Drilling 3D holes with a chained ball magnet electrode in ECM

This paper presents a novel method for fabricating 3D holes using a chained ball magnet (CBM) electrode in electrochemical drilling (ECD) process. The CBM electrode provides an extended magnetic control range and is driven by two cylindrical magnets mounted on separate three-axis motion stages. A simple and effective method for fabricating the CBM module is introduced, incorporating an insulation technique to prevent short circuits during ECD. Optimal ECD parameters such as applying voltage, pulse frequency, and pulse duty ratio were experimentally investigated. The magnetic forces acting on the CBM were analytically formulated, and their validity was verified through experimental tests and comparison with ANSYS Maxwell simulations. Ultrasonic vibrations were applied to the electrolyte to enhance sludge removal and reduce machining time. The proposed method successfully fabricated a blind deep hole in Al 6061 alloy with a 3.8 mm entrance diameter and a high aspect ratio (A/R) of 20, as well as complex 3D holes. This technique shows strong potential for practical applications, as it imposes virtually no limitations on the achievable hole length or shape.