adaptive Slicing

Computer Integrated Adaptive Slicing and Vision Technologies for High Performance Rapid Prototyping System

Conference paper

https://repositories.lib.utexas.edu//bitstreams/26e08cf1-98fe-4e8e-92ec-f3add531fcf6/download

null

This paper discusses the application of adaptive slicing algorithm and computer vision technology on Rapid Prototyping (RP) system to enhance fabrication performance of Model Maker (MM) RP system. Usually, the layer number determines the RP system performance in terms of fabrication time and accuracy. In this research, a new practically adaptive slicing algorithm is developed and easily implemented for RP system, because it only recalculates the scanning path according to the criterion of adjacent profile variation. The experimental results of the proposed adaptive slicing algorithm show that saving of 54% fabrication time is achieved and the model accuracy is still remained in the same level. MM presents a problem of stability because of a tiny nozzle. Computer vision technology is employed in this paper to on line inspect the layer accuracy and defect of a model fabricated by RP system. The results of vision inspection is used to close-loop monitor the process to increase the processing stability and accuracy. These new practically adaptive slicing algorithm and machine vision technology are implemented in the commercial Model Maker (MM) RP system to increase its fabrication speed, accuracy and stability, but not accuracy sacrifice. Hence, the performance of the MM RP system can be significantly enhanced using vision and practically adaptive slicing techniques.

The support of this research by the National Science Council of Taiwan, ROC under grant NSC-88-2212-E-011-026.

null

['Reiher, T.', 'Vogelsang, S.', 'Koch, R.']

2021-11-02T20:34:53Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89890

eng

2017 International Solid Freeform Fabrication Symposium

Open

['geometry generation', 'computer integration', 'CAD system', 'optimization', 'additive manufacturing']

Computer Integration for Geometry Generation for Product Optimization with Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/477f6543-9156-4506-9288-f0647892bc53/download

University of Texas at Austin

Designing parts for additive manufacturing (AM) offers a broad range of geometrical and functional potentials. On the one hand the manufacturing technology offers the possibility of manufacturing highly complex freeform shapes, often referred to as bionic shapes. By use of these, perfect force fluxes without stress risings due to imperfect notches are realizable, getting the most value of used material. On the other hand these complex structures require a reliable geometry representation in compatible CAD-files. Conventional CAD systems were developed to generate geometries that are manufacturable with conventional machining. These are not capable of representing the high complex designs for AM. Especially for geometries generated by CAE like from topology optimization the conventional CAD systems fail to take advantage of the combination of CAE and AM. This paper explains why there is a lack of compatibility of well-known CAD systems with the potentials of AM. Therefore the AM-side of the problem is described by showing some potentials of AM and the need of high complex structures for this manufacturing technology. For the other side of the problem conventional methodologies for geometry representation of CAD systems are described and their limitations with regard to AM are worked out. Finally a voxel based geometry representation is presented as a solution for computer aided geometry generation of high complex AM–structures.

null

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

2018-04-12T17:18:53Z

1990

Mechanical Engineering

doi:10.15781/T2MC8S000

http://hdl.handle.net/2152/64268

eng

1990 International Solid Freeform Fabrication Symposium

Open

['Department of Chemical and Materials Engineering', 'Rapid Prototype Development Laboratory', 'Center for Basic and Applied Polymer Research']

A Computer Model for Laser Photopolymerization

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5ec0f045-a8a1-49c2-93b0-13c4008a984a/download

null

A computer model for a laser induced photopolymerization process has been established which simulates stereolithography. The model couples irradiation, chemical reaction, and heat transfer equations to provide insights into rate processes occurring in the volume element contacted by the laser beam. Quantities predicted include the spatial variation in conversion of monomer to polymer, depletion of photoinitiator, and local variations in temperature in and around the spot contacted by the laser. This allows predictions to be made about the laser dwell time, depth penetration and uniformity of the photopolymer formed in the process.

null

['Bernard, Alain', 'Davillerd, Stephane', 'Sidot, Benoit']

2019-03-11T16:49:23Z

1999

Mechanical Engineering

null

['https://hdl.handle.net/2152/73584', 'http://dx.doi.org/10.26153/tsw/726']

eng

1999 International Solid Freeform Fabrication Symposium

Open

['CAD', '3D-laser sensor']

Computer-Aided Process Planning for automatic generation of 3D digitizing process for laser sensors

Conference paper

https://repositories.lib.utexas.edu//bitstreams/caaad483-ba71-4ddd-aa85-24790db64965/download

null

This paper introduces some results of a research work carried out on the automation of digitization process ofcomplex parts using a precision 3D-laser sensor. It will be presented a new way to scan automatically a complex 3-D part in order to measure and to compare the acquired data with the reference CAD model. Due to the fact that rapid prototyping processes do not allow the direct manufacturing of high precision parts, it is very often necessary to measure a first partin orderto modify the process parameters. After introducing the digitization means, basedona CMM machine and a plane laser sensor, the simulation environment will be presented as adapted for simulation and validation of 3D-laser scanning paths. The CAPP (Computer Aided Process Planning) system used for the automatic generation·of the laser scanning process will also be introduced. Keywords: scanning process simulation, inspection, optimization

null

['Xiong, Yi', 'Dharmawan, Audelia Gumarus', 'Tang, Yunlong']

2021-11-18T16:46:36Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90423', 'http://dx.doi.org/10.26153/tsw/17344']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['process planning', 'directed energy deposition', 'knowledge-based engineering', 'design for additive manufacturing']

Computer-Aided Process Planning for Wire Arc Directed Energy Deposition

Conference paper

https://repositories.lib.utexas.edu//bitstreams/13ca29d4-c582-4d6a-8478-a441fb7027c9/download

University of Texas at Austin

Wire arc directed energy deposition provides a rapid and cost-effective method for fabricating low-to-medium complexity and medium-to-large size metal parts. However, the complex nonequilibrium phase transformations, inherent to this process, make it a challenging task to produce consistent and high-quality parts, especially for parts with materials or geometries that have not been manufactured before. This study outlines a holistic and data-centric computer-aided process planning framework utilizing a knowledge base to assist engineers in selecting optimal process parameters that reduce dimensional deviations, and therefore to obtain near-net-shape parts using directed energy deposition only. The knowledge base has a data-knowledge-service architecture and is proposed to synthesize information from various sources, e.g., characterization tests. Based on these collected data, several knowledge representations, including database, metamodels, and planning rules, are constructed to support decision-making in the process planning. The proposed framework is demonstrated in the fabrication of components from industrial applications.

null

['Cima, M.J.', 'Sachs, E.', 'Cima, L.G.', 'Yoo, J.', 'Khanuja, S.', 'Borland, S.W.', 'Wu, B.', 'Giordano, R.A.']

2018-10-03T15:25:24Z

1994

Mechanical Engineering

doi:10.15781/T2959CS8Q

http://hdl.handle.net/2152/68644

eng

1994 International Solid Freeform Fabrication Symposium

Open

['Microstructures', '3D Printing', 'Solid free-form fabrication']

Computer-derived microstructures by 3D Printing: Sio- and Structural Materials

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d9cbed21-790b-4677-8490-1af1aa108dcf/download

null

3D Plinting is a rapid prototyping technique to manufacture functional components directly from computer models. The process involves spreading the powder in thin layers and then selective binding of the powder using a technology similar to ink-jet ptinting. Layers are added sequentially until a part is completed. 3DP has been used to make complex-shaped components from several monolithic matetials, including cOlnponents for use in structural applications. This paper focuses, however, on the ability to control microstlucture and local composition by 3DP. We envision cases where cOlnputer delived-microstructlu'es can be created by approptiate control of the ptinting paralneters. Thus, one can build components with the desired microstlucture independent of the complexity of the desired shape. Examples for both structural matetials and biomedical devices are discussed.

null

Thompson, Scott M.

2021-11-16T15:43:56Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90319', 'http://dx.doi.org/10.26153/tsw/17240']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['design for additive manufacturing', 'education', 'training', 'conceptual design']

Conceptual Design for Additive Manufacturing: Lessons Learned from an Undergraduate Course

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c58786fc-f646-4e80-b22d-81c2bc03dd70/download

University of Texas at Austin

Design for additive manufacturing (DfAM) guidelines continue to emerge and evolve as various additive manufacturing (AM) technologies, and the knowledge of their associated end-users/designers, matures. This work summarize important pedagogical and technical lessons learned from the conceptual re-design of several, diverse parts/assemblies submitted by ~50 undergraduate students cognizant of recent DfAM strategies and guidelines. All students were enrolled in a traditional, semester-long metals AM course designed by the author herein. Students were instructed to select an existing, metallic product and provide a conceptual redesign of that product for subsequent, effective laser-powder bed fusion (L-PBF). Students were instructed that the redesigned concept should have enhanced functionality/specifications and consist of features (e.g. thin walls, bore diameters, etc.) that can be fabricated with minimal risk via current L-PBF systems. The presented results include the types of parts that attract an ‘AM redesign’ effort and the most popular AM-enabled detailed design decisions made. To encourage a more detail-inspired design, DfAM topics were presented ‘backwards’; from post-manufacturing considerations to conceptual design while considering emerging design rules and heuristics. Results indicate that students can become preoccupied with DfAM rules to a point where the design failure modes are not properly accounted for.

null

['Yang, S.', 'Zhao, Y.F.']

2021-11-01T20:42:42Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89740

eng

2016 International Solid Freeform Fabrication Symposium

Open

['assembly-level DFAM', 'conceptual design', 'additive manufacturing', 'functional design', 'FBS modeling']

Conceptual Design for Assembly in the Context of Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/e552f158-8b8b-44ac-aa73-92636b7d935a/download

University of Texas at Austin

As additive manufacturing (AM) emerges as an end-of-use product manufacturing process, design for additive manufacturing (DFAM) as a new design philosophy receives more and more attention. However, current DFAM research focuses on downstream and part-level design activities such as structural optimization and design rules. Design freedom enabled by AM such as, part consolidation and function integration has not been fully investigated. These design freedom forces designers to rethink about assembly-level design so as to embrace integrated functionality. To understand how to integrate AM characteristics into design process, three questions are investigated: 1) why does conceptual design need to be redone for assembly? 2) what has changed by AM in design concept generation? 3) how to do conceptual design in AM context? Afterwards, a conceptual design framework is proposed to aid design flow management. In the end, a throttle pedal redesign case is demonstrated as verification of the proposed design framework.

null

['Gobert, Christian', 'Arrieta, Edel', 'Belmontes, Adrian', 'Wicker, Ryan B.', 'Medina, Francisco', 'McWilliams, Brandon']

2021-11-16T16:12:15Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90329', 'http://dx.doi.org/10.26153/tsw/17250']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['machine learning', 'additive manufacturing', 'conditional generative adversarial networks', 'in-situ monitoring']

Conditional Generative Adversarial Networks for In-Situ Layerwise Additive Manufacturing Data

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a2948b08-58a6-490a-a826-bb4a20d9f4d0/download

University of Texas at Austin

Conditional generative adversarial networks (CGANs) learn a mapping from conditional input to observed image and perform tasks in image generation, manipulation and translation. In-situ monitoring uses sensors to obtain real-time information of additive manufacturing (AM) processes that relate to process stability and part quality. Understanding the correlations between process inputs and in-situ process signatures through machine learning can enable experimental-driven predictions of future process inputs. In this research, in-situ data obtained during a metallic powder bed fusion AM process is mapped with a CGAN. A single build of two turbine blades is monitored using EOSTATE Exposure OT, a near-infrared optical tomography system of the EOS M290 system. Layerwise images generated from the in-situ monitoring system were paired with a conditional image that labeled the specimen cross-section, laser-scan stripe overlap and z-distance to part surfaces. A CGAN was trained using the turbine blade data set and employed to generate new in-situ layerwise images for unseen conditional inputs.

null

['Gibbons, D.W.', 'Ko, H.']

