Study on an evaluation method of micro CMM spherical stylus tips by µ-EDM on-machine measurement

This paper describes an on-machine measurement function of a micro electro-discharge machine (µ-EDM) to evaluate the quality of micro ball-ended stylus tips fabricated by a combination of wire-electro-discharge grinding (WEDG) and one-pulse-electro-discharge (OPED) technology. A low-voltage contacting trigger function without any capacitor between a stationary wire and the spindle of a µ-EDM was used to measure the outer profile and evaluate the forming quality. The measurement results show that the deviation of the largest radius between the micro ball-ended tip and stem is approximately 3 µm. Moreover, OPED/WEDG is also easily able to produce high-quality micro spherical stylus tips with a standard deviation as small as 0.7 µm through use of sharp-needle-shaped electrode tools. With further improvements in electro-discharge position, OPED and WEDG technology are promising and excellent approaches for manufacturing micro coordinate measurement machine (CMM) spherical stylus tips.