490 research outputs found

    Tool-Path Problem in Direct Energy Deposition Metal-Additive Manufacturing: Sequence Strategy Generation

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    The tool-path problem has been extensively studied in manufacturing technologies, as it has a considerable impact on production time. Additive manufacturing is one of these technologies; it takes time to fabricate parts, so the selection of optimal tool-paths is critical. This research analyzes the tool-path problem in the direct energy deposition technology; it introduces the main processes, and analyzes the characteristics of tool-path problem. It explains the approaches applied in the literature to solve the problem; as these are mainly geometric approximations, they are far from optimal. Based on this analysis, this paper introduces a mathematical framework for direct energy deposition and a novel problem called sequence strategy generation. Finally, it solves the problem using a benchmark for several different parts. The results reveal that the approach can be applied to parts with different characteristics, and the solution to the sequence strategy problem can be used to generate tool-paths.This work was supported in part by the Project HARITIVE under Grant HAZITEK 2017 and in part by the Project ADDISEND under Grant ELKARTEK 2018 through Basque Government, and in part by the European Union Horizon 2020 Research and Innovation Programme under Grant 822064. The work of Roberto Santana was supported in part by IT-1244-19, in part by the ELKARTEK Programmes through Basque Government, and in part by the Spanish Ministry of Economy, Industry and Competitiveness under Grant TIN2016-78365-R

    Experimental Investigation and Optimization of Cutting Parameters in Plasma Arc Cutting

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    Experimental investigation of plasma arc cutting has been carried out using AISI 4140 and AISI 304 stainless steel as work-piece. The process parameters were considered as follows: feed rate, cutting current, cutting speed, gas pressure, voltage and torch height. The response parameters were chosen as follows: material removal rate (MRR), surface roughness (SR), right bevel angle (RBA), chamfer, dross, kerf width and heat affected zone (HAZ) which are the main cut quality characteristics of plasma arc cutting operation. The optimization of the process parameters have been carried out using desirability function, grey based principal component analysis (PCA) hybrid approach, genetic algorithm (GA), particle swarm optimization (PSO), simulated annealing (SA) and teaching-learning-based-optimization (TLBO) algorithm coupled with response surface methodology (RSM). A regression model was developed that represents the relationship between independent and dependent variables based on RSM. This type of novel approach has been proposed to evaluate and estimate the influence of plasma arc machining parameters on the quality of cut. This user-friendly mathematical approach is straight forward and the results thus obtained have also been validated by running confirmatory tests. The premise attributes provide beneficial knowledge for managing the machining parameters to enhance the preciseness of machined parts by plasma arc cutting. The obtained results indicate that the TLBO approach was significantly affected by the machining parameters directly with easy operability and economically

    Nonterrestrial utilization of materials: Automated space manufacturing facility

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    Four areas related to the nonterrestrial use of materials are included: (1) material resources needed for feedstock in an orbital manufacturing facility, (2) required initial components of a nonterrestrial manufacturing facility, (3) growth and productive capability of such a facility, and (4) automation and robotics requirements of the facility

    Additive Manufacturing of Metals

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    This book is an exciting collection of research articles that offer a unique view into the fast developing field of metal additive manufacturing, providing insights into this advanced manufacturing technology. The articles span recent advances in metal AM technologies, and their application to a wide range of metals, exploring how the processing parameters offer unique material properties. This book encapsulates the state of the art in this rapidly evolving field of technology and will be a valuable resource for researchers in the field, from Ph.D. students to professors, and through to industrial end users

    General model of tool path problem for the CNC sheet cutting machines

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    The formalization of the tool path problem for the CNC sheet metal/material cutting equipment is considered. General model of tool path problem for laser/plasma/gas/water-jet machines is offered. Model uses the term “the basic cutting segment” proposed by author. The existing classification of the tool path problem is expanded. In the paper also the discretization of offered general statement of optimization problem is described. Results of computing experiments for some instances are given. © 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.Russian Foundation for Basic Research, RFBR: № 17-08 -01385The work was supported by the Russian Foundation for Basic Research ( grant № 17-08 -01385) and by Act 211 Government of the Russian Federation, contract № 02.A03.21.0006

