Troubleshooting: Excessive Flash

Defect: Flash----Excessive Flash

Excessive Flash is one
of those major problems that come across during the Extrusion blow molding operations.
Basically, In the process of molding, when a parison is extruded it is pinched
off at the top and bottom. The pinch-off creates surplus material in the form
of top and bottom flash.  In other words,
Flash emerge on the edges of parison beside the parting line of the mold.

Flash is an essential feature
of extrusion blow molding. Since most of the plastics can be reprocessed, the
flash is not thrown away rather used as regrind resin back with virgin
material. However, if flash is excessively being produced during the extrusion
blow molding process, it would be a defect that demands your serious attention.

There are a variety of
causes that may lead to Excessive Flash. The most probable causes of excessive
flash with recommended solutions are discussed below.

Cause:
High Extrusion rate is a major
cause of excessive flash.

Solution:
by reducing the Extrusion rate or
pressure, the problem of Excessive flash will possibly be resolved.

Cause:
Low melt temperature can also cause
Excessive Flash.

Solution:
enhance melt temperature.

Cause:
if Mold of the machine is not
properly aligned with die, it can lead to excessive flash. In other words, a
misaligned mold assembly can be a cause of this problem.

Solution:
check the alignment of mold and die
and if it is found misaligned, correct it.

Cause:
sometimes, when Mandrel or core pin
of extrusion tooling is not centered, it creates Excessive flash.

Solution:
middle the mandrel in die.

Cause:
Narrow die gap is another possible
reason of excessive flash. The area between the die and mandrel of extrusion
tolling is known as Die gap.

Solution:
by increasing the weight of
container, you will get away this problem.

Cause:
if the pre-blow air pressure or
time is excessively high, it can be a source of Excessive flash.

Solution:
simply reduce the pre-blow air
pressure or time and eventually reduce the possibility of Excessive Flash.

Cause:
too large diameter of Parison is
also considered a possible cause for the defect of Excessive flash.

Solution:
decrease the diameter of tooling.

Cause:
if the resin you are using is
displaying Excessive die swell, it may manifest into the form of excessive
flash.

Solution:
so if you are encountering this problem,
check your resin selection. You may need to change to a lower die swell resin
in order to diminish excessive flash.

In this regard, talk to
some resin specialist and seek his advice about lower die swell resins.

 Cause: if the Flash
pockets of mold are too shallow, Excessive flash may occur.

Solution:
in order to resolve the issue of
shallow pockets, consult your mold maker.

Cause:
Improper mold closure is another significant
reason that may leads to generate excessive flash during the extrusion blow
molding process.

Solution:
if you really find out that your
mold is not closing properly with perfect fit, first of all check for any
obstruction that may prevent the mold halves to accurately close. In addition,
enhance the locking and also check for any mismatch in the mold.

Pet Bottle,Mineral Water,Plastic Packaging,Pet Bottes,Containers,Plastic