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Lee, Sang-Joon John. "Powder layer generation for three dimensional printing". Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/12452.
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Fan, Tailin. "Droplet-powder impact interaction in three dimensional printing". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10948.
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Bredt, James Frederic. "Binder stability and powder/binder interaction in three dimensional printing". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/10999.
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Saxton, Patrick C. (Patrick Charles) 1975. "Reducing powder bed layer defects in slurry-based three dimensional printing". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9423.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.Includes bibliographical references (leaf 141).
Slurry-based Three Dimensional Printing is being used to create ceramic parts directly from CAD files. Discrete slurry layers are deposited, into which a binder material is selectively ink-jet printed. This process is repeated until the last layer of the powder bed is deposited. Afterwards, the powder bed is re-dispersed in water, leaving behind the printed green part. The green part is then sintered to full density. This thesis focuses on methods of depositing the slurry layers. Currently, slurry layers are deposited by nozzle rastering. In this approach, a nozzle mounted to an x-y linear positioning system deposits adjacent discrete lines of slurry on a powder bed. Powder beds produced by nozzle rastering contain defects that occur between line and layer interfaces. The top surface has an inherent roughness due to the peaks and valleys between discrete lines. Line merging is a new method of slurry layer deposition that has been developed in an effort to eliminate inter-line defects, improve layer surface finish, and increase throughput This new technique has been used to rapidly produced slurry layers containing fewer internal defects and smooth surface finishes. Line merging occurs when adjacent lines of slurry are deposited in rapid succession such that they merge together prior to slip casting. Line merging differs from nozzle rastering in two ways: lines are deposited in only one direction (during the return pass the nozzle is put into a catch position), and the cycle time between depositing lines is reduced from approximately I second to as little as 0.1 second. A model was developed in an effort to identify the conditions required to achieve successful line merging, while avoiding layer defects such as bubbling and irregular surface finish caused by slurry migration. This model emphasized three relationships: the ratio of cycle time for line deposition to slip casting time for a slurry layer, the ratio of line width to line spacing, and the inverse of the width of the wet slurry zone where lines have merged prior to slip casting. A 3-D plot was constructed relating an objective function comprised of the three relationships to the control parameters (flow rate divided by nozzle velocity and cycle time). A plot for each alumina slurry solids loading was used to guide experiments. These experiments supported the model, though some relationships were proved more accurate than others. The model was ultimately used to target the ideal line merging conditions that were used to produced a 60 layer alumina powder bed out of 50 micron thick layers of 18 vol% alumina slurry. This powder bed exhibited excellent surface finish, with a maximum variation of 11 microns peak to valley. SEM analysis of cross-sections revealed that internal defects between deposited lines, previously seen with nozzle rastering, had been eliminated. Micro-bubbles along the interface between layers persisted, however. Follow-up SEM analysis of a 5 layer powder bed built with 22 vol% alumina slurry revealed no inter-line or inter-layer defects.
by Patrick C. Saxton.
S.M.
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Esterman, Marcos. "Characterization of the powder/binder interaction in the three dimensional printing process". Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13671.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1990.Title as it appears in the Sept. 1990 M.I.T. Graduate List: Characterization of powder/binder interaction in the three dimensional printing process.
Includes bibliographical references (leaves 131-132).
by Marcos Esterman, Jr.
M.S.
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Nur, Hassan Mohammed. "Fabrication of advanced ceramics and selective metallization of non-conductive substrates by inkjet printing". Thesis, Brunel University, 2002. http://bura.brunel.ac.uk/handle/2438/4823.
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Inkjet printing of ceramic components and gold conductive tracks was carried out in this study. A commercial inkjet printer, designed for printing one layer of 2D images on paper, was modified to give adequate resolution, to reverse the substrate for overprinting many layers and to accommodate the increase in thickness of 3D components during printing. Ceramic inks were prepared by wet ball milling and printed to form 3D structures. The powders used were alumina, zirconia, lead zirconate titanate (PZT) and barium titanate. The substrate used for printing the ceramic parts was an overhead transparency. Methods to stop or reduce ink flow were devised and used during printing of the ceramic parts. The alumina and zirconia powders were used for the fabrication of multi-layered laminates. The lead zirconate titanate was used to fabricate components with pillars, walls, vertical channels and x-y-z channel network. During printing of the x-y-z channel network, carbon was used as a support structure and then removed during firing. Barium titanate and carbon powders were used to form the first storey of a capacitor with a multi-storey car park structure. The printed parts were pyrolysed and fired in an oxidising environment and then characterised with scanning electron microscopy. The causes of micro structural defects found were discussed and prevention methods suggested. Organic gold powder was dissolved in methanol and then printed on three different substrates to form conductive gold tracks. The substrates used included alumina, glazed tile and microscope glass slides. The printed tracks were fired in air. The decomposition characteristics of the organic gold compound were studied with TGA and Differential Scanning Calorimetry (DSC). Scanning electron microscope was used to examine the fired gold film for defects and conductivity measurement of the tracks was carried out with a programmable multimeter.
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Touma, Rikard, i Nathalie Pettersson. "3D-printing med träEn möjlighet för framtiden?" Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-92364.
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3D-skrivare har många användningsområden och de har blivit vanliga i många industrier.Idag talas det om att denna teknik kan vara en möjlig väg till mer hållbart byggande.Tekniken anses lovande inom byggproduktion bland annat för att det visat sig att den kanreducera materialspillet och ge kortare byggtider. Till viss del används tekniken redan förbyggnadstillverkning, men då främst med betong.Målet med arbetet är att beskriva nuvarande kunskap rörande 3D-printing medträbaserad massa, samt att undersöka möjligheten till att använda en träbaserad massabestående av sågspån, vatten och lignin vid 3D-printing.För att kunna nå målet användes en kombination av litteratursökning och laborativaexperiment. Litteratursökningen användes både för att undersöka tidigare genomförda studiergällande träbaserade material i samband med 3D-printing, samt som inspiration för deingredienser och proportioner som används i de laborativa experimenten.Enbart studier om träbaserad 3D-printing studerades. De testobjekt som togs fram i delaborativa experimenten utvärderades i hållfasthet, dimensionsstabilitet och vidhäftning.Resultaten av det laborativa arbetet tyder på att det framtagna materialet går att extrudera,men att det har låg draghållfasthet. Lagren bands samman bra för samtliga tester, medantryckhållfastheten gav varierande resultat. Högst tryckhållfasthet gavs av den blandning somhade högst andel lignin, samt torkades under längst tid.Slutsatsen är att materialet kan vara till nytta, men att rätt användningsområde börbestämmas, då materialet inte tål alltför stora laster.3D printers have many uses and they have become common in many industries. Today, thistechnology is seen as a possible route to more sustainable construction. The technology isconsidered promising in construction engineering, among other things because it has beenshown that it can reduce material waste and provide shorter production times. To someextent, the technology is already being used for building construction, but then mainly withconcrete.The aim of this study is to describe current knowledge regarding 3D printing with woodbasedpulp and to investigate the possibility of using a wood-based pulp consisting ofsawdust, water and lignin for 3D printing.In order to reach the goal, a combination of literature search and laboratory experiments wasused. The literature search was used both to investigate previously conducted studiesregarding wood-pulp based materials in 3D printing and as inspiration for the ingredients andproportions used in the laboratory experiments.Only studies on wood-based 3D printing were studied. The test objects produced in thelaboratory experiments were evaluated in strength, dimensional stability and adhesion. Theresults of the laboratory work indicate that the produced material can be extruded, but that ithas low tensile strength. The layers bonded well for all tests, while the compressive strengthresults varied. The highest compressive strength was given by the mixture with the highestproportion of lignin and the longest drying time.The conclusion is that the material might be useful, but that the correct area of use should bedetermined, as the material cannot withstand excessive loads.Keywords:
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Pruitt, Beth L. (Beth Lynn). "The design of an automated powder deposition system for a three-dimensional printing machine". Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13049.
