Design of Spindle Supported by High Stiffness Water Hydrostatic Thrust Bearing

A precision spindle is a key component of the ultra-precision machine tools that are used for machining precision molds for producing various lenses and other precise parts. The machining accuracy required for the parts now reaches several tens of nanometers. In order to achieve the desired machining accuracy, the precise spindle system with high stiffness bearings is inevitably needed for the ultra-precision machine tools. The paper thus deals with a design of a spindle supported by water hydrostatic bearings. An objective of the study is to design the precision spindle supported by the water hydrostatic bearings with the bearing stiffness of 1 kN/μm. Thus the paper presents the design procedure of the hydrostatic thrust bearings. In particular, the design of the bearing restrictors is introduced. The characteristics of water hydrostatic thrust bearings of the designed spindle are investigated theoretically. The influences of the gap sizes and the supply water pressure on the bearing stiffness are given. It is indicated that the bearing stiffness of 1 kN/μm can be obtained by the spindle design. Structure and materials of the developed spindle are also introduced.