Modal analysis and experimental study for A 3-DOF parallel machine tool

Parallel machine tools have many advantages theoretically, e.g. stricter accuracy, higher stiffness, high force-to-weight ratio and better dynamic performance. In fact there are common problems of lower dynamic rigidity and lower precision processing in the most prototypes in our country. The dynamic property of a 3-DOF Parallel machine tool is analyzed with the theory of vibration modal analysis in this paper. Reasonable and standard testing methods are proposed. The structural dynamic properties in both horizontal and vertical directions are tested for a prototype of the machine; the natural vibration frequency, damping ratio and vibrating mode are obtained. The resonant frequency in vertical direction is apparently higher than the horizontal one. With high z increased, the parallel machine tool became less rigidity, and with the move from the centre platform, this machine tool rigidity is not changed evident. The conclusions have reference value for other parallel machine tools.