The hammer mill is an impact mill employing a high speed rotating disc, to which are fixed a number of hammer bars which are swung outwards by centrifugal force. An industrial model is illustrated in 1.0 and a laboratory model in Figure 2.0 Material is fed in, either at the top or at the centre, and it is thrown out centrifugally and crushed by being beaten between the hammer bars, or against breaker plates fixed around the periphery of the cylindrical casing.
The material is beaten until it is small enough to fall through the screen which forms the lower portion of the casing. Since the hammer bars are hinged, the presence of any hard material does not cause damage to the equipment. The bars are readily replaced when they are worn out .The machine is suitable for the crushing of both brittle and fibrous materials, and, in the latter case, it is usual to employ a screen with cutting edges. The hammer mill is suitable for hard materials although, since a large amount of fines is produced, it is advisable to employ positive pressure lubrication to the bearings in order to prevent the entry of dust. The size of the product is regulated by the size of the screen and the speed of rotation. A number of similar machines are available, and in some the hammer bars( hammer mill ) are rigidly fixed in position. Since a large current of air is produced , the dust must be separated in a cyclone separator or a bag filter.
What is a Hammer mill
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