Research on error averaging effect of hydrostatic guideways

Hydrostatic guideways can obtain high motion accuracy due to their error averaging ability. In order to optimize the structural and accuracy design of hydrostatic guideways, the mechanism and affecting factors of the error averaging effect are investigated in detail in this paper. A new method is proposed to quantitatively analyze the motion errors of a typical closed hydrostatic guideway with four pads, and the restrictor is also taken into consideration. A hydrostatic guideway in an ultra-precision grinding machine LGF750 is analyzed with the method. The results show that the wavelength of each profile error component is a main affecting factor on the error averaging effect. Fluid films usually show obvious error averaging effect on each profile error component when the wavelength λ is shorter than twice of the pad length 2l_u. However, for each component with the wavelength λ over 2l_u, the error averaging effect becomes obvious only when the ratio of the pad length to the evaluation length of motion straightness l_u/l_e is greater than 0.5. Furthermore, the instability of the oil supply system is taken into consideration, and possible influences on the error averaging effect due to the supply pressure fluctuation are investigated preliminarily.