High speed hydrodynamic spindle

摘要

A machine tool assembly, and particularly a spindle unit therefor, is provided wherein the spindle unit is relatively small and is designed to run at rotary speeds of between 30,000 rpm's and 40,000 rpm's utilizing hydrodynamic bearings for the spindle shaft. The hydrodynamic bearings are effective to take increased loads versus similarly sized conventional metal-to-metal contacting bearings to provide a very stiff machining system even with the higher loads generated by the increased rotary operating speeds for high speed machining contemplated for the spindle unit herein. The bearings are also designed to use a water-based fluid which is compatible with the cutting fluid. Non-contacting fluid barrier seals limit and control the amount of bearing fluid leaked to the cutting fluid. Due to the compatible nature of the two fluids, small fluid leakage from the bearings will not hurt the cutting fluid. The cutting fluid circulated at an ambient inlet temperature, e.g., 70 DEG F., and leaves at a higher discharge temperature, e.g., 120 DEG F., to cool the spindle and bearings. A cutting tool mounting adapter is provided which is attached to the spindle shaft by expansion of the shaft socket with high pressure hydraulics for shrink fitting of the socket onto the adapter when the hydraulics are removed so that the traditional highly tapered sockets and tool supports are not necessary, keeping the size of the front of the spindle small. The adapter also allows a commercially available tool to be employed in the high speed spindle unit herein.