Ultraprecision Positioning by Preload Change of Lead Screws (Characteristics of Fine Feed)

摘要

The ultraprecision positioning is examined against the fine feed system utilized the elastic deformation of lead screws accompanying preload change in double nuts. The nonlinear deformation due to Hertzian contact of ball screw can ignore within a feed of 1 μm under adequate initial preload. The influence of load on table displacement of nanometer order is not observed in the range from 10 to 50 kg. The displacement obtained under increase in preload coincide well with the result under decrease in preload also. Feed control with preload change based on one to one correspondence of preload change and displacement is effective to avoid the hysteresis phenomenon of PZT actuator adopted as deformable spacing part between double nuts. Further, preload can use as a measure to detect table displacement in place of position sensor which sometimes shows unreliability owing to unstable situation in nanometer region. The minimum step feed deduced from preload change is 1 nm for sliding screw and 5 nm for ball screw.