This thesis presents the research work carried out in an experimental study on High Speed Milling and a predictive force model. The Oxley??s machining theory [36] that can be considered a purely theoretical approach, which has not yet been applied to the high speed milling process is used to model this process in order to predict the cutting forces. An experimental programme was carried out in order to study and understand the high speed milling process and to collect force data for machining of AISI 1020 plain carbon steel at speeds from 250 to 500m/min, feed rates 0.025 to 0.075mm/tooth and 0.5 and 0.8mm depths of cut, using three different tool configurations with different nose radii. The model developed by Young [5] using the Oxley??s machining theory, for conventional milling, was first applied to the high speed milling operation. The force predictions were satisfactory compared to the measured forces. Using this as the basis, a theoretical model was developed to predict the cutting forces in high speed milling. A smaller chip element was considered in applying the machining theory to satisfy the assumption of two dimensional deformation in the machining theory. Using the flow stress properties for plain carbon steels obtained by Oxley and his co-workers, the cutting force components: tangential, radial and vertical, were predicted with the new developed model for AISI 1020 steel for the same cutting conditions used in the experiment. The model was able to accurately predict the tangential force, while the other two components showed a good agreement with the experimental forces. Then the model was verified using two other materials namely, AISI 1045 plain carbon steel and AISI 4140 alloy steel. The alloy steel was used in both the states, virgin and hardened (heat treated) for the experiment. The comparison of predictions with experimental forces showed good results for these additional two materials. From the results obtained, it is concluded that the developed model can be used to predict the tangential cutting force accurately, while predicting the other force components with a favourable accuracy.

This thesis presents the research work carried out in an experimental study on High Speed Milling and a predictive force model. The Oxley??s machining theory [36] that can be considered a purely theoretical approach, which has not yet been applied to the high speed milling process is used to model this process in order to predict the cutting forces. An experimental programme was carried out in order to study and understand the high speed milling process and to collect force data for machining of AISI 1020 plain carbon steel at speeds from 250 to 500m/min, feed rates 0.025 to 0.075mm/tooth and 0.5 and 0.8mm depths of cut, using three different tool configurations with different nose radii. The model developed by Young [5] using the Oxley??s machining theory, for conventional milling, was first applied to the high speed milling operation. The force predictions were satisfactory compared to the measured forces. Using this as the basis, a theoretical model was developed to predict the cutting forces in high speed milling. A smaller chip element was considered in applying the machining theory to satisfy the assumption of two dimensional deformation in the machining theory. Using the flow stress properties for plain carbon steels obtained by Oxley and his co-workers, the cutting force components: tangential, radial and vertical, were predicted with the new developed model for AISI 1020 steel for the same cutting conditions used in the experiment. The model was able to accurately predict the tangential force, while the other two components showed a good agreement with the experimental forces. Then the model was verified using two other materials namely, AISI 1045 plain carbon steel and AISI 4140 alloy steel. The alloy steel was used in both the states, virgin and hardened (heat treated) for the experiment. The comparison of predictions with experimental forces showed good results for these additional two materials. From the results obtained, it is concluded that the developed model can be used to predict the tangential cutting force accurately, while predicting the other force components with a favourable accuracy.

