the invention relates to a method and apparatus for making thick - walled plastic parts , in particular blanks for optical lenses . in accordance with the invention , a two - phase production process is proposed in order to make thick - walled lenses with high optical quality and homogenous material properties , wherein in a first phase , a thin lens is first made through injection molding , and in a second step the lens is enlarged , i . e . “ inflated ”, until the final thickness through continued injection of plastic material .