Method and installation for making sand cores. The method includes a generating step which is implemented in a first station of the installation, in which the cores are generated with the desired shape in an inner space demarcated by a job box by means of 3D manufacturing, in which layers of a granular material and of an additive that solidifies the granular material are applied in an alternating manner on a platform of the job box. The method also includes a subsequent hardening step which is implemented in a second station of the installation, in which the cores generated in the generating step are hardened. In the hardening step, in order to harden the previously generated cores microwaves and a drying stream are applied in the inner space of the job box.