Dentro da cadeia produtiva de moldes e matrizes, a usinagem tem o maior peso, considerando tanto os custos envolvidos, quanto o tempo de programação e execução. O emprego das tecnologias CAD/CAM/CNC e HSC atualmente é um atributo básico de competitividade. O que determinará a vantagem estratégica das empresas será o uso otimizado dessas tecnologias. Nos processos de usinagem, o acabamento é uma operação que demanda muito tempo, e muitas vezes não se atinge o resultado desejado, seja por falta de conhecimento dos fenômenos envolvidos na usinagem, seja pelo uso de estratégias de usinagem sem conhecimento detalhado do processo de fabricação. A otimização da etapa de acabamento terá um ganho enorme na repetibilidade da usinagem, uma economia de ferramentas e, principalmente a eliminação de uma etapa, considerando a usinagem do molde/matriz com o material já tratado termicamente com a dureza final de utilização. O objetivo deste trabalho é estudar a usinagem de acabamento de superfícies planas utilizando fresas de topo esférico, demonstrando que os valores teóricos de altura de crista fornecidos pelos softwares CAM não são valores reais. A determinação de fatores ligados à etapa de acabamento de superfícies planas, indicando a melhor alternativa na usinagem do aço ferramenta WNr 1.2367, mostra que os parâmetros de usinagem estudados tiveram grande influência na rugosidade, principalmente o sentido de corte. O conhecimento dos melhores parâmetros de usinagem e suas influências no resultado final, assim como outros fatores, tem o intuito de oferecer informações às empresas e aos seus programadores no sentido de agilizar o planejamento e execução de moldes e matrizes. / In die mould production sequence, the milling is the most important factor, considering both the programming costs and the manufacturing time. In fact, the application of CAD/CAM/CNC and HSC technologies is a basic competitiveness edge. The optimized use of these technologies will determine the strategic advantage for industries. The finishing by milling is a step that spend a long time and, in most cases, the final result is not the desired one. That is a consequence of the lack of knowledge on the involved phenomenon or by the use of milling strategies without the enough knowledge on milling processes. The optimization of the finishing by milling will provide a gain on the next operations, save tools, and mainly because of the possibility of eliminating one step, consider a mould being machined in hardened state. The main objective of the present work is to study the finishing milling on flat surfaces using ball nose end mills and shows that the theoretical scallop height values yielded by CAM softwares is not reached on practical operations. Also, the factors governing flat surfaces as well as the best parameters for the WNr. 1.2367 tool steel showing that the studied milling parameters has a strong influence in the roughness, manly the cut sense. The knowledge of the best milling parameters and their influences on the final result, as well as others some factors, intend to offer information for industries and their programmers to optimize the die and moulds cutting plan and manufacturing.

Dentro da cadeia produtiva de moldes e matrizes, a usinagem tem o maior peso, considerando tanto os custos envolvidos, quanto o tempo de programação e execução. O emprego das tecnologias CAD/CAM/CNC e HSC atualmente é um atributo básico de competitividade. O que determinará a vantagem estratégica das empresas será o uso otimizado dessas tecnologias. Nos processos de usinagem, o acabamento é uma operação que demanda muito tempo, e muitas vezes não se atinge o resultado desejado, seja por falta de conhecimento dos fenômenos envolvidos na usinagem, seja pelo uso de estratégias de usinagem sem conhecimento detalhado do processo de fabricação. A otimização da etapa de acabamento terá um ganho enorme na repetibilidade da usinagem, uma economia de ferramentas e, principalmente a eliminação de uma etapa, considerando a usinagem do molde/matriz com o material já tratado termicamente com a dureza final de utilização. O objetivo deste trabalho é estudar a usinagem de acabamento de superfícies planas utilizando fresas de topo esférico, demonstrando que os valores teóricos de altura de crista fornecidos pelos softwares CAM não são valores reais. A determinação de fatores ligados à etapa de acabamento de superfícies planas, indicando a melhor alternativa na usinagem do aço ferramenta WNr 1.2367, mostra que os parâmetros de usinagem estudados tiveram grande influência na rugosidade, principalmente o sentido de corte. O conhecimento dos melhores parâmetros de usinagem e suas influências no resultado final, assim como outros fatores, tem o intuito de oferecer informações às empresas e aos seus programadores no sentido de agilizar o planejamento e execução de moldes e matrizes. / In die mould production sequence, the milling is the most important factor, considering both the programming costs and the manufacturing time. In fact, the application of CAD/CAM/CNC and HSC technologies is a basic competitiveness edge. The optimized use of these technologies will determine the strategic advantage for industries. The finishing by milling is a step that spend a long time and, in most cases, the final result is not the desired one. That is a consequence of the lack of knowledge on the involved phenomenon or by the use of milling strategies without the enough knowledge on milling processes. The optimization of the finishing by milling will provide a gain on the next operations, save tools, and mainly because of the possibility of eliminating one step, consider a mould being machined in hardened state. The main objective of the present work is to study the finishing milling on flat surfaces using ball nose end mills and shows that the theoretical scallop height values yielded by CAM softwares is not reached on practical operations. Also, the factors governing flat surfaces as well as the best parameters for the WNr. 1.2367 tool steel showing that the studied milling parameters has a strong influence in the roughness, manly the cut sense. The knowledge of the best milling parameters and their influences on the final result, as well as others some factors, intend to offer information for industries and their programmers to optimize the die and moulds cutting plan and manufacturing.