2021-12-01T22:13:55Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90635', 'http://dx.doi.org/10.26153/tsw/17554']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['configuration control', 'additive manufacturing', 'digital twins']

Configuration Control for Additive Manufacturing Digital Twins

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3e8d0dd2-ea51-4d00-8ecf-938161d2a135/download

University of Texas at Austin

The additive manufacturing workflow is a ductile entity, often varying depending on the design, the product, the process, the material, and the application. Information models and schemas have been developed that can provide structure to data and information throughout the workflow. The result has been a well-characterized outline of an additive manufacturing digital thread. However, implementation-specific details are often missing from these characterizations, creating challenges in establishing part-specific workflows necessary for product configuration control and management. While software vendors are increasingly filling this gap, a software-agnostic workflow is yet to be defined. This paper investigates the additive manufacturing workflow and establishes the fundamentals of a standardized, configuration-control approach including formats and interoperability while addressing versioning, digital rights, and ownership.

null

['Hopkinson, Neil', 'Dickens, Phill']

2019-09-23T17:09:49Z

2000

Mechanical Engineering

null

['https://hdl.handle.net/2152/75976', 'http://dx.doi.org/10.26153/tsw/3075']

eng

2000 International Solid Freeform Fabrication Symposium

Open

Sintered

Conformal Cooling and Heating Channels using Laser Sintered Tools 490

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6771c526-9d82-4307-be58-022cd63dcfd9/download

null

The EOS Direct Metal Laser Sintering (DMLS) and DTM Rapid Steel 2 processes may be used to create tools incorporating conformal channels behind the tool surface through which fluids may be passed. To date, a significant amount of work has been carried out to investigate the efficiency of using conformal channels to cool tools. This work suggests the use of conformal channels to both cool and heat a single tool. This may appear self-defeating at first but the selective nature by which conformal channels may make this a worthwhile means of generating hitherto unavailable thermal conditions within a tool. Such conditions may then allow the successful production of geometries which had previously been impossible to mould.

null

['Nguyen, Jason', 'Park, Sang-In', 'Rosen, David W.', 'Folgar, Luis', 'Williams, James']

2021-10-05T15:58:51Z

2012

Mechanical Engineering

null

['https://hdl.handle.net/2152/88400', 'http://dx.doi.org/10.26153/tsw/15339']

eng

2012 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'Conformal Lattice Structures', 'computer-aided design', 'stress distributions', 'heuristic', 'Micro Air Vehicle']

Conformal Lattice Structure Design and Fabrication

Conference paper

https://repositories.lib.utexas.edu//bitstreams/446e81f5-c1a0-4631-af72-897a0d6cf767/download

University of Texas at Austin

One application of additive manufacturing is for fabrication of customized, light-weight material called Conformal Lattice Structures (CLS), a type of cellular structure with dimensions of 0.1 to 10 mm. In this paper, two advances are reported for designing CLS. First, computer-aided design technologies were developed for efficiently generating and representing CLS, given selected part model surfaces. Second, a method is presented for efficiently optimizing CLS by utilizing a heuristic that reduces the multivariate optimization problem to a problem of only two variables. The heuristic is: stress distributions are similar in CLS and in a solid body of the same shape. Software will be presented that embodies this process and is integrated into a commercial CAD system. In this paper, the method is applied to design strong, stiff, and light-weight Micro Air Vehicle (MAV) components.

null

['Hayasi, Mohammad', 'Asisbanpour, Bahram']

2021-10-06T21:12:35Z

8/15/12

Mechanical Engineering

null

['https://hdl.handle.net/2152/88445', 'http://dx.doi.org/10.26153/tsw/15382']

eng

2012 International Solid Freeform Fabrication Symposium

Open

['sloped-edge adaptive slicing', '5-axis cutting', 'rapid functional part fabrication', 'rapid tooling', 'fully dense freeform fabrication (FDFF)']

Conformed-to-CAD Design Sloped-Edge Adaptive Splicing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d50a515a-c02d-4fc8-8781-6a4c81d8e943/download

University of Texas at Austin

Many mathematical and simulation based researches have shown the effectiveness of adaptive and angular slicing and layering in minimizing errors in layered manufacturing processes and improving surface quality and build time. Recent technological advances such as 5-axis laser cutters, abrasive waterjets, and CNC machines have enabled physical part fabrication beyond typical vertical layered manufacturing with staircase errors. In this paper, a new curvedform adaptive slicing method is presented. In this method, multiple cuts of the edge boundary of each adaptive layer with variable cutting vector angles conform well to CAD model curved surfaces. The proposed system is compatible with 5-axis abrasive waterjet machines. This system has been successfully tested on several virtual 3D CAD models.

null

['Kigure, T.', 'Yamauchi, Y.', 'Ninno, T.']

2024-03-25T22:22:01Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124319', 'https://doi.org/10.26153/tsw/50927']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['PEEK', 'laser sintering', 'temperature', 'additive manufacturing']

Considerations of internal void generation process by observation of melting and solidification behavior in low temperature laser sintering of PEEK

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6d880f5e-d1ca-48cb-a2f6-097bedbc2d33/download

University of Texas at Austin

Laser sintering of PEEK performed below the crystallization temperature has been achieved in previous study by low temperature process that anchors the part to a rigid base plate to suppress warpage during processing. However, significant surface roughness and large internal voids are sometimes generated in the parts built by low temperature process, and there are problems in stability of parts quality. The purpose of this study is to contribute to quality improvement of laser sintering of PEEK by low temperature process. It was attempted that clarify the process of surface roughness and void generation by observing the melting and solidification behavior of the material during process with a video camera. From these observation results, it was assumed that the amount of volume change from powder to liquid due to melting and the amount of shrinkage due to solidification affect part quality such as surface roughness and internal voids.

null

['Schumacher, Christian', 'Schöppner, Volker', 'Guntermann, Jonas']

2021-11-02T17:50:01Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89837

eng

2017 International Solid Freeform Fabrication Symposium

Open

['machine-specific influence', 'process-specific influence', 'custom-built', 'fused deposition modeling']

Considering Machine- and Process-Specific Influences to Create Custom-Built Specimens for the Fused Deposition Modeling Process

Conference paper

https://repositories.lib.utexas.edu//bitstreams/53b73205-c410-49f7-9e9b-edd065fb0eaa/download

University of Texas at Austin

Compared to conventional polymer processing technologies the material selection in the Fused Deposition Modelling (FDM) process is restricted. To expand the range of materials the requirements for the material properties and the semi-finished products (filaments) must be clarified. For this, a machine- and process-independent rating of the processability is necessary. The established standards for the tensile strength test apply to specimens with nearly isotropic mechanical properties. The FDM process generates anisotropic parts. The properties are mainly influenced by the machine quality and the data processing. It is not possible to test a material for FDM independently of the machine and the data processing. In this paper, machine and process-specific influences are investigated. Considering these influences, a custom-built specimen is created to test the tensile strength of the welding seams for polyamide 6. This procedure allows a machine- and process-independent rating of the processability in terms of tensile strength for different materials.

null

['Khoshnevis, Behrokh', 'Yuan, Xiao', 'Zahiri, Behnam', 'Xia, Bin']

2021-10-21T22:02:09Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89455

eng

2015 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'Contour Crafting', 'sulfur concrete', 'planetary']

Construction by Contour Crafting Using Sulfur Concrete with Planetary Applications

Conference paper

https://repositories.lib.utexas.edu//bitstreams/312e1f1d-0866-4842-9134-159c8902fc33/download

University of Texas at Austin

This paper reports on the experiments with the Contour Crafting Automated Construction process using sulfur concrete as the choice of construction material. Sulfur concrete has numerous terrestrial applications and is potentially an ideal construction material for planetary construction. On Mars, sulfur can be found in abundance and the range of temperature variation on the planet is within the safe zone for the structures to be built and survive over reasonable length of time with sulfur concrete. Several experiments have been performed at centimeter and meter scales. A FEA simulation model for the behavior of sulfur concrete based structures has been developed. Experimental results were compared with the results of simulation.

null

['Shen, Yiju', 'Li, Yingqi', 'Tsai, Hai-Lung']

2021-11-02T19:42:52Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89878

eng

2017 International Solid Freeform Fabrication Symposium

Open

['metallic glass', 'laser-foil-printing', 'amorphous foils', 'foils', 'additive manufacturing']

Construction of Metallic Glass Structures by Laser-Foil-Printing Technology

Conference paper

https://repositories.lib.utexas.edu//bitstreams/324f4cea-abc3-49b4-9d49-cadff220bd28/download

University of Texas at Austin

Metallic glasses (MGs) have superior mechanical properties such as high tensile strength, hardness, and corrosion resistance, as compared to crystalline metals. Although newly developed MGs have significantly reduced critical cooling rates down to 10 K/s, products of MGs are still limited to simple geometries such as foils/plates or rods with thin section-thickness which is mainly caused by the decrease of thermal conductivities of the new MGs. Recently, we developed a new Laser-foil-printing (LFP) additive manufacturing technology which welds foils, layer by layer, to construct desired 3D structures. With the LFP and Zr-based amorphous foils, 3D, large amorphous structures with complex geometry have been successfully manufactured. To better understand the evolution of crystalline phase, we integrate the finite element based heat transfer model and classic nucleation theory (CNT) based crystal nucleation/growth model. The model was used to demonstrate the evolution of crystal phase as a function of time during laser welding at different locations including the fusion zone (FZ) and heat-affected zone (HAZ). The model is also compared favorably with the experiment results. The reported susceptibility to crystallization in HAZ were discussed and explained.

null

['Lawrence, Jacob', 'Peña Vega, Hector Andres', 'Stegman, Bryant', 'Roberts, Caleb', 'Spencer, Joseph', 'James, Clinton', 'Christensen, McKay', 'Crane, Nathan']

2023-01-31T13:52:42Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117366', 'http://dx.doi.org/10.26153/tsw/44247']

eng

2022 International Solid Freeform Fabrication Symposium

Open

Binder jetting

Construction of Open-Source Laboratory-Scale Binder Jetting System for High-Speed Synchrotron X-Ray Imaging

