Page 21 - Curriculum Visions Dynamic Book

(Above) Gears are powder formed.
(Below) Body panels on automobiles and other vehicles, such as the combine harvester and aircraft, are pressed into shape. That is what allows intricate curves to be produced.
Powder forming
None of the processes described so far can produce complex shapes. However, a modern alternative is now available. It is called powder forming. Metals are first reduced to
a powder. The powder is then mixed with a liquid and pushed into a die. The powder is next heated, or sintered, until the tiny grains of the powder begin to fuse together. This happens below the melting point of the metal.
This process is use routinely with metals, such as platinum and tungsten, that have to be heated to very high temperatures before
they will melt. Tungsten filaments for light bulbs are produced this way.
Powder techniques are now also used widely for metals such as iron that do not have high melting points. For example, steel gears are mainly made
this way because it saves all of the time and effort
that would be needed if the gears had to be cut by machine. Similarly, small parts made of aluminium are also mainly made by pressing powdered aluminium into a die and then heating it.
Most metal powders are produced by spraying the metal as a liquid and allowing the droplets to fall and cool into solid powder.
21