Mechanical design of a precision instrument for measuring the roundness profiles of micro shafts

This paper presents a new instrument for measuring roundness profiles of axially symmetric micro shafts with diameters below 250 micrometers. The instrument will measure form error in cutting tools used for micro machining, small-hole metrology probes, and other high aspect ratio micro structures. This instrument operates on the same physical principle as scanning tunneling microscopes, which measure surface topography using fluctuations in tunneling of electrons between probe and sample. The instrument will measure roundness profiles using a fixed-sensitive-direction arrangement of the detector, similar to macro scale metrology instruments. Challenges resulting from dimensional scaling necessitate an entirely new instrument compared to conventional instruments. We describe the need for this instrument, its working principle, architecture, the design of the traction drive mechanism, and the design of the nano positioning stages.