Browsing by Author "Oleaga, I."
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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 New methodology for the design of ultra-light structural components for machine tools(2015-04-03) Bustillo, A.; Oleaga, I.; Zulaika, J.-J.; Loix, Nicolas; MAQUINASEnergy consumption is the key to the ecological impact of many machine tools, especially milling machines. One promising strategy for minimising the energy consumption of machine tools is to reduce the mass of their structural components. This solution, however, has a clear drawback: the mechanical stiffness of the machine is reduced, impairing its performance and, in the long run, its productivity. This study proposes a new methodology to overcome such limitations, which involves the design of machine tools with ultra-light structural components, and the development of strategies to counteract the loss of productivity as a consequence of lightweight machines. The new methodology includes the use of modular boxes built with carbon-fibre trusses, calculation of the dynamic stiffness of the new design, the identification of its weaknesses in terms of its cutting processes, and the design and integration of active damping systems in the machine to soften the expected vibrations under the most critical cutting conditions. This methodology has been tested in the new design of a ram of a bridge-type machining centre of medium size. The results show that a 60% reduction in mass can be achieved and that an active damper system can compensate a 60% reduction in mechanical stiffness, maintaining a level of performance that is comparable to heavier standard machines under high-cutting conditions.