It is a kind of crushing equipment,using impact energy to crush materials. When materials get into the area where the board hammer plays a part, under the impact function of board hammer at a high speed, the crushed ones are trown to the impact device above the rotor continuously, And then they are rebounded from the impact liner to the area where the board hammer plays a parts ,anfd are impacted again. The process is going on until the materials are crushed to the required sizes and then discharged from down part of the machine.