Structure design of four-axis linkage precision machine tool for hydrostatic motion pair

Large aperture planar, spherical and aspherical optical components are widely used in optical systems of lithography machine, high energy lasers, high resolution cameras and other high-end equipment. In the grinding stage of large aperture optical components, the size ≥400 mm×400 mm, surface profile accuracy Root Mean Square (RMS) ≤1 μm are the key technical indicators. The main problems in grinding process are high smooth surface profile machining and depth control of sub-surface damage layer. According to the available results, the high precision hydrostatic motion pair is used in grinding machine, which can effectively improve the smoothness of the surface profile and reduce the thickness of the sub-surface damage layer after polishing the optical element. High-performance grinding machines with the above characteristics are prohibited to China abroad, and there are no mature products in China. In this paper, a four-axis linkage precision machining machine tool with hydrostatic motion pair is developed. The main configuration of the machine tool is analyzed. The precision distribution for the main moving parts of the machine tool is carried out. The design scheme of the X/Y/Z/C four axis based on the hydrostatic motion pair has been completed. Finally, experiments on the grinding process of optical components were conducted. For the 380 mm×541 mm size microcrystalline glass, the surface shape accuracy and surface roughness reached ±0.471 μm and Ra 0.3 μm, respectively.