New methodology for the design of ultra-light structural components for machine tools

Energy 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.