3. Blow molding is a molding process in which air
pressure is used to inflate soft plastic inside a
mold cavity.
The technology is borrowed from the
glass industry with which plastic
compete in the disposable and
recyclable bottle market.
Blow molding is a manufacturing process widely
used to create hollow thin-wall plastic objects
such as bottles, cases, containers, and bellows.
4.
5. Extrusion blow molding is the oldest,
simplest, and most common type of blow
molding.
Parison is formed from by forcing the plastic
through an extrusion die.
Material enters the die, flow around the
mandrel so that extrudate would be cylindrical.
The die would have a hole at the center so
that air could be blown into the cylinder.
In some blow molding operations, the air is
introduced from the bottom through an inlet.
Extrusion Blow Molding
6. Stretch blow molding is a two-stage process similar to
that of injection blow molding.
First, a test-tube like preform is made using injection
molding or a similar process.
The neck of the preforms is fully finished but the diameter
and length of the body portion are much smaller than the
final product.
The preform then undergos a stretch-and-blow process.
Stretch Blow Molding
7. The
polymer is
formed by
the
injection of
molten
resin into a
mold cavity
and around
a core pin
The
polymer is
not a
finished
product, but
it is
subjected
to
subsequent
step to
form the
final shape
Second step,
blowing of
the
intermediat
e part in a
second
mold
Because of
distinct
separation
of the two
steps, the
polymer
made by
injection
molding is
called a
preform
Injection
Blow
Molding
8.
9. Place the blow stem in an injection mold
Inject melted thermoplastic material into the
mold to create the preform around the blow
stem
Place both the preform and the blow stem into a two
piece molding chamber and inject compressed air
through the blow stem into the preform
The molded plastic will be left to cool and harden.
Once released from the mold, the plastic part can be
post-processed to have the holes rimmed or residues
trimmed.
Bottle Making Process
10.
11. Many types of materials to choose from
Quick product revisions for increased flexibility
Tooling is less expensive than Injection Molding
Each part price is less than Rotational Molding (faster
cycle)
One piece construction (no need to connect part halves)
Excellent ESCR (environmental stress crack resistance)
