De uma forma geral, conhecer os limites de estabilidade dinâmica de uma máquinaferramenta durante a usinagem, é um desafio para o fabricante de máquinasferramentas, bem como, para o usuário, que precisa escolher uma máquina que garanta a produtividade desejada. Neste trabalho, um modelo teórico foi utilizado para o desenvolvimento de um método de comparação dos limites de estabilidade dinâmica entre máquinas-ferramentas. Duas ferramentas de corte com seus respectivos sistemas de fixação foram selecionados, uma apropriada às operações de desbaste e outra às operações de acabamento. Utilizando as constantes de corte relacionadas ao material selecionado e a geometria das ferramentas, obteve-se experimentalmente o diagrama de estabilidade para três máquinas sob teste, e utilizando-os, comparou-se os limites de estabilidade para cada máquina, o que ilustra a utilização do método em desenvolvimento. A validação e a precisão dos diagramas foram realizadas por meio de ensaios de usinagem em uma das máquinas sob investigação. Os primeiros resultados demonstram as diferenças entre máquinas-ferramentas usando-se como critério a sua estabilidade dinâmica avaliada pelo diagrama de lóbulos. Os critérios e conceitos aqui discutidos contribuíram para o conhecimento do desempenho e produtividade das máquinas-ferramentas. / Knowing the dynamic stability of a machine tool during the metal cutting process is a challenge to the machine tool builder as well as to the end user, especially when choosing or selecting a machine that achieves the desired productivity and performance. This document proposes and describes a theoretical model to determine a method to compare the dynamic stability limits among several machine tools. Two different tool systems were previously selected and addressed, one of them for roughing and another for finishing operations. Using metal cutting constants related to the selected materials and tool geometry, the stability diagram was obtained experimentally for all the three different machine tools and they were used to compare the dynamic stability limits amongst machines illustrating the application of the developed method. The validation of the proposed method was achieved by machining tests executed in one of the machines under investigation. The first results, based on the practical experiments, show the differences amongst machine tools using as criterion the dynamic stability evaluated by the stability lobe diagram. Such concept has contributed to enhance the knowledge on the machine tool productivity and performance.

O aumento da produtividade é sem dúvida um dos maiores desafios para a indústria de manufatura. Neste sentido, a vibração tem se apresentado ao longo das últimas décadas como um dos principais limitantes para a melhoria da produtividade, especialmente em operações de usinagem. Nos últimos anos muitas pesquisas foram conduzidas com o objetivo de suprimir ou minimizar os efeitos causados pelo fenômeno de vibrações regenerativas ou chatter. Este trabalho contribui propondo o desenvolvimento de um método para minimizar os efeitos da vibração em operações de torneamento por meio da variação dinâmica de parâmetros de corte relacionados com a área da seção de corte. No presente estudo optou-se pela operação de torneamento cilíndrico e a atuação dinâmica na profundidade de usinagem. Uma análise teórica e uma verificação das condições técnicas necessárias para a aplicação do método proposto são apresentadas. Além disso, simulações numéricas foram realizadas para verificação dos modelos analíticos e correlação com os ensaios práticos. Finalmente, utilizou-se o método em um processo de usinagem real e os resultados demonstram que é possível minimizar consideravelmente os efeitos do fenômeno de chatter variando dinamicamente a profundidade de usinagem sem afetar a qualidade final da peça usinada. / Improve productivity is with no doubts one of the greatest challenges for manufacturing industries nowadays. In that way, chatter vibrations has been arisen in last decades as a major limiting issue for productivity, especially on machining operations. In the last years many investigations has been carried out to suppress or minimize chatter vibrations effects on machining. In this work a development of a method to minimize chatters vibrations on turning operations by dynamically variation of cross section of the chip is proposed. Cylindrical turning operation was selected as the main target for this study and depth of cut as the parameter to be dynamically varied. A theoretical and essentials technical features analyses to apply the proposed method on a market machine tool are. Furthermore, numerical simulations were performed to validate and correlate analytical model to practical experiments. Finally, the proposed model was applied on real machining process and the results show that it is possible to substantially minimize the chatter vibration phenomenon by dynamically variation on depth of cut without affect the surface finishing.

