Stability prediction in high-speed milling including the thermal preload effects of bearing

Dynamic stability of machine tool spindle during operations is dependent on many parameters including the spindle speed, bearing preload, and thermal effect. In this article, a finite element-based model of spindle is presented, which uses the Timoshenko beam theory to obtain the frequency response of the spindle at the tool tip. The effects of the bearing preload and temperature rising on the stability characteristics of the milling system are therefore investigated. It was found that the temperature rising has the same effects on the critical cutting depth as on the first natural frequency of the milling system. This result verifies the fact that the critical cutting depth has close relationship with the first nature frequency of the milling system. On conditions that the temperature rising varies with the spindle rotational speed, the increment of the lowest critical cutting depth shifts with the spindle rotational speed. The above conclusions help to predict the stability of milling system under temperature rising situations for better controlling the machining process.