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Ramos, Juan David. "Design of humidifying system for the powder bed of the three-dimensional printing machine". Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12442.
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Caradonna, Michael Anthony. "The fabrication of high packing density ceramic powder beds for the three dimensional printing process". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/9316.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.Includes bibliographical references (leaf 123).
Three Dimensional Printing is a solid freeform fabrication process which can be used to create parts directly from CAD models. In the past, the 3DP process has been used to create structural ceramic parts using spray dried powders. Although fully dense parts have been made, it has been necessary to use an iso-static pressing step before sintering. Such a step has many disadvantages such as causing anisotropic shrinkage, warping, and lower part yields. In order to eliminate the iso-static pressing step, an improved process which uses slurries instead of dry powders makes it possible to fabricate green parts with high enough packing density that printed parts can be sintered directly. The main effort on the slurry-based 3DP process focused on fabricating powder beds which had high packing density and good surface finish. Three possible approaches were investigated: repeated tape-casting, spray deposition, and ink-jet printing of slurry. The repeated tape-casting approach was able to produce powder beds with excellent surface finish (4 [mu]m peak-to-peak roughness), high packing density (60-65% of theoretical), and small pore size (typically 0.3 [mu]m or less). Such powder beds can also be fabricated relatively quickly since a layer is produced in a single pass. However, this approach can be difficult to control. The spray deposition approach was determined to be a poor candidate for layer fabrication. Besides having relatively rough surface finish, nozzle performance problems make it impossible to build thick powder beds with good dimensional control. The ink-jet printing approach has produced large powder beds up to 8.5 mm in height. For such powder beds, good surface finish (8 [mu]m local peak-to-peak roughness) and dimensional control was evident. Ink-jet printed powder beds also have good packing density (55-62% of theoretical) and pore size distribution. One problem with powder beds which have been printed is that velocity ripple in the fast-axis shows up as a height ripple on the powder bed surface (typically 4.5% peak-to-peak). This can be eliminated with improved machine design. The ink-jet printing approach appears to be the leading method of fabricating complex ceramic parts with the slurry-based 3DP process.
by Michael Anthony Caradonna.
S.M.
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Gregorski, Steven Joseph. "High green density metal parts by vibrational compaction of dry powder in three dimensional printing process". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/8179.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996.Includes bibliographical references (p. 395-399).
The material properties and dimensional accuracy of metal tooling produced by the Three Dimensional Printing process can be enhanced by increasing the green density of the 3D printed part. Green density is the ratio of metal powder volume to the external volume of the printed part, and is a measure of how tightly packed the powder particles in the printed part are. The central goal of this thesis was to increase the green density of metal parts from the current level of 58% to levels greater than 75%. Two approaches were taken for increasing green density. The first was to utilize bimodal mixtures of metal powders which could be packed to significantly higher densities than the monomodal powders which had been previously used. Three bimodal powder mixtures, with tap densities near 80%, were studied. The second approach was to develop a new powder layering device which could pack these bimodal powders to the tap density during layer creation. New understandings about the relationship between the stresses applied to the powder layer and the resulting packing density changes were required to design this device. Shear cell and unconfined compression tests were performed to characterize the metal powder stress / strain behavior. Particulate stress / strain models, such as the Mohr-Coulomb failure law and the Jenike yield locus theory, were used to interpret the packing behavior of the metal powders under various stress conditions.
(cont.) A simple frictional model of powder behavior was proposed for the low stress levels permissible in the 3DP process. The application of a small static normal stress, in combination with an oscillatory horizontal shear stress, was found to be the most effective means of reducing particle interlocking and provided the best layer densification results. A new layer densification mechanism was constructed and successfully used to generate printed parts with green densities in excess of 75%. Photographic analysis techniques used to analyze part microstructures indicated significant improvements in packing homogeneity. Packing defects between the printed layers were reduced or eliminated. Compositional analysis indicated no significant segregation of the bimodal components during layer spreading.
by Steven Joseph Gregorski.
Ph.D.
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Charnnarong, Jain. "The drying shrinkage in three-dimensional printing and its dependence on the properties of the powder and the binder". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10950.
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Fitzgerald, Shawn. "A pneumatic conveying powder delivery system for continuously heterogeneous material deposition in solid freeform fabrication". Thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/46072.
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Great improvements are continuously being made in the solid free form fabrication (SFF) industry in terms of processes and materials. Fully functional parts are being created directly with little, if any, finishing. Parts are being directly fabricated with engineering materials such as ceramics and metals. This thesis aims to facilitate a substantial advance in rapid prototyping capabilities, namely that of fabricating parts with continuously heterogeneous material compositions. Because SFF is an additive building process, building parts layer-by-layer or even point-by-point, adjusting material composition throughout the entire part, in all three dimensions, is feasible. The use of fine powders as its build material provides the potential for the Selective Laser Sintering (SLS), ThreeDimensional Printing (3DP), and Freeform Powder Molding (FPM) processes to be altered to create continuously heterogeneous material composition. The current roller distribution system needs to be replaced with a new means of delivering the powder that facilitates selective heterogeneous material compositions. This thesis explores a dense phase pneumatic conveying system that has the potential to deliver the powder in a controlled manner and allow for adjustment of material composition throughout the layer.
Master of Science
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Caputo, Matthew P. "4-Dimensional Printing and Characterization of Net-Shaped Porous Parts Made from Magnetic Ni-Mn-Ga Shape Memory Alloy Powders". Youngstown State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1525436335401265.
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Goss, Cullen. "SLM 125 Single Track and Density Cube Characterization for 316L Stainless Steel". DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/2050.
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Selective Laser Melting is a rapidly developing additive manufacturing technique that can be used to create unique metal parts with tailormade properties not possible using traditional manufacturing. To understand the process from a most basic level, this study investigates system capabilities when melting single tracks of material. Individual tracks allow for a wide range of scan speeds and laser powers to be utilized and the melt pools analyzed. I discuss how existing studies and simulations can be used to narrow down the selection of potentially successful parameter combinations as well as the limitations of interpretation for single track information. Once we attain a solid understanding of what parameters perform well at a bead level, we can move onto looking at complete 3D parts. A challenge we have faced is creating near fully dense parts and determining a reliable density measurement technique that is accessible for operators at our university. Our results show that the previously determined optimized scan speed and laser power can consistently create parts with >99.5% density over a range of sizes using an analysis method utilizing readily available equipment and software.
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Hrabal, Michal. "Development of Light Emitting Electroluminescent Device by Means of Material Printing". Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2019. http://www.nusl.cz/ntk/nusl-402111.
