Pulse electrochemical machining of large lead ball nut raceway using a spherical cathode

The large lead ball nut is a key component in high-speed ball screws. To solve the interference problem encountered in traditional machining of large lead ball nuts, a numerically controlled pulse electrochemical machining (NC-PECM) of large lead ball nut raceway has been proposed. This new method is capable of machining a ball nut raceway with an arbitrary lead angle, and a spherical cathode with slant jet has been designed for this process. In this paper, a detailed explanation for this process is presented, including its shaping mechanisms, and the morphology of the machined surface has also been experimentally analyzed. A large lead angle of 45° (four to five times larger than the standard of large lead angle) has been successfully machined with a raceway surface roughness of 0.54 μm Ra, and a profile accuracy of ±0.025 mm (−βc < β < βc) can be reached on the raceway.