Robust design of a composite air spindle

Abstract

If the spindle shaft of an air spindle system is made of high-stiffness carbon fiber composite material, the spindle system will be dynamically robust because the maximum rotating speed of a spindle (or rotor) system is usually restricted by the critical whirling vibration frequency of the spindle shaft, which is proportional to (EI/m)(0.5) (E: Young's modulus, I: 2nd moment of inertia of shaft cross section, and m: mass per unit length of spindle). In this paper, a composite air spindle system composed of a high-modulus carbon fiber composite shaft, powder-containing epoxy composite squirrel cage rotor, and aluminum tool holder is introduced. For the optimal design of the composite air spindle system, the stacking sequence and thickness of the composite shaft were determined by considering the fundamental natural frequency and deformation of the system. Then the dynamic characteristics of the composite spindle system were compared with those of a conventional steel air spindle system.