Development of an Angstrom Positioning System

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It has been reported by the head investigaor that the positioning resolution of the twist-roller friction drive hydrostatic bearing type can be 0.2nm. In the present reearch, a twist-roller friction drive of ball bearing type is proposed for realizing an angstrom positioning system which can be used in ultraprecision machine tools and measuring machines. A positioning system havibg two-axs (X-axis and Z-axis) was made, and the positioning performance of each axis was analyzed. The X-asix employs a large size of twist-roller friction drive and an aeroatatic guideway, while the Z-axis employs a small size of twist-roller friction drive and a cross-roller guideway. The positioning resolution of the X-axis was shown to be 0.5nm, and in spite of the use of ball bearings, it is proved that the twist-roller friction drive can realize the angstrom positioning. The positioning resolution of the Z-axis was 10nm, which is as small as the positioning resolution of the ball screw. A diamond turning test was executed by mounting a work spindle on the X-table and a tool post on the Z-table. A mirror-like surface was obtained by turning, thus the two-axs positioning system can be regarded as an ultra-precision machine tool. The research concludes that the twist-roller friction drive of ball bearing type facilitates the manufacture of an ultraprecision positioning system which can be used in as clean environement, and can take the place of the ball screw.