The jaw crusher is the oldest crushing rocks of mechanical type. The principle of operation of this machines is the slow compression of aggregates between two jaws, one fixed and one mobile which has an oscillatory movement. The parts subjected to wear and tear are: oscillators, trees, support and house support, springs, opening and closing rods, housing, bearings...
In the crushing field, mills are machines very widespread. The hammer mills operate according to the principle of collision: the inert materials that come from the feeding opening are projected from the central rotating body through the internal walls of the machine. The first impact, between inert and hammer, is therefore at the level of the impeller; the second impact occurs at the level of impact bars when the inert is scattered though the lateral walls.
In the bars (or balls) mills the principle of operation is always for crushing: the inert material is introduced into the crushing chamber and rotated with the bars (or balls) that crush it against the internal surface of the mill. Vertical axis mills are particular hammer mills in which the rotor axis is vertical. The principle of operation is the same as the hammer mill: inert are crushed by shock.
The cone mills crush the inert between a wall conical or tapered cylinder fixed and a conical body with eccentric movement.
The parts of the various types of mills subject to wear and tear are: impellers, fedding and discharging opening, trees, cones, frame, transmission, bearings...