........................................................................................................................................................
Blow
Moulding
What
is Blow Moulding?
engineeringinsider
Blow moulding works as its name stated.
The molten material known as parison or preform placing it in
the mould and inflate with compressed air till it cover the mould and cool down
before the mould is removed.
Any hollow plastic product can be made with blow moulding. There
are wide ranges of hollow plastic products around us and we use it in our daily
routine life.
Here are some products that are made with blow moulding plastic bottle making machine.
§
Medical supplies
§
Household items
§
Industry products
§
Toys
§
Plastic bottles
§
Automotive parts
The blow moulding process is similar to glassblowing process.
The first production machines and products are developed in 1930
to manufacture blow moulded bottles.
After the introduction of low and high density polyethylene
which is suitable for blow moulding the market is hiked for blow moulding
products.
The blow moulding process can be done with three different
method according to product, which are
§
Extrusion blow moulding
§
Injection blow moulding
§
Injection stretch blow moulding
The main difference
between these processes is forming the parison.
Extrusion Blow moulding.
In this process the polymer is melted and it is extruded from a
die to make a parison or hollow tube.
The moulds covered the parison and with the pressurised air
blows through the needle and it inflate the shape of mould.
After this the cool air is blown and moulds are opened and eject
the complete product.
The extrusion blow moulding there are two methods for extrusion
which are continuous and intermittent.
In continuous method the parison is extruded continuously and
mould open and close to complete the process.
In the intermittent the plastic is collected by extruder and
then push it to die to make parison.
The products made with this process are bottles, toys,
appliances and automotive parts etc.
Injection Blow moulding.
In this process the polymer is injected into a core to from
hollow tube known as preform.
Then the preforms are rotated on a core rod to blow mould and is
inflated and cooled at blowing station.
The injection blow process is suitable for small bottles.
The process has three steps namely injection, blow moulding and
ejection and all this action done in single machine.
The products like medical supplies, product packages etc.
Injection Stretch Blow moulding.
This process is quite similar to injection blow moulding.
In this process the moulded preform is stretched up to decided
length to get better strength and is light in weight.
The raw material is used for this process is PET or PP and they
are stretched for better physical characteristic.
The wall thickness of final product is high than extrusion and
injection blow moulding.
The injection stretch blow moulding is divided in one step and
two step process.
The One Step process the preforms and blowing in the same
machine. This process is completed in three or four station machines.
At different stations there is different action performs namely
Injection, Conditioning, Blowing and Ejection. This process is suitable
for small to high capacity with different shapes and various size plastic
bottles.
In the Two Step process first the preform is made with injection
moulding. The preforms have necks and threads on the top.
These preforms are cooled and stored for re-heat blow moulding.
The preforms are heated generally with infrared heaters and then stretched and
blow using high pressure air in the mould.
The Two Step process is suitable for 1 litre bottles and
under plastic blow moulding machine.
There materials used for blow moulding are High Density
Polyethylene, Low Density Polyethylene, PET, PVC, Polycarbonate etc.
No comments:
Post a Comment