Electrochemical Curved Hole Drilling by Magnetic Manipulation of a Steel Ball Electrode

In this research, a three-dimensional curved hole drilling technique is developed using a steel ball electrode through electrochemical machining (ECM) process. The ball electrode, made of 100Cr6 bearing steel, is placed inside a workpiece and manipulated by the magnetic force exerted by permanent magnets positioned outside the workpiece. The magnetic force acting on the ball electrode is calculated based on electromagnetic theories, such as Biot–Savart law, Gilbert model, and Coulomb’s law. Arbitrary three-dimensional positioning of the ball electrode can be achieved in the customized ECM system, which consists of two neodymium magnets and an XY motion stage. For drilling precise holes in a short processing time, investigated are the pulsed ECM technique and the optimal feed set-back algorithm. Several three-dimensional holes are successfully drilled using the proposed method with the developed ECM system. This enhancement of the curved hole drilling technique enables the creation of free-shaped fluid channels and hollow structures inside solid metals without design limitations.