Conference paper

https://repositories.lib.utexas.edu//bitstreams/b4bf55d2-8f94-4994-a64b-db93293cd0ca/download

null

Although commercial binder jetting (BJ) printers are available, they typically do not allow sufficient control over process parameters needed to study fundamental process characteristics. This work presents an overview of the design and construction of a custom BJ system used to observe fundamental phenomena in the BJ process. CAD models for the design and information on the software of this system is also given. This system will help elucidate the mechanisms that introduce part defects and other challenges unique to the BJ process. The BJ system was designed for both laboratory-scale experiments with a 100 x 100 mm build box and high-speed synchrotron X-ray imaging with a 500 μm thick powder bed, requiring high-accuracy motion stages and a controller with precise timing. The printer includes functionality for depositing and rolling powder, printing multi-layer parts, and direct observation of the jetting nozzle. This BJ system has enabled experiments that provide insight into the printing process that will aid future efforts to mitigate challenges associated with BJ.

null

['Lawrence, Jacob', 'Peña Vega, Hector Andres', 'Stegman, Bryant', 'Roberts, Caleb', 'Spencer, Joseph', 'James, Clinton', 'Christensen, McKay', 'Crane, Nathan']

2023-01-27T18:04:50Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117352', 'http://dx.doi.org/10.26153/tsw/44233']

eng

2022 International Solid Freeform Fabrication Symposium

Open

Binder jetting

Construction of Open-Source Laboratory-Scale Binder Jetting System for High-Speed Synchrotron X-Ray Imaging

Conference paper

https://repositories.lib.utexas.edu//bitstreams/69e75d53-cecd-4a1c-86f3-852e31c88878/download

null

Although commercial binder jetting (BJ) printers are available, they typically do not allow sufficient control over process parameters needed to study fundamental process characteristics. This work presents an overview of the design and construction of a custom BJ system used to observe fundamental phenomena in the BJ process. CAD models for the design and information on the software of this system is also given. This system will help elucidate the mechanisms that introduce part defects and other challenges unique to the BJ process. The BJ system was designed for both laboratory-scale experiments with a 100 x 100 mm build box and high-speed synchrotron X-ray imaging with a 500 μm thick powder bed, requiring high-accuracy motion stages and a controller with precise timing. The printer includes functionality for depositing and rolling powder, printing multi-layer parts, and direct observation of the jetting nozzle. This BJ system has enabled experiments that provide insight into the printing process that will aid future efforts to mitigate challenges associated with BJ.

null

['Hoglund, R.', 'Smith, D.E.']

2021-10-28T14:53:59Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89657

eng

2016 International Solid Freeform Fabrication Symposium

Open

['topology optimiation', 'continuous fiber angle optimization', 'fused filament fabrication']

Continuous Fiber Angle Topology Optimization for Polymer Fused Filament Fabrication

Conference paper

https://repositories.lib.utexas.edu//bitstreams/de984a93-2713-4dab-9ae9-2f1b8de6f70b/download

University of Texas at Austin

Mechanical properties of parts produced with the Fused Filament Fabrication (FFF) process are known to be dependent on the printed bead direction, especially when short carbon fiber reinforcement is added to the filament. Given that many FFF filament suppliers now offer carbon-fiber filled products, a unique opportunity emerges in the design of polymer composite FFF parts since bead and fiber direction can potentially be prescribed to give the best structural performance. As FFF moves from a technology for rapid prototyping and the hobbyist to a viable additive manufacturing method, it is important to also have a design tool that takes advantage of the opportunities that present themselves when polymer composites are employed. This paper presents a topology optimization method for continuous fiber angle optimization approach (CFAO), which computes optimal material distribution (as in the well known SIMP method) in addition to a preferred fiber angle direction by minimizing compliance of statically loaded structures. Our computed results show the effects of variable orientation angle on fiber reinforced microstructure for the topology of two-dimensional FFF parts. Optimal fiber orientations are shown to align with the axis of structural members that form within the structure as expected. Example design problems are solved and then printed on desktop 3D FFF printers using the material distribution results and a simple infill method which approximates the optimal fiber angle results by a contour-parallel deposition strategy. Mechanical stiffness testing of the printed parts show improved results as compared to structures designed without accounting for the direction of the composite structure. Future work includes extension of the method to three dimensional structures for further application.

null

['Mei, Junfeng', 'Lovell, Michael', 'Mickle, Marlin', 'Heston, Steve']

2020-02-13T20:44:18Z

9/1/04

Mechanical Engineering

null

['https://hdl.handle.net/2152/79975', 'http://dx.doi.org/10.26153/tsw/7000']

eng

2004 International Solid Freeform Fabrication Symposium

Open

photolithography

Continuous ink-jet printing electronic components using novel conductive inks

Conference paper

https://repositories.lib.utexas.edu//bitstreams/72de18f3-16ae-434c-b0dd-94b6d166cdca/download

null

To reduce the cost of electronics fabrication and to take advantage of numerous potential specialized applications, a novel process of manufacturing three-dimensional electronic products is introduced in the present investigation. This process, which is currently being patented by the University of Pittsburgh, utilizes specialized continuous ink jet (CIJ) printing technology and innovative conductive inks that are capable of producing high-resolution conductive traces. Unlike drop-on-demand (DOD) techniques that are aimed at more precise features sizes (1 micron or less) and smaller scale applications, the present investigation demonstrates that the new process can be used in mass production applications where larger feature sizes (~50 microns) are sufficient. It has been found that the traces produced by the process have excellent adherence and have an electrical resistivity of only 2.9 times of bulk silver after curing. The major advantage of the proposed CIJ process is that it not only provides a fast and cost-effective method for applying electronic components (conductors, diodes, capacitors and resistors) on existing products, but it also allows the printing of conductive traces in three-dimensional space. With a throw distance that exceeds 10 cm, it demonstrates how the new fabrication process is not only suitable for desktop microfabrication, but also for large volume applications such as automotive glass.

null

['Yeung, H.', 'Lane, B.', 'Fox, J.', 'Kim, F.', 'Heigel, J.', 'Neira, J.']

2021-11-03T22:39:47Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89953

eng

2017 International Solid Freeform Fabrication Symposium

Open

['continuous laser scan', 'build speed', 'laser powder bed fusion', 'National Institute Standards and Technology', 'NIST']

Continuous Laser Scan Strategy for Faster Build Speeds in Laser Powder Bed Fusion System

Conference paper

https://repositories.lib.utexas.edu//bitstreams/cde24878-27fc-41ea-a6be-131544f49b50/download

University of Texas at Austin

Research has shown significant influence of laser scan strategy on various part qualities in the laser powder bed fusion additive manufacturing process. The National Institute of Standards and Technology developed the Additive Manufacturing Metrology Testbed, which provides open architecture for flexible control and monitoring during a laser powder bed fusion additive manufacturing process. This allows extended control of scan strategies, including control of laser power and speed within each scan line. A ‘continuous’ scan strategy can reduce build times and improve throughput by negating the need to turn the laser off between scan tracks (e.g., sky-writing). Also, less frequent laser power interruption can potentially improve the melt-pool continuity. Multiple experiments are performed utilizing the continuous and traditional scan strategies, and comparisons are made between build time and measured melt-pool qualities.

null

['Altenhofen, C.', 'Luu, T.H.', 'Grasser, T.', 'Dennstädt, M.', 'Mueller-Roemer, J.S.', 'Weber, D.', 'Stork, A.']

2021-11-11T16:32:25Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90238', 'http://dx.doi.org/10.26153/tsw/17159']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['material gradients', 'property gradadtion', 'multi-materials', '3D printing']

Continuous Property Gradation for Multi-Material 3D-Printed Objects

Conference paper

https://repositories.lib.utexas.edu//bitstreams/8580c856-99cd-4fe5-b48f-e6b717de3b1e/download

University of Texas at Austin

Modern AM processes allow for printing multiple materials. The resulting objects can be stiff/dense in some areas and soft/porous in others, resulting in distinct physical properties. However, modeling material gradients is still tedious with current approaches, especially when smooth transitions are required. Current approaches can be distinguished into a) NURBS-BReps-based and b) voxel-based. In case of NURBS-BReps, discrete material distributions can be modeled by manually introducing separate shells inside the object; smooth gradation can only be approximated in discrete steps. For voxel representations, gradation is discrete by design and comes along with an approximation error. In addition, interacting on a per-voxel basis is tedious for the designer/engineer. We present a novel approach for representing material gradients in volumetric models using subdivision schemes, supporting continuity and providing elegant ways for interactive modeling of locally varying properties. Additionally, the continuous volumetric representation allows for on-demand sampling at any resolution required by the 3D printer.

null

['Dwivedi, Rajeev', 'Dwivedi, Indira', 'Dwivedi, Bharat']

2023-01-27T17:44:08Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117344', 'http://dx.doi.org/10.26153/tsw/44225']

eng

2022 International Solid Freeform Fabrication Symposium

Open

staircase effect

Continuous Sculpting as a Novel Method to Reduce the Staircase Effect in Solidfreeform Fabrication Processes that Are Dependent on Phase Transformation

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1a187172-12f1-482b-b3df-c886047f35b4/download

null

Inherent to 2-1/2 axis deposition in Solid Freeform Fabrication is Staircase effect. The surface geometry of parts produced using Solid Freeform Fabrication, therefore is not smooth. Continuous sculpting is a novel method that combines additive manufacturing to surface modification by relative motion of a forming tool. Molten material is added to substrate. A forming tool that can tilt along different axes is connected to the end effector. The forming tool is oriented along a desired angle and then applies force on the molten material to give it desired shape on the fly. This paper introduces the novel method and a simple case studies.

null

['Wu, Ying-Jeng Engin', 'Beaman, J.J.']

2018-04-10T19:15:04Z

1990

Mechanical Engineering

doi:10.15781/T2T14V62C

http://hdl.handle.net/2152/64249

eng

1990 International Solid Freeform Fabrication Symposium

Open

['geometric contour', 'SFF application', 'speed']

Contour Following for Scanning Control in SFF Application : Control Trajectory Planning

Conference paper

https://repositories.lib.utexas.edu//bitstreams/7fb9c2b7-5ae9-4f9e-aadb-e1ba74cf6cec/download

null

Geometric contour following for scanning control in SFF application is used to refine the boundary ofthe parts for increasing the accuracy or to develop the capability to arrange various scanning directions and paths for improving the part strength. The scanners must be driven to follow the prescribed path as fast as possible, limited by available torques. In this paper the minimum time optimal control problem with specified path and limited control torque is formulated. According to the trade-off between various requirements, a control strategy is studied.

null

['Tse, L.Y.L.', 'Kapila, S.', 'Barton, K.']

2021-10-28T15:45:51Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89667

eng

2016 International Solid Freeform Fabrication Symposium

Open

['fiber reinforced polymers', 'additive manufacturing', 'contoured 3D printing', '3D printing']

Contoured 3D Printing of Fiber Reinforced Polymers

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a74a686d-3bc4-471a-958b-dd4939ad0818/download

University of Texas at Austin

Additive manufacturing (AM) is a cost effective approach for small-scale production, providing higher design flexibility and less material waste than traditional manufacturing techniques. Polymers constitute one of the most popular AM materials, yielding lightweight but inherently weak components that cannot hold up against high tension and bending stresses. A need for improved tensile strength has driven a recent interest in AM of fiber reinforced polymers (FRPs). AM-FRPs reinforced with short fibers have demonstrated increased mechanical strength, but with limited design and structural flexibility. AM-FRPs reinforced with continuous fibers provide structural reinforcement within plane; as such, the fibers cannot be extruded along a contoured profile, significantly minimizing the application space for these AM-FRP devices. In this article, we address this current gap through the development of a new FRP additive manufacturing process that is capable of continuous fiber deposition along contoured trajectories. Experimental demonstrations validate the proposed process.

null

['Seufzer, W. J.', 'Taminger, K. M.']

