Development Of Constrained Damping Boring Bar

With the development of modern industry, the deep hole processing of application is increasingly widespread in aerospace, automotive and other fields. The request for deep hole machining quality and machining precision demand is more and more higher. High precision deep hole processing is a major problem in the field of machinery manufacturing. Due to in the processing of deep hole boring, the boring bar length to diameter ratio is large, the dynamic stiffness is small, the boring bar is then prone to generate chatter under the action of dynamic cutting force affecting the machining surface quality and machining precision of workpiece, and lowing the tool life. In order to reduce the vibration of boring bar, a new kind of damping boring bar based on constrained damping effect is proposed.Firstly, based on additional damping vibration reduction structure form, a novel boring bar with constrained damping effect is designed and manufactured, The dynamics model and the mathematical model for the damping boring bar have been established. It is concluded that increasing the boring bar of loss factor or improve its inherent frequency can effectively reduce the vibration of the cutting tool. The damping boring bar’s structural parameters mainly includes the thickness of material layers (substrate layer, damping layer, constraining layer) and the elastic modulus of substrate material and constraining material also have influences on damping boring bar’s performance.Secondly, the three-dimensional solid model of damping boring bar is established. The sensitivity analysis of thickness for substrate layer, damping layer and constraining layer to the boring bar damping performance is conducted in through the finite element analysis method. The optimized layer thickness for each layer is obtained by the finite element method (FEM). Harmonic response analysis is applied to the damping boring bar and traditional boring bar using FEM. The results show that both the natural frequency and the damping ratio for damping boring bar are higher than those for traditional boring bar. It is also shown that the radial amplitude of damping boring bar is lower than that of traditional boring bar. Increasing natural frequency and dynamic stiffness of the boring bar can improve the cutting stability.Lastly, modal experiment analysis is carried out with the two kinds of boring bar. The natural frequency of the boring bar is higher than ordinary boring bar60Hz, the damping ratio increases156%, the amplitude value reduces33%under the same excitation. The validation experiments are performed by the holes boring operation of steels. Experimental results show that the machined surface roughness of the damping boring bar is lower than that of traditional boring bar at the same cutting conditions.All in all, from the theoretical analysis, finite element analysis and experimental analysis, the development of constrained damping boring bar with excellent damping effect, improve the quality of the machined surface.