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Unformatted text preview: ry. The
film blowing process basically to form a thin tubular product that can
be used directly, or slit to form a flat film. Blown
Blown film process Plastic melt is extruded
through an annular slit die.
Air is introduced via a hole in
the centre of the die to blow up
the tube like a balloon.
Mounted on top of the die, a
high-speed air ring blows onto
the hot film to cool it.
The tube of film then continues
upwards, continually cooling,
until it passes through nip rolls
where the tube is flattened to
create what is known as a '
lay-flat' tube of film.
Air inside the bubble is also
exchanged. This is known as
IBS (Internal Bubble Cooling). Cast
Cast Film Extrusion
• In a cast film extrusion process, a thin film
is extruded through a slit onto a chilled,
highly polished turning roll, where it is
quenched from one side Blow Moulding Blow moulding is used to create hollow enclosed
components and there are two basic types of
extrusion blow moulding and injection blow
moulding and stretch blow moulding.
In extrusion blow moulding a parison or tube is
produced by extrusion. A mould is then closed
around the parison and the product is blown into
the shape of the mould with compressed air. Extrusion Blow moulding Process The blow moulding machine is based on a standard extruder
barrel and screw assembly to plasticise the polymer. The
molten polymer is led through a right angle and through a die
to emerge as a hollow (usually circular) pipe section called a
parison. When the parison has reached a sufficient length a hollow
mould is closed around it. The mould mates closely at its
bottom edge thus forming a seal. The parison is cut at the top
by a knife prior to the mould being moved sideways to a
second position where air is blown into the parison to inflate it
to the shape of the mould. After a cooling period the mould is opened and the final article
is ejected.To speed production several identical moulds may
be fed in cycle by the same extruder unit. The process is similar to injection moulding and extrusion.
1. The plastic is fed in granular form i...
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This document was uploaded on 03/14/2014.
- Spring '14