    Additive Manufacturing of Optically Transparent Glass

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    We present a fully functional material extrusion printer for optically transparent glass. The printer is composed of scalable modular elements able to operate at the high temperatures required to process glass from a molten state to an annealed product. We demonstrate a process enabling the construction of 3D parts as described by computer-aided design models. Processing parameters such as temperature, which control glass viscosity, and flow rate, layer height, and feed rate can thus be adjusted to tailor printing to the desired component, its shape, and its properties. We explored, defined, and hard-coded geometric constraints and coiling patterns as well as the integration of various colors into the current controllable process, contributing to a new design and manufacturing space. We report on performed characterization of the printed materials executed to determine their morphological, mechanical, and optical properties. Printed parts demonstrated strong adhesion between layers and satisfying optical clarity. This molten glass 3D printer demonstrates the production of parts that are highly repeatable, enable light transmission, and resemble the visual and mechanical performance of glass constructs that are conventionally obtained. Utilizing the optical nature of glass, complex caustic patterns were created by projecting light through the printed objects. The 3D-printed glass objects described here can thus be extended to implementations across scales and functional domains including product and architectural design. This research lies at the intersection of design, engineering, science, and art, representing a highly interdisciplinary approach.Massachusetts Institute of Technology. Department of Mechanical EngineeringGlass Art Society (Technology Advancing Glass Grant

    Investigation and Modification of Charge Transport in Semiconducting Carbon Nanotube Networks

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    The extraordinary mechanical and charge transport properties of semiconducting single-walled carbon nanotubes (SWNTs) make them a promising material for solution-processable, flexible and stretchable electronics. Many of these remarkable features are even obtained in randomly-oriented SWNT networks that are compatible with established large-scale thin-film processes based on printing techniques or optical lithography. Given the enormous progress in the purification of solely semiconducting nanotubes as well as in the preparation of SWNT networks with a uniform and defined morphology in recent years, their widespread application as active layers in field-effect transistors (FETs) has become feasible. Likewise, this progress raised subsequent questions of what key parameters determine the charge transport processes across these networks and how they can further be optimized. This thesis investigates charge transport and its limitations in polymer-sorted semiconducting SWNT networks with a focus on the precise nanotube network composition. The employed FET geometry enabled a reproducible and undistorted analysis of composition- and temperature- dependent transport parameters such as the charge carrier mobility. A comparison between nanotube networks with various selected or even precisely defined SWNT species distributions and average tube diameters reveals that additional energy barriers created at the junctions of adjacent nanotubes with different diameters result in inferior transport properties. While the network charge transport was formerly considered to be solely limited by the charge transfer across these inter-nanotube junctions, the results of this work imply that also the transport within each individual SWNT is important. The specific diameter dependence of this intra-nanotube transport can rationalize the substantially higher carrier mobilities observed for large-diameter networks with a certain SWNT bandgap distribution compared to monochiral networks that contain only a single small-diameter nanotube species. These findings suggest that composition optimizations for SWNT network FETs with maximum carrier mobilities should aim at monochiral large-diameter nanotubes. Aside from insights into the underlying transport mechanisms, this work demonstrates a novel approach to intentionally modify charge transport in semiconducting SWNT network FETs by adding photochromic spiropyran compounds to the dielectric layer. The strong impact of the spiropyran and its photoinduced isomerization to merocyanine on the charge carrier mobilities give these transistors the properties of basic optical memory devices. Upon UV illumination the carrier mobilities are severely reduced until their recovery is induced by annealing or illumination with visible light. This implemented light responsiveness illustrates the fundamental suitability of SWNT network FETs for multifunctional applications beyond integrated circuits
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