The combine concave performs two important functions in your combine harvester - threshing and separating. Threshing frees the seeds from the plants and separation moves the seeds away from the chaff.
Friction among concave, rotating cylinder and the incoming crop results in the threshing process. The clearance between the cylinder and the concave is adjustable. Once the crop enters the clearance, it gets squashed by the cylinder against the concave and smaller parts start to sift through the openings. As a result, the grain is separated from the plants.
The clearance distance, the bar and wire patterns of the concave, the speed of the rotor, and the crop types determine how clean the samples turn out in the grain tank. It takes a bit of experience to understand how all these factors influence the process.
Achieving a balance between cylinder speed and concave clearance is like walking on a rope. The purpose of this gap between is to control the optimal flow of material. With a large gap, the grains do not separate, while with a narrow one it can lead to grain damage. As a rule, start with the recommended clearance settings. Then you can adjust according to the field conditions.
Combine concaves come with different types of bars and wires. Narrow-wired concaves are great for small grains like wheat and barley. The narrow spacings between the wires allow the small seeds to sift through. Wide-wired ones are for crops like corn or beans.
To improve the threshing process you can use cover plates an addition to the concave clearance and design patterns. The plates are used to cover up certain parts of the concaves to let the material stay longer between the concave and threshing cylinder.