Design of insulation sleeve with tensile stress in electrochemical trepanning

Abstract

Inner blisk has numerous inner blades, which has high requirements for machining stability and consistency. Electrochemical trepanning (ECTr) is a promising and efficient electrochemical machining (ECM) technology. As an important part of ECTr, the role of insulation sleeve is to inhibit the stray corrosion on the machined blade surface. When inner blade was machined by the profiling insulation sleeve (PIS), and the short circuit phenomenon occurred due to local damage of the PIS at concave side. The fluid force model of the PIS in ECTr was established, and the reasons for local failure were obtained. Subsequently, a novel method and model of the arched insulation sleeve (AIS) based on tensile stress was proposed. The outer contour of the PIS was designed to convert compressive stress into tensile stress at CC side. The fluid-structure coupling optimized simulation was carried out. The results indicated that the AIS adjusts the stress distribution and reduces the maximum deformation at CC side. A dynamic strain signal test platform (DSSTP) was built to verify the effectiveness of the AIS model and simulation. Finally, the ECTr experiments of inner blade were carried out, and the feed rate was increased from 1.6 to 2.4 mm/min by using the AIS. In addition, dozens of blades were continuously machined, and the AIS can be used without damage. The machining repeatability was 0.059 mm, which was 41.6% lower than the PIS, and the machining consistency of inner blades has been improved.