A comparative analysis of ceramic and cemented carbide end mills

Milling of ferrous metals is usually performed by applying cemented carbide tools due to their high hardness, temperature and wear resistance. Recently, ceramic tool materials have been on the rise and enhanced the efficiency in machining. As ceramics are brittle-hard materials, tool manufacturing requires a sound knowledge in order to meet the tool requirements such as sharp cutting edges and wear resistance. In this study, milling tools made of the high performance ceramic SiAlON were compared to tools made from cemented carbide. For both tool materials, the influence of a prepared cutting edge was investigated. Both the tool manufacturing process and the cutting edge preparation processes are presented, followed by the application of those tools within milling experiments. In order to evaluate the efficiency of both tool types, the cutting forces and the cumulative process energy demand were analyzed. Additionally, surface roughness of the machined workpieces and tool wear were examined. It was found that the ceramic tools, although process forces were higher than for cemented carbide tools, exhibited by far lower energy consumption, less tool wear and finally generated lower surface roughness. © 2020, The Author(s)

Efeito de parâmetros de corte na qualidade superficial e no desgaste de ferramentas de carboneto no torneamento sem lubrificação do aço SAE 4140 / Effect of cutting parameters on surface quality and wearing of carbide tools in dry turning of SAE 4140 steel

Atualmente as tecnologias limpas estão ganhando muita importância no setor industrial, consequentemente os processos de usinagem também tendem a buscar a redução da geração de resíduos. Uma das alternativas muito usada é a redução ou extinção do uso de fluidos de corte, o que é conhecida como usinagem limpa ou verde. Este estudo avalia a relação da variação da velocidade de corte e do avanço no torneamento a seco de amostras de aço SAE 4140 utilizando pastilhas de metal duro sinuosas com revestimento triplo com o desgaste da ferramenta e a qualidade superficial da amostra. Foram realizados ensaios aplicando quatro combinações usando duas velocidades (160 e 250 m/min), dois avanços (0,100 e 0,316 mm/rev) e profundidade de 1mm. A definição dos melhores parâmetros se baseou no estudo dos mecanismos de desgaste das ferramentas, nos diferentes tempos de usinagem e nos melhores resultados de rugosidade. Os melhores resultados em relação à rugosidade foram obtidos com velocidade de 250 m/min e avanço de 0,100 mm/rev enquanto a combinação de menores valores gerou os desgastes mais baixos

Correlation between edge radius of the cBN cutting tool and surface quality in hard turning

In this study, the attempt has been made to investigate the correlation between the cutting tool edge radius and surface quality in terms of the surface roughness and subsurface deformation through a FE simulation and experiment. Machining tests under different machining conditions were also conducted and the surface roughness and subsurface deformation were measured. Surface roughness and subsurface deformation were produced by the cutting tools with different edge radii under various cutting parameters. Both results from the FE simulation and machining tests confirmed that there was a significant influence on the surface quality in terms of both the surface roughness and subsurface quality from the edge radius. There is a critical edge radius of cBN tools in hard turning in terms of surface quality generated.У даному дослідженні було зроблено спробу дослідити взаємозв’язок між радіусом закруглення крайки різального інструменту і якістю поверхні, які оцінюються шорсткістю поверхні і деформацією підповерхневого шару, методами скінчено-елементного моделювання і експериментально. Було здійснено низку експериментів при різних умовах обробки з одночасним вимірюванням шорсткості поверхні і деформації підповерхневих шарів. Також застосовували різальні інструменти з різними радіусами різальної крайки при різних режимах різання. Результати моделювання і випробувань підтвердили значний вплив радіуса закруглення крайки на якість і шорсткість поверхні, а також якість підповерхневого шару. Виявлено оптимальний радіус округлення крайки інструменту з КНБ, який треба застосовувати при обробці надтвердих матеріалів для отримання найкращої якості поверхні.В данном исследовании была сделана попытка изучить взаимосвязь между радиусом скругления кромки режущего инструмента и качеством поверхности, оцениваемой шероховатостью поверхности и деформацией подповерхностного слоя, методами конечно-элементного моделирования и экспериментально. Были проведены испытания при различных условиях обработки с одновременным измерением шероховатости поверхности и деформации подповерхностного слоя. Применялись режущие инструменты с различными радиусами режущей кромки при различных режимах резания. Результаты моделирования и испытаний подтвердили значительное влияние радиуса скругления кромки на шероховатость поверхности, а также на качество подповерхностного слоя. При точении закаленной стали инструментом из сBN имеется оптимальный радиус режущей кромки инструмента, который следует применять при обработке сверхтвердых материалов для получения наилучшего качества поверхности

On deformation characterisation of machined surfaces and machining-induced white layers in a milled titanium alloy

Machining-induced white layers and severely deformed layers are undesirable surface integrity features which can be formed when machining high-strength aerospace alloys. An orthogonal milling process has been designed and performed to assess the impact of cutting speeds, tool wear, cutting edge radius and climb vs conventional milling on white layer formation and plastic strain distribution. The plastic deformation in the machined surface associated with the formation of white layers in Ti-6Al-4V has been quantified using micro-grids of different length scales printed using the electron beam lithography technique. It was found that white layers formed via the severe plastic deformation mechanism, at equivalent plastic strain values in excess of 1.2 and in regions of the cutting arc with the instantaneous chip thickness of less than the cutting-edge radius and ploughing and rubbing being the dominant mechanisms. The results indicated that the magnitude of the measured strains and the depth of plastically deformed material was greater at lower cutting speeds, during climb milling and when machining with a larger cutting edge radius and tool flank wear land

INFLUENCE OF SIZE EFFECTS ON SURFACE GENERATION DURING FINISH MACHINING AND SURFACE INTEGRITY IN TI-6AL-4V

Finish machining is an essential manufacturing process that is used to enhance the mechanical characteristics of critical components. The deformation that occurs at the tool and workpiece interface in finish machining significantly affects a host of component properties, commonly referred to as “surface integrity” properties. Surface roughness is a machining deformation-affected characteristic that is of high relevance in contemporary manufacturing. However, over recent decades it has been made clear that the material properties of the deformed surface layers are relevant to component performance as well. Predicting the overall surface quality of a machined component is of great relevance to the manufacturing industry. Current state-of-the-art predictive models in the area of machining-induced surface integrity are typically founded in two-dimensional F.E.M. analysis. These investigations frequently show the advantages of tool geometry manipulation. However, most efforts focus solely on the prediction of two-dimensional surface integrity qualities such as those found in orthogonal machining. Indeed, most recent models largely ignore three-dimensional properties such as surface roughness, and do not incorporate three-dimensional machining parameters that are highly relevant to the surface integrity state of typical finished components. In light of these shortcomings, the nature of surface integrity in three-dimensional machining is explored, and a physics-based geometric model of surface generation is applied to some areas of surface integrity prediction. The main focus of this work is to investigate and model the relationship between the more dominant parameters in finish turning (feed, nose radius, and edge geometry) and the surface generation phenomena that occur in the application of tools with varied geometries of this scope. The presented geometric model is derived from unique assumptions that allow for the close approximation of surface generation. The model is subsequently validated with experiments that utilize modified turning inserts of precise edge geometry, as well as pedigreed data from previous literature. Good agreement with experimental roughness results is obtained, thus verifying the validity of the surface generation assumptions. In addition, subsurface properties are found to correlate well with the geometry of ploughed areas predicted by the modeling methodology presented in this text