Suppliers of Plastic Blow moulding machines, blow moulding machine, stretch blow
moulding machine, film blowing machines, pet stretch blow moulding machines. Extrusion
blow moulding machines, Injection Blow moulding machines , Stretch blow moulding machines ,PET Stretch Blow Moulding Machines, fully automatic stretch blow moulding machines.
Extrusion blow molding
blow moulding machine, stretch blow moulding machine, film blowing machine, film blown machine, pet stretch blow moulding machines, blow moulding machines, plastic blow moulding machine,
In Extrusion Blow Moulding (EBM), plastic is melted and extruded into
a hollow tube (a parison). This parison is then captured by closing it
into a cooled metal mold. Air is then blown into the parison, inflating
it into the shape of the hollow bottle, container or part. After the plastic
has cooled sufficiently, the mold is opened and the part is ejected. Extrusion
Blow Moulding processes may be either continuous (constant extrusion of
the parison, or intermittent. Examples of parts made by the Extrusion
Blow Moulding process include dairy containers, shampoo bottles, and hollow
industrial parts such as drums.
Basic polymers, such as PP, HDPE, PVC
and PET are increasingly being coextruded with high barrier resins, such
as EVOH or Nylon, to provide permeation resistance to water, oxygen, CO2
or other substances. In dairy applications, it is possible to extrude
a black light-blocking layer in the center layer of containers, with opaque
white resin used in the inner and outer layers.
Compared to injection molding, blow molding
is a low pressure process, with typical blow air pressures of 25 to 150
psi. This low pressure process allows the production of economical low-force
clamping stations, while parts can still be produced with surface finishes
ranging from high gloss to textured. The resulting low stresses in the
moulded parts also help make the containers resistant to strain and environmental
stress cracking.
Stretch blow moulding
In the Stretch Blow Molding process, the plastic is first molded into
a "preform" using the Injection Molded Process. These preforms
are produced with the necks of the bottles, including threads (the "finish")
on one end. These preforms are packaged, and fed later (after cooling)
into an Extrusion Blow Moulding blow moulding machine. In the SBM process,
the preforms are heated (typically using infrared heaters) above their
glass transition temperature, then blown using high pressure air into
bottles using metal blow molds. Usually the preform is stretched with
a core rod as part of the process. The stretching of some polymers, such
as PET (PolyEthylene Terepthalate) results in strain hardening of the
resin, allowing the bottles to resist deforming under the pressures formed
by carbonated beverages, which typically approach 60 psi.
The main applications are bottles, jars
and other containers. The Injection blow moulding process produces bottles
of superior visual and dimensional quality compared to extrusion blow
molding. The process is ideal for both narrow and wide-mouthed containers
and produces them fully finished with no flash. A sign of injection blow
moulding is the seam where the two halves of the mold meet.
Courtesy : http://plastics.inwiki.org/Blow_molding
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