Characteristics of Additional Load Losses of Spindle System of Machine Tools

Energy consumption of machine tool has drawn wide attention in recent years. The additional load losses of machine tools are of great importance for investigating the energy consumption of machine tools because those account for 15-20% of the cutting power and may even be up to nearly 30% of the cutting power in our researches. For lack of adequate understanding of the characteristics of additional load losses in the past, the additional load losses coefficient, defined as the ratio of additional load losses to cutting power, was regarded as a constant while the spindle speed was unchanged. However, it is discovered in our practical measurements that it is not so. In this paper, it proposes an additional load losses model based on power flow model, under the condition of the slip of spindle motor being small, in order to fully understand the characteristics of additional load losses. The characteristics of additional load losses include the relationship between additional load losses and cutting power, the relationship between additional load losses and spindle speed, and the relationship between additional load losses and cutting torque. Further more, an experimental system is developed to acquire the additional load losses through measuring cutting torque, spindle speed and input power of machine tool. As an example, several experiments are carried out on the CNC lathe by adjusting cutting parameters including spindle speed, feed rate and cutting depth. The experimental results show that the additional load losses coefficient varies with spindle speed and cutting torque, which can be fitted by a 1st order polynomial.