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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

From Digital to Physical: Computational Aspects of 3D Manufacturing

Baecher, Moritz Niklaus 10 October 2015 (has links)
The desktop publishing revolution of the 1980s is currently repeating itself in 3D, referred to as desktop manufacturing. Online services such as Shapeways have become available, making personalized manufacturing on cutting edge additive manufacturing (AM) technologies accessible to a broad audience. Affordable desktop printers will soon take over, enabling people to fabricate / Engineering and Applied Sciences
182

Dynamic micro-3D-printed substrates for characterizing cellular responses to topography

Ali, Maryam 22 September 2014 (has links)
Cell cultures provide researchers the opportunity to observe cell behavior in response to specific, well-defined environmental cues, leading to insights that enable better engineering design for tissue culture and other biomedical applications. Chemical and electrical stimuli have been successfully applied to cultured cells to approximate aspects of the dynamic conditions experienced in vivo. However, in vitro topographical cues have mostly been limited to static substrates that do not subject cells to the dynamic conditions they experience in vivo when tissue remodels during development and wound healing. Delivering dynamic topographical cues to cultured cells can answer long-standing questions about mechanisms of cell morphology changes. Such capabilities could also facilitate engineering of wound-healing matrices and nerve guidance conduits by promoting migration of cells and providing directional guidance to cellular processes. This dissertation describes the development of approaches for introducing in situ topographical cues to cell cultures and inducing responses such as neurite guidance and cell alignment. Both strategies undertaken in this work make use of multiphoton-promoted photochemistry to print and manipulate three-dimensional microscopic protein hydrogel structures. In one approach, a technique referred to as micro-3D printing, topographical guidance cues are printed in the proximity of cultured cells to guide the growth of cellular processes. By translating a tightly-focused pulsed laser beam through a printing reagent solution flooding cultured cells, features are printed that provide physical guidance to extending neurites from NG108-15 cells, a neuronal model cell type. In another approach, an innovative technique known as micro-3D imprinting is developed for producing micrometer-scale depressions on the surfaces of photoresponsive protein hydrogels. The impact of various experimental parameters on topographical feature dimensions is characterized. Micro-3D imprinting is used to introduce dynamic topographical changes on a cell culture substrate, demonstrating that NIH-3T3 cells, a fibroblast cell model, alter their morphology and alignment in response to the introduction of a grooved surface topography. This set of approaches introduces new tools to the repertoire of cell biologists for exploring the behavior of cells growing in a spatio-temporally dynamic environment, opening possibilities for studies of cellular behavior in conditions that may better reflect environments cells experience in vivo. / text
183

Economic aspects of additive manufacturing : benefits, costs and energy consumption

Baumers, Martin January 2012 (has links)
Additive Manufacturing (AM) refers to the use of a group of technologies capable of combining material layer-by-layer to manufacture geometrically complex products in a single digitally controlled process step, entirely without moulds, dies or other tooling. AM is a parallel manufacturing approach, allowing the contemporaneous production of multiple, potentially unrelated, components or products. This thesis contributes to the understanding of the economic aspects of additive technology usage through an analysis of the effect of AM s parallel nature on economic and environmental performance measurement. Further, this work assesses AM s ability to efficiently create complex components or products. To do so, this thesis applies a methodology for the quantitative analysis of the shape complexity of AM output. Moreover, this thesis develops and applies a methodology for the combined estimation of build time, process energy flows and financial costs. A key challenge met by this estimation technique is that results are derived on the basis of technically efficient AM operation. Results indicate that, at least for the technology variant Electron Beam Melting, shape complexity may be realised at zero marginal energy consumption and cost. Further, the combined estimator of build time, energy consumption and cost suggests t AM process efficiency is independent of production volume. Rather, this thesis argues that the key to efficient AM operation lies in the user s ability to exhaust the available build space.
184

The characterization of 3D printed plastics sterilized by hydrogen peroxide vapour

