2. Introduction A combine is a large, self-propelled
agricultural machine used to harvest grain crops such as wheat,
corn, soybeans and rice. As its name suggests, the combine performs
two, and sometimes more, basic functions of harvesting: first it
reaps (cuts) the crop, and then it threshes it, separating the
kernels of grain from the seed coverings and other debris (chaff).
Some combines may also bale the straw that remains after threshing;
the machines can also be equipped to pick cotton.
3. Raw Materials Sheet steel Round steel bars and hollow,
square steel channels Complex subassemblies such as the engine and
transmission are either built at other company plants or are
purchased from smaller. After assembly, the combine is painted with
water-based paint that is mixed with highly purified water.
4. The Manufacturing Process Cutting the steel into blanks The
steel is cut into blanks, basic rectangular shapes that are later
welded together to form the body of the combine and the top-
mounted grain tank.
5. Welding the formed parts Small batches of parts are moved
from the sheet metal shop to the welding area, much of the welding
of sheet steel components is done by powerful, computer-controlled
units. Hydraulic lifts properly position components that are then
welded by one-armed robots. As the smaller components of the
combine are assembled, the body begins to take shape.
6. Painting After welding, the conveyor transports work-part
and submerges it in the paint tank, full of electrostatically
charged paint. Because combines are used and stored outside, their
paint must be able to resist the harmful effects of sunshine and
moisture, and the electrostatic process insures that it will.
7. Welding the grain tank After the combine body, the other
significant structural assembly is the grain tank. Skilled workers
weld the grain tank parts in ten to twenty minutes. Final assembly
After the body and grain tank have been painted, they are brought
to the final assembly line, where major components like the engine
module are installed, wiring and hydraulic lines are connected, and
all systems are tested. Oil, anti-freeze, and gas are added, and
the engine is started. On the outside, a final coating of clear
polyurethane is applied across the top of the wide, flat surfaces
of the cab, grain tank, and engine module, and decals are
applied.
8. How it works 1. Cereal crops are gathered in by the header
at the front, which has a pair of sharp pincers called crop
dividers at either end.
9. 2. A slowly rotating wheel called the reel (or pickup reel)
pushes the crops down toward the cutter. The reel has horizontal
bars called bats and vertical teeth or tines to grip the plant
stalks.
10. 3. The cutter bar runs the entire length of the header
underneath the reel. Its teeth open and close repeatedly to cut off
the crops at their base.
11. 4. Behind the cutter bar, the cut crops are fed toward the
center by spinning augurs (screws) and travel up a conveyor to the
processing mechanism inside the main part of the combine.
12. 5. A threshing drum beats the cut crops to break and shake
the grains away from their stalks. 6. The grains fall through
sieves into a collecting tank below.
13. 7. The chaff (unwanted material) passes along conveyors
called straw walkers toward the back of the machine. 8. When the
grain tank is full, a tractor with a trailer on the back pulls
alongside the combine. The grain is carried up from the tank by an
elevator and shoots out of a side pipe (sometimes called the
unloader) into the trailer.
14. 9. The unwanted straw chaff tumbles from the back of the
machine.Some combines have a rotating spreader mechanism that
throws the straw over a wide area. Sometimes the straw is baled up
by a baling machine and used for animal bedding.
