Study of the friction error for a high-speed high precision table

Friction is one of the important factors resulting in the contour error of feed servo systems for high-speed, high precision CNC machine tools. A mathematical model of a high speed high precision feed servo table with PID controlling has been established with consideration of friction effects. The friction can be calculated according to the sliding speed and the oil film between the two contact surfaces by using a two-component mixed friction model. The protrusion error occurring at the quadrant boundary in the circular motion is profoundly studied by means of numerical simulation and experiments under different work conditions, and the conclusion that the quadrant protrusion error lags with the rising of the feed rate is obtained. Comparisons between the simulation results and the experimental results demonstrate that with the mathematical model, the dynamics of high speed high precision servo feed systems under PID controlling can be accurately simulated, and the friction error and its characteristics in the course of feeding can be precisely predicted.