Projeto geométrico e estrutural de minimáquina-ferramenta multifuncional de precisão

Abstract

This research covers the preliminary structural design of a multifunctional mini size machine tool of synthetic granite applied in advanced ultraprecision manufacturing. The demand for machine tools and manufacture cells capable of performing additive and subtractive multiple processes in macro and micro scale supports the development of small size CNC multifunctional machine. Several geometric structures and construction materials are described in the literature and applied in commercial precision and ultraprecision machines. However, the state of the art has a shortfall of comparative studies on the influence of geometrical forms in the performance of synthetic granite machines. The study aims a initial comparative structural design of six synthetic granite structures, namely, C (EC), gantry (EP), tetrahedral (ET), octahedral (EO), double tetrahedral (ETD), and octahedral plus tetrahedral (EOT) forms, being the ETD and EOT original geometries. Boundary conditions included an working envelope of 400 mm x 400 mm x 400 mm and a static stiffness of 1 000 N/µm. Comparative performances in mass, size, manufacturing complexity, vibration modes, tension distribution, and deformation were analyzed through mechanical engineering design methodology and finite element analysis (FEA). The results of the static simulation showed less deformations of conventional EC and EP structures for the action of gravity isolated and from the action of gravity and machining force simultaneously, while the ETD and EOT structures presented the largest deformations. The dynamic simulation results returned higher vibration modes for EC and EP, respectively, and the lowest vibration for ETD. As for the masses of the structures, in ascending order, the results were EC, EP, ET, EOT, EO, and ETD. In conclusion, among the presented geometries, it is possible to obtain the desired stiffness regardless of the structural geometry chosen, however with masses, manufacturing complexities, and different vibration modes that can expressively reflect on the cost-benefit of the structure. Although the structures have been subjected to several optimization iterations cannot rule out the possibility of existing similar structures with smaller mass, volumes, and even with better static and dynamic performances.