Orientador: Marcos Valério Ribeiro / Banca: José Vitor Candido de Souza / Banca: Manoel Cleber de Sampaio Alves / Banca: Rosemar Batista da Silva / Banca: João Roberto Ferreira / Resumo: Reduzir o uso de fluidos de corte em operações de usinagem é uma meta que tem sido buscada na indústria devido aos problemas ecológicos e de saúde humana, causados pelos fluidos de corte. No entanto, os fluidos de corte ainda promovem uma vida de ferramenta mais longa para muitas operações de usinagem. Este é o caso da operação de fresamento de acabamento da liga de titânio Ti6Al4V usando pastilhas de metal duro recobertas. Portanto, o objetivo deste trabalho é estudar condições de corte mais adequadas para o uso da técnica de mínima quantidade de fluido, ou seja, condições que tornem a vida da ferramenta na técnica MQF, mais próximas ou superiores àquelas obtidas com corte sem lubri-refrigeração e corte com jorro de fluido, sem prejudicar a rugosidade da peça. Para alcançar estes objetivos vários experimentos de fresamento de acabamento foram realizados, variando-se a velocidade de corte e taxa de avanço com aplicação da técnica MQF com o uso de três diferentes fluidos comparados com o corte sem lubri-refrigeração e corte com jorro de fluido. A principal conclusão deste estudo foi que a aplicação da técnica MQF no processo de fresamento de acabamento do Ti-6Al-4V aumenta a vida da ferramenta, melhorando a produtividade e rugosidade, quando mantidas as mesmas condições de corte originalmente propostas / Abstract: To reduce cutting fluids use in machining operations is one goal that has been searched in industrial companies, due to ecological and human health problems caused by the cutting fluid. However, the cutting fluids still provide a longer tool life for many machining operations. This is the case of Ti6Al4V titanium alloy end milling operation using coated carbide inserts. Therefore, this work objective is to study cutting conditions more suitable for minimum quantity of fluid technique use, i.e., conditions which make tool life in MQF technique, closer or over to that obtained with dry cutting and cutting with fluid fload, without damaging the workpiece roughness. To reach these goals several end milling experiments were carried out, varying up cutting speed and feed rate with MQF technique application with three different fluids compared with dry cutting and cutting with fluid fload. The main study conclusion was that applying the MQF technique in Ti-6Al-4V end milling process increases tool life, improving productivity and roughness, when kept up the same cutting conditions proposed originally / Doutor

The proliferation of electric machines has drastically increased in recent years and is likely to increase into the future. This interest in the production of advanced, high power density electrical machines that are small in size has heightened the need for flexible manufacturing processes to produce their laminated components during short batch and prototyping production runs. A means of cost effective, accelerated prototyping of these machines will have a substantial impact on their design and optimization, reducing time requirements to produce and test a given design. A review of the current manufacturing methods for prototyping electric machines was conducted. In particular, laser cutting, electric discharge machining, and abrasive waterjet (AWJ) machining were researched as competitive processes. Each of these methods exhibits marked advantages and disadvantages that present the opportunity for a new process to compete. This work investigates the applicability of high throughput profile milling (HTPM) for the prototyping of advanced electric machines, specifically, the process parameter space for milling of electrical steels. The material response will be determined by characterizing its specific cutting energy and utilizing this to develop a model to predict cutting forces during the milling process. Optimal process parameters will be investigated to obtain maximum productivity and minimal burr formation. Finally, the impact of HTPM processing on the magnetic properties of electrical steels will be compared to that of a leading prototyping technology, AWJ machining.

Face milling machinability investigation of two difficult-to-machine nickel-based superalloys, namely Inconel 718 and Waspaloy, has been carried out with four different types of tungsten carbide tools under various cutting conditions. The tools comprised of one double-layer CVD-TiCN+Al2O3 coated (KC994M), two PVD-TiN coated (KC720 and KC730) and one uncoated (KMF) tungsten carbide tools. The objectives of the study include investigation of tool performance, failure modes and wear mechanisms under the cutting conditions employed. In addition, surface integrity of the machined surfaces, with regard to surface finish, subsurface microhardness and metallographic examination of the subsurface microstructure, was investigated. CVD-coated KC994M gave the best overall performance in terms of tool life at low and high cutting conditions on both workpieces. The second best-performing tool was the uncoated KMF grade which gave as high tool lives as KC994M at lower cutting speeds. However at higher cutting speeds, KMF was generally outperformed by PVD-TiN coated tools. Short tool lives were obtained at higher cutting speeds of 75 and 100 m/min due to premature failure by chipping. Tool wear at low cutting speed range was due to a combination of progressive microchipping and plucking through a fracture/attrition related wear mechanism associated with cyclic workpiece adhesion and detachment and abrasion/diffusion-related flank wear. Plucking and microchipping were the dominant wear mechanisms. Coating layers on the rake face of both CVD and PVD coated tools were almost completely removed within the first few seconds of cutting at all cutting speeds tested, thus becoming ineffective. On the flank face, however, they remained intact for a longer period and hence increasing tools performance at the medium cutting speed range. Analysis of the subsurface microstructures and microhardness measurements showed that plastic deformation was the predominant effect induced onto the machined surface, the degree of which influenced by the cutting speed, tool wear and prolonged machining. In addition surface irregularities in the form of tearing and embedded hard particles were found to occur which was mainly associated with the chipping dominated wear mode.