2020-03-09T13:16:09Z

2007

Mechanical Engineering

null

['https://hdl.handle.net/2152/80171', 'http://dx.doi.org/10.26153/tsw/7190']

eng

2007 International Solid Freeform Fabrication Symposium

Open

Electron Beam Free Form Fabrication

Control Methods for the Electron Beam Free Form Fabrication Process

Conference paper

https://repositories.lib.utexas.edu//bitstreams/8542016b-f8b5-45a9-a934-7f8601b77574/download

null

Engineering a closed-loop control system for an electron beam welder for additive manufacturing is challenging. For earth and space based applications, components must work in a vacuum and optical components must be protected from becoming occluded with metal vapor. For extraterrestrial applications added components increase launch weight and increase complexity. Here we present three different control methods for electron beam free form fabrication. A relatively simple coarse feedback control method is introduced that couples path planning and electron beam parameter controls into the build process to increase flexibility and improve build quality. The different approaches may be applied separately or together to provide enhanced EBF3 system performance.

null

['Boddu, Mallikharjuna R.', 'Landers, Robert G.', 'Liou, Frank W.']

2019-10-18T16:19:50Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76251', 'http://dx.doi.org/10.26153/tsw/3340']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Laser Cladding

Control of Laser Cladding for Rapid Prototyping--a Review

Conference paper

https://repositories.lib.utexas.edu//bitstreams/70109e14-caa4-45bf-8995-d0b4fac574f2/download

null

Lasers have wide–ranging applications in the manufacturing field (e.g., cladding, welding, cutting, machining, drilling). Extensive work is being conducted to apply laser cladding as a Rapid Prototyping (RP) process. In this paper the authors illustrate various principles of laser cladding in rapid prototyping. Important process parameters for the control of the laser cladding process are discussed as well as the experimental methods adopted, and results obtained by, various authors.

null

['Chin, R.K.', 'Beuth, J.L', 'Amon, C.H.']

2018-11-02T14:15:36Z

1995

Mechanical Engineering

doi:10.15781/T2PG1J73P

http://hdl.handle.net/2152/69329

eng

1995 International Solid Freeform Fabrication Symposium

Open

['Shape Deposition Manufacturing', 'carbon steel', 'inelastic compression-tension']

Control of Residual Thermal Stresses in Shape Deposition Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a8ca57b1-c209-4e55-a861-2dd9dd7b8e31/download

null

Layer-level thermal and mechanical modeling ofthe microcasting stage of ShaPe Deposition Manufacturing is presented. Thermo-mechanical models of carbon steel deposited onto a carbon steel substrate are described. Mechanics modeling addresses the issue of residual stress build-up. The effects of substrate heating and bending constraint on the build-up of residual stresses are shown. Results show that thermal cycling from newly applied droplets drastically changes the stress state in the top of the substrate. Originally unstressed regions go through an inelastic compression-tension stress cycle. Residual stresses reach values that may cause yielding in carbon steel. Moderate heating of the substrate above room temperature prior to droplet deposition reduces stresses significantly. Bending constraint during part manufacture allows partial relaxation of stresses as the constraint is removed.

null

['Yang, Feifei', 'Jiang, Tianyu', 'Chen, Xu', 'Lalier, Greg', 'Bartolone, John']

2021-12-01T23:50:07Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90663', 'http://dx.doi.org/10.26153/tsw/17582']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['selective laser sintering', 'surface quality', 'polyamide 12', 'additive manufacturing']

A Control of Surface Quality in Selective Laser Sintering Additive Manufacturing with Reclaimed Polyamide Materials

Conference paper

https://repositories.lib.utexas.edu//bitstreams/4a47d471-d13e-4d87-af94-bfd7ef098d30/download

University of Texas at Austin

In selective laser sintering (SLS) additive manufacturing (AM), a substantial amount of polyamide 12 materials remains un-sintered, recyclable, and reusable. However, using reclaimed polyamide 12 powder in SLS results in undesirable part surface finish. Very limited research has been done on the improvement of part surface quality and results barely exist on improving or modifying the surface quality of parts using extremely aged powders (powders held close to the heat-affected zones). Aiming to improve the surface quality, we propose a novel approach for SLS with (extremely) aged polyamide 12 powders. By combining material preparation, powder and part characterizations, and SLS with a customized method of post-heating, we obtain parts with improved surface quality (e.g., reduced roughness and porosities, and eliminated un-sintered particles). Particularly, parts 3D-printed using the 30%-30%-40% new-aged-extremely aged mixed powders exhibit the smoothest and flattest surface with no unmolten particles and nearly zero porosity.

null

['Wang, Jiwen', 'Shaw, Leon L.', 'Marcus, Harris L.', 'Cameron, T.B.']

2019-11-21T17:48:04Z

2003

Mechanical Engineering

null

['https://hdl.handle.net/2152/78543', 'http://dx.doi.org/10.26153/tsw/5599']

eng

2003 International Solid Freeform Fabrication Symposium

Open

Cross Section

Control of the Cross Section Geometry of Extruded Dental Porcelain Slurries for Rapid Prototyping Applications

Conference paper

https://repositories.lib.utexas.edu//bitstreams/06ad576b-bf4e-4b46-a1d5-3aa01017c6a8/download

null

This study investigates the dependence of the cross section geometry of extruded dental porcelain slurries on the rheological property of the slurry and the extrusion conditions. It is found that a pseudoplastic slurry is a basic requirement for obtaining extruded lines with rectangular cross sections. The cross section geometry of the extrudate is also strongly affected by extrusion parameters including the extrusion nozzle height, nozzle moving speed, and extrusion rate. Proper combinations of these extrusion parameters are necessary in order to obtain extrudates with near rectangular cross sections. The results obtained have been explained in terms of the interactions among the rheological properties of the slurry, the shear rate imposed on the slurry during extrusion, the wettability of the slurry on the substrate, and the forced flow of the slurry during extrusion.

The authors gratefully acknowledge financial support provided by the National Science Foundation under Grant Nos: DMI-9908249 and DMI-0218169.

null

['Capps, Nicholas', 'Goldstein, Jonathan', 'Landers, Robert', 'Kinzel, Edward']

2024-03-26T20:27:20Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124396', 'https://doi.org/10.26153/tsw/51004']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'glass']

Control of Track Morphology in Digital Glass Forming

Conference paper

https://repositories.lib.utexas.edu//bitstreams/8a88a902-81ae-421d-a01d-7e93c7eb50ae/download

University of Texas at Austin

Digital Glass Forming involves locally heating a glass filament using a laser while continuously feeding relative to the workpiece. This enables precise control of the viscosity of the molten region. This viscous melt pool is deformed by forces from the filament and workpiece. This paper investigates the relationships between the input parameters, laser power, feed rate, and scan speed, with the resulting track morphology. Tracks are used to build larger, more complex structures. By underfeeding the filament relative to the able scan speed, the glass is locally drawn to produce tracks with significantly smaller cross-sectional areas than the feedstock material. This technique allows for the production of arbitrary geometries and surface features using a smaller equivalent diameter than the input feedstock. The paper explores the available process zone for this underfed deposition mode and the limitations of this method.

null

['Comb, James W.', 'Priedman, William R.']

2018-05-03T17:11:43Z

1993

Mechanical Engineering

doi:10.15781/T2CJ8836K

http://hdl.handle.net/2152/65042

eng

1993 International Solid Freeform Fabrication Symposium

Open

['Stratasys', 'Fused Deposition Modeling', 'FDM']

Control Parameters and Materials Selection Criteria for Rapid Prototyping Systems

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3bd0a48d-d944-45de-92c8-f76d39af5a92/download

null

Since the introduction ofrapid prototyping technology as a tool for time compression and concurrent engineering in the design and manufacturing process, many enhancements and refinements have been made based on the experience ofusers and manufacturers ofrapid prototyping equipment. These improvements contribute significantly to faster production of quality output from rapid prototyping systems. There are diverse control and material selection parameters that affect prototype models built using the Fused Deposition Modeling (FDM®) process. This paper reviews the role of several ofthese parameters in the process. Data will be presented to help the user choose the appropriate material for specific applications including density, tensile stiffhess, flexural stiffhess, tensile strength, flexural strength, tensile ductility, shock resistance, and hardness.

null

['Nycz, Andrzej', 'Noakes, Mark W.', 'Masuo, Christopher J.', 'Love, Lonnie J.']

2021-11-11T16:19:33Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90234', 'http://dx.doi.org/10.26153/tsw/17155']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['control system framework', 'control system', 'G-code', 'printing paths', '3D printing', 'robot manipulator', 'robotic arm', 'degrees of freedom']

Control System Framework for Using G-Code-Based 3D Printing Paths on a Multi-Degree of Freedom Robotic Arm

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6948cc90-39cc-4d0a-9533-1619a6e00f8e/download

University of Texas at Austin

This paper describes a control system framework using G-Code-based 3D printing paths on a serial link robot manipulator with multiple degrees of freedom. Usually, G-Code is created by a software application, commonly referred to as a slicer, meant for gantry systems. However, G-Code does not address the kinematic complexity nor take advantage of the flexibility available in serial link robot manipulators. This paper provides an overview of the additive manufacturing process and G-Code, types of additive manufacturing deposition movements, common terminology used, the roles of parsers and translators, step-by-step instructions on how to implement this control system, and results and findings from this research. The presented framework can be used for a number of additive manufacturing methods, hybrid solutions, or applications not directly related to additive manufacturing. The implementation was successfully tested on a manipulator with seven degrees of freedom that successfully performed hundreds of hours of large-scale wire arc metal deposition.

null

['Levy, Gideon N.', 'Boehler, Paul', 'Martinoni, Raffaele', 'Schindel, Ralf', 'Schleiss, Peter']

2020-02-21T14:38:53Z

2005

Mechanical Engineering

null

['https://hdl.handle.net/2152/80057', 'http://dx.doi.org/10.26153/tsw/7079']

eng

2005 International Solid Freeform Fabrication Symposium

Open

['Rapid Prototyping', 'Selective Laser Sintering', 'Elastomer']

Controlled Local Properties in the Same Part with Sintaflex A New Elastomer Powder Material for the SLS Process

Conference paper

https://repositories.lib.utexas.edu//bitstreams/0c33c8bd-2c49-43e2-bb01-f7af105e54d9/download

null

A new powder material for the SLS (Selective Laser Sintering) process was recently released. The material is a result of fruitful research programs involving industry and university. The well known and widely used DuraFom™ (PA12) and theCastForm™ (PS) SLS-materials were developed by the same team. In the search for new powder materials many properties of the candidate polymer, e.g. the pulverization, the laser absorption and sintering parameters have to be tuned carefully. Previous Elastomer options materials were poor in strength, detailing, and long-term use. The new product overcomes most of the known deficits. It open completely new practices in many branches like: automotive, house appliances, office equipment, foot ware, medical, and many more. The Sintaflex has a Shore hardness variability 45-75 A and Elongation up to around 300%. The attainable yield strength range is 1.3 - 4.2 MPa. The resolution on the SLS part is up to 0.6 mm. It is positioned in good agreement compared with other commonly used injection plastics. Furthermore, the appeal of all SFF process beside geometry and complexity is thought in varying locally the mechanical properties. Some published patents make suggestions in this direction. The new material, due to the particular properties range in function of the sintering parameter, allows first time to realize this wish. The generated part has controlled variable local properties; a new and unique opportunity opens for the SLS process. The paper describes the basic material properties. Further the main sintering parameters are describes and indications on machine settings are given. RP (Rapid Prototyping) applications and the recent practical experience are illustrated. Distinctive examples of local variable properties in the same part and given limits are shown. Some conclusions are stated.

null

['Liu, Y.', 'Beck, S.', 'Nicolleau, F.', 'Majewski, C.E.']

