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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.
1

Technologie výroby součástky se zaměřením na využití nekonvenční paprskové metody (LASER) / Technology of production parts with a view to exploitation unconventional beam method (LASER)

Šebela, Jiří January 2008 (has links)
The diploma work is aimed to a the solution of a complete manufactoring technology of an unit in the conditions of a small company which is specialized in the LASER technology use. The introductory part of the work cantains the division of LASER method according to the different categories. There is mentioned in which fields laser is used and especially which kinds of lasers are used in the industry. The main part of the work is aimed to the scheme of the manufacturing technology of an unit which is focused on a concrete device (TRUMATIC L 4030). Further part of the work contains a safety of work from the standpoint of notions, machine operation and dangers review. In the conclusion of the work there is performed a technical and economical evaluation of the manufactured unit according to the machining times and the cutting length.
2

Reducing Curvature in Complex Tool Paths by Deviating from CAM-Produced Tool Paths Within a Tolerance Band

Naseath, George Benjamin 12 December 2007 (has links) (PDF)
This thesis develops an algorithm to decrease high-curvature sections in tool paths for complex parts to achieve shorter machining times resulting in higher production rates. In the research sample cases, the algorithm decreased machining times by 1% to 9% for design-induced sections of high curvature and by 16% to 75% for CAM induced ripples using high path tolerances. High-curvature sections in tool paths are caused by complex part geometry, noise, and discontinuities in the model. The curvature is decreased by deviating the tool path within an allowable path tolerance. The feedrate along the tool path is directly related to the curvature of the tool path. High-curvature sections cause the NC machine to reduce the feedrate along the tool path due to acceleration and jerk limits. These lower feedrates increase machining time and slow production rates. This new algorithm decreases curvature, which increases feedrates and decreases machining times, thereby increasing production rates for manufacturing companies. The tool paths are represented by cubic B-splines. The algorithm is based on the basic principle that the curvature of a B-spline directly relates to the geometry of its control polygon. If the control polygon's geometry has many tight corners then the B-spline will have high curvature. If the control polygon's geometry is a straight line then the B-spline will be a straight line with zero curvature. The algorithm deviates the control polygon's points so that they move towards forming a straight line. The control polygon will rarely form a straight line because the spline is limited by the path tolerance. However, as the control polygon moves towards forming a straight line, the curvature decreases, which allows the feedrate to increase. Six sample cases are explored in which the machining time is decreased. Three of the cases are tool paths that contain curvature sections with a range of unnecessary curvature from low to high. One sample is the tool path for the complex geometry in a snow tire mold. Another sample tool path contains ripples caused by noise in the CAD model. The last tool path contains ripples caused by tangency discontinuities in the CAD model. The percent of time saved directly relates to the severity of the curvature in the part. This thesis provides a quick and efficient means to reduce curvature in complex parts, resulting in decreased machining times and increased production rates.
3

Contribuição para os usuários de sistemas CAD/CAM/CNC em operação de fresamento de topo em aço para moldes e matrizes / Contribution to the users of systems CAD/CAM/CNC in end milling operation in steel for molds and dies

