Comparison of Positioning Resolution of Feed Drive Devices for Ultra-precision Machine Tools

Abstract

To show the most suitable positioning system for ultra-precision machine tools and measuring machines of the next generation having angstrom positioning resolution and long stroke, three types of feed drive devices are compared. The feed drive devices compared are the capstan drive, the hydrostatic lead screw and the twist-roller friction drive. The experimental analysis shows that the positioning resolution of the hydrostatic lead screw and the twist-roller friction drive can be angstrom order, however, that of the capstan drive is at most one nanometer. The reason for such result is the difference of the relative movement between the driving and the driven parts in these feed drive devices. In the capstan drive, relative movement between these parts should be as small as the required positioning resolution because there is no reduction mechanism of motion. Because of the motion reduction mechanisms in the other two devices, the relative movement between the parts can be much larger than the positioning resolution. The paper concludes that the hydrostatic lead screw and the twist-roller friction drive are suitable for the angstrom positioning system in spite of the complexity of their structure and the difficulty of manufacturing.