Thesis (M.S.)--Ohio University, June, 2004. / Title from PDF t.p. Includes bibliographical references (leaves 96-99).

Thesis (Ph. D.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references (leaf 111-114).

Thesis (MScEng (Industrial Engineering))--Stellenbosch University, 2008. / There is a growing global demand for titanium. The aircraft industry is the driving force behind the demand for titanium. The reason for this is that titanium has attractive properties that justify its use both economically and environmentally. Titanium alloys have superior strength-to-weight ratios. This implies that by substituting components manufactured from other metals in the aircraft with titanium components, a substantial reduction in structural weight can be achieved. From an economical point of view a lower mass implies lower fuel consumption. From an environmental point of view lower fuel consumption implies less harmful greenhouse emissions. Ti6Al4V components are the most widely used titanium alloy products in aircraft components. Ti6Al4V is known as a difficult-to-machine material. This is due to its low thermal conductivity and small contact area between the tool and the chips causing higher temperatures to be generated closer to the cutting edge of the insert. This will subsequently increase the rate at which the cutting tool wears. For this reason relatively low cutting speeds and feed rates are employed for the machining of Ti6Al4V compared to the machining of steels. Ti6Al4V is an exceptionally high cost material. The low cutting speeds and feed rates used in Ti6Al4V machining raises the machining cost of parts and contributes to an increase in the price of Ti6Al4V parts. By employing higher cutting speeds and feed rates machining times on Ti6Al4V products could be decreased, subsequently lowering the price for Ti6Al4V components. An increase in cutting speeds and feed rates will subsequently cause an increase in generated cutting temperatures, resulting in an increase in tool wear. This stresses the importance of controlling the cutting temperature during machining of Ti6Al4V in order to prolong tool life. The focus of this work was to investigate different lubrication strategies for polycrystalline diamond (PCD) and tungsten carbide inserts for Ti6Al4V milling operations in the quest to develop improved feasible cutting parameters. The results of this study showed that flood lubrication should be utilized for PCD inserts, while a “softer” 60 bar high pressure through spindle lubrication worked best for the tungsten carbide inserts. By utilizing these lubrication strategies, cutting speeds of 100 m/min and feeds per tooth of 0.05 mm/rev for both the PCD and tungsten carbide grades could be attained with satisfactory tool life.

