Ultrasonic tooling system design and development for single point diamond turning (SPDT) of ferrous metals

In ultra-precision diamond turning, work pieces with a surface roughness of R (a) < 5 nm and a form accuracy of < 250 nm can be machined. Materials such as alumina, copper, electroless nickel and some plastics are mainly used in this process. In conventional ultra-precision diamond turning, it is not possible to machine ferrous metals such as hardened steel. A chemical reaction between carbon of the diamond and iron of the steel takes place and increases the tool wear significantly. The method of adding ultrasonic vibrations to the cutting process was developed to reduce the contact time between tool and work piece. This method leads to a significant reduction of the chemical process and thus enables the machining of ferrous materials with diamond tools. For the realization of this method, an ultrasonic tool holder was designed and a prototype of this tool holder was elaborated. Based on a longitudinal excited transducer, a longitudinal wave is transformed through a flexural sonotrode into a transversal wave. The aim of the new development was to reach a higher operating frequency of 100 kHz and minimize disadvantageous features related to weight and geometry of such devices.