Dans le processus de fabrication en fraisage à grande vitesse ‘FGV’, l’étude de la réaction de la machine au cours de l’usinage est une tâche très délicate et importante. En effet, l’identification du comportement de la machine nécessite la modélisation de la loi de mouvement des axes et de la trajectoire réelle aux niveaux des discontinuités. Le nombre important de discontinuités engendrent une instabilité de la vitesse de déplacement des axes, ce qui implique une augmentation du temps d’usinage et un non-respect de la vitesse d’avance programmée, se traduisant par des problèmes de productivité et une sous-estimation du coût de l’usinage pour l’industriel. L’objectif de cette thèse est de développer un outil informatique qui permet de calculer la vitesse d’avance et de faire une estimation précise du temps de cycle pour n’importe quelle trajectoire générée par un logiciel de FAO. Pour ce faire, nous avons déterminé un modèle qui permet d’identifier le comportement cinématique des axes d’un centre d’usinage en FGV pour toute forme de trajectoire. À partir de la modélisation de la variation de la vitesse d’avance, nous avons déterminé le temps réel selon les trajectoires et l’erreur imposée par le bureau des méthodes. Enfin, nous utilisons ces résultats pour mettre en place une méthodologie pour l’aide au choix du diamètre de l’outil et de la stratégie d’usinage. Afin de valider les modèles et les méthodologies développés, une étude expérimentale a été réalisée sur des applications didactiques et industrielles. / In the context of high speed milling ‘‘HSM’’, the feed rate does not always reach the programmed value during the machining process which implies an increase of machining time and non-compliance with the programmed feed rate. This phenomenon leads to productivity issues and an underestimation of the cost of machining for the industry.The aim of this study is to develop a computerised tool in order to automate the determination process of the evolution of the feed rate for an imposed error and the estimation of cycle time and production cost. To begin with,a modeling approach in order to evaluate feed rate during any type of discontinuity between linear and circular contours in different combination by taking into account the specific machining tolerances.is presented. Then, the cycle time will be estimated with a maximum error of 7% between the actual and the prediction cycle time. The proposed method permits to develop a methodology to determine the optimal diameter of the tool and the optimal strategy. Finally, an industrial application was carried out in order to validate models and to determine the influence of feed rate evolution on the cycle time.

Atualmente, nota-se um crescimento na fabricação de produtos utilizando moldes e matrizes contendo formas geométricas complexas. No entanto, a fabricação destes ferramentais onde se emprega, principalmente, operações de fresamento, não tem acompanhado esta evolução com a mesma velocidade. O advento dos sistemas CAD/CAM, máquinas CNC e da tecnologia de usinagem em altas velocidades (HSC) influenciaram positivamente a fabricação de superfícies complexas. Contudo, nota-se ainda ineficiências neste processo produtivo. A qualidade superficial após as operações de usinagem ainda não é suficiente para que estes ferramentais entrem diretamente na linha de produção. Assim, operações manuais de acabamento são exigidas, elevando o tempo e custo de produção, comprometendo a qualidade dimensional. Com a finalidade de aprimorar a fabricação de moldes e matrizes, este trabalho apresenta uma revisão bibliográfica sobre a usinagem HSC; um estudo sobre a força de usinagem para o fresamento de formas complexas e uma análise sobre a metodologia utilizada por sistemas CAD/CAM e CNC para gerar e interpretar programas NC que contenham movimentações complexas de ferramenta. Análises práticas foram realizadas em um centro de usinagem HSC, e os resultados indicam que as limitações tecnológicas atuais na cadeia CAD/CAM/CNC limitam a usinagem de formas complexas com altas velocidades, reduzindo a velocidade de avanço programada e que as características intrínsecas deste processo de remoção de material demonstrou ser bastante complexo, acarretando em constantes alterações na força de usinagem / In recent years the number of products containing free-form shapes produced by dies and molds have been growing noticeably. However, the milling process used to manufacture those dies and molds does not meet their requirements. The arrival of the CAD/CAM systems and the High Speed Cutting Technology (HSC) helps to improve this manufacturing process. Although to obtain the surface quality needed to meet the dies and molds requirements, a hand finishing still requires. It involves time, money and decrease the product quality. Technological limitations in the CAD/CAM/CNC chain limit the feed rate when milling free-form shape. It also has a negative effect on the surface roughness. Besides, this kind of milling still lacks scientific knowledge of the cutting process. With the aim to support the dies and moulds fabrication, this work presents an overview about HSC Technology; the cutting forces in a non-planar milling; the cutting tool deflection; a detailed description of the process chain involving the CAD/CAM/CNC systems and the methodologies used by those systems to generate and accomplish free-free tool-paths. Free-form milling experiments applying the HSC Technology were made to study the behavior of this process, and the outcomes are presented