Made available in DSpace on 2015-12-10T14:24:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-05-27. Added 1 bitstream(s) on 2015-12-10T14:30:39Z : No. of bitstreams: 1 000852079_20160527.pdf: 384748 bytes, checksum: d13287fe4bb4e50857976157165dd2ee (MD5) Bitstreams deleted on 2016-05-30T11:37:07Z: 000852079_20160527.pdf,. Added 1 bitstream(s) on 2016-05-30T11:37:52Z : No. of bitstreams: 1 000852079.pdf: 3951366 bytes, checksum: 259ae6df8d263a1d123b5707ff472b77 (MD5) / Reduzir o uso de fluidos de corte em operações de usinagem é uma meta que tem sido buscada na indústria devido aos problemas ecológicos e de saúde humana, causados pelos fluidos de corte. No entanto, os fluidos de corte ainda promovem uma vida de ferramenta mais longa para muitas operações de usinagem. Este é o caso da operação de fresamento de acabamento da liga de titânio Ti6Al4V usando pastilhas de metal duro recobertas. Portanto, o objetivo deste trabalho é estudar condições de corte mais adequadas para o uso da técnica de mínima quantidade de fluido, ou seja, condições que tornem a vida da ferramenta na técnica MQF, mais próximas ou superiores àquelas obtidas com corte sem lubri-refrigeração e corte com jorro de fluido, sem prejudicar a rugosidade da peça. Para alcançar estes objetivos vários experimentos de fresamento de acabamento foram realizados, variando-se a velocidade de corte e taxa de avanço com aplicação da técnica MQF com o uso de três diferentes fluidos comparados com o corte sem lubri-refrigeração e corte com jorro de fluido. A principal conclusão deste estudo foi que a aplicação da técnica MQF no processo de fresamento de acabamento do Ti-6Al-4V aumenta a vida da ferramenta, melhorando a produtividade e rugosidade, quando mantidas as mesmas condições de corte originalmente propostas / To reduce cutting fluids use in machining operations is one goal that has been searched in industrial companies, due to ecological and human health problems caused by the cutting fluid. However, the cutting fluids still provide a longer tool life for many machining operations. This is the case of Ti6Al4V titanium alloy end milling operation using coated carbide inserts. Therefore, this work objective is to study cutting conditions more suitable for minimum quantity of fluid technique use, i.e., conditions which make tool life in MQF technique, closer or over to that obtained with dry cutting and cutting with fluid fload, without damaging the workpiece roughness. To reach these goals several end milling experiments were carried out, varying up cutting speed and feed rate with MQF technique application with three different fluids compared with dry cutting and cutting with fluid fload. The main study conclusion was that applying the MQF technique in Ti-6Al-4V end milling process increases tool life, improving productivity and roughness, when kept up the same cutting conditions proposed originally

Made available in DSpace on 2014-12-02T11:16:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-08-21Bitstream added on 2014-12-02T11:20:56Z : No. of bitstreams: 1 000792987.pdf: 4111727 bytes, checksum: 017f0ba351e83931e66d4d3b81d00708 (MD5) / A usinagem de moldes e matrizes possui grande potencial de expansão e expressiva importância econômica. O processo de fresamento é amplamente empregado na confecção de cavidades de moldes e pode ser um substituto ao processo de eletroerosão (EDM), gerando superfícies com melhor integridade superficial. Sabe-se que as tensões residuais podem ser geradas nos processos de usinagem e são apontadas como uma das possíveis causas de falhas em componentes, tendo como agravante o fato de na maioria das vezes permanecerem como incógnita, desde a fabricação até a falha. Este trabalho mediu experimentalmente o campo, a magnitude, a profundidade e a direção das tensões residuais pelo Método do Furo-Cego, após o fresamento de acabamento do aço para moldes e matrizes VP100 com durezas diferentes obtidas por meio de tratamento térmico de têmpera. Os resultados foram correlacionados com a microdureza superficial da peça, microestrutura subsuperficial, pressão específica de corte e temperatura na interface cavaco-ferramenta. Os ensaios foram conduzidos em um centro de usinagem vertical CNC, com fresa  25 mm e dois insertos revestidos de TiNAl. Os resultados mostraram que as tensões residuais dependem dos parâmetros de corte empregados no fresamento, e por meio de simulação mostrou-se que o dispositivo de fixação não interferiu na geração de tensões residuais. O aumento do avanço tende a gerar tensões trativas em peças beneficiadas, ao passo que o incremento da velocidade de corte resulta em tensões compressivas em peças temperadas. A microdureza superficial da peça e a pressão específica de corte apresentaram relação inversa e não linear com a tensão residual. Grãos próximos à superfície fresada podem ser deformados pela ação mecânica da aresta de corte da ferramenta desde que tenham orientação preferencial com a das tensões principais máximas. / Machining of moulds and dies has a promising potential of expansion and expressive economic importance. The milling process is widely used in the manufacture of mold cavities and can be a substitute to the process of EDM (EDM) and generate surfaces with better surface integrity. Residual stress may be produced in machining processes and they are the main causes of failure in structural components. This research experimentally measured the field, magnitude, depth and orientation of residual stress by using Hole Drilling Method after finishing milling of VP100 steel for moulds and dies with distinct hardness. The results where correlated with part surface microhardness, subsurface microstructure, specific cutting energy and chip-tool interface temperature. The milling tests were carried out in a CNC machining center by using 25 mm diameter endmill with two TiNAl coated carbides. The results showed residual stresses depend on cutting parameters. Tensile stress is yielded in annealed parts as the tool feed increases, whereas compressive one is generated in quenched workpieces as the cutting speed grows. Part surface hardness and cutting specific pressure presented inverse non-linear relationship with residual stress. Grains near milled surface may be deformed by mechanical action of cutting tool edge since they have preferential orientation regarding to maximum principal stresses.

