Motion straightness of hydrostatic guideways considering the ratio of pad center spacing to guide rail profile error wavelength

Abstract

Due to the error averaging effect of pressured oil film in hydrostatic guideways, motion straightness of the slider is smaller than the profile error of guide rails. In spite of this, structural parameters of the guideway system have dramatic effects on the error averaging coefficient. Therefore, it is necessary to investigate the relationship between the structural parameters of the guideway system and slider motion straightness. In this paper, effect of the ratio (m λ ) of pad center spacing to guide rail profile error wavelength on motion straightness was the primary focus. A static analysis model based on the error averaging effect considering pad center spacing in open hydrostatic guideways with four pads was established. Linear displacement motion error of the slider with different system structural parameters was solved, and slider motion straightness was calculated using least-square method. A grinding machine LGF1000 was used in experiments, and the slider vertical motion straightness was improved to 0.98 μm/600 mm from 2.08 μm/600 mm after using the lapping process on a specific guide rail along the Y-axis for change the m λ . In addition, precision was improved by 52.9 %. Results show that m λ has significant influence on vertical motion straightness of the slider. Increasing the pad center spacing m allows a reduction in motion straightness for m λ equal or lesser than 0.5. However, a decrease in the pad center spacing is useful to decrease the motion straightness, when m λ is equal or larger than 0.72.