Sosnowski, Emil-Peter 05 January 2017 (has links)
3D printers that precisely fuse plastic filament are enabling medical manufacturers to produce high-quality plastic medical devices and implants. However, the low-temperature fusing process implies that post-production sterilization must also occur at a low temperature or destroy the precision of the product. This study characterizes the effects of hydrogen peroxide (H2O2) vapour sterilization on ASTM-compliant tensile samples of polylactic acid, polycaprolactone, and polycarbonate. The sterilization process caused physical deformations in polycaprolactone. Additionally, increases were observed in polycaprolactone and polycarbonate sample thickness, and in polycarbonate sample width. Decreases in E were found in all three materials, while UTS decreased in polycarbonate, and strain at UTS increased in polycaprolactone. The findings demonstrate that the materials can be compatible with H2O2 vapour sterilization, but products must be designed to accommodate for changes that occur due to sterilization. / February 2017
185

3D-Teknik : ett användbart hjälpmedel för möbelkonservering?

Helgesson, Robin, Dudzina, Ela January 2016 (has links)
Föreliggande rapport syftar till att redogöra för hur olika 3D-tekniker kan fungera som praktiskt användbara hjälpmedel i arbeten rörande möbelkonservering och möbelrestaurering. Arbetet behandlar olika tekniker för att skanna och skriva ut, presenterar ett urval av tidigare forskning vilket berör det aktuella ämnet, samt ger inblick i praktiska fallstudier. Den tekniska utvecklingen av 3D-printing och skanning går stadigt framåt vilket väcker frågan om tekniken kan vara ett lämpligt hjälpmedel inom området för föremålsbevarande arbete. I arbetet presenteras ett antal fallstudier där 3D-tekniken har använts för dokumentation och restaurering av olika föremål. Teknikerna har sedan jämförts med konventionella metoder. PLA är ett utskriftsfilament, kanske främst avsett för kommersiellt bruk. I arbetet undersöks detta material och dess kompabilitet med andra material. Efter åldring genomgår materialet ett hållfasthets- och kulörtest. Resultaten visar att PLA kan vara känsligt för UV-strålning och temperaturer över 60°C. Vi anser att 3D-tekniken i flera fall kan fungera som ett användbart hjälpmedel för möbelkonservering. / This thesis seeks to explain how the various 3D-technologies can serve as a practical aid in applied furniture conservation. The thesis deals with various techniques to scan and print, presents a selection of previous research relevant to the topic, and provides insight into the practical case studies. The technical development of 3D printing and scanning is advancing rapidly which raises the question whether the technology can be a useful tool in the field of conservation. The thesis presents a number of case studies where 3D technology has been used for documentation and restoration of various objects. These techniques have been compared with conventional methods. PLA is a printing fillament, perhaps primarily intended for commercial use. The work examines this material and its compatibility with other materials. After aging, the fillament undergoes a structural and color test. The results show that PLA is sensitive to UV-radiation and temperatures above 60°C. We believe that 3D technology can, in many cases, serve as a useful tool for furniture preservation.
186

Investigation of Several Novel Radio-Frequency Techniques - Biologically Inspired Direction Finding, 3D Printed RF Components and Systems, and Fundamental Aspects of Antenna Matching

