Fabrication and Experimental Verification of Electrochemical Machining Tool for Complex-shaped Hole

The demand for processing of reverse-tapered holes and other complex-shaped holes made of difficult-to-cut materials has increased in recent years. The hole processing by the electrolysis processing is thought to be suitable because there are no heat affected layer and tool wear in electrochemical machining (ECM). It has been reported that, a tool with insulated side surface had been used to process reverse-tapered holes from straight pre-drilled holes by controlling the applied voltage as well as feeding speed. However, the processing efficiency is low because the anodic dissolution occurs only in the area nearing the electrode‘s end surface, also control of the power supplied or the electrode feed is necessary. To solve the problem of low processing efficiency, an ECM tool with changed conductive area ratio along the axial direction was proposed by our research group, and the effectiveness was confirmed through computer simulation. The purpose of this study is to experimentally confirm the processing possibility of the proposed ECM tool for complex-shaped holes. First, the ECM tool was fabricated by winding a copper wire over the cylindrical surface of a non-conductive shaft. The shaft with pitch-changed spiral groove was produced by a 3D printer. Then, machining experiments were carried out by inserting the fabricated tool into a pre-drilled straight hole. In order to investigate the influence of experimental conditions, the current value and processing time were changed in experiments. As the results, reverse-tapered and complex-shaped holes were shaped from a straight hole of 7 mm in diameter and 45 mm in depth. The experimental results showed that our proposed ECM tool is effective in processing complex-shaped holes. In addition, it was found that the processing quantity can be controlled through the current value and processing time.