Machining, Measurement, and Control Laboratory

Vibration analysis of machine tools considering contact stiffness of supports
Daisuke Kono

The vibration characteristic of a machine tool is simulated considering the contact stiffness in the support. First, a 3D stiffness model of machine tool supports considering the contact stiffness is described. The stiffness in each direction is modeled by the bulk stiffness and the contact stiffness connected in series. Then, the stiffness of a popular screw jack is calculated using the described stiffness model to investigate the influence of the contact stiffness on the total stiffness of the support. The calculation showed that the contact stiffness has to be taken into consideration to estimate the stiffness of ordinary screw jacks. Finally, the influence of the mass of the bed on the relative vibration between the tool and the table is investigated for the drive and ground disturbance vibrations. The comparison of the natural frequency showed that the 1st natural frequency is not directly influenced by the mass of the machine. The effect similar to the one with higher stiffness of the support can be achieved by increasing the mass of the bed.
Key words: machine tools, contact stiffness, stiffness of support, vibration analysis.