Embodiments of the present invention generally relate to a method and apparatus for planarizing a substrate by electropolishing techniques. The base has opposite first and second surfaces. The moveable element has a long axis and a magnetic material. An anti-slip surface is provided on the top wall and configured to receive the mobile device thereon. After the amount of forward rotation identical to the amount of reverse rotation amount is detected, printing is resumed by the printing head. The teeth of at least one of the toothing systems have tooth tip lines that are curved convexly in the axial direction away from a tooth root.