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Cílem této práce je vývoj světelného zdroje založeného na technologii tlustostěnného elektroluminiscenčního panelu napájeného střídavým napětím (ACPEL). V současné době se jedná se o jedinou technologii založenou na metodách materiálového tisku vhodnou pro přípravu velkoplošných, flexibilních a vzorovaných zdrojů světla. Důraz je v této práci kladen na představení, prozkoumání a odstranění typických problémů, které jsou spojovány s touto technologií. Tyto problémy jsou omezený odstín barvy emitovaného světla a dlouhodobá stabilita elektroluminiscenčního prvku, který je vystaven vlivům prostředí. Rešeršní část dizertační práce je zaměřena na představení a identifikaci depozičních technik, vhodných pro reprodukovatelnou přípravu ACPEL panelů. Dalším cílem je identifikace fyzikálních parametrů, vhodných pro charakterizaci velkoplošných zdrojů světla. Praktickým cílem práce je nalezení vhodné metodologie pro popis a charakterizaci panelů, jakožto plošných světelných zdrojů. Fotometrická veličina jas L a spotřeba elektrické energie P byly vyhodnoceny jako vhodné parametry, určující aplikaci ACPEL panelů. Na modrém panelu bylo dosaženo maximální hodnoty jasu L = 133 cd•m2 při napětí Upp = 500 V a frekvenci f = 1000 Hz. Hodnoty spotřeby elektrické energie, vztažené na jednotkovou plochu panelů zkoumaných v této práci, jsou (7±3) mW. Tyto dosažené hodnoty dělají ze světelných zdrojů založených na ACPEL technologii zajímavé kandidáty pro různé aplikace. Vlivu rostoucí amplitudy a frekvence budícího napětí na dlouhodobou stabilitu panelů je důležitým cílem této práce. Pro popis stability byly zavedeny parametry L50 and L75. Bylo zjištěno, že rostoucí frekvence budícího napětí zkracuje životnost panelů. Laminovaný panel napájený napětím s přibližně trojnásobně vyšší frekvencí vykazoval přibližně třetinové hodnoty parametrů L50 a L75. Nejvyšších hodnot stabilitních parametrů dosahoval panel enkapsulován mezi skleněné pláty – přibližně sedminásobnou hodnotu oproti laminovanému panelu s trojnásobnou frekvencí. Optimální stability panelů lze dosáhnout při nastavení frekvence v rozmezí 400–800 Hz a zapouzdřením mezi sklo. Úzká paleta odstínů barev emitovaného světla je jeden z typických problémů, který dále zkoumán v dizertační práci. Tato práce zkoumá nadějnou metodu, přídavek vhodného materiálu pro konverzi barvy (CCM). Nový derivát diketopyrrolopyrrolu (DPP), absorbující v modré oblasti, byl přidán k modrému fosforu a byl pozorován sedminásobný narůst hodnot absolutního spektrálního ozáření v oblasti vlnových délek odpovídajících maximální emisi CCM materiálu. Jednoduchost přípravy vyvinutých zdrojů světla spolu s velmi nízkou spotřebou a vysokou dobou života dělají z ACPEL panelů zajímavé kandidáty pro podsvícení prvků například v automobilovém průmyslu, pro dekorativní osvětlení, pro „branding“ – zvýraznění reklamních značek.
17
Westbeld, Julius. "Investigation of support structures of a polymer powder bed fusion process by use of Design of Experiment (DoE)". Thesis, KTH, Lättkonstruktioner, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-243867.
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In this thesis, support structures of a polymer powder based process called XXXXXXXX™ are examined. These structures are crucial for most additive manufacturing processes. The effects of several factors on five industrially important characteristics of support structures are examined by use of the Design of Experiment (DoE) method. It describes the planning as well as the analysis of the experiments. The experiments are planned in a fractional factorial 211-5 design with 64 specimens, resulting in a resolution of IV. The analysis of the data is done by use of the ANOVA method, with which the significance of effects and interaction effects are checked.I detta examensarbete undersöks stödstrukturer för en polymer-pulverbaserad process kallad XXXXXXXX. Dessa strukturer är väsentliga för de flesta aditiv tillverkning. Med hjälp av metoden "Design of Experiment" (DoE) undersöks effekten av flera faktorer på fem industriellt viktiga egenskaper för stödstrukturer. DoE beskriver både planeringen och analysen av experiment. Experimenten planeras i en fraktionerad faktoriell 211-5 design med 64 provexemplar vilket resulterar i en upplösning av IV. Dataanalysen genomförs med hjälp av ANOVA-metoden, med vilken signifikansen av effekter och interaktionseffekter kan undersökas.
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Clark, Jared A. "The Effects of Build Orientation on Residual Stresses in AlSi10Mg Laser Powder Bed Fusion Parts". Youngstown State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1578819644598848.
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Miller, Jacob T. "Sulfuric Acid Corrosion to Simulate Microbial Influenced Corrosion on Stainless Steel 316L". Youngstown State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ysu151621775594905.
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Fan, Zongyue. "A Lagrangian Meshfree Simulation Framework for Additive Manufacturing of Metals". Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1619737226226133.
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Seluga, Kristopher J. (Kristopher Joseph) 1978. "Three dimensional printing by vector printing of fine metal powders". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/85726.
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Baker, Peter R. (Peter Ross). "Three dimensional printing with fine metal powders". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/46287.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.Includes bibliographical references (leaf 97).
In the area of direct metal part manufacture, the 3DPTM process has several inherent advantages over traditional machining and P/M technologies: hard tooling is not required to manufacture parts, geometries may be created which can not be made by conventional processes, and the composition of parts may be controlled locally on a 100 gm scale. The surface finish of 3DPTM parts will be a key factor in the determination of what parts are candidates for direct manufacture via the 3DPTM process. Powder size is the limiting factor in the determination of the surface finish of 3DPTM parts. On the micro scale, it determines the roughness due to particle arrangement, and on the macro scale it determines the thinnest layers from which parts may by built. The 3DPTM process has been adapted to a fine metal powder (ten micron particle diameter) material system. Powder spreading, ink-jet technology, and the effect of print parameters on printing with fine metal powders have been examined. Powder spreading experiments were conducted to examine the limits of layer thickness and packing density. 420 ss, S-7 tool steel, and 316L ss powderbed beds were generated in fifty micron layers. Packing densities of 55%, 59% and 59% respectively were obtained for the three powders. Line printing experiments were conducted with both continuous jet (CJ) and drop on demand (DOD) printheads to examine the relationship between droplet frequency, droplet spacing and the quality of printed lines. Lines were printed at droplet frequencies ranging from 100 Hz to 40 kHz and with droplet spacings from ten to fifty microns. Low print frequencies and small droplet spacings result in the highest quality lines. A droplet spacing of thirty microns and a droplet frequency of 667 Hz was chosen for the printing of 3-D parts with a Hewlett- Packard DOD printhead. 3-D part geometries were generated using fifty micron layers of ten micron 420 ss powder. These parts demonstrated the improvement in surface finish achieved with fine metal powders and the capability to create parts from fields identified as promising for the direct fabrication of metal parts via the 3DPTM process.
by Peter R. Baker, Jr.
S.M.
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GROPPO, RICCARDO. "Sviluppo e Industrializzazione di una macchina LPF e validazione attraverso l'ottimizzazione dei parametri di processo di Ottone CuZn42 e Acciaio Armonico C67". Doctoral thesis, Università degli studi di Modena e Reggio Emilia, 2021. http://hdl.handle.net/11380/1245517.
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Le tecnologie di costruzione additiva, dalla loro nascita alle prime applicazioni industriali, hanno fatto un grande salto in termini di sviluppo di hardware e materiali.
La continua ricerca di nuovi mercati e la crescente domanda hanno reso più accessibili i costi di tali tecnologie. Dall'uso dei polimeri per fare prototipi alle polveri metalliche per fare parti meccaniche reali i concetti sono sempre gli stessi, costruendo la parte strato per strato. In termini di denaro dagli anni Ottanta ad oggi il processo di stampa 3D mantiene un trend positivo con molti più aumenti per il futuro.
In termini di flussi monetari ed energetici durante la produzione di parti complesse, le tecnologie di costruzione additiva possono avere incrementi positivi. Con le tecnologie di costruzione additiva viene anche preso in considerazione l’aspetto legato alla misurazione del consumo energetico di produzione per le valutazioni dell'inventario del ciclo di vita. [2]
In molte catene di produzione tradizionali, dove stime affidabili del consumo energetico potrebbero non essere disponibili, l'adozione della tecnologia per costruzione additiva consente ai produttori di fornire ai propri clienti dati affidabili sull'energia incorporata nei prodotti o nei componenti durante la fase di produzione. [2]
È stato dimostrato che la selezione della configurazione dei costi minimi in Additive Manufacturing potrebbe portare all'effetto secondario della riduzione al minimo del consumo energetico di processo. [2]
La mia tesi di dottorato discuterà una specifica tecnologia di produzione additiva, basata sul processo di fusione del letto in polvere utilizzando un LASER come fonte di fusione.
