These images explain the basics of how the Axial Flow type of combine functions. Agco has pioneered this design in the Gleaner N series of combines, and has continued on into the current R series. This information is from the book 'Combines and combining' published by Ohio State University.

The transverse flow rotor combine feeds the material directly into the rotor (1) from the feeding unit. The material then changes direction in the rotor threshing cage and spirals around the cage toward the exit at the left end. The rotor (cylinder) (2) is made up of eight equally spaced rasp bars (3) and mounted inside a perforated metal cylindrical cage (4). The material is fed perpendicularly to the cylinder. The first portion of the cage which the crop is fed into is an adjustable open concave section (5) where most of the threshing action takes place. Helical bars (6) on the inside of the cage and the angled rasp bars (3) on the cylinder then move the material from right to left in a spiral path around the cylinder. Grain is separated from the material by centrifugal force. Since the cage is completely perforated, separation takes place in all parts of the cage. At the left end of the cage, paddles (7) on the cylinder shaft direct the material to a beater (8) which discharges the material to a straw spreader (9). To prevent buildup of chaff on top of the cage, an oscillating cage sweep (10) is provided. For cleaning, the material passing through the perforated cage falls into the distribution auger (11) which deliver it to a pair of accelerator rolls (12). The rolls have overlapping flutes and turn in opposite directions to accelerate the material through a band of high velocity air (13), where initial cleaning takes place, onto the shoe grain pan (14). In the second stage of cleaning, the fan (15) directs air to the shaker type cleaning shoe (16) Clean grain falls into the clean grain auger (17) and is delivered to the clean grain tank. The tailings pass over the end of the cleaning shoe and fall into the tailings auger (18) where they are returned to the accelerator rolls for recleaning. This particular combine has a corn head on it, but other than that, the functions are identical for harvesting other crops. Here is an enlarged view of the initial feeding section and the cylinder assembly. The grain and chaff fall from the cylinder cage (1) into the distribution augers (2). The material is then delivered to the accelerator rolls (3). The accelerator rolls speed movement of the grain and chaff to over four times the natural rate of falling, past a blast of air for pre-cleaning (4). Much of the chaff is blown out the rear of the machine; the remainder of the material falls onto the cleaning shoe area (5). The air for the two stages of cleaning is provided by the fan (6). Unthreshed heads fall into the tailings auger (7) where they are returned to the accelerator rolls (3). The clean grain then falls into the clean grain auger (8) and is delivered to the clean grain tank.