The blow molding machine is based on a standard extruder barrel and screw assembly to
plasticize 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 mold is closed around it. The mold mates closely at its bottom edge thus forming a seal. The parison is cut at the top by a knife prior to the
mold being moved sideways to a second position where air is blown into the parison to inflate it to
the shape of the mold.

After a cooling period the mold is opened and the final article is ejected.
To speed production several identical molds may be fed in cycle by the same extruder unit. The process is not unlike that used for producing glass bottles, in that the molten material is forced into a mold under air pressure.

INJECTION BLOW MOLDING

Injection blow molding is used for the Production of hollow objects in large quantities. The main applications are bottles, jars and other containers. The Injection blow molding process is ideal for both narrow and wide-mouthed containers and produces them fully finished with no flash.

Injection
The injection blow molding machine is based on an extruder barrel and screw assembly which melts the polymer. The molten polymer is fed into a manifold where it is injected through nozzles into a hollow, heated pre-form mold. The pre-form mold forms the external shape and is clamped around a mandrel (the core rod) which forms the internal shape of the pre-form The pre-form consists of a fully formed bottle/jar neck with a thick tube of polymer attached, which will form the body.

Blowing
The pre-form mold opens and the core rod is rotated and clamped into the hollow, chilled blow mold. The core rod opens and allows compressed air into the pre-form, which inflates it to the finished article shape.

Ejection
After a cooling period the blow mold opens and the core rod is rotated to the ejection position. The finished article is stripped off the core rod and leak-tested prior to packing. The pre-form and blow mold can have many cavities, typically three to sixteen depending on the article size and the required output. There are three sets of core rods, which allow concurrent pre-form injection, blow molding and ejection.