Design and testing of a micro-dynamometer for desktop micro-milling machine

The emerging miniaturized 'high-tech' products are required to have increased functionalities of systems within a volumetric size on the order of 1 cm3. Hence, the parts are mesoscopic with complex microscopic features of a few mm length with machining accuracy of better than 1 micrometer with secured surface integrity as components will require high surface finish, tensile stress and crack free surfaces in order to function reliably. One of the characteristics to be measured is the cutting forces on the parts being machined. This paper will present the design, manufacture and testing of a miniature dynamometer capable of measuring cutting forces within a low range of 50N but with a resolution better than 1 mN and high frequency since the micromachining involves small cutting forces but the spindle rotates at high speed. The dynamometer is capable of measuring forces in five directions (±x, ±y, and -z). The instrument was calibrated and exhibit very good results leading to a true validation. This instrument is assembled on a micro milling desktop machine designed in-house. It will not only support predicting the surface finish and chip thickness but also monitoring tool wear evolution and hence prevents/reduce tool breakage known to be one of the main issues in micro-milling.