Verranno analizzate le principali componenti costruttive presenti nella macchina prototipo, cercandone le principali criticità (sistema di filtraggio e recupero delle polveri, abbattimento polvere nera, flusso del gas in camera, misura delle perdite di carico nei tratti caratteristici dell’impianto, sistema di raccolta delle polveri, sistema di distribuzione e di deposizione delle polveri sul piatto di stampa) e, nel caso queste causino un arresto anomalo oppure un’irregolarità nella qualità nel componente stampato, se ne svilupperà una modifica oppure una sostituzione radicale del componente in esame.
Verificata la stabilità meccanica dell’intera macchina verranno analizzate le proprietà meccaniche dei campioni ottenuti con acciaio inossidabile X2CrNiMo17-12-2 - AISI316L, polvere di ottone CuZn42 e acciaio C67 - Acciaio Temperato. Le principali proprietà meccaniche richieste per un componente costruito per costruzione additiva sono in termini di resistenza meccanica porosità, densità, durezza Brinell, carico a rottura e tensione di snervamento.
In particolare, verranno effettuati dei rilevamenti della densità del provino mediante misurazione della densità volumetrica relativa con metodo di Archimede. Successivamente verrà stabilita la bontà della rugosità superficiale attraverso acquisizione di mappe per mezzo di un microscopio ottico e attraverso un software per l’analisi d’immagine ne verrà poi misurata la rugosità superficiale media. Lo stesso campione verrà poi utilizzato per misurare la durezza media del materiale per mezzo di un durometro.
Per testare il carico a rottura e il limite di snervamento verranno prodotti dei campioni con geometria ad osso di cane a sezione circolare a cui verrà montato un estensimetro analogico. Il software di elaborazione dei dati elabora la curva sforzo – deformazione.The additive manufacturing technologies, from their birth to the first industrial applications, made a big jump in terms of hardware and material development. The continuing research for new markets along with a growing demand have made sure that the costs of such technologies have become more accessible. From the using of polymers to do prototypes to metal powders to do real mechanical parts the concepts are always the same, building the part layer by layer. In terms of money from the eighties to present days the 3D printing process maintain a positive trend with much more increases for the future. In terms of monetary and energy flows during the production of complex parts, the additive manufacturing technologies can have positive increments. Thus the adoption of Additive Manufacturing also simplifies measurement of the manufacturing energy consumption for life cycle inventory assessments. In many traditional supply chains, where reliable estimates of cumulative energy consumption may be unavailable, the adoption of AM allows producers to provide their customers with reliable data on the energy embedded into products or component during the manufacturing stage. It has been shown that selecting the minimum cost configuration in Additive Manufacturing is likely to lead to the secondary effect of minimizing process energy consumption. My PhD thesis will discuss a specific additive manufacturing technology, based on the powder bed fusion process using a LASER as a melting source. The main construction components present in the prototype machine will be analyzed, looking for the main critical issues (filtering and powder recovery system, black powder abatement system, in-chamber gas flow, measurement of load losses in the characteristic sections of the plant, powder collection system, distribution and powder deposition system on the printing plate) and, if these cause a crash or an irregularity in the quality in the printed component, a radical modification or replacement of this component will develop. Once the mechanical stability of the entire machine has been verified, the mechanical properties of the samples obtained with stainless steel X2CrNiMo17-12-2 - AISI316L, CuZn42 brass powder and C67 steel - Tempered steel will be analyzed. The main mechanical properties required for a component built for additive manufacturing are in terms of mechanical strength porosity, density, hardness, ultimate tensile strength, and yield tension. Measurements of the density of the specimen will be carried out by measuring the relative volumetric density by Archimedes method. Subsequently, the quality of surface roughness will be measured through the acquisition of maps by means of an optical microscope and through an image analysis software the average surface roughness will then be measured. The same sample will then be used to measure the average hardness of the material by means of a durometer. To test the ultimate tensile strength and the yield strength, samples with circular section will be produced to which an analog extensometer will be mounted. Data processing software processes the strain -strain curve.
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Zubricky, James R. III. "Physical Models of Biochemicallly Important Molecules Using Rapid Prototyping Techniques". Bowling Green State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1151350496.
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Norton, Joseph. "Bronze powders - a study of the surface coating". Thesis, University of Huddersfield, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239691.
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Cestari, Francesca. "3D printing of bone scaffolds using powders derived from biogenic sources". Doctoral thesis, Università degli studi di Trento, 2023. https://hdl.handle.net/11572/363403.
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This doctoral work was developed in the frame of bone tissue engineering, dealing with the fabrication of scaffolds for the regeneration of bones. At this purpose, calcium phosphates derived from natural sources are very interesting because they are more similar to the bone mineral and possess better bioactivity. Indeed, the bone mineral is different from synthetic hydroxyapatite as it is non-stoichiometric, nanosized, it presents a high degree of disorder and contains many additional ions and impurities such as CO32-, Mg2+, Sr2+, Na+, etc. These characteristics can be easily obtained by synthesizing hydroxyapatite from natural sources, such as corals, starfishes, seashells, animal bones, bird eggshells etc. The natural sources used in the present work are three types of biogenic calcium carbonate, i.e. calcium carbonate that is produced by living organisms in the form of aragonite or calcite. Among the different sources, three biogenic calcium carbonates were chosen: cuttlefish (Sepia Officinalis) bones, mussel (Mytilus Galloprovincialis) shells and chicken eggshells. Besides their abundance and availability, they were selected because of their different composition: aragonite in cuttlebones, calcite in eggshells and a mixture of aragonite and calcite in mussel shells. After the first chapter, which is a theoretical introduction, this thesis is divided into other five chapters. Chapter 2 contains a careful characterization of the three biogenic raw materials while Chapter 3 deals with the synthesis of hydroxyapatite starting from these natural sources. The process developed here takes place entirely at nearly room temperature, which allows the organic part of the biological materials to be preserved. This synthesis process is basically a wet mechanosynthesis followed by a mild heat treatment (up to 150°C). The study focuses on the influence of several process parameters on the synthesis efficiency: temperature, milling time, pH and raw material. The temperature used to dry the slurry after the wet ball-milling was found to be the most important parameter, the higher the temperature the faster the conversion of CaCO3 into hydroxyapatite. Moreover, aragonite was found to transform more easily into hydroxyapatite with respect to calcite, and also to follow a different reaction path. The synthesis process described in Chapter 3 allowed to produce different bio-derived powders that were found to be non-stoichiometric, nanosized, carbonated hydroxyapatites, containing also additional ions, especially Mg2+ in the eggshell-derived material and Sr2+ in the cuttlebone-derived one. These powders were then used as a starting point for the studies presented in the next three chapters.
