How Combines Work on Corn

How Combines Work on Corn

The combine harvester, a cornerstone of modern agriculture, performs a complex series of operations in a single pass across the field. When harvesting corn, its function is to efficiently gather the crop, separate the valuable grain from the cob and stalk, and clean it for storage. Understanding this process highlights the engineering behind this essential machine.

The harvesting process begins at the front of the combine with the corn head. This header is specifically designed for corn, featuring pointed snouts that guide the stalks into gathering chains. These chains pull the stalks down towards the rotating rollers, which then pull the stalks through and sever the ear from the stalk. The ears, comprising the cob and kernels, are conveyed laterally into the machine's feeder house, while the remaining stalks are left on the ground.

Once inside the combine, the ears are transported via the feeder house up an elevator into the main threshing and separation chamber. However, unlike wheat, corn requires a different threshing mechanism due to its tough cob. Most combines use a specialized rotary concaves or rasp bar cylinders. Here, the ears are beaten and rubbed against the concaves. This action effectively breaks the ears apart, separating the hard kernels from the cob.

The mixture of grain, pieces of cob, husk, and other material, known as material other than grain (MOG), then moves to the separation system. This typically involves a set of shaking sieves or rotors that use oscillating or centrifugal force to allow the heavier, denser kernels to fall through the sieves. The lighter MOG, such as the cobs and husks, is carried out the back of the machine and ejected onto the field as residue.

The kernels that fall through the sieves land on a cleaning shoe, a system of fans and oscillating sieves. The fan generates a stream of air that blows the lighter chaff and dust away, while the clean kernels are sifted through the sieves. Finally, the cleaned grain is augered into an elevator that carries it up to the grain tank on top of the combine.

When the grain tank is full, the combine operator unloads the grain via an unloading auger into a waiting cart or truck traveling alongside. Modern combines are equipped with monitors in the cab that provide the operator with real-time data on harvest yield, moisture levels, and machine performance, allowing for precise and efficient harvesting.