2021-10-12T18:04:16Z

2013

Mechanical Engineering

null

['https://hdl.handle.net/2152/88709', 'http://dx.doi.org/10.26153/tsw/15643']

eng

2013 International Solid Freeform Fabrication Symposium

Open

['Sierpinski pyramids', 'laser sintering', 'air flow', 'turbulence', 'fluid flow', 'flow control']

Controlled Multi-Scale Turbulence through the Use of Laser Sintered Sierpinski Pyramids

Conference paper

https://repositories.lib.utexas.edu//bitstreams/e696ae79-c58c-41a7-ad2e-24eb85c25d02/download

University of Texas at Austin

The research presented here is the result of a new collaboration between the Centre for Advanced Additive Manufacturing (AdAM) and the Thermofluids group at The University of Sheffield, regarding the use of fractal geometries for the control and influence of fluid flow. It is believed that the use of multiscale objects can be used to introduce many different orders of turbulence into a flow. However, whilst substantial simulations have been carried out in this area, the complexity of the physical geometries means that to date these have not been validated via physical testing. In this work, varying orders of Sierpinski pyramids were produced using Laser Sintered PA2200 and analysed in a wind tunnel with regards to their effects on air flow through the structures. As predicted by theoretical analyses, the coarsest pyramids induced large vortices into the air-stream, whereas the more complex orders induced vortices at a number of different scales, rapidly developing into a standard turbulent flow. Further investigations are planned to isolate the effects of the smaller-scale turbulence in this situation.

null

['Zak, Gene', 'Shiu, Matthew']

2019-10-09T16:22:45Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76155', 'http://dx.doi.org/10.26153/tsw/3244']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Laminated

Controlled-Depth Laser Cutting of Aluminum Sheet for Laminated Object Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/199d09b0-7ef3-4529-bdf8-5417483beaf6/download

null

Replacing paper with metal in laminated object manufacturing would bring improvements in terms of part's longevity, and its mechanical and thermal properties. In fabricating laminated parts, a challenging step is blind cutting of the metal sheet. Challenges to overcome are (1) maintaining consistent depth of cut, (2) achieving good surface quality of the cut groove walls, and (3) minimizing the formation of recast. Results are presented of an experimental investigation into controlled-depth laser cutting of aluminum sheet. Thin (0.12-mm) aluminum sheet specimens were cut with a 10-W Nd:YLF laser while varying scan speed and laser power. To accurately observe the cut profiles, specimens were mounted in resin and sectioned. Special handling procedure was developed to handle thin sheet material while avoiding damage. Relationship between cut profile and process parameters was established and shown to conform to established theoretical models.

We gratefully acknowledge the financial support of Centre for Automotive Materials and Manufacturing and Canada Foundation for Innovation.

null

['Liu, Bochuan', 'Gibbons, Gregory J.']

2024-03-25T23:31:12Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124337', 'https://doi.org/10.26153/tsw/50945']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['L-PBF', 'preferential evaporation', 'chemical composition', 'AlSi10Mg', 'tensile properties', 'additive manufacturing']

CONTROLLING CHEMICAL COMPOSITION CHANGES IN LASER POWDER BED FUSION OF ALSI10MG

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f4113aa3-b725-4bfa-b788-deb8cc177641/download

University of Texas at Austin

Due to the large energy input during the laser powder bed fusion process, some elements of metal alloy will reach vaporisation temperature. Significant differences between the volatility of various elements in the alloy may change the chemical composition after manufacturing. This study used this preferential evaporation effect to control the final composition to a targeted value, potentially for alloy and component tracing. Different laser process parameter sets were studied, and the mechanical properties changes associated with various compositions were investigated.

null

['Palmer, E.', 'Rosser, J.', 'Ritchie, M.', 'Bromley, C.', 'Brown, S.G.R.', 'Lavery, N.P.']

2023-03-30T16:00:37Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117694', 'http://dx.doi.org/10.26153/tsw/44573']

eng

2022 International Solid Freeform Fabrication Symposium

Open

IN625

Controlling Grain Evolution of IN625 Parts Produced by LPBF-AM

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1e256991-f838-498b-b0c5-f533f7ea6916/download

null

Laser Powder Bed Fusion (LPBF) Additive Manufacturing (AM) is rapidly being adopted globally due to its capability of producing complex net-shape parts in a range of alloys with mechanical properties as good as, or better than conventional processes. The alluring possibility is in controlling microstructural features during processing such as grain size, solidification morphology and texture, giving mechanical properties tailored for intended applications. LPBF-AM microstructures are dominated by sizeable columnar growth, which along with even small levels porosity contribute to lower fatigue and creep strength in comparison to wrought. This would limit high temperature applications where IN625 is used in aeroengine exhaust sections. In contrast, the less dominating equiaxed grains lead to a reduction in crack propagation and improve fatigue performance at the surface. In this work a combination of physical experiments and modelling is used to study the controllability of grain growth and orientation of IN625 made by LPBF-AM.

null

['Soylemez, Emrecan', 'Beuth, Jack L.']

2021-09-30T19:01:40Z

2010

Mechanical Engineering

null

['https://hdl.handle.net/2152/88280', 'http://dx.doi.org/10.26153/tsw/15221']

eng

2010 International Solid Freeform Fabrication Symposium

Open

['electron beam-based additive manufacturing', 'melt pool dimension', 'material deposition rates', 'electron beam deposition', 'electron beam']

Controlling Melt Pool Dimensions Over a Wide Range of Material Deposition Rates in Electron Beam Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/084f5aa6-1f5c-4494-babc-58dfcad0c981/download

University of Texas at Austin

Electron beam-based additive manufacturing processes are being seriously considered for manufacturing and repair applications in the aerospace industry. To be successful, these processes must work over a wide range of material deposition rates to combine affordability (requiring high deposition rates) with the ability to precisely deposit fine geometries (requiring low deposition rates). Melt pool size and shape are key characteristics to control in these processes. Control of melt pool dimensions will greatly increase the ability to successfully build shapes, and may play an important role in controlling solidification microstructure. In this paper, we present an analytically-guided approach for maintaining melt pool cross sectional area and thermal finite element simulation results are presented over a wide power range (1-5kW) to evaluate the approach. Single bead finite element simulations include the effects of temperature-dependent properties, latent heat, material addition and the distribution of power by a rapidly moving beam. Experiments were carried out on electron beam deposition equipment at NASA Langley Research Center and results show the same trends as those seen in the models. Ultimately, a map of curves of constant melt pool cross sectional areas and length-to-depth ratios is presented, covering power and velocity ranges over roughly a factor of 5.

null

['Starr, Thomas L.', 'Rafi, Khalid', 'Stucker, Brent', 'Scherzer, Christopher M.']

2021-10-06T19:55:31Z

8/22/12

Mechanical Engineering

null

['https://hdl.handle.net/2152/88426', 'http://dx.doi.org/10.26153/tsw/15363']

eng

2012 International Solid Freeform Fabrication Symposium

Open

['selective laser melting', 'stainless steels', 'phase composition']

Controlling Phase Composition in Selective Laser Melted Stainless Steels

Conference paper

https://repositories.lib.utexas.edu//bitstreams/971821cb-85d6-43ad-9cbb-380adfe40b8c/download

University of Texas at Austin

Commercially important stainless steels can be austenitic or martensitic and this phase composition fundamentally controls the mechanical properties of the material. With selective laser melting (SLM), 17-4 stainless steel can be produced in either phase depending on powder composition, SLM conditions and post-build heat treatment. This behavior is examined using optical and electron microscopy and high temperature x-ray diffraction in order to better understand the formation of metastable austenite and its transformation to martensite. Control of phase composition can produce a material with either extremely large strain-to-failure or high yield strength and can provide a method for completely eliminating residual stress.

null

['Fussell, P.S.', 'Kirchner, H.O.K', 'Prinz, F.B.', 'Weiss, L.E.']

2018-04-17T18:18:46Z

1991

Mechanical Engineering

doi:10.15781/T2H41K447

http://hdl.handle.net/2152/64342

eng

1991 International Solid Freeform Fabrication Symposium

Open

['rapid tooling', 'NOODLES', 'stereolithography']

Controlling the Microstructure of Arc Sprayed Shells

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3f313338-f9ad-47d0-8841-e33ce583859d/download

null

Techniques for controlling the microstructure of sprayed steel structures are discussed in this paper. Steel is arc sprayed onto shaped substrates to form tooling. The quality of the tool is greatly influenced by the microstructure of the material and the interlamella regions of the deposit. This work is focused on characterizing the microstructure, improving the state of the inter-lamella regions, and discusses our success in forming pseudo-alloys and graded shells by mixing sprayed materials. Microstructure control has interesting implications for other research as well, such as the MASK & DEPOSITS approach of forming objects.

null

['Rüsenberg, S.', 'Weiffen, R.', 'Knoop, F.', 'Schmid, H.-J.']

2021-10-07T14:59:58Z

8/22/12

Mechanical Engineering

null

['https://hdl.handle.net/2152/88471', 'http://dx.doi.org/10.26153/tsw/15408']

eng

2012 International Solid Freeform Fabrication Symposium

Open

['laser sintered parts', 'laser sintering', 'powder quality', 'cooldown phase', 'process quality']

Controlling the Quality of Laser Sintered Parts Along the Process Chain

Conference paper

https://repositories.lib.utexas.edu//bitstreams/521213c7-46fc-4fd8-b7b2-186321e26c73/download

University of Texas at Austin

The quality of laser sintered parts, in this work, manufactured by polymer laser sintering by using an EOSINT P395 Laser Sintering system, depends on several steps along the process chain. The first step is the characterization of the powder quality, whereas the rheological and physical investigations of nylon 12 powder are shown. By changing some important influencing factors, for example the powder ratio, the powder ageing and the moisture content, the influence on mechanical and physical properties, density and porosity, are investigated. The composition of the used powder is known. The previous process (storage conditions, etc.) as well as the laser sintering process (regarding energy density, temperature, etc.) is kept constant for the duration of this work. Regarding the post process in this work the cooling down phase is investigated as well. With an automatically blasting system it is possible to keep the post process parameters blasting distance and blasting time, constant. All of the tests will be performed using dry and conditioned test specimens. This work is showing the dependence on mechanical, rheological and physical parameters by varying important influencing factors along the laser sintering process quality chain.

null

['Milward, S.S.', 'Swygart, H.', 'Eccles, L.', 'Brown, S.G.R.', 'Lavery, N.P.']

