Ultra-precision high performance cutting of nickel silver using a magnetically levitated feed axis

High speed cutting offers the possibility to significantly speed up diamond milling processes. It not only increases the economic efficiency but also has a positive impact on the material removal mechanisms and the resulting tool wear. Electromagnetic feed axes provide the potential to enable the required precision and reduction of vibration at the increased feed velocities and axis dynamics. This paper comprises first results obtained by combining diamond fly-cutting on a high-speed air bearing spindle with an electromagnetic feed axis on a custom-built 3-axis machining setup. After balancing the spindle with a fly-cut-head (Dfly = 160 mm), two sets of experiments were conducted: first, the cutting speed was varied by setting the respective spindle speed between n = 4,000 and 7,500 min-1 (i.e. vc = 33 to 63 m⋅s -1 ). During these runs, the feed velocity was adapted to maintain a theoretical surface roughness of Rkin = 10 nm. In the second set of experiments, the feed velocity was varied for a constant spindle speed of n = 7,500 min -1 between vf = 600 mm⋅min-1 and 4,800 mm⋅min-1 in order to observe the behaviour of the magnetic axis at very high speeds. In both cases, live data (e.g. axis position/velocity/acceleration) was captured during machining and measurements of the machined surface were taken by coherence scanning interferometry. The results show that the setup including the magnetically levitated axis is capable of producing high precision surfaces with sub-40 nm RMS surface roughness. No significant deterioration of the performance at high feed velocities is observed. However, deviation occurring at higher speeds tend to affect long-wave surface features, i.e. the waviness.