A molding apparatus (200) includes a fixed molding unit (210), a movable molding unit (220), and a guiding sleeve (230). The fixed molding unit includes a first columnar element (212) having a first forming face (226) at a first end (224) thereof. The movable molding unit includes a second columnar element (222) having a second forming face (216) facing the first forming face at a second end (214) thereof. The guiding sleeve defines a guiding through-hole (234) and an opening (232) communicating with the guiding through-hole. The guiding through-hole is configured for receiving and centering the two ends therein. The opening is configured for exposing the ends when the molding apparatus is assembled.