Design of a passive damper with tunable stiffness and its application in thin-walled part milling

The optimal parameters of a passive damper (i.e., frequency ratio and damping ratio) for the machining vibration attenuation of thin-walled part are quite affected by the material removal process, and the damper becomes ineffective easily due to its narrow vibration band. A design of passive damper with tunable stiffness is proposed for being adaptive to the varying machining process, and the frequency tuning is carried out by orienting the mass block inside the damper. Modal tests are performed to verify the amplitude reduction of the target mode of the thin-walled part. It shows that the optimal vibration suppression is reached when the orientation is 20° due to a smaller frequency difference between the damper and target mode, and the amplitude of the damped frequency response function is reduced to 1.3 %. Finally, machining tests are carried out, and the machining vibration and surface quality validate the large increase of machining stability. The experimental critical depth of cut under optimal tuning is increased by 1.8-folds compared with the most ineffective tuning, and the machined surface roughness is reduced by more than 80 %.