a first plier arm with one end provided with a fixing plate, wherein a plurality of molding columns of different diameters are connected on the fixing plate, a mounting plate is rotatably connected on each of the molding columns, a molding protrusion is connected on each mounting plate, and a molding gap for molding a wire is arranged between the molding protrusion and a corresponding molding column; and

a second plier arm rotatably connected to the first plier arm, wherein the second plier arm is provided with a connecting part, the connecting part is configured to be rotatably switchable between an initial position and a molding position, the connecting part is in motion-transmission connection with a plurality of mounting plates through a motion-transmission assembly, and in a process of the connecting part rotating from the initial position to the molding position, the molding protrusion molds a wire located in the molding gap onto the corresponding molding column to form an O ring.