Atualmente, devido à globalização das empresas e de seus produtos, tem havido uma competição acirrada no mercado mundial entre as organizações. Estas empresas se veêm obrigadas a contemplar as expectativas do mercado quanto à alta tecnologia, a qualidade do produto, os baixos custos e a redução dos tempos de desenvolvimento do produto. Todo este mecanismo gera uma busca contínua de desenvolvimento da tecnologia dentro das empresas na área de fabricação, as quais estão intimamente relacionadas ao surgimento de novos materiais de difícil usinagem, assim como de novos revestimentos para ferramentas e de máquinas-ferramentas cada vez mais rápidas e eficientes. A utilização da tecnologia de usinagem com altas velocidades de corte – HSM (High Speed Machining) tem demonstrado grande eficiência para a fabricação de moldes e matrizes com formas complexas, propiciando uma vantagem competitiva para as organizações. Entretanto, o fresamento de formas complexas ainda apresenta vários gargalos na linha produção. Após as operações de desbaste, além do sobremetal deixado para as operações de acabamento, um volume excedente de material indesejado permanece na geometria. Este volume está relacionado à estratégia de desbaste em 2 1/2 eixos, ao grau de curvatura da superfície e à geometria da ferramenta de desbaste. Por não ser uniforme esta quantidade excedente de material acaba prejudicando o processo, especialmente quando uma das exigências é uma extrema precisão dimensional. Este trabalho procura identificar as características mais relevantes para preservar a qualidade superficial em função da flexão da ferramenta, devido a esse excedente de sobremetal. Desta forma, as variáveis de influência consideradas foram o balanço e o diâmetro da ferramenta, sua trajetória e o volume não-uniforme de material a ser removido. Os piores valores de rugosidade ocorreram com o máximo balanço independentemente de sua inclinação. Também foi possível constatar que a estratégia de usinagem ascendente gerou uma melhor rugosidade comparada com a descendente. Contudo em superfícies com pouca inclinação horizontal e com variações bruscas de sobremetal a usinagem descendente obteve melhores resultados do que a ascendente. / Nowadays the companies and their products have become global and, consequently, are facing an intense competition in the world market. These companies are forced to match the expectations of the market regarding technology, product quality, low costs and reduction of product development time. This entire mechanism generates continue search for the development of manufacturing technology, which are intimately linked to the arise of new and difficult to cut materials, as well as of new coatings for tools, fast and more efficient machine-tools. The use of high speed milling has demonstrate to be of great efficiency for the production of moulds and dies with complex forms, leading to a competitive advantage for companies. However, milling complex form still presents several bottle necks in the production line. After the roughing operations, besides the stock removal left for the finishing operations, an extra volume of unwanted material remains on the workpiece. This material is related to the roughing strategy in 2 1/2 axes, to the degree of curvature of the surface and the geometry of the cutting tool. Since the distribution of that material is not uniform, it affects the product quality, especially when one of the requirements is a high dimensional precision. The present work aims at identifying the most important characteristics necessaries to obtain a good high superficial quality despite of the tool flexion during cutting. The tool length and its diameter are considered as well as the cutting strategy to remove the stock and its excess. The highest roughness values occurred with the largest in-balance length, independently on the surface inclination. It was also verified that for some cases upward cutting has produced smaller roughness being compared to the downward strategy. However, on surfaces with little horizontal inclination and with abrupt variations of stock removal the downward cutting can produce better result than upward cutting.

