A unique characteristic of hammer mill grinding is that material must pass through the screen to exit the mill. This guarantees the final product maximum size. Hammer configuration, rotation speed and screen sizes can be varied to process different grains. Each component can be changed individually. More hammers, faster speeds, and finer screens produce a finer grind.
Hammer mills eliminate the need to screen product. When you fine-grind with a hammer mill, it may take more power per ton and maintenance costs may be higher compared to roller mills. The possibility of overgrinding—creating too many fines—is also something the distiller should consider when using a hammer mill.
ROLLER MILLS Roller mills use compression to reduce the size of the grain as it passes between stacked pairs of rollers. The smooth rolls may turn at different speeds to introduce shearing forces, and the addition of grooved rolls adds tearing and grinding to the milling actions. Their slow speed doesn’t cause heating of the grain or related moisture loss. Small amounts of fine materials are produced, keeping dust down. The shape of the particle produced is irregular, cubical and spherical so the grain doesn’t tend to pack or become a solid mass. Bulk density is about 10 percent less than grain milled by a hammer mill, as the ground material is coarser. Roller mills may have a larger capital cost but use less horsepower per ton. Corn is an abrasive grain and may wear out a roller mill. Rollers mills may require screening to get a specific grain size distribution.
CAGE MILLS The cage mill consists of one or more rotating cages enclosed in a steel housing. Material to be ground is fed into the center of the revolving inner cage and passes outward via centrifugal force from row-to-row, finally discharging through the bottom of the mill. The source of size reduction in a cage mill is the result of impaction between the material being fed and the pins of the revolving WWW.ARTISANSPIRITMAG.COM
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