2021-11-04T19:30:16Z

2017

Mechanical Engineering

null

['https://hdl.handle.net/2152/90010', 'http://dx.doi.org/10.26153/16931']

eng

2017 International Solid Freeform Fabrication Symposium

Open

['co-efficient of thermal expansion', 'CTE', 'lattice structures', 'high precision optical system', 'laser powder bed fusion']

Controlling Thermal Expansion with Lattice Structures Using Laser Powder Bed Fusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d546d12d-39cb-41a1-a333-25c3865474fe/download

University of Texas at Austin

Tuning the Co-efficient of Thermal Expansion (CTE) of a component is traditionally limited by material choice. Laser Powder Bed Fusion (LPBF) enables the designer to create complex geometries including lattice structures. When combined with a secondary material, these metallic lattice structures can be designed to exhibit different CTE’s whilst retaining stiffness. This allows the designer the freedom to adjust the CTE by changing CAD variables such as lattice angle, and member thicknesses. This paper aims to develop an arrangement for CTE matched components for high precision optical systems. Development pursued using a Static Thermo-Structural Finite Element Analysis model to determine the best arrangements for the required CTE change. The results are incorporated into a new design prototype of a full cylindrical lens system in metal on a Laser Powder Bed Fusion machine.

null

['Masoomi, Mohammad', 'Soltani-Tehrani, Arash', 'Shamsaei, Nima', 'Thompson, Scott M.']

2021-11-11T16:34:39Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90239', 'http://dx.doi.org/10.26153/tsw/17160']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['laser powder bed fusion', 'convective heat transfer coefficient', 'temperature gradient', 'numerical simulation']

Convection Heat Transfer Coefficients for Laser Powder Bed Fusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/abc68337-42aa-4b11-9426-6e7a88f61820/download

University of Texas at Austin

This study investigates the effects of convection heat transfer during the laser-powder bed fusion (L-PBF) additive manufacturing process. For the L-PBF process, parts are fabricated under a purged, inert environment to avoid oxidation. Part of the delivered laser energy is transferred to the process chamber/environment through radiation and convection during fabrication. In this study, customized computational fluid dynamics (CFD) software is used to simulate the L-PBF of a single layer of stainless steel 17-4 PH. Local temperature and temperature gradients, as well as dimensionless numbers descriptive of important thermophysics, are provided in order to quantify local convective heat transfer. The results are used to predict local heat transfer coefficients during the L-PBF additive manufacturing process.

null

['Zhu, Feng', 'Chen, Ke-Zhang', 'Feng, Xin-An']

2020-02-17T14:18:06Z

8/4/04

Mechanical Engineering

null

['https://hdl.handle.net/2152/79994', 'http://dx.doi.org/10.26153/tsw/7019']

eng

2004 International Solid Freeform Fabrication Symposium

Open

functionally graded materials

Converting a CAD Model into a Manufacturing Model for the Components Made of a Multiphase Perfect Material

Conference paper

https://repositories.lib.utexas.edu//bitstreams/46d57997-59fa-4091-a36f-5651774c4977/download

null

To manufacture the component made of a multiphase perfect material (including homogeneous and multi heterogeneous materials), it CAD model should be processed and converted into layered manufacturing model for further transformation of numerical control (NC) coding. This paper develops its detailed approaches and corresponding software. The process planning is made first and includes: (1) determining the build orientation of the component; and (2) slicing the component into layers adaptively according to different material regions since different materials have different optimal layer thickness for manufacturing. After the process planning, the layered manufacturing models with necessary information, including fabrication sequence and material information of each layer, are fully generated.

null

['Kim, C.Y.', 'Cuaron, A.', 'Perez, M.A.', 'Espalin, D.', 'MacDonald, E.', 'Wicker, R.B.']

2021-10-12T21:19:27Z

2014

Mechanical Engineering

null

['https://hdl.handle.net/2152/88742', 'http://dx.doi.org/10.26153/tsw/15676']

eng

2014 International Solid Freeform Fabrication Symposium

Open

['cooperative fabrication', 'harmonic fabrication', 'embedded three-dimensional wire in', 'degrees of freedom', 'Cartesian coordinate']

Cooperative Fabrication Methodology for Embedding Wireon Corved Surfaces

Conference paper

https://repositories.lib.utexas.edu//bitstreams/675364f3-0458-48db-beff-9f1192c1117d/download

University of Texas at Austin

In conventional additive manufacturing (AM), an object is fabricated by depositing material in a layer by layer fashion. Typically, this process is retained so that deposition can occur on flat surfaces and motion can be constrained to requiring only three degrees of freedom (DOF) in a Cartesian coordinate system. When incorporating wire in three-dimensional (3D) objects, there is sometimes a need for placement along curved surfaces on which positions are defined not only by 3D Cartesian coordinates but also angular ones. Therefore, a minimum of two additional DOFs are required allowing movement to be generated at the build platform as well as of the extrusion head. This paper addresses a method for trajectory planning of both systems, that is, the extrusion head and the movable build platform, allowing for cooperative and harmonic motion between the two.

null

['Rhodes, Andrew', 'Walker, Roo', 'Smith, Tyler', 'Lindahl, John', 'Kunc, Vlastimil', 'Duty, Chad']

2021-12-06T21:43:37Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90682', 'http://dx.doi.org/10.26153/tsw/17601']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['print parameters', 'fiber length', 'mechanical properties', 'fiber-reinforced composites', 'big area additive manufacturing']

Correlating Large-Format AM Print Parameters to Fiber Length and Mechanical Performance of Reinforced Polymer Composites

Conference paper

https://repositories.lib.utexas.edu//bitstreams/cf90fc05-8f89-4840-9ae4-3dc581555251/download

University of Texas at Austin

This paper aims to correlate processing conditions to fiber length and mechanical properties in fiber-reinforced composites on the Big Area Additive Manufacturing (BAAM) system at Oak Ridge National Laboratory. The processing of fiber-reinforced composites has a significant influence on their microstructure, which dictates the properties of the final product. The effect of processing is poorly documented in systems like the BAAM, leaving significant opportunities to improve the mechanical performance of printed structures. In this work, fiber length distributions from pelletized feedstock were compared against those of specimens extruded under different processing speeds. The mechanical strength of each specimen was evaluated to correlate processing speed to fiber length and mechanical properties. Experimental results showed that fiber length decreases slightly with increasing screw speed. Mechanical performance was not found to be affected by the decrease in fiber length. This research will guide future modifications to hardware design and print parameters to maintain fiber length and maximize mechanical performance.

null

['Lee, Y.S.', 'Bandari, Y.', 'Simunovic, S.', 'Richardson, B.', 'Kirka, M.M.']

2021-11-09T19:44:02Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90143', 'http://dx.doi.org/10.26153/tsw/17064']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['LMD-wire', 'distortion', 'inter-layer time', 'finite element method', 'additive manufacturing', 'plate oscillation', 'Ti-6Al-4V']

Correlations of Interlayer Time with Distortion of Large Ti-6Al-4V Components in Laser Metal Deposition with Wire

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6ddb9727-07d8-4c1b-b85c-e5f889da3000/download

University of Texas at Austin

Laser metal deposition with wire (LMD-w) is one of the emerging additive manufacturing (AM) technologies for large-scale aerospace components due to high deposition rates and material efficiency. However, it often results in undesired stresses and distortions due to non-uniform expansion and contraction of material during printing. Controlling inter-layer time, preheating, and clamping are the effective methods to mitigate the thermally induced stress and deformation. In this study, the effect of inter-layer cooling time on part distortion is investigated using a finite element method (FEM). The model accounts for actual tool paths, power, and cooling conditions. The results show that the model effectively captures the fluctuation of the Ti-6Al-4V plate during printing. Also, it shows an asymmetric distortion on the plate edges. Ultimately, the sequentially coupled thermal-stress simulation provided a quantitative understanding of the inter-layer cooling time on titanium plate distortion for the large-scale LMD-w process.

null

['Ertay, Deniz Sera', 'Ma, Henry', 'Vlasea, Mihaela']

2021-11-09T15:27:15Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90094', 'http://dx.doi.org/10.26153/tsw/17015']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['pore defects', 'beam path', 'toolpath', 'border discontinuities', 'laser powder bed fusion']

Correlative Beam Path and Pore Defect Space Analysis for Modulated Powder Bed Laser Fusion Process

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d513f523-0fe0-45e6-9848-2946f15faf76/download

University of Texas at Austin

There are ongoing challenges in achieving full density metal parts via Laser Powder Bed fusion (LPBF). Numerous of studies have shown that the part density depends on the process parameters, the powder characteristics and the process environment conditions. The scan strategy and the interactions of scan paths at discontinuities such as borders, create regions with high probability of pore occurrence. In this work, the complex relation between the defects and the toolpath at border discontinuities is investigated for a print recipe which gives >99.95% solid fraction in the core of the part. Samples are scanned by X-ray Computed Tomography (CT). The pore space was analyzed to extract the pore frequency, size, shape and location with respect to the scan path, border and contour strategies.

null

['Lindemann, Christian', 'Koch, Rainer']

2021-10-26T18:01:37Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89542

eng

2016 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'product development processes', 'PDPs', 'cost efficiency']

Cost Efficient Design and Planning for Additive Manufacturing Technologies

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5de7d8bb-0446-47a3-abc9-c80a974310c9/download

University of Texas at Austin

null

This paper discusses additive manufacturing with regards to the current available PDP's while setting a focus on the economic aspects of the integration.

null

['Baumers, M.', 'Holweg, M.']

