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Extrusion molding
Extrusion molding is used for plain plastic parts, such as plastic sticks and boards. A plastic stick
is made through pressing out the melted plastic from a round opening. The board is made through
a thin flat opening. Changing the shape of the opening, various kinds of plastic can be made.
The section deciding the shape is called a
die
. It can be compared to a tube of toothpaste. The
mouth of the tube is a die and toothpaste is melted plastic. If the mouth of the tube had a star
shape, you could squeeze out star shaped toothpaste. The star shaped plastic can be produced
in the same way.
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Blow molding
Blow molding is for making hollow objects, such as a plastic bottle. The outer surface of the bot-
tle could be formed with injection molding but inner space cannot be made. To make the hollow,
the mold for making the inside wall would be needed, but it could not be taken out from the inside
of the plastic bottle. The blow molding uses air to make the inside hollow. The melted plastic in a
form of a balloon will be placed between the molds, and air will be blown inside. Then, the plastic
bottle is made when it cools and becomes solid.
There are also other molding methods, such as vacuum molding and foam molding.
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Extrusion molding
Roller
Refrigerated water
Motor
Die : Shapes the plastic.
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Blow molding
Balloon shaped plastic
Blow air
Completed
Mold
