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Plastic Manufacturing
Types of Molding
Processes
By Philippa Jones
Different types of molding processes
form plastic into the desired shape based on the plastic’s intended use.
Plastic manufacturing relies on
different types of molding in a variety of shapes.
Plastic is a synthetic material that is
soft or semi-liquid when hot. The soft plastic is placed in molds, and then the
plastic cools, or sets.
After setting, the plastic is in the
desired shape and is removed from whatever types of molding were used to create
it.
Thermoplastics can be melted down and
reformed if necessary, however thermoset plastics cannot be reheated.
TL; DR (Too Long; Didn't Read)
Plastic manufacturing relies on
different types of molding processes to form liquid, melted plastic into solid
shapes.
Casting, injection molding, blow
molding, compression molding and rotational molding have different uses and
advantages in plastic manufacturing.
Plastic Molding
Using Casting
Plastic molding using casting is the
simplest method as plastic manufacturing as it requires the least amount of
complex technology.
Plastic is simply heated so it turns
into a fluid, and then transferred into a mold. The plastic is left to cool and
the mold is removed.
This process can be used for intricate
shapes and is performed under low pressure.
Injection Molding
of Plastic
Injection molding of plastic creates
high-quality three-dimensional objects that can be commercially reproduced.
The injection molding process begins by
melting plastic in a hopper. The melted, liquid plastic is injected into a
tightly closed, chilled mold.
The plastic quickly takes the shape of
the surrounding mold. Once it has completely set, the mold is opened to release
the plastic object.
The mold can generally be used many
times before needing to be replaced. Plastic items such as yogurt cups, butter
tubs, plastic toys and bottle caps use the injection molding process.
Blow Molding
Plastic Manufacturing
Blow molding is a process used for
making hollow objects such as piping or milk bottles.
In the blow molding plastic manufacturing
process, plastic is heated until molten. The liquid, molten plastic is injected
into a cold mold.
The mold has a tube set within it, which
has a particular shape when inflated.
While the plastic is molten, air is
blown into the tube and the plastic is formed around the tubing. The plastic is
left to cool and removed from the mold.
Compression
Molding of Plastic
Compression molding of plastic is the
most labor-intensive type of molding process.
Since compression molding is more
complicated, it is typically only used for large-scale production purposes
rather than mass production.
For example, boat hulls and car tires
are made using the compression molding method.
Molten plastic is poured into a mold.
Then a second mold is pressed into it.
This squeezes the plastic into the
desired shape before the plastic is left to cool and removed from the mold.
Rotational Molding
of Plastic
Toys, shipping drums, storage tanks and
consumer furniture made of plastic are all made using rotational molding.
In this method, liquid plastic forms
each object as it is added to the mold from the inside.
Two mechanical arms hold the mold in
place. The arms constantly rotate the mold at the same level, while molten
plastic is placed inside.
As the mold turns, the plastic coats the
inside of the mold to create a new hollow, plastic object.
Based in Bristol, Philippa
Jones has been a music journalist and script writer since 2007, working
across a range of radio programs in the U.K. and Australia. Her articles have
appeared in "Impact Magazine," "The Mic" and in local
newspapers. She holds a Bachelor of Arts in politics from the University of
Nottingham.
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