2021-11-01T20:38:22Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89738

eng

2016 International Solid Freeform Fabrication Symposium

Open

['manufacturing costs', 'build failure', 'laser sintering', 'additive manufacturing']

Cost Impact of the Risk of Build Failure in Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/09a029e5-f9ad-484b-b957-d67609e8dbac/download

University of Texas at Austin

While the feasibility of adopting Additive Manufacturing (AM) has been demonstrated in a range of industrial sectors, the total costs associated with the operation of the technology are not fully understood. This study reports the results of a series of build experiments in a controlled environment for the analysis of the total cost of the AM technology variant Laser Sintering (LS). Incorporating a structured representation of the process flow of LS, the developed cost model shows for a LS system of the type EOSINT P100 that the expected cost impact of build failure has a substantial effect, responsible for a share of up to 38% of total costs. The analysis further demonstrates that, due to the adverse effects of such ill-structured costs, the cost efficient level of build volume utilization is sub-maximal. This result is discussed in the context of the operational reality of using LS technology and the availability of economies of scale.

null

['Barclift, Michael', 'Joshi, Sanjay', 'Simpson, Timothy', 'Dickman, Corey']

2021-11-01T20:55:42Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89747

eng

2016 International Solid Freeform Fabrication Symposium

Open

['cost modeling', 'depreciation', 'resused powders', 'powder feedstocks', 'powder bed fusion', 'additive manufacturing']

Cost Modeling and Depreciation for Reused Powder Feedstocks in Powder Bed Fusion Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c2115481-a9ed-4649-8239-8340e5d73c29/download

University of Texas at Austin

Cost modeling for Powder Fusion (PBF) has traditionally treated the material feedstock as a fixed cost. Given that a built-up geometry in PBF must be in a bed filled with surrounding powder, the material feedstock is susceptible to satellites, chemical contamination, and dissimilar properties with each subsequent reuse. In this paper, we extend an existing PBF cost model and propose a new financial depreciation model for reused metal powders. Using Sum-of-the-Years Digits depreciation, powder feedstock is valued as a function of build cycles endured by the material feedstock. A case study is presented on two example parts in Direct Metal Laser Sintering (DMLS). Results show that cost models using a fixed material cost can undervalue build jobs with a high value virgin powder by as much as 3-11% or 13-75% depending on the material and its maximum build cycles in PBF.

null

['Kearns, Alexa', 'Farahbakhsh, Nasim', 'Venditti, Richard', 'Jur, Jesse']

2021-10-27T22:57:00Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89641

eng

2016 International Solid Freeform Fabrication Symposium

Open

['3D printing', 'cotton', 'pulverized cotton', 'low-density polyethylene', 'nanofibrillated cellulose', 'NFC']

Cotton Fibers in 3D Printing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/02310db7-492e-4a9e-b46f-e9f7af17ab28/download

University of Texas at Austin

This work explores the materials challenges of cotton-loaded with polymer composites toward sustainable solutions in 3D printed free forms. A key step toward composite filament development is the reduction in size of the original cotton fibers. Mechanical processing of the cotton is introduced as a means of reducing the size of cotton fibers to form a material of an ultra-high aspect ratio (>250) structure that is nanometers in diameter and micrometers in length. Mechanical advantages are low density polyethylene loaded with the high aspect ratio cotton and is observed to maintain a mechanically robust material at loading up to 40 wt%. In addition, attempts to print with 25 wt% cotton fillers (~10-15 aspect ratio) in LDPE is demonstrated. Finally, considerations to processing challenges from a sustainable and practical viewpoint are provided.

null

['McCarthy, D.L.', 'Williams, C.B.']

2021-10-05T15:52:50Z

8/22/12

Mechanical Engineering

null

['https://hdl.handle.net/2152/88398', 'http://dx.doi.org/10.26153/tsw/15337']

eng

2012 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'electroless plating', 'electroforming', 'laser sintering']

Creating Complex Hollow Metal Geometries using Additive Manufacturing and Electroforming

Conference paper

https://repositories.lib.utexas.edu//bitstreams/97319f36-4ae6-4fa7-9def-be3e74f18d5c/download

University of Texas at Austin

Additive manufacturing introduces a new design paradigm that allows the fabrication of geometrically complex parts that cannot be produced by traditional manufacturing and assembly methods. In this paper, the authors investigate the combination of laser sintering with an electroforming process using electroless nickel plating to produce complex, thin-walled, hollow, metal geometries. The resulting geometries cannot be produced directly with other additive manufacturing systems. The resulting process is used to produce a cellular nickel structure featuring 800µm walls that is 65 vol% air from a polyamide substrate with 3mm pores.

null

['Phillips, T.', 'Milroy, C.', 'Beaman, J.']

2021-12-06T21:28:45Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90677', 'http://dx.doi.org/10.26153/tsw/17596']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['lithium batteries', 'composite materials', 'conductivity', 'electroactivity']

Creating Conformable Lithium Batteries Using Selective Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/0d694d62-7465-4032-8a05-1a31e81b4be5/download

University of Texas at Austin

Selective laser sintering is an additive manufacturing technique that uses a laser to consolidate powdered material and create complex three dimensional parts. Typically, SLS utilizes thermoplastic polymer media to create dense plastic components (direct SLS). It is also possible, however, to use composite powders with non-melting additives paired with a suitable binder to create highly functional materials (indirect SLS). This paper will describe the formulation of composite materials containing conductive and electroactive material additives to fabricate lithium-ion battery components (i.e. anodes, cathodes, separators, and cases). Selective laser sintering adds to the geometric flexibility of the lithium battery components and enables batteries that conform to their surroundings, effectively reducing their geometric footprint. Preliminary galvanostatic charge/discharge test results will be presented for the functional Li-ion cathodes created using SLS, as well as next steps to improve capacity and reliability.

null

['Dumene, Richard L.', 'Kennedy, Paul', 'Williams, Christopher B.', 'Sweeney, Dennis', 'Earle, Greg']

2021-10-21T22:05:17Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89456

eng

2015 International Solid Freeform Fabrication Symposium

Open

['radiofrequency', 'RF structures', 'embedding', 'PolyJet', 'material jetting']

Creating Embedded Radiofrequency Structures Using PolyJet Material Jetting

Conference paper

https://repositories.lib.utexas.edu//bitstreams/04ceb5ed-3337-409c-a438-5d2a48eada45/download

University of Texas at Austin

Embedding of integrated systems via Additive Manufacturing (AM) offers the potential to save weight, space, and time in the production of electronics and vehicles. Of specific interest are embedded electrical systems that operate in the radiofrequency (RF) range as they have great potential utility in communication systems and aircraft avionics including navigation. However, systems in this frequency range pose unique manufacturing challenges such as the need to minimize impedance discontinuities in the system. In this work, the authors explore various techniques for embedding RF structures such as antennas and filters via a multi-material jetting AM process. Specifically, the dielectric constants and loss tangents of Vero White and Tango Black polymers were determined to facilitate the design of RF structures with these materials. It is shown that measurements of S-parameters of the resultant embedded RF structures approach or match the performance of non-embedded electronics.

null

['Frank, Matthew C.', 'Joshi, Ashish', 'Lei, Shuangyan', 'Anderson, Donald D.', 'Tochigi, Yuki', 'Brown, Thomas D.']

2021-10-05T19:18:48Z

2012

Mechanical Engineering

null

['https://hdl.handle.net/2152/88415', 'http://dx.doi.org/10.26153/tsw/15354']

eng

2012 International Solid Freeform Fabrication Symposium

Open

['Subtractive Rapid Prototying', 'bone implants', 'human allograft bone']

Creating Implants from Allograft Bone using Subtractive Rapid Prototyping

Conference paper

https://repositories.lib.utexas.edu//bitstreams/0efb0040-f1d4-4d48-ab05-6e14636b4c07/download

University of Texas at Austin

This research involves the development of rapid manufacturing for bone implants using human allograft bone in a Subtractive Rapid Prototyping process. Using CT-derived CAD models of missing bone due to high energy trauma or tumor resection, surgical reconstruction could be improved with custom rapid implants made from natural bone. The bone “stock” material is of arbitrary shape and material distribution in the form of frozen donated cadaveric bones. Each is unique in shape and has highly anisotropic material properties; likewise for each final bone implant geometry and its material distribution. This work utilizes a PLY input file, instead of the more common STL, using color texture information that can be utilized for advanced process planning depending on whether the surface is fracture, periosteal or articular in origin. Moreover, we present a new PLY assembly model, called the Matryoshka model, where successively nested PLY files are used to designate changing material distributions in the donated bone; a method that could also aid in the use of multi-material additive RP systems. Using color Matryoshka models and their subsequent color slice files; this work presents novel solution methods for the selection of implant harvesting sites and automated process planning for the physical rapid prototyping process. Early implementations using bone surrogate materials will be presented.

null

['Roschli, Alex', 'Post, Brian', 'Chesser, Phillip', 'Borish, Michael', 'Love, Lonnie', 'Kim, Seokpum']

2021-11-18T16:51:55Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90425', 'http://dx.doi.org/10.26153/tsw/17346']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['toolpaths', 'extruder modification', '3D printing', 'extrusion-based systems']

Creating Toolpaths Without Starts and Stops for Extrusion-Based Systems

Conference paper

https://repositories.lib.utexas.edu//bitstreams/fb0ed156-649d-4419-b27e-13bdefcc6f62/download

University of Texas at Austin

Toolpath generation for extrusion-based additive manufacturing systems, called slicing, involves operations on polygonal contours that are derived from an STL file. Slicing generates multiple paths per layer (both closed-loop and open-loop) that are designed to optimally fill the space outlined by the polygon(s). In the course of printing a layer, the extruder must start and stop, the tip must be wiped, and the extruder must travel between paths without printing. Any amount of time the printer spends moving without printing is considered wasted time because the part isn’t being constructed. In addition, the start/stop point, known as the seam, is often a blemish on the surface of the part that contributes to weaker material properties. Therefore, a single path for creating multi-bead walled structures is desirable because it would save machine time and create parts with better surface finish. This paper will cover one method of modifying the CAD file and slicing engine to allow for parts to be printed without starting and stopping the extruder.

null

['Moeskops, Eef', 'Kamperman, Nico', 'van de Vorst, Bart', 'Knoppers, Rik']

2019-12-05T18:26:15Z

2004

Mechanical Engineering

null

['https://hdl.handle.net/2152/78652', 'http://dx.doi.org/10.26153/tsw/5708']

eng

2004 International Solid Freeform Fabrication Symposium

Open

Polyamide

Creep Behaviour of Polyamide in Selective Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d9beaf74-76f1-42f0-bc25-a13e71ddbc72/download

null

The use of Rapid Prototyping technology to produce fully-functional end use products (Rapid Manufacturing) requires understanding of the material's time dependency. Creep is the time dependent strain as a result of a constant load. Creep behaviour of sintered polyamide-12 processed by the Selective Laser Sintering process has been investigated. To study the effect of temperature on this material, tests have been performed at room temperature as well as at elevated temperatures of 60°C and 100°C. Although the SLS processed material is more sensitive to creep than most other thermoplastics it is shown to be affected less than injection molded polyamide-12, which has been tested as a reference. The results show an almost linear behaviour on a logarithmic time scale, which enables the creep behaviour of SLS processed polyamide-12 to be predicted for at least 11 years.

null

['Schultz, J.', 'Kander, R.', 'Suchicital, C.']

2019-03-13T16:19:43Z

1999

Mechanical Engineering

null

['https://hdl.handle.net/2152/73641', 'http://dx.doi.org/10.26153/tsw/783']

eng

1999 International Solid Freeform Fabrication Symposium

Open

['Selective Laser Sintering', 'Mechanical Alloying']

Cryogenic Mechanical Alloying of Poly (ether ether ketone) - Polycarbonate Composite Powders for Selective Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9978f603-04cf-442f-b686-ad4fcfdb58cc/download

null

Mechanical alloying is a solid state processing technique traditionally used in the metallurgical industry to extend solubility limits in alloy systems. Mechanical alloying can also be used to blend polymer systems at ambient or cryogenic temperatures. In this work, cryogenic mechanical alloying was employed to create composite powders of Poly (ether ether ketone) (PEEK) - Polycarbonate (PC) for use in selective laser sintering applications. The microstructural development of the PEEK-PC system that occurs during laser sintering and the effects of this microstructure on mechanical properties of the laser sintered parts was investigated.

null

Wudy, K.