Orientador: Alessandro Roger Rodrigues / Co-orientador: Adriano Fagali de Souza / Banca: Wyser Jose Yamakami / Banca: Aldo Braghini Júnior / Resumo: A usinagem de moldes e matrizes possui grande potencial de expansão e expressiva importância econômica. O processo de fresamento é amplamente empregado na confecção de cavidades de moldes e pode ser um substituto ao processo de eletroerosão (EDM), gerando superfícies com melhor integridade superficial. Sabe-se que as tensões residuais podem ser geradas nos processos de usinagem e são apontadas como uma das possíveis causas de falhas em componentes, tendo como agravante o fato de na maioria das vezes permanecerem como incógnita, desde a fabricação até a falha. Este trabalho mediu experimentalmente o campo, a magnitude, a profundidade e a direção das tensões residuais pelo Método do Furo-Cego, após o fresamento de acabamento do aço para moldes e matrizes VP100 com durezas diferentes obtidas por meio de tratamento térmico de têmpera. Os resultados foram correlacionados com a microdureza superficial da peça, microestrutura subsuperficial, pressão específica de corte e temperatura na interface cavaco-ferramenta. Os ensaios foram conduzidos em um centro de usinagem vertical CNC, com fresa  25 mm e dois insertos revestidos de TiNAl. Os resultados mostraram que as tensões residuais dependem dos parâmetros de corte empregados no fresamento, e por meio de simulação mostrou-se que o dispositivo de fixação não interferiu na geração de tensões residuais. O aumento do avanço tende a gerar tensões trativas em peças beneficiadas, ao passo que o incremento da velocidade de corte resulta em tensões compressivas em peças temperadas. A microdureza superficial da peça e a pressão específica de corte apresentaram relação inversa e não linear com a tensão residual. Grãos próximos à superfície fresada podem ser deformados pela ação mecânica da aresta de corte da ferramenta desde que tenham orientação preferencial com a das tensões principais máximas. / Abstract: Machining of moulds and dies has a promising potential of expansion and expressive economic importance. The milling process is widely used in the manufacture of mold cavities and can be a substitute to the process of EDM (EDM) and generate surfaces with better surface integrity. Residual stress may be produced in machining processes and they are the main causes of failure in structural components. This research experimentally measured the field, magnitude, depth and orientation of residual stress by using Hole Drilling Method after finishing milling of VP100 steel for moulds and dies with distinct hardness. The results where correlated with part surface microhardness, subsurface microstructure, specific cutting energy and chip-tool interface temperature. The milling tests were carried out in a CNC machining center by using 25 mm diameter endmill with two TiNAl coated carbides. The results showed residual stresses depend on cutting parameters. Tensile stress is yielded in annealed parts as the tool feed increases, whereas compressive one is generated in quenched workpieces as the cutting speed grows. Part surface hardness and cutting specific pressure presented inverse non-linear relationship with residual stress. Grains near milled surface may be deformed by mechanical action of cutting tool edge since they have preferential orientation regarding to maximum principal stresses. / Mestre

Thesis (MScEng (Industrial Engineering))--University of Stellenbosch, 2009. / The titanium alloys have found wide application in the aerospace, biomedical and automotive industries. Soaring fuel prices and environmental concerns are the fundamental drivers that intensify the demand situation for titanium. From a machining viewpoint, one of the challenges companies face, is achieving high material removal rates while maintaining the form and function of the part. The ultimate aim for a machining business remains to make parts quickly. Conventional cutting speeds range from 30 to 100 m/min in the machining of Ti-6Al-4V. Milling this alloy faster however is challenging. Although titanium is becoming a material of choice, many of the same qualities that enhance titanium‟s appeal for most applications also contribute to its being one of the most difficult materials to machine. The author explored the potential for Polycrystalline diamond (PCD) inserts in high speed milling of Ti-6Al-4V, by trying to understand the fundamental causes of tool failure. The objective was to achieve an order of magnitude increase in tool life, while machining at high speed, simply by reducing some of the failure mechanisms through different cutting strategies. Tool wear is described as a thermo-mechanical high-cycle fatigue phenomenon. The capability of a higher material removal per tool life is achieved in the case of PCD inserts compared to Tungsten carbide (WC). The average surface roughness produced was relatively low. The collected chips were also analyzed. The work demonstrated progress over the performance reported in current literature. The work confirms that there is a region where a sufficiently high temperature in the cutting zone may contribute to extended tool life, provided that the tool material can withstand these extreme conditions.