Grinding is a very essential process in both domestic and industrial applications. A hammer mill is commonly used in the grinding process to shred large material into small fragments. It consists of a rotary shaft containing swinging hammers at the two ends. The hammers rotate in an enclosed metallic casing and in the process bump against the coarse material fed into the machine. The hammers grind through friction and physical hammering. The ground fragments are sent to the filter section where they are screened. The section contains a screen that is used to grade the size of particles that pass through to the collecting unit.
There are numerous types of the hammer mill that are used for different applications. Some are only meant for domestic use while others can be used to grind extremely large pieces in industrial set-ups. Basically, there are three main types of mills. These are the primary, secondary and tertiary types. They are grouped according to their power specification and grinding capability. The primary crusher is mainly meant for small domestic applications. It has a low power requirement and can only be used to grind small pieces of fragile material. For example, most primary grinders are used to crush maize into flour that can be used for cooking.
The secondary hammer mill has greater power specifications and capabilities than the primary type. It can be used in light industrial applications where light grinding is required. It can also be used for domestic grinding in place of the primary type. The tertiary type on the other hand is meant for heavy industrial applications. It can be used to grind hard bulky substances into fine fragments. The size of materials fed and expelled from the machine can be graded according to the specific job at hand. Each of the mentioned types of mills can be powered by electricity or diesel. However, diesel is mostly used in heavy industrial applications or in light domestic applications where electric power is not available.