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Chatter vibration is apt to occur when machining thin-walled parts with insufficient rigidity. The harmful excitation of periodical cutting forces can be mitigated by enhancing the dynamic stiffness or increasing the damping of the part. A composite viscous damper including air damping and eddy current damping is designed, which can be attached on the thin-walled part by the vacuum. Based on the formulations of air damping and eddy current damping, the optimal equivalent viscous damping is derived for achieving the maximum critical depth of cut. Furthermore, the geometries of the damper are determined for damping a specific thin-walled part after investigating its relationship with viscous damping. The modal test indicates that the damper can suppress multiple modes of the cylindrical thin-walled part, and the amplitude of the first mode of the frequency response function (FRF) is reduced by 57%. The composite viscous damper is applied to suppress the chatter and resonant vibration of the thin-walled part during machining. Milling tests demonstrate that the machining vibration is reduced by 55% and 76% after employing single damper and four dampers, respectively. [ABSTRACT FROM AUTHOR]

The tuned mass damper (TMD) has been used in machining processes for reducing forced vibration, suppressing chatter, and improving machined surface quality. In micro-milling process, the tiny size of the cutting tool-tip and the high rotating speed bring challenges in implementing the TMD. Besides, the TMD needs to have two degrees-of-freedom (DOFs) for reducing vibrations of micro-mill in two orthogonal directions. This paper presents the chatter suppression for micro-milling by attaching a two-DOF TMD to the tool shank and rotates with the cutting tool. The frequency response function (FRF) at the tip of the micro-mill clamped by an aerostatic spindle is predicted using receptance coupling analysis. A two-DOF TMD is designed via graphical approach based on the FRF result at the tool-tip. The natural frequencies and damping ratio of the TMD are optimized under different spindle speeds in order to enhance the cutting stability. The chatter stability of micro-milling is predicted considering the gyroscopic and centrifugal effects of the TMD structure. Modal tests and micro-milling experiments are conducted to validate the effect of the TMD on chatter stability. The results show that the TMD is able to improve the critical depth of cut by 13 folds, and satisfy the compact design requirement for micro-milling. • Shank-mounted TMD satisfies the specific geometric requirement in micro-milling. • Design of TMD using graphical approach based on synthesized FRFs of substructures. • The centrifugal and gyroscopic effects of TMD on chatter stability are studied. • Chatter-free axial depth of micro-milling operation is enhanced by 13 folds. [ABSTRACT FROM AUTHOR]

A milling cutter with large length–diameter ratio has been essential in machining structural parts with deep cavity and deep hole features. However, chatter vibration is apt to occur with the increase of tool overhang. A damped milling cutter is developed by employing a single-degree-of-freedom passive damper located inside the arbor. The stiffness and damping design of the embedded damper are carried out by following the equal peaks criterion. A novel design is fulfilled to avoid the disequilibrium of the cutter during high-speed rotation, and an accurate experimental tuning of the design parameters is required to achieve the optimum vibration suppression due to a low mass ratio of 2.5%. Modal analysis demonstrates that the damped cutter with an approximate length–diameter ratio of 8 can reach 75% magnitude reduction at all orientations, which is benefical to resist milling force excitation varying with the rotation angle. Chatter stability simulation demonstrates that the damped cutter is able to increase the stability limits based on the evaluation of undamped and Sandvik cutters. Three configurations of machining tests are carried out and the design of the damped cutter is validated by the machining audio signals and machined surface roughness in the end. [ABSTRACT FROM AUTHOR]

Thin-walled workpieces are largely manufactured in the aerospace industry. The manufacturing process has been a problem due to its flexibility, and chatter vibrations are apt to occur, which restricts the machining efficiency and quality. A vibration suppression device for thin-walled workpieces is presented based on the electromagnetic induction principle, which utilizes machining vibrations to generate resistant force on the workpiece. The formulated force varies with the workpiece vibration velocity, but in an opposite direction. Excitation tests using the electromagnetic shaker illustrate that the device is effective in vibration attenuation. Finally, machining tests are carried out with applications to two thin-walled structures for further verification. The machining vibrations and surface quality demonstrate the damping promotion of the workpiece assembly, and milling stability limit is increased by more than twofold. [ABSTRACT FROM AUTHOR]

The productivity of many industrial cutting processes is limited by high amplitude chatter vibrations. An optimization technique based on the use of the stability lobes helps to increase the productivity of these processes, improving the life of machine elements and reducing the tool wear as well. The best-known lobes correspond to Hopf bifurcations. However, in case of interrupted cutting, additional lobes appear due to period doubling or flip bifurcation. When the system has more than one dominant vibration mode, important variations can appear in stability due to interaction between modes. The basic mathematics for the appearance of these new lobes are shown in this article. The frequency domain study shows that lobes related to flip bifurcation are a special case of the interaction between modes. The results of these interactions are verified by comparison with semi-discretization method and time domain simulations, respectively. [ABSTRACT FROM PUBLISHER]

Abstract: A new-type nonlinear tuned mass damper (TMD) containing an additional element of elastic support dry friction compared with the common linear TMD is proposed to suppress machining chatter. The design and tuning process of this nonlinear TMD have used a combination of analytical modeling with experimentally measured frequency response function (FRF) of the machining system. Theoretical studies and experimental results show that the proposed nonlinear TMD can remarkably improve the machining stability by effectively suppressing the magnitude of the real part of the FRF of the damped machining system. [Copyright &y& Elsevier]