The Design And Analysis Of Machine Tool Headstock Based On Hydrostatic Bearing Technology

Precision is the main direction of development of floor boring and milling machine, one of whose most important component units is the headstock; the hydrostatic bearing technology, which features many advantages, including a low coefficient of friction, high support stiffness and vibration absorption, has been widely used in a variety of large and medium-sized machines. At this present, the hydrostatic bearing technology has been rarely applied in the headstock ram of homemade floor boring and milling machine. This paper mainly investigates the application of hydrostatic technology in the headstock ram of floor boring and milling machine.(1) The ram support has its structural and load-carrying requirements. This paper started from the principle of hydrostatic support, proving that the hydrostatic bearing technology can meet the ram support’s structural and load-carrying requirements, respectively, and deriving the relationship between the carrying capacity W of the hydrostatic bearing mode of constant pressure or constant current, oil film rigidity J, oil chamber’s effective bearing length l1, width b1, oil film thickness h, capillary length L, and oil supply flow Q; the hydrostatic bearing mode of constant pressure was ultimately selected, by comparing factors including manufacturing cost, manufacturability, and carrying capacity of the two modes.(2) According to the design parameters, the headstock was designed by changing the original ram support from hard track support to hydrostatic support. Through analyzing the stress and structural of the ram, the parameters including the shape and position of the oil chamber、 the pressure of oil supply system 、the pressure of oil chamber was designed. And schematic diagram of the oil supply system was drawn; Finally the headstock was designed by using the hydrostatic bearing technology.(3)Kinetic models of the headstock’s spindle components and the ram were established by using the finite element software ANSYS, and the natural frequency and main vibration mode of the spindle components and the ram were obtained through solving the equation, and the critical speed of the spindle was calculated. According to comparison of the ram dynamic stiffness between the hard track bearing and hydrostatic bearing, we found that the use of hydrostatic bearing could significantly improve the dynamic stiffness of the ram.