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more flash and also forces the metal to fill completely the die cavity. In the end
of this operation the flash is removed.
A variation of impression die forging is believed to be flashless forging, or
true closed die forging. In this type of forging the die cavities are completely
closed to keep the workpiece from forming flash. The major advantage of this
process is that there is little or no escape of excess metal. The disadvantages in-
clude additional cost due to a more complex die design and the need for better
lubrication and workpiece placement.
There is a variety of sheet metal forming manufacturing processes, such as
stamping, punching, bending, etc. These types of forming processes are per-
formed at room temperature. However, some recent developments involve the
heating of dies or workpieces. Sheet metal forming is characterized by the fact
that the thickness of the sheet metal changes little while processing.
Metal components can also be formed by using metal powder instead
of molten metal, billets, bars or ingots. The powder is placed into a die and
compressed into a solid mass, and then it is heated until the powder particles
join together structurally. This process is often called sintering. Besides, metal
powder can be shaped by rolling, extruding, etc.
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