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Dry Milling

PC 7.05 Density Sorting

In the early 1930s, Oliver Steel began to produce a machine that became widely known as an Oliver table. This machine has been widely reproduced, and the technology has become a key piece of equipment, helping to ensure that the only thing that leaves a dry mill is coffee beans. These machines are used around the word for many different kinds of grains.The machine controls the following variables: 


Feeding rate: how many beans cover the table at any given point 

Longitudinal slope: how steeply the table is angled downwards towards the exit 

Transversal slope: how steeply the table banked sideways, a bit like a cycling track

Air pressure: velocity of the air coming up from many small holes beneath the layer of beans

Intensity of vibration: the variable rate at which the surface of the table vibrates