CD and DVD blanks are produced by injection molding on specially equipped machines with a high cycle frequency. Pour the water over the center of the pane. After the solidification process, the so-called sprue remains. This is punched out directly in the injection molding tool. A hydropneumatic cylinder with spring return is used for this purpose. The force generated by the compressed air on the primary piston is increased by a factor of 7 by the secondary piston on the hydraulic side due to the corresponding surface ratios. As an option, an additional pneumatic ejector can be integrated into the piston rod to ensure safe ejection of the punched part.