Browsing by Keyword "Damping"
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Item A method to measure the damping introduced by linear guides in large milling machines(2022-05-15) Oleaga, I.; Zulaika, J.J.; Campa, F.J.; Hernando, J.; MAQUINASSimulation of the dynamic behavior of a milling machine requires accurate stiffness, inertia, and damping values. Unlike the properties of stiffness and inertia, damping values are not generally available in the bibliography, which only contains reference values. In the present work, a method is proposed to measure the damping introduced by one linear guide when assembled in large-scale milling machines, unlike current available methods which measure the damping capacities of such guides. Linear guides of same size and type can introduce different damping values at different joints even in the same machine, so that these damping values depend both on the damping capacities of the guide and on the dynamic properties of the joint. This method will allow identifying linear guides that can introduce highest damping values. This identification has been done first by measuring frequency responses at the linear guides of the machine and calculating the modal vectors of that linear guides with finite element models. Secondly, energy dissipation that takes place in these guides has been represented by associating the damping of each linear guide in a discrete way. Next, the method has been validated on a real large machine by comparing estimated and measured frequency responses at tool center point. One immediate advantage of this method will be to improve the dynamic frequency responses of milling machines, and therefore, their productivity for the manufacturing processes in which chatter phenomena arise.Item Thin-Wall Machining of Light Alloys: A Review of Models and Industrial Approaches: A review of models and industrial approaches(2019-06-01) Del Sol, Irene; Rivero, Asuncion; López de Lacalle, Luis Norberto; Gamez, Antonio Juan; SGThin-wall parts are common in the aeronautical sector. However, their machining presents serious challenges such as vibrations and part deflections. To deal with these challenges, different approaches have been followed in recent years. This work presents the state of the art of thin-wall light-alloy machining, analyzing the problems related to each type of thin-wall parts, exposing the causes of both instability and deformation through analytical models, summarizing the computational techniques used, and presenting the solutions proposed by different authors from an industrial point of view. Finally, some further research lines are proposed.Item Vibrations characterization in milling of low stiffness parts with a rubber-based vacuum fixture(2021-06) RUBIO-MATEOS, Antonio; CASUSO, Mikel; RIVERO, Asuncion; UKAR, Eneko; LAMIKIZ, Aitzol; Tecnalia Research & Innovation; FABRIC_INTEL; SGFixtures are a critical element in machining operations as they are the interface between the part and the machine. These components are responsible for the precise part location on the machine table and for the proper dynamic stability maintenance during the manufacturing operations. Although these two features are deeply related, they are usually studied separately. On the one hand, diverse adaptable solutions have been developed for the clamping of different variable geometries. Parallelly, the stability of the part has been long studied to reduce the forced vibration and the chatter effects, especially on thin parts machining operations typically performed in the aeronautic field, such as the skin panels milling. The present work proposes a commitment between both features by the presentation of an innovative vacuum fixture based on the use of a vulcanized rubber layer. This solution presents high flexibility as it can be adapted to different geometries while providing a proper damping capacity due to the viscoelastic and elastoplastic behaviour of these compounds. Moreover, the sealing properties of these elastomers provide the perfect combination to transform a rubber layer into a flexible vacuum table. Therefore, in order to validate the suitability of this fixture, a test bench is manufactured and tested under uniaxial compression loads and under real finish milling conditions over AA2024 part samples. Finally, a roughness model is proposed and analysed in order to characterize the part vibration sources.