Identification of a Machine Tool Spindle Critical Frequency through Modal and Imbalance Response Analysis

The most important part for machine tool system is spindle system. The structural properties of spindle will affect to the productivity of machining process and the work pieces quality. Thus it is necessary and very important to know its spindle dynamic behaviors for avoiding forced vibration due to resonance. The Finite Element Method (FEM) has been adopted for obtaining spindle dynamic behaviors. FEM model and analysis of dynamic behaviors for the spindle system are similar to those developed in rotor-dynamic. The main purpose of this study, we implemented an ANSYS Parametric Design Language (APDL) program based on finite element method for obtaining full analysis of rotor dynamic in order to investigate the spindle dynamic behaviors. The programs efficiently performed the full analysis by determining the Campbell diagrams, critical speeds and response of imbalance due to mass unbalance at the cutting tool. Results show that the critical speeds were calculated previously are far enough from the spindle speeds operating range, then the spindle would not experience resonance and the maximum response of imbalance occurs on operating speed is also in acceptable limit. ANSYS Parametric Design Language (APDL) can be used by spindle designer as tools in order to increase the product quality, reducing cost and time consuming in the design and development stages.