Micro ball-ended tips stylus fabrication with pipe-electrode by micro-EDM process

Abstract

Micro spherical stylus tips have been utilized widely in contacting metrology such as coordinate measurement machine (CMM). The materials of micro spherical stylus such as ruby, glass fiber, and silicon nitride are popular for commercial micro-CMM probing head. However, it is still very difficult to fabricate a micro spherical stylus with the ball-ended tips diameter less than 0.15 mm. Not only the high cost problem but also accuracy of the concentricity between the shank and ball-ended tips is a critical challenge during the gluing process. The measurement scale and resolution of micro-CMM depend on the dimension and accuracy of micro spherical stylus. In order to measure micro parts, it is necessary to produce a ball-ended tips probe with diameter smaller than 0.1 mm. In this study, a new process was developed to fabricate micro spherical stylus tips with pipe electrode by combination the micro-EDM and WEDG process. Compared to commercial micro probe, the new low-cost process can produce tungsten carbide micro spherical stylus with diameter smaller than 0.05 mm. Moreover, the tungsten carbide micro spherical stylus tip fabrication process is integrated on the one-machine without any glue-bonding process for high concentricity and accuracy. The tungsten carbide ball-ended tips not only could be used on micro CMM’s probing head but also available for micro ball-shape cutting tool in the future.