Yu, Xiaoju, Yu, Xiaoju January 2016 (has links)
This dissertation presents the investigation of biologically inspired direction finding (DF) and localization systems, 3D printing solution for RF components and systems, and fundamental aspects of antennas regarding bandwidth and power efficiency. Biologically inspired direction finding and localization systems are explored first. Inspired by the human binaural auditory system, an improved direction of arrival (DoA) estimation technique using two antennas with a lossy scatterer in between them to achieve additional magnitude cues is proposed. By exploiting the incident-angle- dependent magnitude and phase differences between the two antennas with specially designed scatterer, the DoA of an incident signal from two-dimensional (2-D) / three- dimensional (3-D) space can be estimated. Besides, compact DF systems with enhanced directional sensitivity using a scatterer of high permittivity in between adjacent closely spaced electrically-small antennas are examined. Inspired by the human monaural auditory system, a novel single-antenna DF technique is also proposed by exploiting the incident-angle-dependent spectra for a broadband RF signal only. In addition, a wideband superior DF system utilizing Luneburg lens and uniformly placed detectors on the equator of the lens is evaluated. The DoA is estimated using the amplitude distribution of the received signals at the detectors. Moreover, A portable inventory localization system utilizing hybrid RF (for direction, using previously introduced DF techniques) and ultrasound (for distance) signals is proposed and experimentally demonstrated. Next, a multilayer phased array system is designed and individual parts are printed to demonstrate the applicability of hybrid thermal wire-mesh embedding (for conductors) and thermoplastic extrusion (for dielectrics) techniques for additively manufacturing RF17integrated systems. Finally, fundamental aspects of antennas in terms of bandwidth limit for reactive matching and power efficiency for non-Foster matching are analyzed.
187

Triboelectricity and Piezoelectricity Based 3D Printed Bio-skin Sensor for Capturing Subtle Human Movements

Mo Lv (6640484) 14 May 2019 (has links)
This thesis present the fabrication of 2 types of soft wearable electrical devices, utilizing the 3D printing technique. The devices are capable to detect human heart pulse waves and sound waves for health evaluation and speech recognition.
188

Lead-time reduction and rapid prototyping of tools and fixtures, therefore I AM : A case study about additive manufacturing in the automotive industry

Gustafsson, Christopher January 2019 (has links)
The purpose of this thesis is to investigate how to decrease lead-times of conventionally manufactured prototypes of tools and fixtures. Which could lead to increased knowledge of how an operations site within the automotive industry could utilize additive manufacturing when producing company specific prototypes of tools and fixtures.  The research approach applied in this case study combines a literature review to systematically find relevant literature aligned with the research topic of additive manufacturing or 3D printing related to lead-time reduction and generative design terms. With the help of interviews and observations profound knowledge was gained as preparation before continuing the research. Thereafter, a pre-study was conducted in order to further enhance the understanding of the industrial context of the two chosen fixtures (study objects). Rapid prototyping activities with additive manufacturing processes and technologies of experimentation character was conducted iteratively with both 3D CAD and 3D printing software and hardware. Analysis of the data was conducted through a comparison between lead-times of conventionally manufactured and 3D printed prototypes of the two chosen fixtures. Moreover, identifying potential effects with additive manufacturing of prototypes have with a SWOT analysis.  The case study found that additive manufacturing could significantly decrease lead-times when producing prototypes compared to conventional manufacturing. Furthermore, the results showed that the effects of additive manufacturing are plenty and rather complex due to the fact of this new way to manufacture prototypes. Therefore, the term design for additive manufacturing need first class priority if next steps were to be taken in the additive manufacturing field to enhance industrial and academic benefits.  The research on this subject is strongly constrained by the scarcity of empirical experience and, consequently, by the scarcity of available empirical data. Research publication on the topic are fruitful and plenty but their findings specified to their chosen study objects. This case study gives an up-to-date contribution to the topic of additive manufacturing with endless possibilities to reduce lead-time with rapid prototyping activities that utilizes additive manufacturing. Moreover, the research approach used in this thesis combines 3D CAD data through theoretical concepts and physical objects with additive manufacturing practice. Overall, the results can be used to improve academic research in the topic and promote discussion among different actors entering or within the additive manufacturing field.
189

"Manufatura rápida - avaliação das tecnologias de impressão 3D e FDM na fabricação de moldes rápidos" / Rapid Manufactory – Comparative evaluations of 3D printing system against FDM system for Rapid Tooling

