It is necessary to increase the damping of a machine support structure (support damping) to reduce the residual vibrations caused by rocking vibration. The stiffness of the machine support system (support stiffness) is also an important parameter that needs to be considered while designing machine tools, to avoid low frequency vibrations. However, conventional passive damper supports decrease the support stiffness while increasing the damping. In our previous study, a passive viscoelastic non-linear damper system for shear vibrations, where the vertical preload determines its damping coefficient, was developed to increase the support damping without decreasing the stiffness by focusing on the horizontal component of rocking vibration. The magnitude dependency of the damping capacity has been modeled. However, this damper system has a tradeoff relationship between natural frequency and damping capacity caused by changes in the preload distribution. Thus, adjustment of the vertical preload applied on the damper is essential for the model-based installation of this damper system. So far, no method has been proposed considering this issue. The vertical preload has been adjusted by trial and error methods. This study proposes a method to determine the damper preload conditions systematically by considering the tradeoff relationship between natural frequency and damping capacity caused by changes in the preload distribution. This method is described based on the case study of a machining center. First, the relationship between preload distribution and support stiffness is investigated using the support stiffness model. Then, the relationship between damping capacity and vertical preloads on the damper is investigated based on material test results. Based on these investigations, the tradeoff relationships are simulated on a machining center by utilizing the damper model. The simulation results are verified with the experimental results. The results show that the proposed method can estimate the tradeoff relationship between natural frequency and damping capacity caused by the changes in the preload distribution. By utilizing this estimated relationship, the preferred preload condition can be decided depending upon the user’s demand.

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