Chapter 4 shows a very preliminary evaluation of the interaction with human cells in vitro. First, the as-synthesized powders were consolidated by uniaxial pressing and sintering at temperatures between 900°C and 1100°C and their crystallographic composition was analyzed. Then, after having established the non-cytotoxicity of the sintered pellets, osteoblasts from human osteosarcoma cell line were seeded on the pellets and their behavior after 1, 3 and 5 days of culture was observed by confocal microscopy. In general, all materials promoted good cell adhesion and proliferation, especially the eggshell-derived one. At this point, the bio-derived materials were found to induce a good cellular response but, in order to foster the regeneration of bones, a scaffold must also contain a large amount of interconnected porosity. Among the numerous methods to fabricate porous structures, additive manufacturing is surely very attractive due many advantages, such as the possibility of customizing the shape based on tomography images from the patients, the fact that no mold is needed and the freedom of fully designing the porosity. Indeed, not only the size and the amount of porosity are important, but also the shape of the pores and their position and orientation have a deep effect on the interaction with the cells. Therefore, Chapter 5 and Chapter 6 deal with the fabrication of scaffolds by 3D printing, following two different approaches. In the study presented in Chapter 5, the powders synthesized from cuttlebones, mussel shells and eggshells were used in combination with a thermoplastic polymer (PCL, polycaprolactone) to obtain bioactive composites. Composite materials made of 85 wt% PCL and 15 wt% bio-derived hydroxyapatite were used to fabricate porous scaffolds by extrusion 3D printing. The biological in vitro tests showed that the composite scaffolds possess better bioactivity than the pure PCL ones, especially those containing mussel shell- and cuttlebone-derived powders, which promoted the best cell adhesion, proliferation and metabolic activity of human osteosarcoma cells after 7 days of culture. In addition, the elastic compressive modulus, which was found to be between 177-316 MPa, thus in the range of that of trabecular bone, was found to increase of about ∼50% with the addition of the bio-derived nanopowders. Finally, in Chapter 6, the cuttlebone-derived powder was used to fabricate porous bioceramic scaffolds by binder jetting 3D printing. Due to serious technical issues related to the printing of a nanosized powder, 10 wt% of bio-derived powder was mixed with a glass-ceramic powder with bigger particle size. Moreover, the organic part of the cuttlebone had to be previously eliminated by a heat treatment at 800°C. Thanks to the great freedom of design that is allowed by the binder jetting process, scaffolds with two different pore geometries were fabricated: with pores of uniform size and with a size-gradient. Indeed, natural bone possesses a gradient in porosity from the core to the surface, from porous trabecular bone to dense cortical bone. The sintered scaffolds showed a total porosity of ∼60% for the pure glass-ceramic and ∼70% for the glass-ceramic with 10 wt% of cuttlebone-derived nanoparticles, which most probably slowed down the densification by limiting the contact between the glassy particles. All the bioceramic scaffolds promoted good adhesion and proliferation of human bone marrow-derived mesenchymal stem cells in vitro, without any significant difference between the different samples. However, the scaffolds with the cuttlebone-derived powder and with gradient porosity showed the greatest decrease of metabolic activity after 10 days of culture, which could be accounted as a sign of differentiation of stem cells.
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Ramírez, Jiménez Guillermo. "Electric sustainability analysis for concrete 3D printing machine". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-258928.
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Nowadays, manufacturing technologies become more and more aware of efficiency and sustainability. One of them is the so called 3D printing. While 3D printing is often linked to plastic, the truth is there are many other materials that are being tested which could have several improvements over plastics.One of these options is stone or concrete, which is more suitable the architecture and artistic fields. However, due to its nature, this new technology involves the use of new techniques when compared to the more commonly used 3D printers. This implies that it could interesting to know how much energy efficient these techniques are and how can they be improved in future revisions.This thesis is an attempt to disclose and analyze the different devices that make up one of these printers and with this information, build a model that accurately describes its behavior.For this purpose, the power is measured at many points and later it is analyzed and fitted to a predefined function. After the fitting has been done, an error is calculated to show how accurate the model is when compared to the original data.It was found that many of these devices produce power spikes due to its nonlinear behavior. This behavior is usually related to switching, and can avoided with different devices.Finally, some advice is given focused on future research and revisions, which could be helpful for safety, efficiency and quality.Numera blir tillverkningstekniken alltmer medveten om effektivitet och hållbarhet. En av dem är den så kallade 3Dutskriften. Medan 3Dutskrift ofta är kopplad till plast, är verkligheten att det finns många andra material som testas, vilket kan ha flera förbättringar över plast.Ett av dessa alternativ är sten eller betong, vilket är mer lämpligt inom arkitektur och konstnärliga fält. På grund av sin natur inbegriper denna nya teknik användningen av nya tekniker jämfört med de vanligare 3Dskrivarna. Detta innebär att det kan vara intressant att veta hur mycket mer energieffektiva dessa tekniker är och hur de kan förbättras i framtida revisioner.Denna avhandling är ett försök att studera och analysera de olika enheter som utgör en av dessa skrivare och med denna information, bygga en modell som exakt beskriver dess beteende.För detta ändamål mäts effekten på många punkter och senare analyseras och anpassas den till en fördefinierad funktion. Efter anpassning har gjorts beräknas felet för att visa hur exakt modellen är jämfört med originaldata.Det visade sig att många av dessa enheter producerar spänningsspikar på grund av dess olinjära beteende. Detta beteende är vanligtvis relaterat till omkoppling och kan undvikas med olika enheter.Slutligen ges några råd om framtida forskning och revideringar, vilket kan vara till hjälp för säkerhet, effektivitet och kvalitet.
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Gregory, Scott W. "‘The Wuding Editions’: Printing, Power, and Vernacular Fiction in the Ming Dynasty". BRILL ACADEMIC PUBLISHERS, 2017. http://hdl.handle.net/10150/625956.
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The vernacular fiction 'novel' is a genre typically associated with the explosion of commercial printing activity that occurred in the late sixteenth century. However, by that time, representative works such as the Shuihu zhuan and Sanguo yanyi had already been in print for several decades. Moreover, those early print editions were printed not by commercial entities but rather the elite of the Jiajing court. In order to better understand the genre as a print phenomenon, this paper explores the publishing output of one of those elites: Guo Xun (1475- 1542), Marquis of Wuding. In addition to vernacular fiction, Guo printed a number of other types of books as well. This paper examines the entirety of his publishing activities in order to better contextualize the vernacular novel at this early stage in its life in print.
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Das, Ajay Kumar. "An investigation on the printing of metal and polymer powders using electrophotographic solid freeform fabrication". [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0005385.
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Ma, Da. "Improving the Strength of Binder Jetted Pharmaceutical Tablets Through Tailored Polymeric Binders and Powders". Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/101030.
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Additive Manufacturing (AM) provides a unique opportunity for fabrication of personalized medicine, where each oral dosage could be tailored to satisfy specific needs of each individual patient. Binder jetting, an easily scalable AM technique that is capable of processing the powdered raw material used by tablet manufacturers, is an attractive means for producing individualized pharmaceutical tablets. However, due to the low density of the printed specimens and incompatible binder-powder combination, tablets fabricated by this AM technology suffer from poor strength. The research is introducing an additional composition in the binder jetting powder bed (e.g., powdered sugar) could significantly enhance the compressive strength of the as-fabricated tablets, as compared with those tablets fabricated without the additional powder binding agent. However, no previous research demonstrated comprehensive approaches to enhance the poor performance of the 3D printed tablets. Therefore, the goal of this work is to identify processing techniques for improving the strength of binder jetted tablets, including the use of (i) novel jettable polymeric binders (e.g., 4-arm star polyvinylpyrrolidone (PVP), DI water, and different i) weight percentage of sorbitol binder) and (ii) introducing an additional powder binding agent into the powder bed (e.g.., different wt% of powdered sugar).M.S.
Three-dimensional printing is well-known as 3D printing. 3D printing pills are printed from the 3D printer. As of today, we now stand on the brink of a fourth industrial revolution. By the remarkable technological advancements of the twenty-first century, manufacturing is now becoming digitized. Instead of using a large batch process as traditional, customized printlets with a tailored dose, shape, size, and release characteristics could be produced on- demand. The goal of developing pharmaceutical printing is to reduce the cost of labor, shorten the time of manufacturing, and tailor the pills for patients. And have the potential to cause a paradigm shift in medicine design, manufacture, and use. This paper aims to discuss the current and future potential applications of 3D printing in healthcare and, ultimately, the power of 3D printing in pharmaceuticals.
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Ehlert, Ryan. "The design of a volumetric dispensing system for free-flow powders used in three dimensional printing". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11605.
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Doshi, Parag Mahendra. "Fundamental understanding and integration of rapid thermal processing, PECVD, and screen printing for cost-effective, high-efficiency silicon photovoltaic devices". Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/14783.
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Sharan, Kumar Varun. "Study of Binding Copper Powders by Electrochemical Deposition". University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1471346137.
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Zhao, Kunchen. "3D Printed Frequency Scanning Slotted Waveguide Array with Wide Band Power Divider". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555589955819802.
