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Patented in 1830 with the initial intention of crushing rocks, hammermills have since become an equipment staple for agricultural, residential, industrial and research purposes. They have a simple design but high efficiency, and are used to crush and grind a material into smaller pieces.
The basic setup of most hammermills is a steel drum containing a rotating shaft. The shaft can be situated horizontally or vertically, although the horizontal orientation is more common. The shaft has hammers attached that either stay in one place or swing as a motor drives the rotor. The material is fed into a hopper as the shaft rotates, causing it to be shredded and broken down when it comes in contact with the solid heads of the machine. Screens in the drum allow pieces that are the proper size to fall through, while retaining bigger chunks for further treatment.
The speed of the tips used will determine the grain of the material. High speeds result in finer grinding, while low speeds produce a coarser product. Another factor in how fine the material is ground is in the distance of the tips from the screen. Very little clearance is generally used for fine grinding, but the settings typically depend largely on the material being worked with. Most of these machines are adjustable and capable of switching tasks just by changing the output screen.
These machines can be for single, double or triple reduction. Depending on their grinding purpose, the inner workings of the machine may be slightly different. The models that are made for double and triple reduction sometimes have discs or knives attached to one side of the rotor for the purpose of chopping materials before they meet the hammers. Alfalfa and maize fodder are examples of materials that benefit from this addition. Some have a breaker plate that rebounds materials back into the range of the moving and crushing parts.
The material that is being grinded can be fibrous, hard, or tough, so these machines have to be made so they can perform even when conditions are demanding. A stiff, sturdy frame prevents vibrations from altering the set clearance levels, which could result in longer processing times or the output being the wrong size. The addition of a reversing starter can allow the inside components to wear more evenly, thus extending the lifespan of the machine.
In 1990 a screenless version of this device was created. Screenless hammermills do not use hammers, but instead utilize airflow for the breakdown of larger particles into smaller ones. These usually have two airflow sources as a means of improving production. The screen is the most fragile element of the machine, and the hassle associated with its replacement can be the reason that some businesses opt for the screenless alternative. Some hammermills are small enough to sit on a table and operate on the electricity that a house provides, while others are massive and require diesel engines.
These devices are used to facilitate recycling and grinding grain to produce ethanol. They are an important piece of equipment in the animal feed industry, as well as in mining and construction businesses. They operate in production facilities, and scrapyards, and are just as useful for waste fragmentation as they are for milling grain. From making fruit juice to crushing rocks, hammermills are very useful in a variety of industries.
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