Impact crusher is used for primary, secondary, fine crushing mining and rocks (for example, the granite, marble, and limestone) materials no more than 500mm in length and compressive strength less than 350 MPa. It is widely used for sand and rock producing in the industry of roads, railways, reservoir, electricity power and building materials and so on. Impact Crusher Working principle: The impact crushe materials with impact force. When the materials enter the blow bar area, they are crushed due to the high-speed impact of the blow bar and are thrown to the impact plates on the rotor for secondary crush. Then the materials will be shot back to the blow bar again for the third crush. This process repeats until the materials are crushed to the required size and discharged from the lower part of the machine. The size and shape of the finished powder can be changed by adjusting the gap between the impact rack and rotor support. The impact crusher employs self-weigh security device in its back frame. When other objects enter the impact cavity, they will be forced out of the machine by the impact rack in the front and back of the machine.