Dans un contexte d’optimisation des lignes de production, la maîtrise de la qualité des pièces et des capacités machines est primordiale. Plusieurs études se sont intéressées à la formation des bavures en usinage mais les mécanismes sont encore peu connus, bien qu’un lien fort avec les efforts de coupe soit établi par divers auteurs. Ainsi, la maîtrise des efforts de coupe a un intérêt double : optimiser les lignes de production et servir de donnée d’entrée pour la prédiction de la taille des bavures. Cette étude propose donc de renforcer les connaissances concernant les mécanismes de formation des bavures générées par un outil en sortie matière, et de prédire les efforts de coupe en fraisage grande vitesse, dans l’alliage d’aluminium AlSi7Mg0,3+0,5Cu. Divers mécanismes de formation de bavures sont étudiés en coupe élémentaire. Une nouvelle méthode de mesure in situ permet d’identifier l’influence des conditions opératoires sur l’évolution statistique de critères géométriques caractérisant les bavures générées de façon hétérogène dans le cas de l’alliage étudié, dont le comportement est fortement dépendant de son état de contrainte local ainsi que de sa microstructure. Une analyse des champs de déplacement et déformation par corrélation d’images couplée ainsi qu’un modèle de simulation par éléments finis permettent d’identifier plus finement les mécanismes de formation des bavures. Le surfaçage est étudié pour modéliser les efforts de coupe puis comparer les efforts produits lors de la sortie des dents avec les caractéristiques des bavures obtenues. Enfin, une stratégie de minimisation de la hauteur des bavures en surfaçage à la fraise grande avance est étudiée. / In a context of production lines optimization, parts quality and machine capabilities control is essential. Several studies have been carried out on machining burr formation but the mechanisms are not fully understood, although a strong link between burrs formation and cutting forces is established by several authors. Hence, controlling the cutting forces has two advantages: optimize the production lines and be used as input data for a burr height model. This study proposes to consolidate the knowledge on burr formation mechanisms during the exit of a tooth, and to predict cutting forces during high speed milling of the AlSi7Mg0.7+0.5Cu alloy. Various burr formation mechanisms are studied in orthogonal cutting. A new in situ measurement method allows to identify the statistical influence of some operational conditions on the evolution of some newly introduced geometrical parameters defining the burrs heterogeneously formed in the case of the studied alloy, whose behavior strongly depends on its local stress state as well as its microstructure. A displacement and strain field analysis using Digital Image Correlation, as well as a finite element model provide a better understanding of the burr formation mechanisms. Face milling is studied to model cutting forces and compare the forces produced during the exit of a tooth to the obtained burr morphologies. Finally, a burr height reduction strategy is proposed using a high feed mill.

Atualmente, devido à globalização das empresas e de seus produtos, tem havido uma competição acirrada no mercado mundial entre as organizações. Estas empresas se veêm obrigadas a contemplar as expectativas do mercado quanto à alta tecnologia, a qualidade do produto, os baixos custos e a redução dos tempos de desenvolvimento do produto. Todo este mecanismo gera uma busca contínua de desenvolvimento da tecnologia dentro das empresas na área de fabricação, as quais estão intimamente relacionadas ao surgimento de novos materiais de difícil usinagem, assim como de novos revestimentos para ferramentas e de máquinas-ferramentas cada vez mais rápidas e eficientes. A utilização da tecnologia de usinagem com altas velocidades de corte – HSM (High Speed Machining) tem demonstrado grande eficiência para a fabricação de moldes e matrizes com formas complexas, propiciando uma vantagem competitiva para as organizações. Entretanto, o fresamento de formas complexas ainda apresenta vários gargalos na linha produção. Após as operações de desbaste, além do sobremetal deixado para as operações de acabamento, um volume excedente de material indesejado permanece na geometria. Este volume está relacionado à estratégia de desbaste em 2 1/2 eixos, ao grau de curvatura da superfície e à geometria da ferramenta de desbaste. Por não ser uniforme esta quantidade excedente de material acaba prejudicando o processo, especialmente quando uma das exigências é uma extrema precisão dimensional. Este trabalho procura identificar as características mais relevantes para preservar a qualidade superficial em função da flexão da ferramenta, devido a esse excedente de sobremetal. Desta forma, as variáveis de influência consideradas foram o balanço e o diâmetro da ferramenta, sua trajetória e o volume não-uniforme de material a ser removido. Os piores valores de rugosidade ocorreram com o máximo balanço independentemente de sua inclinação. Também foi possível constatar