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fanning mill[′fan·iŋ ‚mil]
a machine designed to separate weeds, such as ryegrasses, knapweeds, wheatgrasses, and wild oats, from seeds and to sort the seeds of grain, legume, and other vegetable crops by specific weight. Fanning mills are also used in the processing of hybrid and varietal corn kernels to separate damaged kernels and stalk sections from the bulk harvested material.
In a fanning mill the seeds fall onto an inclined separating platform with a mesh bottom. They are then subjected to longitudinal shaking and are blown with a stream of air from a fan to form layers. The seeds with the highest specific weight descend through the layers to the bottom and form the first yield. Seeds of low specific weight and weed seeds rise and mix together on the surface to form the second yield (weed seeds and contaminants with average specific weight) and third yield (the lightest seeds and contaminants). Fanning mills used in the USSR can process up to 1.5 tons of seeds per hr. The working elements of the machine are driven by an electric motor.