In a process for molding a plastic component onto a prefabricated plastic part, a first mold plate (1) and a second mold plate (105) are closed, a cavity in which the prefabricated plastic part (101) is located being formed between the closed mold plates (1, 105). One of the mold plates (105) is formed with a depressed zone (108) and a polymer feed (115) opening out into the depressed zone (108) for molding the plastic component onto a region of the prefabricated plastic part (101) that lies opposite the depressed zone (108). Subsequently, polymer melt is injected into the depressed zone (108) and, during the injection of polymer into the depressed zone (108), the mold plates (1, 105) are moved apart.