① Self-hardening: The binder and hardener are both added during sand mixing. After the sand mold or core is made, the binder reacts under the action of the hardener to cause the sand mold or core to harden by itself. The self-hardening method is mainly used for modeling, but it is also used to manufacture larger cores or cores with small production batches. ②Aerosol hardening: Add binder and other auxiliary additives when mixing sand, do not add hardener first. After modeling or core making, blow in gaseous hardener or liquid hardener atomized in the gas carrier to disperse it in the sand mold or core to cause the sand mold to harden. The aerosol hardening method is mainly used to make cores, and sometimes it is also used to make small sand molds. ③Heat hardening: Add binder and latent hardening agent that does not work at room temperature when mixing sand. After the sand mold or core is made, it is heated. At this time, the latent hardener reacts with certain components in the binder to generate an effective hardener that can harden the binder, thereby hardening the sand mold or core. The heating hardening method is mainly used to make cores in addition to the manufacture of small thin-shell sand molds.