De uma forma geral, conhecer os limites de estabilidade dinâmica de uma máquinaferramenta durante a usinagem, é um desafio para o fabricante de máquinasferramentas, bem como, para o usuário, que precisa escolher uma máquina que garanta a produtividade desejada. Neste trabalho, um modelo teórico foi utilizado para o desenvolvimento de um método de comparação dos limites de estabilidade dinâmica entre máquinas-ferramentas. Duas ferramentas de corte com seus respectivos sistemas de fixação foram selecionados, uma apropriada às operações de desbaste e outra às operações de acabamento. Utilizando as constantes de corte relacionadas ao material selecionado e a geometria das ferramentas, obteve-se experimentalmente o diagrama de estabilidade para três máquinas sob teste, e utilizando-os, comparou-se os limites de estabilidade para cada máquina, o que ilustra a utilização do método em desenvolvimento. A validação e a precisão dos diagramas foram realizadas por meio de ensaios de usinagem em uma das máquinas sob investigação. Os primeiros resultados demonstram as diferenças entre máquinas-ferramentas usando-se como critério a sua estabilidade dinâmica avaliada pelo diagrama de lóbulos. Os critérios e conceitos aqui discutidos contribuíram para o conhecimento do desempenho e produtividade das máquinas-ferramentas. / Knowing the dynamic stability of a machine tool during the metal cutting process is a challenge to the machine tool builder as well as to the end user, especially when choosing or selecting a machine that achieves the desired productivity and performance. This document proposes and describes a theoretical model to determine a method to compare the dynamic stability limits among several machine tools. Two different tool systems were previously selected and addressed, one of them for roughing and another for finishing operations. Using metal cutting constants related to the selected materials and tool geometry, the stability diagram was obtained experimentally for all the three different machine tools and they were used to compare the dynamic stability limits amongst machines illustrating the application of the developed method. The validation of the proposed method was achieved by machining tests executed in one of the machines under investigation. The first results, based on the practical experiments, show the differences amongst machine tools using as criterion the dynamic stability evaluated by the stability lobe diagram. Such concept has contributed to enhance the knowledge on the machine tool productivity and performance.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2004. / Includes bibliographical references (p. 87-89).

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The machine tool industry is one of several branches of the engineering industry which developed as a manufacturing industry during the second half of the nineteenth century. It is perhaps the most important of all the capital goods industries, since its products are used by, and are indispensable to, all other industries processing metals. The production of industrial machine tools thus made possible the considerable advances in the use of metals which took place during the nineteenth and twentieth centuries, on which much of modern industrial society is based. This thesis is the first attempt to write a comprehensive economic history of the English machine tool industry during the period of its transition from a craft, or handicraft, industry to a full manufacturing industry. Professor [?] Saul has discussed the industry, largely from the standpoint of individual firms, in several articles, but there has been no other extended treatment of the industry. Two separate lines of approach to the history of the machine tool industry are used, firstly, the growth and performance of the industry is analysed in aggregate terms, principally through two major statistical sources, which have not previously been used in such a way, the trade directories of the period and the statistics of the imports of machine tools into France, a major customer for the machine tools of Britain and her competitors. It is argued that the machine tool industry can only be understood within the context of the engineering industry as a whole, and the relationships between the manufacture of machine tools and other metal goods is investigated. The size of the machine tool industry, in terms of the number of firms making machine tools at any one time, is shown to be directly related to the fluctuations in the demand for machinery within the domestic economy. The success of the industry is considered in relation to American and other foreign competition, and it is argued that simplified explanations of English decline and American growth as producers of machine tools do not accord with the chronology of competition which is established. Possible explanations are then explored for the changes in the competitive position of English exporters and producers of machine tools. Secondly an analysis is made of the experience of one machine tool producer, Greenwood and Batley, to provide information on characteristics of the industry which could not easily be approached through aggregate analysis. The very extensive cost and sales records of the firm, covering all its production between 1856 and 1900, are used in this study. The market for one of the principal products of the firm, machine tools for the production of small-arms, is described in detail, and the sales made by the firm are analysed and its pricing policies investigated. The production of machine tools by the firm is considered through an analysis of chances in productivity; it is argued that the productivity of labour employed by the firm was increasing at a substantial rate throughout the period of analysis, and that this can largely be explained by the effects of technical change in the industry. The implications of this rise in labour productivity for the machine tool and engineering industries as a whole are also briefly considered. Throughout the thesis, the major emphasis is placed upon the use of statistical sources and techniques in writing the history of the industry. This emphasis, together with considerations of space and time, prevented more than incidental reference to some aspects of the industry, principally the experience of its labour force. Because of the imperfections of the evidence, it was impossible also to discuss trends in output or prices for the industry as a whole. As a counterweight to this, three major sources of statistical evidence on the industry, trade directories, trade statistics, and the records of Greenwood and Batley, have been analysed in detail. Computer data processing and analysis methods were used to enable those records to be utilised, and the value of this type of approach to the writing of economic history is discussed.