que a estratégia de usinagem ascendente gerou uma melhor rugosidade comparada com a descendente. Contudo em superfícies com pouca inclinação horizontal e com variações bruscas de sobremetal a usinagem descendente obteve melhores resultados do que a ascendente. / Nowadays the companies and their products have become global and, consequently, are facing an intense competition in the world market. These companies are forced to match the expectations of the market regarding technology, product quality, low costs and reduction of product development time. This entire mechanism generates continue search for the development of manufacturing technology, which are intimately linked to the arise of new and difficult to cut materials, as well as of new coatings for tools, fast and more efficient machine-tools. The use of high speed milling has demonstrate to be of great efficiency for the production of moulds and dies with complex forms, leading to a competitive advantage for companies. However, milling complex form still presents several bottle necks in the production line. After the roughing operations, besides the stock removal left for the finishing operations, an extra volume of unwanted material remains on the workpiece. This material is related to the roughing strategy in 2 1/2 axes, to the degree of curvature of the surface and the geometry of the cutting tool. Since the distribution of that material is not uniform, it affects the product quality, especially when one of the requirements is a high dimensional precision. The present work aims at identifying the most important characteristics necessaries to obtain a good high superficial quality despite of the tool flexion during cutting. The tool length and its diameter are considered as well as the cutting strategy to remove the stock and its excess. The highest roughness values occurred with the largest in-balance length, independently on the surface inclination. It was also verified that for some cases upward cutting has produced smaller roughness being compared to the downward strategy. However, on surfaces with little horizontal inclination and with abrupt variations of stock removal the downward cutting can produce better result than upward cutting.

Atualmente, nota-se um crescimento na fabricação de produtos utilizando moldes e matrizes contendo formas geométricas complexas. No entanto, a fabricação destes ferramentais onde se emprega, principalmente, operações de fresamento, não tem acompanhado esta evolução com a mesma velocidade. O advento dos sistemas CAD/CAM, máquinas CNC e da tecnologia de usinagem em altas velocidades (HSC) influenciaram positivamente a fabricação de superfícies complexas. Contudo, nota-se ainda ineficiências neste processo produtivo. A qualidade superficial após as operações de usinagem ainda não é suficiente para que estes ferramentais entrem diretamente na linha de produção. Assim, operações manuais de acabamento são exigidas, elevando o tempo e custo de produção, comprometendo a qualidade dimensional. Com a finalidade de aprimorar a fabricação de moldes e matrizes, este trabalho apresenta uma revisão bibliográfica sobre a usinagem HSC; um estudo sobre a força de usinagem para o fresamento de formas complexas e uma análise sobre a metodologia utilizada por sistemas CAD/CAM e CNC para gerar e interpretar programas NC que contenham movimentações complexas de ferramenta. Análises práticas foram realizadas em um centro de usinagem HSC, e os resultados indicam que as limitações tecnológicas atuais na cadeia CAD/CAM/CNC limitam a usinagem de formas complexas com altas velocidades, reduzindo a velocidade de avanço programada e que as características intrínsecas deste processo de remoção de material demonstrou ser bastante complexo, acarretando em constantes alterações na força de usinagem / In recent years the number of products containing free-form shapes produced by dies and molds have been growing noticeably. However, the milling process used to manufacture those dies and molds does not meet their requirements. The arrival of the CAD/CAM systems and the High Speed Cutting Technology (HSC) helps to improve this manufacturing process. Although to obtain the surface quality needed to meet the dies and molds requirements, a hand finishing still requires. It involves time, money and decrease the product quality. Technological limitations in the CAD/CAM/CNC chain limit the feed rate when milling free-form shape. It also has a negative effect on the surface roughness. Besides, this kind of milling still lacks scientific knowledge of the cutting process. With the aim to support the dies and moulds fabrication, this work presents an overview about HSC Technology; the cutting forces in a non-planar milling; the cutting tool deflection; a detailed description of the process chain involving the CAD/CAM/CNC systems and the methodologies used by those systems to generate and accomplish free-free tool-paths. Free-form milling experiments applying the HSC Technology were made to study the behavior of this process, and the outcomes are presented