Costa, Gustavo Guilherme dos Santos 16 June 2011 (has links)
The increased in the demand for plastic products and the need for reduction manufacturing times, and the growing dependence of man on the computer in present day, especially in manufacturing activities, has resulted in constant research of technological developments in order to supply these needs. In dies and molds manufacturing industry for plastic injection requiring machining operations such as (milling, drilling and polishing, among others), is increasing dependence by computer systems, such as CAD/CAM. This technology helps in the manufacturing steps, provides fast and high accuracy in the manufacturing of complex geometries. Therefore, to understand and to use efficiently these resources that aided in manufacturing are of enormous importance for the optimization of a production process. In this context, this work presents a study on the use of resources programming CAD/CAM in milling operation of cavities steel VP50 with inserts cemented carbide with ball nose. The influence of two types of interpolation (linear and circular) and tolerances bands (0.05 mm and 0.1 mm) that define the tool path for machining of a cavity that has a similar form the a mold of a battery cover cell phone. As output variables evaluated were machining time, the number of lines of the program, the parameters of surface roughness (Ra, Rq, Rz) of parts, the radius of curvature, form deviation of any line profile and the tool wear. The results showed that, from the statistical point of view (ANOVA), none of the conditions of interpolation and tolerance employed significantly influenced the values of surface roughness in form deviation of any line and tool wear. Linear interpolation with tolerance of 0.1 mm was most viable for the production of such cavity in the conditions investigated because the produced good finish, low tool wear and machining time is shorter. / O aumento pela demanda por produtos plásticos e a necessidade de redução nos tempos de fabricação, além da crescente dependência do homem pelo computador em dias atuais, especialmente nas atividades de fabricação, tem implicado na busca por constantes desenvolvimentos tecnológicos a fim de suprir estas necessidades. Na indústria de fabricação de matrizes como também de moldes para injeção de plásticos (que necessitam de operações de usinagem tais como fresamento, furação e polimento, dentre outros), é cada vez maior a dependência pelos sistemas computacionais, como o sistema CAD/CAM. Essa tecnologia auxilia nas etapas de fabricação, oferece rapidez e alta exatidão na fabricação de geometrias complexas. Portanto, entender e saber utilizar de forma eficiente estes recursos que auxiliam na manufatura são de enorme importância para a otimização de um processo produtivo. Neste contexto, este trabalho apresenta um estudo sobre a utilização de recursos de programação CAD/CAM em fresamento de cavidades de aço VP50 com insertos de metal duro ponta de esférica. Foi investigada a influência de dois tipos de interpolações (linear e circular) e tolerâncias (0,05mm e 0,1 mm) que definem o percurso da ferramenta na usinagem de uma cavidade que possui forma semelhante a um molde da tampa da bateria do aparelho celular. Como variáveis de saída foram avaliadas o tempo de usinagem, o número de linhas do programa, os parâmetros de rugosidade superficial (Ra, Rq, Rz) das cavidades, o raio de curvatura, o desvio de forma de uma linha qualquer e o desgaste das ferramentas. Dos resultados obtidos, constatou-se que, sob o ponto de vista estatístico (ANOVA), nenhuma das condições de interpolação e tolerância empregadas influenciou significativamente nos valores de rugosidade da superfície, no desvio de forma de uma linha qualquer e desgaste das ferramentas. A interpolação linear com tolerância de 0,1mm mostrou-se a mais viável para a produção de tal cavidade nas condições investigadas devido a bom acabamento produzido, pequeno desgaste e tempo de usinagem mais curto. / Mestre em Engenharia Mecânica
4

Qualification multi-critères des gammes d'usinage : application aux pièces de structure aéronautique en alliage Airware® / Multi-criteria qualification of machining sequence : application to aerospace structural parts made from Airware® alloy

Hassini, Sami 07 July 2015 (has links)
L’optimisation des gammes d'usinage n’est pas aisée, car elle souffre de deux lacunes importantes. La première est axée sur l'adaptabilité des gammes existantes aux moyens actuels de production et à leurs évolutions au fil des années pour répondre aux évolutions technologiques. Le second point concerne, l’absence de prise en compte du comportement mécanique de la pièce durant l'usinage dans l'élaboration de la gamme. Ces travaux de thèse abordent ces problématiques dans le cadre du projet FUI OFELIA. Ils étudient, dans un premier temps l'influence de la gamme d’usinage sur la déformation de la pièce. L'objectif est de pouvoir prédire le comportement mécanique de la pièce pour identifier les gammes minimisant les déformations. Le second point s'intéresse à l’évaluation multicritères des gammes de fabrication. Les critères retenus prennent en compte la déformation de la pièce, la productivité à travers une estimation rapide des temps d'usinage et la recyclabilité des copeaux obtenus lors de l'usinage. D’autre part, nous proposons un modèle géométrique des états intermédiaires de la pièce durant l’usinage pour à la fois évaluer les gammes de fabrication et conduire les calculs de simulation de la déformation de la pièce durant l’usinage. / The optimization of machining sequences is not easy because it suffers from two major shortcomings. The first focuses on the adaptability of existing ranges to current production facilities and their evolution over the years to respond to technological developments. The second point concerns the lack of consideration in the mechanical behavior of the part during the development of machining sequence. This thesis addresses these in relation to the FUI OFELIA project. At first, they study the influence of the machining parameters on the deformation of the workpiece. The aim is to predict the mechanical behavior of the part to identify recommendations with minimal distortion. The second issue deals with multi-criteria evaluation of manufacturing ranges. The criteria take into account are the deformation of the workpiece, productivity through a quick estimate of machining time and recyclability of chips produced during machining. On the other hand, we propose a geometric model of the intermediate states of the workpiece during machining in order to both assess the manufacturing recommendations and to drive the simulation calculations of the deformation of the workpiece during machining.

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