Martins, José Roberto 16 May 2006 (has links)
Este trabalho avaliou a aplicação das tecnologias de prototipagem rápida por Impressão 3D e FDM (Fused Deposition Modeling) na produção de moldes rápidos. Esta avaliação foi feita com base nas qualidades das peças obtidas por vazamento nos moldes produzidos, bem como nas limitações encontradas em suas utilizações. Foram estabelecidas as principais diferenças do ponto de vista de qualidade, custos, tempos gastos e praticidade. Foram construídos moldes para peças que contemplando vários graus de dificuldades. Para cada ferramental foram obtidos lotes de peças, através dos quais foram analisadas e comparadas as qualidades dos protótipos. / This work evaluated the application of the Rapid Prototyping technologies 3D printer and FDM (Fused Deposition Modeling) in the rapid manufacturing of molds. This evaluation is based on the quality of the parts molded, as well as in the limitations found in the molds applications. As result the main differences related to quality, and usability was established. The molds produced parts with different degrees of geometric difficulties. For each mold, a few prototypes were produced and their qualities compared.
190

Synthèse de formes fabricables à partir de spécifications partielles / Synthesis of fabricable shape from partial specifications

Hergel, Jean 01 February 2017 (has links)
Les techniques de fabrication rapide, issues des techniques de prototypage rapide comme l’impression 3D ou la découpe laser permettent de fabriquer des pièces uniques sans demander d’expertise particulière du procédé mis en œuvre. En revanche la modélisation de nouveaux objets tout comme la personnalisation d’objets existants restent difficiles. En effet, les techniques de prototypages rapides imposent des contraintes sur la géométrie du modèle qui doivent être respectées. Cette thèse présente un ensemble de techniques qui ont pour point commun d’assister l’utilisateur dans la modélisation d’un objet, en tenant compte des contraintes du procédé qui permettra de le fabriquer. À cette fin, l’algorithme prend en charge tout ou partie de la modélisation. En particulier, les problématiques suivantes sont abordées : Tout d’abord, je propose d’améliorer la qualité des objets fabriqués avec une imprimante 3D en minimisant certains défauts qui apparaissent lors de la fabrication. Les approches développées modifient uniquement les algorithmes de pilotage de l’imprimante. En second lieu, je propose d’aider l’utilisateur à prendre en compte les contraintes de fabrication pendant la modélisation. Mes techniques utilisent des informations partielles sur la forme que l’utilisateur souhaite fabriquer, comme le dessin en deux dimensions d’un mécanisme, ou un modèle paramétrique qui définit un meuble. L’algorithme optimise une forme finale qui améliore des critères liés à sa fabrication (gaspillage, encombrement, etc.). Enfin, dans certains cas (e.g. grand public) l’utilisateur n’est pas forcément à même de modéliser ces formes via des logiciels spécialisés. Pour ce cas précis, je propose une technique de synthèse de meubles à partir de spécifications fonctionnelles, e.g. la spécification de poids à porter dans l’espace / The Rapid Manufacturing techniques that emerged from Rapid Prototyping techniques such as 3D printing or laser cutting allow to fabricate unique objects. However, the design of those objects with existing CAD software remain a difficult task: rapid prototyping processes impose constraints on the geometry of the model. This thesis presents a set of techniques that assist the user in the design of an object by taking into account the constraints of the fabrication process. To achieve this, the algorithm automatically performs part of the modelling process. The following problems have been tackled: First, I propose to improve the quality of 3D printed objects by minimizing defects that appear during the fabrication. The technique developed impacts only the algorithm that drives the printer. Then, I propose to help the user to take into account the fabrication constraints during the modelling process. My techniques rely on partial information about the shape that the user wants to fabricate like the 2D sketch of a mechanism or a parametric model of a furniture. The algorithm optimizes the initial shape to improve fabrication objectives(Wastage, etc.) Finally, in some cases, the user does not know how to operate dedicated software. In this case, I propose a synthesis technique of furniture from functionnal specification, e.g. loads that have to be supported in space

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