Modeling and compensation for radial thermal error of a vertical machining center spindle

In recent times, high-precision machine tools such as computer numerical control machines have been widely utilized to attain better machining accuracy. However, thermal errors associated with machine tools reduce their precision and accuracy. In this research article, spindle’s radial thermal drift errors (RTDEs) have been studied to acknowledge its thermal behavior. Nonlinear characteristics of the spindle due to thermal bending are explained theoretically and practically. Spindle’s RTDEs are tested at 0 rpm to understand the impact of environmental temperature on thermal error. Impact of cooling oil on thermal error is also analyzed by measuring radial thermal drift errors during tests performed at spindle speeds ranging from 7500 to 10500 rpm. A thermal error model has been proposed, which helps in the compensation of RTDEs of spindle. For developing the thermal error model, temperature of key points and RTDEs of spindle are tested at 7500, 8500, 9500, and 10500 rpm. Thermal error models for ten thermal deformations have been developed. An inverse model is used for the identification of parameters. Compensation efficacy of the proposed model is confirmed by simulation and experimental validation. Efficiency of the proposed model in compensating RTDEs of spindle is 85.75%, which suggests that the proposed thermal error model has high accuracy and robustness. Results also reveal that even with random variation in spindle’s rotational speed, strong robustness and high accuracy can be attained by using the proposed model.