Analysis And Applications Of High-precision Machine Tool Spindle Rotor System

Numerically-controlled machine tool is an important production tool for industrialization and modernization, which has gained much attention for getting the higher efficiency and benefit. The future will witness its broader development. As the electric spindle directly provides power and connects the tool cutter for processing, it is very important to the whole system. However, with the increasing rotating speed and the complexity of its structure, its centrifugal and rotation effect play an increasing effect on the dynamic performance of the spindle. So it is critically important to give a detailed and intensive research on the dynamics of the electric spindle.Targeting on the special electric spindle used for jewelcrafting, this paper gives a statical analysis of the angle contact ceramic ball bearing, including the influence of the preload to the contact angle, considering the centrifugal force and the gyro torque, which shows the relationship between the contact angle with the rotating speed. Basing on the nonlinear characteristic of the bearing, the relevant numerical calculation method and computer program are made to work out the stiffness and damping in the working condition.Basing on the statical characteristics of the supporting structure, the parametric finite element model of this spindle is established and proved to be accurate. The dynamic analysis of this spindle is main carryed out by the dynamics analysis module in ANSYS, including interference fit analysis, which analyses the relationships between the magnitude of interference and rotating speed with the maximum von mises stress and the maximum torque the spindle can transfer. Modal analysis gets the first four natural frequencies and the relevent vibration modes. Critical speed analysis considers the gyroscopic effect and the axial preload of the bearing, pointing out the reason why the natural frequencies do not match the critical speeds, and the harmonic response analysis gains the realtionship between the displacements of each node of the spindle with the exciting frequency, which can accurately simulate the working condition of the spindle. Transient dynamics analysis focuses on the displacement response of the spidle's termianal under an impulsive load, considering the imbalance quality of the spindle rotor.Using APDL optimization technology to optimize the parameters of the spindle for better rotation accuracy, the best value of bearing span is obtained. The effects of these structual parameters on the critical speeds are also analysised. Thr ough the dynamic analysis of the spindle rotor and the structual parameters optimization, the dynamic characteristics of the motorized spindle are improved, and the reference basis is provided for impproving the machining accuracy and efficiency.