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Joshi-Kumar, Monica. "Headspace Analysis of Smokeless Powders: Development of Mass Calibration Methods using Microdrop Printing for Chromatographic and Ion Mobility Spectrometric Detection". FIU Digital Commons, 2010. http://digitalcommons.fiu.edu/etd/150.
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Smokeless powder additives are usually detected by their extraction from post-blast residues or unburned powder particles followed by analysis using chromatographic techniques. This work presents the first comprehensive study of the detection of the volatile and semi-volatile additives of smokeless powders using solid phase microextraction (SPME) as a sampling and pre-concentration technique. Seventy smokeless powders were studied using laboratory based chromatography techniques and a field deployable ion mobility spectrometer (IMS). The detection of diphenylamine, ethyl and methyl centralite, 2,4-dinitrotoluene, diethyl and dibutyl phthalate by IMS to associate the presence of these compounds to smokeless powders is also reported for the first time. A previously reported SPME-IMS analytical approach facilitates rapid sub-nanogram detection of the vapor phase components of smokeless powders. A mass calibration procedure for the analytical techniques used in this study was developed. Precise and accurate mass delivery of analytes in picoliter volumes was achieved using a drop-on-demand inkjet printing method. Absolute mass detection limits determined using this method for the various analytes of interest ranged between 0.03 - 0.8 ng for the GC-MS and between 0.03 - 2 ng for the IMS. Mass response graphs generated for different detection techniques help in the determination of mass extracted from the headspace of each smokeless powder. The analyte mass present in the vapor phase was sufficient for a SPME fiber to extract most analytes at amounts above the detection limits of both chromatographic techniques and the ion mobility spectrometer. Analysis of the large number of smokeless powders revealed that diphenylamine was present in the headspace of 96% of the powders. Ethyl centralite was detected in 47% of the powders and 8% of the powders had methyl centralite available for detection from the headspace sampling of the powders by SPME. Nitroglycerin was the dominant peak present in the headspace of the double-based powders. 2,4-dinitrotoluene which is another important headspace component was detected in 44% of the powders. The powders therefore have more than one headspace component and the detection of a combination of these compounds is achievable by SPME-IMS leading to an association to the presence of smokeless powders.
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Stephenson, Joshua A. "A Study of RF/Microwave Components Using Fused Deposition Modeling and Micro-Dispensing". Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6955.
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The design and study of multiple RF direct digital manufactured (DDM) devices are presented in this work. A 2.45 GHz, 180°; hybrid coupler is designed to provide the space required for other system components. The coupler is designed and manufactured on a 32 mil Rogers 4003C substrate and adapted to a 100% in-fill acrylonitrile butadiene styrene (ABS) substrate. A size reduction of 66% is accomplished with a bandwidth of 16%. A DDM Ku band connector is modeled and fabricated using varying relative dielectric constants of 50% and 100% in-fill ABS. The connector maintains less than 0.45 dB of insertion loss up to 14 GHz and greater than 10dB of return loss up to 15 GHz. A lumped component model is also developed to model the damaged transition of the connector with agreement to numerical electromagnetic simulation software. Lastly, a thermal and RF study of a Ku band power amplifier (PA) is performed. Two 5 mil 100% in-fill ABS PA test fixtures are fabricated with a varying number of vias. The designs are biased at various operating points to collect thermal and RF data. The PA operates at 151°C before melting the ABS substrate. A thermal model is developed from the measurement data to predict the temperatures at given power levels with good agreement between simulation and model data.
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Thienen, Stefan, i Thomas Gellner. "Flexible and easy to engineer servo-hydraulic actuators using 3D printing manufacturing process". Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71208.
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Already since some time, Bosch Rexroth offers solutions as compact servo hydraulic actuators (SHA). Because there are lot of requests from the market, we thought about reducing the inquiry processing time and delivery time by designing a kit system for the SHA solutions. This system should be flexible enough to cover different technical solutions (e.g. cylinder), functionalities and design styles [... aus dem Text]
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Feng, Ziang. "Wearable Power Sources and Self-powered Sensors Based on the Triboelectric Nanogenerators". Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/103020.
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The triboelectric nanogenerator (TENG) has attracted global attention in the fields of power sources and self-powered sensors. By coupling the omnipresent triboelectrification effect and the electrical induction effect, the TENGs can transduce ambient mechanical energy into electrical energy. Such energy could be consumed instantaneously or stored for later use. In this way, they could be deployed distributedly to be compatible power sources in the era of the internet of things (IoTs), completing the powering structure that is currently relying on power plants. Also, the electrical signals can reflect the environment changes around the TENGs. Thus, the TENGs can serve as self-powered sensors in the IoTs. In this work, we adopted two approaches for TENG fabrication: the thermal drawing method (TDP) and 3D printing. With TDP, we have fabricated scalable fiber-based triboelectric nanogenerators (FTENG), which have been woven into textiles by an industrial loom for wearable use. This fabrication process can supply FTENG on a large scale and fast speed, bridging the gap between the TENG and weaving industry. With 3D printing, we have fabricated TENGs that are compatible with the shape of arbitrary substrates. They have been used as biocompatible sensors: human-skin-compatible TENG has been used to recognize silent speech in real-time by sensing the chin movement; the porcine-kidney-shaped fiber mesh has been used to monitor the perfusion rate of the organ. These works have extended the territory of TENGs and can be critical components in the IoTs.Ph.D.
Portable electronic devices have become important components in our daily lives, and we are entering the era of the Internet of Things (IoTs), where everyday objects can be interconnected by the internet. While electricity is essential to all of these devices, the traditional power sources are commonly heavy and bulky and need to be recharged or directly connected to the immobile power plants. Researchers have been working to address this mismatch between the device and power systems. The triboelectric nanogenerators (TENG) are good candidates because they can harvest energy in the ambient environment. The users can use them to generate electricity by merely making the rubbing motion. In this work, we report two fabrication methods of the fiber-based triboelectric nanogenerators (FTENG). With the thermal drawing process, we have fabricated sub-kilometer-long FTENG and wove it with the regular cotton yarn into textiles. The wearable power source is human friendly as it does not induce any extra weight load for the user. Besides, we have demonstrated that such long fibers can work as self-powered distributed sensors, such as a Morse code generator. With 3D printing, we have fabricated FTENG-based devices that conform to the working substrates, which can be any shape. We have employed them as biofriendly sensors to translate the chin movement during speaking to language and to monitor the perfusion rate of a pig kidney. The FTENGs have offered excellent comfortability to the users and can play a vital role in reframing the power structure to be compatible with IoTs.
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Wienhausen, Arne Hendrik [Verfasser], Doncker Rik W. [Akademischer Betreuer] De i Andrei [Akademischer Betreuer] Vescan. "High integration of power electronic converters enabled by 3D printing / Arne Hendrik Wienhausen ; Rik W. de Doncker, Andrei Vescan". Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1220082368/34.
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Jiang, Chen. "All-inkjet-printed low-voltage organic thin-film transistors". Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/285012.
