I believe that understanding and purchasing a machine for cleaning grains is a great stride towards growing of grains. Before I can clean my grains, the threshing process is important. Threshers separate the grains from the stem of the plant. Many grains such as rye and wheat leave the combine harvester ready for cleaning and drying.
Fanning Mills
Fanning mills use shape, size, and weight to clean the grains. When a batch of grain is fed into the mills, a series of screens vibrates back and forth to clean the grain. This machine has three screens with a mesh of varying size. The first mesh removes large foreign material from the grain and also remaining grain stems. The second screen has a smaller diameter and thus is responsible for removing any material bigger than the grain desired. The final screening stage involves the use of pressurized air which utilizes the principle of the weight to sift off all material lighter than the grain. An example of a fanning mill is Clipper Eclipse 324.
Spiral Cleaners
One key difference between fanning mills and spiral cleaners is that the latter has no moving parts. This cleaner has a finned central part that allows the grains to trickle down the fins and hence efficiently cleaning them. As the seed moves down, centrifugal force pulls the grains onto the periphery of the cleaner hence separating it from the other foreign materials. Spiral cleaners work well when grains of comparable size, but a marginally different shape is involved. A good example of spiral cleaners is Amos spiral cleaner.
Gravity Tables
Gravity tables utilize vibration and pressurized air to separate grain from foreign material according to the mass of the material. The air pressure, the flow rate of the grain and angle of the deck is adjusted depending on the type of grain being cleaned. After the process, the denser grain settles at the bottom while the lighter material settles on top hence easily separated. An example of a gravity table is Garratt Pro-Series Gravity Tables.