2021-11-18T01:41:15Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90397', 'http://dx.doi.org/10.26153/tsw/17318']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['laser sintering', 'thermoset', 'thermoplastic', 'multi-material part']

Curing and Infiltration Behavior of UV-Curing Thermosets for the Use in a Combined Laser Sintering Process of Polymers

Conference paper

https://repositories.lib.utexas.edu//bitstreams/031c8c40-5536-463d-bbd9-d1c1f17a664d/download

University of Texas at Austin

The investigation in this study addresses a new additive manufacturing process, which enables the production of multi-material parts consisting of thermosets and thermoplastics. A liquid thermoset resin will be applied with a micro value syringe in the laser sintering (LS) system. The liquid thermoset reacts parallel to the laser exposure of the thermoplastic powder. Therefore, in this study the UV curing and the infiltration behavior of the thermoset will be investigated under process relevant conditions. The investigations show a strong temperature dependent absorption of the liquid in the powder bed, whereas, the surface tension of the liquid plays a minor role. Furthermore, the UV curing of the thermosets takes place at low interaction times and at lamp powers between 100 and 300 mW/cm².

null

['Brady, G. Allen', 'Chu, Tien-Min', 'Halloran, John W.']

2018-11-14T20:47:02Z

1996

Mechanical Engineering

doi:10.15781/T28C9RQ08

http://hdl.handle.net/2152/70264

null

1996 International Solid Freeform Fabrication Symposium

Open

['SL technique', 'uv-polymerized binder', 'HA ceramics']

Curing Behavior of Ceramic Resin for Stereolithography

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9078d708-b07c-44ee-805a-b9a5b514daba/download

null

Ceramic green bodies have been created with stereolithography methods by using ultraviolet curable suspension of ceramic powders, a "ceramic resin", on a Stereolithography Apparatus (SLA). A minivat system with mini-recoater blade was designed to run small batch experiments on an SLA-250/40 machine. With the ceramic resins developed from hydroxyapatite for biomedical application and from alumina and silica for making metal casting molds, ceramic green bodies were built. Diagnostic parts of these ceramic resins were made with the Accumax diagnostic kit (3D Systems) and the curing parameters determined. The effect ofshrinkage stress and scattering will be discussed.

null

['Wudy, K.', 'Drummer, D.']

2021-11-09T15:41:22Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90099', 'http://dx.doi.org/10.26153/tsw/17020']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['curing behavior', 'thermosets', 'multimaterial SLS parts', 'selective laser sintering', 'additive manufacturing']

Curing Behavior of Thermosets for the Use in a Combined Selective Laser Sintering Process of Polymers

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a3e4cc8e-0d87-4cbc-9bae-ed6d95bbc36a/download

University of Texas at Austin

Selective laser sintering (SLS) of polymers is an additive manufacturing process, which enables the production of functional technical components. Unfortunately, the SLS process is restricted regarding the materials that can be processed and thus resulting component properties are limited. The investigations in this study illustrates a totally new additive manufacturing process which combines reactive liquids like thermoset resins and thermoplastics to generates multi material SLS parts. To introduce thermoset resins into the regular SLS process, the time-temperature-dependent curing behavior of the thermoset and the infiltration behavior has to be understood in order to assess the process behavior. The curing behavior was analyzed by rotational viscosimeter. Furthermore, the fundamental infiltration behavior was analyzed with micro dosing infiltration experiments. Finally, a thermoset resin in combination with a dosing system was chosen for integration in a laser sintering system.

null

['Law, Andrew Chung Chee', 'Southon, Nicholas', 'Senin, Nicola', 'Stavroulakis, Petros', 'Leach, Richard', 'Goodridge, Ruth', 'Kong, Zhenyu']

2021-11-09T14:59:52Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90089', 'http://dx.doi.org/10.26153/tsw/17010']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'polymer powder bed fusion', 'in-process monitoring', 'fringe projection', '3D point cloud processing', 'curvature', 'segmentation']

Curvature-Based Segmentation of Powder Bed Point Clouds for In-Process Monitoring

Conference paper

https://repositories.lib.utexas.edu//bitstreams/432050c5-d01a-43ff-bd43-66f110bf7fc7/download

University of Texas at Austin

This paper presents a curvature-based analysis of point clouds collected in-process with fringe projection in a polymer powder bed fusion process. The three-dimensional point clouds were obtained from outside of the build chamber with a fringe projection measurement system which was provided with access through an observation window. The curvature-based thresholding of powder bed point clouds demonstrates the ability to separate consolidated areas from the powder bed effectively. This segmentation of the point clouds with masks enables the detection of changes in the outline of consolidated areas between layers, computation of average drop due to the consolidation of the powder bed and separate analysis of both powder bed and consolidated areas. The high-level insights extracted from the analysis of the point clouds could improve process control strategies, such as in-line defect detection during an additive manufacturing build as well as an in-process feedback system for tuning the optimal values of additive process parameters. In summary, we show curvature-based thresholding as an effective segmentation for fringe projection point clouds, which can be further applied to detect defects, such as geometric defects and dimensional inaccuracy.

null

['Klosterman, Donald A.', 'Chartoff, Richard P.', 'Osborne, Nora R.', 'Graves, George A.', 'Lightman, Allan', 'Han, Gyoowan', 'Bezeredi, Akos', 'Rodrigues, Stan']

2019-03-01T17:27:06Z

1998

Mechanical Engineering

null

['https://hdl.handle.net/2152/73513', 'http://dx.doi.org/10.26153/tsw/663']

eng

1998 International Solid Freeform Fabrication Symposium

Open

['LOM', 'rapid prototyping']

Curved Layer LOM of Ceramics and Composites

Conference paper

https://repositories.lib.utexas.edu//bitstreams/87b9a3a5-76fc-4614-9c36-40e8d3c47daa/download

null

A novel rapidprototyping (RP) technology incorporating a curved layer building style has been developed. The new process,based on Laminated Object Manufacturing (LOM), is suited for efficient fabrication of curved layer structures made from ceramics and fibrous composites. Anew LOM machine was developedithatuses ceramic tapes and fiberprepregs as a feedstock and outputs at11fee dimensional green form. The green ceramic is then processed to a seamless, fully dense ceramic structure using traditional ceramic techniques. Thisreport summarizes the new LOM process. and necessary hardware. Also reviewed is the development of ceramic preforms and accompanying process technology for net shape fabrication of ceramic matrix composites (CMCs). Compared to making curved objeds with the standard flat.layer LOMprocess, the curved process affordsthe advantages of eliminated stair-step effect,increased build speed, reduced waste,reduced need for decubing, and the ability to maintain continuous fibers in the direction of curvature.

null

Kalmanovich, Gary

2018-11-14T17:20:08Z

1996

Mechanical Engineering

doi:10.15781/T2H12VT2W

http://hdl.handle.net/2152/70244

eng

1996 International Solid Freeform Fabrication Symposium

Open

['LOM', 'manufacturing process', 'curved-layer']

"Curved-Layer" Laminated Object Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1fd8fc07-fd5a-420d-97e1-9dafbff943c1/download

null

A process where a freeform solid object is built by bonding cut layers of material together is called a Laminated Object Manufacturing process. Until today, all ofthe LOM processes utilized straight forward planar cross-sections of the intended object for manufacturing. The "CurvedLayer" project's objective is to perform the LOM manufacturing process on a non-planar crosssection. Thus, the layers are going to be bonded together as non-planar surfaces providing additional strength to the built part as well as expedition ofthe built time for many objects. This project entails both software and hardware development for the implementation of the manufacturing process.

null

['Nambiar, R.V.', 'Jones, R.E.', 'Gomez, J.R.']

2019-10-18T16:52:50Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76259', 'http://dx.doi.org/10.26153/tsw/3348']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Reconstruction

Custom Fabrication of Hard Tissue Reconstructive Frameworks

Conference paper

https://repositories.lib.utexas.edu//bitstreams/2bb1971e-1d46-4bac-be00-dea8204bff10/download

null

The feasibility of fabricating custom frameworks for tissue regeneration utilizing three-dimensional inkjet printing technology followed by slip casting was investigated. A CAD solid model of mold was created with structures within the mold cavity to provide variable, customized porosity in the cast framework. The polymer mold was printed using a 3D ink-jet printer. The mold was then infiltrated by an aqueous suspension of hydroxyapatite to produce porous frameworks that were tested for mechanical properties.

null

['Remmers, Richard', 'Cook, Doug', 'Gervasi, Vito']

2021-10-01T00:14:19Z

2010

Mechanical Engineering

null

['https://hdl.handle.net/2152/88305', 'http://dx.doi.org/10.26153/tsw/15246']

eng

2010 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'fluid power industry', 'custom pneumatic rotary actuator', 'active ankle-foot orthosis']

Custom, Integrated, Pneumatic, Rotary Actuator for an Active Ankle-Foot Orthosis

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6eab6d2a-4e2e-4c21-b30a-be46b92a3f49/download

University of Texas at Austin

End-use objects produced via additive manufacturing (AM) are on the rise and new applications in the fluid power industry are emerging. Recently, a custom, pneumatic, rotary actuator was been designed and additively manufactured for integration into an active ankle-foot orthosis that is being developed in the National Science Foundation’s Center for Compact and Efficient Fluid Power. All necessary plumbing, between the valves and vanes, is integrated into the additively-manufactured housing of the actuator; and, the silicone translating seals were vacuum-transfer molded using additively-manufactured molds and inserts. This nonconventional actuator has more theoretical torque, and weighs less, than the off-the-shelf component that it replaced. Further development will reduce seal leakage, and optimize designs for additional mass reduction. Results-to-date are presented, in addition to several other examples of the growing use of AM in the fluid-power industry.

null

['Mohammed, Mazhar I.', 'Fitzpatrick, Angus P.', 'Malyala, Santosh K.', 'Gibson, Ian']

2021-10-28T21:50:29Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89709

eng

2016 International Solid Freeform Fabrication Symposium

Open

['patient specific', 'mandible', 'implant', 'design', '3D printing']

Customised Design and Development of Patient Specific 3D Printed Whole Mandible Implant

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6502fcd6-dc4b-43f7-9e7c-5148eb259ccc/download

University of Texas at Austin

In this study we assessed the design criteria for the creation of a patient specific, whole mandible implant based on a patient’s medical imaging data and 3D printing. We tailor this procedure to a patient who will undergo a mandibulectomy due to cancer infiltration of the jaw. The patient CT scan data was used to generate a 3D representation of the patient’s skull, before the corrupted mandible was extracted. We examined two approaches based on classical symmetry matching and digital reconstruction of the defect to form the final model for printing. The final designs were then 3D printed and assessed for efficacy against a patient specific representative model of the skull and maxilla, where the final optimised design was found to provide an excellent fit. Ultimately, this technique provides a framework for the design and optimisation of a patient specific whole mandible implant.

null