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This thesis presents the development of all-inkjet-printed low-voltage organic thin-film transistors. Organic thin-film transistors (OTFTs), taking advantage of low-temperature printability, mechanical flexibility, and multi-functionality, are promising for a wide range of emerging applications such as wearable electronics. Printed OTFTs provide great benefits in fabrication cost reduction, but they need a very high operating voltage and exhibit severe instability during storage and operation in ambient environment. In this study, all-inkjet-printed OTFTs with a low operating voltage of less than 3 V are demonstrated through reducing trap density in the fabricated devices. The transistors use 6,13-bis(triisopropylsilylethynyl)pentacene as the semiconductor, poly(4-vinylphenol) as the dielectric, silver as the electrodes, and CYTOP as the encapsulation. Several aspects of physical and chemical properties of polymer dielectrics are studied to achieve this goal, including cross-linking, wetting, and moisture affinity. Through the careful selection of device architecture and control of the inkjet-printing processes, the semiconductor-dielectric interface trap density of the fabricated OTFTs is significantly reduced. The applicability of this approach to different materials is also investigated and confirmed, including polyvinyl cinnamate as the dielectric, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene as the semiconductor, and anisole as the solvent for semiconductor inks. Based on the investigation of different materials, the characteristics and parameters of all-inkjet-printed OTFTs are optimised, demonstrating an ultra-steep subthreshold of 60.2 mV/decade approaching the theoretical limit and a low operating voltage of 1 V. In order to explore their feasibility in real-world applications, the stability of all-inkjet-printed OTFTs is investigated and the factors of instability are analysed. Based on these findings, the stability of the fabricated device is improved, such that the threshold voltage shift is less than 0.1 V in ambient environment storage for 3 months and operation for 1 hour. The electrical characteristics of OTFTs in the subthreshold regime are studied for analogue circuit design. Based on the developed low-voltage stable transistors, an ultra-low-power (< 1 nW) high-gain (> 200 V/V) amplifier is presented and utilised to detect electrophysiological signals from the human body.
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Mitchell-Williams, Thomas Benjamin. "Tailoring superconductor and SOFC structures for power applications". Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/267811.
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High temperature superconductors (HTS) and solid oxide fuel cells (SOFCs) both offer the possibility for dramatic improvements in efficiency in power applications such as generation, transmission and use of electrical energy. However, production costs and energy losses prohibit widespread adoption of these technologies. This thesis investigates low-cost methods to tailor the structures of HTS wires and SOFCs to reduce these energy losses. Section I focusses on methods to produce filamentary HTS coated conductors that show reduced AC losses. This includes spark-discharge striation to pattern existing HTS tapes and inkjet printing of different filamentary architectures. The printed structures are directly deposited filaments and ‘inverse’ printed tracks where an initially deposited barrier material separates superconducting regions. Furthermore, the concept and first stages of a more complex ‘Rutherford’ cable architecture are presented. Additionally, Section I investigates how waste material produced during the manufacture of an alternative low-AC loss cable design, the Roebel cable, can be used to make trapped field magnets that produce a uniform magnetic field profile over a large area. This trapped field magnet work is extended to study self-supporting soldered stacks of HTS tape that demonstrate unprecedented magnetic field uniformity. Section II looks at how nanostructuring porous SOFC electrodes via solution infiltration of precursors can improve long-term stability and low temperature performance. Inkjet printing is utilised as a scalable, low-cost technique to infiltrate lab-scale and commercial samples. Anode infiltration via inkjet printing is demonstrated and methods to increase nanoparticle loading beyond ~1 wt% are presented. Symmetric cells with infiltrated cathodes are shown to have improved performance and stability during high temperature aging. Additionally, the sequence of solution infiltration is found to be important for samples dual-infiltrated with two different nanoparticle precursors.
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Stephen, Juanita Peche. "3-D Printing, Characterizing and Evaluating the Mechanical Properties of 316L Stainless Steel Materials with Gradient Microstructure". Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/102780.
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Making gradient in the microstructure of metals is proven to be a superior method for improving their mechanical properties. In this research, we 3D print, characterize and evaluate the mechanical properties of 316L Stainless Steel with a gradient in their microstructure. During 3D printing, the gradient in the microstructure is created by tailoring the processing parameters (hatch spacing, scanning speed, and laser power and scanning speed) of the Selective Laser Melting (SLM). The Materials with Graded Microstructure (MGMs) are characterized by optical and scanning electron microscopy (SEM). Image processing framework is utilized to reveal the distribution of cells and melt pools shapes and sizes in the volume of the material when the processing parameters change. It is shown that the laser power, scanning speed and the hatch spacing have a more significant effect on the size and shape of cells and melt pools compared to the speed. Multiple Dog bones are 3D printed with a microstructure that has smaller features (cells and melt polls) at the edges of the structure compared to the center. Tensile and fatigue tests are performed and compared for samples with constant and graded microstructures.Master of Science
The mechanical performance of Selective Laser Melting (SLM) fabricated materials is an important topic in research. Strengthening the performance of these materials can be achieved through implementing a gradient within the microstructure, referred to as Materials with Graded Microstructure (MGMs). A complicated microstructure can weaken the microstructure, and this can be resolved by optimizing the microstructure during SLM 3D printing, in which the processing parameters are tailored. In this study, the mechanical properties of these MGMs were characterized and evaluated. The gradient in these materials were created by modifying SLM process parameters (scanning speed, hatch spacing, and laser power and scanning speed) during the build. Optical and scanning electron microscopy (SEM) was used to characterize these the microstructure of these MGMs, and image processing was used to examine the distribution of cells and melt pools characteristics throughout the region where the processing parameters changed. This investigation shows that laser power, scanning speed, and hatch spacing have a direct effect on the size and shape of the cells and melt pools, compared to scanning speed, which shows an effect on melt pools. Dog bone structures are 3-D printed with a graded microstructure that has small cells and melt pools at the edges, compared to the center, by changing the laser power and scanning speed. Tensile and fatigue analysis are performed and compared for samples with constant and graded microstructures, which reveal that the mechanical properties of the MGMs perform similar to the parameter at the edges, but differently in fracture mechanics.
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Stratton, John W. i. "A Study of Direct Digital Manufactured RF/Microwave Packaging". Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/6031.
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Various facets of direct digital manufactured (DDM) microwave packages are studied. The rippled surface inherent in fused deposition modeling (FDM) fabricated geometries is modeled in Ansoft HFSS, and its effect on the performance of microstrip transmission lines is assessed via simulation and measurement. The thermal response of DDM microstrip transmission lines is analyzed over a range of RF input powers, and linearity is confirmed over that range.
Two IC packages are embedded into DDM printed circuit boards, and their performance is analyzed. The first is a low power RF switch, and the second is an RF front end device that includes a low noise amplifier (LNA) and a power amplifier (PA). The RF switch is shown to perform well, as compared to a layout designed for a Rogers 4003C microwave laminate substrate. The LNA performs within datasheet specifications. The power amplifier generates substantial heat, so a thermal management attempt is described.
Finally, a capacitively loaded 6dB Wilkinson power divider is designed and fabricated using DDM techniques and materials. Its performance is analyzed and compared to simulation. The device is shown to compare favorably to a similar device fabricated on a Rogers 4003C microwave laminate using traditional printed circuit board techniques.
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Karpavičius, Povilas. "Ofsetinės ir fleksografinės spaudos kokybės palyginimas". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2007. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2007~D_20070629.145854-26727.
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Baigiamajame magistro darbe buvo lyginama ofsetinės ir fleksografinės spaudos kokybė spausdinant spalvines kontrolines skales, spalvų sutapdinimo kryžius, skiriamosios gebos elementus. Atspaudai buvo atspausdinti ofsetine lapine spaudos mašina ir siauraritinine fleksografinės spaudos mašina su centriniu spaudos cilindru. Mikroskopu buvo matuojamas spalvų sutapdinimo tikslumas, skiriamosios gebos elementų dydis. Densitometru buvo matuojamas atskirų ir binarinių spalvų rastrinių taškų santykinis plotas bei įvertintas gradacinis tikslumas. Pagal gautus kiekybinius rezultatus nustatyta, jog fleksografinės spaudos kokybė prastesnė negu ofsetinės spaudos. Darbą sudaro šios dalys: įvadas, literatūros apžvalga, kokybės reikalavimai, problemos analizė, eksperimento eiga ir rezultatų analizė, išvados, literatūros sąrašas. Darbo apimtis – 80 p. teksto be priedų, 65 pav., 43 lentelės, 18 literatūros šaltinių.In master thesis was compared the offset and flexographic printing quality. Printing quality was evaluated using control strips, register crosses, resolving power test elements. Jobs were printed with offset sheet-fed printing press and flexographic narrow web press with central impresion cilinder. Register accuracy and resolving power were investigated using microscope. Dot area of single and binary colors wes measured with densitometer and halftone graduation characteristics were evaluated. On the basis of quantitative results it was determined that offset printing quality in comparison with flexography is higher. Master thesis comprise of folowing chapters: literature review, quality requirements, experimental, results and discusion, conclusions, references. Amount – 80 pages, 65 figures, 43 tables, 18 references.
