Browsing by Keyword "Machining"
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Item Analysis of ultrasonic-assisted drilling of Ti6Al4V(2009-05) Pujana, J.; Rivero, A.; Celaya, A.; López de Lacalle, L. N.; SGIn this study ultrasonic vibration was applied on the drilling of Ti6Al4V workpiece samples. Several parameters of ultrasonic-assisted drilling were monitored, including feed force, chip formation by means of high-speed imaging, and temperature measurement on the drill tip by means of infrared radiation thermometry. Ultrasonic assistance offered lower feed force and higher process temperatures as compared to conventional drilling. It has also shown higher force reductions and higher temperature increments when vibration amplitude was increased.Item Effects of Machining Parameters on the Quality in Machining of Aluminium Alloys Thin Plates(2019-09) Del Sol, Irene; Rivero, Asuncion; Gamez, Antonio J.; SGNowadays, the industry looks for sustainable processes to ensure a more environmentally friendly production. For that reason, more and more aeronautical companies are replacing chemical milling in the manufacture of skin panels and thin plates components. This is a challenging operation that requires meeting tight dimensional tolerances and differs from a rigid body machining due to the low stiffness of the part. In order to fill the gap of literature research on this field, this work proposes an experimental study of the effect of the depth of cut, the feed rate and the cutting speed on the quality characteristics of the machined parts and on the cutting forces produced during the process. Whereas surface roughness values meet the specifications for all the machining conditions, an appropriate cutting parameters selection is likely to lead to a reduction of the final thickness deviation by up to 40% and the average cutting forces by up to a 20%, which consequently eases the clamping system and reduces machine consumption. Finally, an experimental model to control the process quality based on monitoring the machine power consumption is proposed.Item The milling of airframe components with low rigidity: A general approach to avoid static and dynamic problems(2005-11) Herranz, S.; Campa, F. J.; De Lacalle, L. N.López; Rivero, A.; Lamikiz, A.; Ukar, E.; Sánchez, J. A.; Bravo, U.; SGAt present, airframes are mainly composed of monolithic components, instead of small parts joined using welding or riveting. Ribs, stringers, spars, and bulkheads can be included in this category. After milling, they are assembled and joined to the aircraft skins, which have also been milled. The aim of these parts is to obtain a good strength-weight ratio, owing to their homogeneity. The milling of a monolithic structural part implies removing up to 95 per cent of the weight from the raw block material. Therefore, the main objective is to achieve the highest removal rate possible. However, conditions required to achieve this (high feed, large depth of cut) in milling imply high cutting forces, which in turn induce part deflection or vibrations in those zones (thin walls and floors) where stiffness is not sufficiently high. These static and dynamic problems often lead to inaccuracy of geometry, roughness, and possible damage to the machine spindle. This paper proposes a working methodology for efficient process planning, based on previous analysis of the static and dynamic phenomena that can occur during high-speed cutting. This methodology provides several steps that can be taken in order to minimize the bending and vibration effects; suggests optimal monitoring methods to detect process instability; and describes the best way to tune the cutting conditions and chip load, by means of simulation at different machining stages. In this way, the reliability of aeronautical production significantly increases. The global approach presented in this paper has been applied to two test pieces and two real parts, which were milled without suffering either static or dynamic problems.Item Study on the distortion of steel worm shafts(2009-06) Silveira, E.; Irisarri, A. M.; Caracterización y Validación. Materiales; Tecnalia Research & InnovationThis paper analyses the root causes for the distortion observed in some C45E grade steel worm shafts during the last steps of machining. Research carried out on two round bars of the steel where distortion was observed and two other ones of a batch machined without distortion were studied. Moreover, two worm shafts in the last steps of the machining process were also analysed. Residual stresses measurements revealed lower and more homogeneous distribution in the bars which do not exhibit the problem. Yield stress and ultimate tensile stress values recorded in the steel of these bars were also lower than those measured in the bars which presented the problem. Metallographic study of the first ones revealed a broken morphology of cementite in the pearlite pointing towards a material stress relieved after the rolling process, eliminating, at least partially, those stresses generated during the deformation of the bar. On the other hand, the pearlite in the steel which suffers distortion looked to be formed during the cooling process after rolling and no given posterior stress relief heat treatment. A stress relief heat treatment of the bars and/or a kinder machining are recommended.Item Surface integrity investigations for prediction of fatigue properties after machining of alloy 718(2021-03) Holmberg, Jonas; Wretland, Anders; Hammersberg, Peter; Berglund, Johan; Suárez, Alfredo; Beno, Tomas; FABRIC_INTELFatigue performance is crucial for gas turbine components, and it is greatly affected by the manufacturing processes. Ability to predict the expected fatigue life of a component based on surface integrity has been the objective in this work, enabling new processing methods. Alloy 718 samples were prepared by different machining setups, evaluated in fatigue testing and surface integrity investigations. These results generated two predictive statistical multi-variate regression models. The fatigue correlated well with roughness, residual stresses and deformation. The two models showed great potential, which encourages further exploration to fine-tune the procedure for the particular case.Item Tool-path effect on the geometric deviations in the machining of UNS A92024 aeronautic skins(2017) Del Sol, I.; Rivero, A.; Salguero, J.; Fernández-Vidal, S.R.; Marcos, M.; SGTraditionally, aeronautics skins are being machined by chemical milling, a high-pollutant process. An efficient alternative to this technology is conventional machining. However, to ensure the parts machined with this process keeps the industrial quality controls, the effect of tool-path might be characterized, specially analyzing final thickness and roughness. In this paper, five different tool-paths have been applied under the same machining parameters in the dry milling of Al-Cu UNS A92024 thin plates. Machining time, final thickness and roughness have been evaluated. Most roughness and thickness results are under the industrial quality limits stablished for this type of parts.