Prediction of the effect of speed on motion errors in hydrostatic guideways

Motion errors of hydrostatic guideways are affected not only by the geometric errors of the guide rails but also by the speed of the table as well as the supply pressure. Currently, the mechanisms causing motion errors are studied under the condition that the table is moved at a low speed or incrementally. To make a more realistic prediction of motion errors, a new model is developed to analyse the straightness and the yaw of closed hydrostatic guideways with four pads. This model is based on the motion equations of the table and the Reynolds equation of the fluid film in the consideration of the fluid compressibility and the squeeze film effect. The results show that the influences of the table speed on the motion errors of the table are different at different wavelengths of geometric errors, and the motion errors are rarely affected by the supply pressure when the table operates at a low speed. Moreover, the influences of the table speed on the motion errors are smaller at higher supply pressure. Increasing the film thickness can reduce the motion errors of the table. Finally, validation experiments are conducted on a hydrostatic guideway with different speeds.

► We model motion errors of hydrostatic guideways with speed.
► We consider fluid compressibility and the squeeze film effect.
► Speed, supply pressure and film thickness greatly affect the motion errors.
► The experimental results agree with the model predictions.