A method for manufacturing an impeller with a number of impeller blades and a cover disc covering the impeller blades. Plastic is injected into an injection mold using a cascade injection molding process to form the impeller. The injection mold has a number of shut-off nozzles to feed the plastic at various joint positions and different opening times. The number of shut-off nozzles is determined as a function of the number of impeller blades.