Full center feeding: the materials fall into the feeding hopper of the sand making machine, enter the high-speed rotating swing wheel through the central feeding hole, and are rapidly accelerated in the swing wheel. The acceleration can reach multiple times the gravitational acceleration, and then shoot out from the swing wheel at high speed. First, they collide with another part of the materials that fall freely after rebound, and then they collide with the material lining (stone striking stone) or counterattack block (stone striking iron), and are bounced up to the top of the vortex chamber, It also changes its movement direction, deflects downward, and collides with the materials emitted from the impeller channel to form a continuous material curtain. In this way, a piece of material is subjected to two or more times of probability impact, friction and grinding crushing in the vortex crushing chamber. The crushed materials are discharged from the lower discharge port.