Investigation on the ECM Cut-in of Large-lead Ball Nut Raceway

The large-lead ball nut is a key component in the industry of machinery and equipment, and its raceway is hard to machine by traditional method. The pulse ECM using spherical cathode is an effective method to machine the raceway of ball nut. However, when the helical angle is smaller than 90 degrees (beta<90 degrees), the flow field is not uniform in the machining gap, which would affect the machining stability. This paper investigated the cut-in of electrochemical machining large-lead ball nut raceway. The influences of helical angle on the flow field in the machining gap were analyzed by numerical and experimental method, and results showed that there were non-uniform flow field with the helical angle decreased, and it cannot be machined at 25 degrees of helical angle. A movable confinement ring was put forward based on different helical angle, and it turned out that, with the assistance of movable confinement ring, the machining process was stabilized, and any cut-in angle can be achieved. (C) 2018 The Authors. Published by Elsevier B.V.