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Sinclair, Melissa Ann. "Modeling and Design of Antennas for Loosely Coupled Links in Wireless Power Transfer Applications". Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1538705/.
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Wireless power transfer (WPT) systems are important in many areas, such as medical, communication, transportation, and consumer electronics. The underlying WPT system is comprised of a transmitter (TX) and receiver (RX). For biomedical applications, such systems can be implemented on rigid or flexible substrates and can be implanted or wearable. The efficiency of a WPT system is based on power transfer efficiency (PTE). Many WPT system optimization techniques have been explored to achieve the highest PTE possible. These are based on either a figure-of-merit (FOM) approach, quality factor (Q-factor) maximization, or by sweeping values for coil geometries. Four WPT systems for biomedical applications are implemented with inductive coupling. The thesis later presents an optimization technique for finding the maximum PTE of a range of frequencies and coil shapes through frequency, geometry and shape sweeping. Five optimized TX coil designs for different operating frequencies are fabricated for three shapes: square, hexagonal, and octagonal planar-spirals. The corresponding RX is implemented on polyimide tape with ink-jet-print (IJP) silver. At 80 MHz, the maximum measured PTE achieved is 2.781% at a 10 mm distance in the air for square planar-spiral coils.
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Beckmann, Bastian. "Additive manufacturing of hydraulic manifolds - a holistic approach across the entire value chain". Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71083.
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Manifolds usually consist of metallic, rectangular base bodies into which lines are inserted by means of drilling, thus logically linking the built-on or built-in valves according to the hydraulic circuit diagram. Using additive manufacturing methods, additional degrees of freedom can be used in the design of manifolds, resulting in further benefit in hydraulic drives and their controls. The challenge is not only to understand and apply additive manufacturing technology, but also to align the entire value chain with it.
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Thompson, John Ryan. "RELATING MICROSTRUCTURE TO PROCESS VARIABLES IN BEAM-BASED ADDITIVE MANUFACTURING OF INCONEL 718". Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1401699643.
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Kuntz, Sarah Louise. "Feasibility of Attaining Fully Equiaxed Microstructure through Process Variable Control for Additive Manufacturing of Ti-6Al-4V". Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1464557846.
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Andriamiharivolamena, Fanamperana Tsitoha. "Contribution au développement d'antennes intégrables aux vêtements : application aux gilets militaires". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAT019/document.
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Actuellement, les fantassins de l'armée française sont équipés d'un système de radiocommunication quand ils sont en intervention sur le terrain. L'antenne utilisée pour émettre et recevoir les signaux radiofréquences (RF) est du type monopole appelée antenne fouet placée parallèlement au corps du fantassin au niveau de la clavicule gauche. Cependant, l'antenne fouet perturbe le champ de vision des fantassins surtout lorsqu'ils tournent leur tête vers la gauche. De plus, la position de l'antenne fouet gêne les fantassins gauchers lorsqu'ils sont en position de tir. Enfin, l'antenne fouet rajoute un poids supplémentaire. Il est évident alors que l'intégration de l'antenne dans les gilets militaires permet de mieux répondre aux besoins des fantassins notamment en termes d'ergonomie. Cependant une telle intégration doit aussi répondre aux besoins d'efficacité de rayonnement, de couverture spatiale et de protection du corps vis-à-vis du rayonnement de l'antenne. De plus les contraintes liées à la technologie de réalisation doivent être prises en compte. La thèse est focalisée sur la conception et la caractérisation d'antennes intégrées aux gilets militaires. Le travail de recherche s'est fait dans le cadre du projet collaboratif GIANTE, soutenu par le dispositif DGA-RAPID, associant les partenaires complémentaires : SAFRAN Sagem, le laboratoire LCIS et ARDEJE. Le travail inclue tous les développements relevant de la conception électromagnétique avec la prise en compte du corps humain et le suivi de la réalisation par impression numérique assurée par ARDEJE qui possède la technologique jet d'encre. Il concerne également la caractérisation RF (adaptation, bande passante, diagramme de rayonnement) des antennes avec un banc expérimental adapté et l'évaluation des performances globales des antennes en environnements fonctionnels (milieu dégagé, milieu urbain, forêt)Nowadays, the infantrymen of French army are equipped with a radio communication system when they are in field action. The antenna used to transmit and receive Radiofrequency (RF) signals is a monopole antenna called as whip antenna. It is placed parallel to the infantryman's body at the left clavicle. However, the whip antenna disrupts the field of view of infantrymen particularly when they turn their head to the left. Moreover, the position of the whip antenna bothers the left-handed infantrymen when they are in fire position. Finally, the whip antenna adds an additional weight to the infantrymen. Thus, it is obvious that the integration of the antenna into the military jackets allows to better meet the needs of infantrymen particularly in terms of ergonomy. However such an integration must also meet the needs in terms of radiation efficiency, spatial coverage and protection of the body against the antenna radiation. Moreover, the constraints of realization technology must be taken into account. The thesis is focused on the design and characterization of integrated antennas into military jackets. The research work is performed within the collaborative project GIANTE, supported by the DGA-RAPID frameproject, associating complementary partners: SAFRAN Sagem, laboratory LCIS, and ARDEJE. The work includes all the electromagnetic studies required by the environmental constraints by taking account the human body. It also includes the follow-up of the realizations made by ARDEJE that masters inkjet printing technologies. The RF characterization (impedance matching, bandwidth, radiation pattern) of antennas with a suitable bench test and the evaluation of global performances of antennas in functional environments (environment free from obstructions, urban areas, forest) are also part of the thesis work
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Lin, Jiou-Wei, i 林久瑋. "3D metal powder printing sintering parameter studies". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/vbf7f7.
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碩士國立虎尾科技大學
機械與電腦輔助工程系碩士班
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In the current industry, integrated manufacturing is highly competitive. As 3D printing continue to develop, the techniques and output value are also expending. In the present domestic market, 3D printing with PLA or ABS filament wires are the most common materials. Due to the low-cost and easy operation, the machine is often purchased by schools as a teaching tool. As for the metal 3D printing, it needs to insert protective gas in a closed off space, through laser sintering and stack-build to create an object with metal powder, although such techniques can produce complex parts, very few technical developments are found in the domestic market due to the high cost. The purpose of this study is to focus on the research of 3D metal powder sintering techniques and process. Through laser sintering experiments with different metal powder mixtures to confirm possible powder sintering, then use different laser power, scanning speeds, frequencies and path spacing parameters to conduct powder sintering experiments under different experimental conditions. By using optical microscope and Vickers Hardness tester to verify sintering products and using Taguchi method to find out best parameter combinations. The conclusions of the study are summarized as follow 1.In this study, the powder mixing mechanism was designed and used, the ratio of copper and tin powder for the mixing mechanism was 18: 1 2.If the scanning rate is higher than 30mm/s, the powder indicates insufficient temperature and shows a splash phenomenon which is not conducive to sintering. This will subsequently impact on the porosity and hardness analysis experiments. 3.Through Taguchi analysis, the best combine parameters for pore-space were found. The best pore-space is 4.712%, the laser power is 80%, and the scanning speed is 7mm/s, the frequency is 30k, and the path-space is 0.05mm. 4.Through Taguchi analysis, the best combine parameters for Vickers Hardness were found. The best pore-space is 134.423HV, the laser power is 100%, the scanning speed is 7mm/s, the frequency is 33K, and the path-space is 0.07mm.