Injection molding is a commonly used plastic processing method where plastic is heated and injected into a mold. There are several plastic molding methods that use the heating, forming, and cooling (HFC) process including injection molding, blow molding, and extrusion blow molding. Blow molding uses a preform tube called a parison that is positioned in a mold and inflated with air to form the final shape. Extrusion blow molding creates the parison directly from an extruder while injection blow molding injects molten plastic into a mold to form the parison. These methods are used to manufacture various plastic products like bottles, containers, and toys.

1. Abdul Rehman
14-MCE-55
UET-Lhr

2.  INJECTION MOLDING.
 BLOW MOLDING.
 INJECTION BLOW MOLDING.
 EXTRUSION BLOW MOLDING.
 STRETCH BLOW MOLDING.

3.  Injection molding is one of the most
commonly used processing method for the
plastic components.
 It is defined as
“ A manufacturing process for forming
objects, as of plastic or metal, by heating
the molding material to a fluid state and
injecting it into a mold “.

4.  All the methods used for processing of plastics
like Injection molding, blow molding ,
thermoforming , extrusion e.t.c. , have a raw
material i.e. plastic in some form which is then
heated , formed and cooled to get the desired
design and product.
 So , the term to memorize in all plastic processing
methods is HFC ( heating , forming , cooling ).

5.  It is used to process thin walled plastic
parts for a wide variety of shapes and
products .
BASIC PRINCIPLE
Plastic material is melted in a heated
chamber and then injected in the mold ,
where it cools and finally the finished
plastic part is ejected out of the cavity .

6. The raw material in the form of
powder/pellets is introduced through
hopper into the cylinder.

7.  Hopper is a tapered container working with a
hopping motion to transfer grains into cylinder.
 Inside the cylinder there is a piston /plunger
which is used to move the material from
cylinder into the mold.
 Heating arrangement is placed above and below
the cylinder .
 The mold is in two halves , it has a mold cavity
and the mold has two ejector pins.

8. When the plastic solidifies the ejector pins are
hydraulically moved backwards .
The cavity will be filled by the pressure of the piston
and the mold should not be opened until the plastic
solidifies.
As soon as the plastic is melted it will be pushed by
the piston into the sprue through which the material
would go into the mold cavity .

9. Clamping : The two halves
of mold are tightly closed
before the molten plastic
is injected.
Injection : Injection of
raw material from hopper
into cylinder to the cavity
is called the injection
stage.
Cooling : The material is
cooled for at least 30-60
sec.
Ejection : The 2nd mold
plate moves back by
ejector pins and the
product is tapped out .

10.  PRODUCTION RATE :
Production rate depends upon the clamping and de-
clamping time of the mold halves.
 INJECTION TIME:
The filling process should be optimal not too slow in
order to stop the production of cracks.
 SHOT VOLUME :
The amount of material that is injected into the mold
is referred to as shot volume.
 PRESSURE and CYCLE TIME :
The pressure applied is in the range of 35-140 MPa
while the cycle completes in 2-60 sec.

11.  Acetate.
 Acrylonitrile butadiene styrene (ABS).
 Cellulose acetate.
 PVC ( poly vinyl chloride.)
 Polycarbonate.
 Polyesters.
e.t.c.

12.  Higher production rate.
 Minimum wastage of material.
 Complex geometry can easily be produced.
DISADVANTAGES
• Tooling cost higher.
• High setup cost.
• Large undercuts can not be formed.

13.  It can be used to produce thin walled plastic
products of varying size and dimensions
For Example:
 Medical devices such as surgical syringes.
 Open container like buckets.
 Plastic housings of different tools.
 Daily use products such as tooth brushes.

14.  “ It is a plastic processing technique which is
used to produce hollow plastic parts by
inflating a heated plastic until it fills a mold
and forms the desired shape”.
 The raw material used for processing in blow
molding is called parison.
 Parison is a preform tube that is hollow and
it has a hole at one end.

15. After sufficient cooling , the mold opens to release the product.
The mold closes over the tube and the hot air is injected from the
blower into the hollow tube . The air expands the tube against the
sides of the mold.
Above the preform there is a blower and the preform is positioned
between two split halves of the mold.
First the parison is obtained by means of extrusion or injection
molding process.

17.  Cooling temperature of plastic material.
 Air pressure required ( usually 2-4 Mpa).
 Cooling time.
o Pressure is exerted both axially and radially
, both cavities are pressurized with a non-
reactive gas such as argon.

18.  Extrusion blow molding.
 Injection blow molding.
 Stretch blow molding.
 MAJOR DIFFERENCE:
All the types have one primary difference
that is making of parison by extrusion ,
injection and stretching .

19. In this process the blow
molding machine is based
on a standard extruder
barrel and screw
assembly to plasticize the
polymer.
The polymer is heated
inside the barrel , the
molten polymer is led
through a right angle and
through a die to emerge
as a hollow section.
When the parison has
moved enough length it is
cut through by a knife
and fits inside the bottle
mold .
The bottle mold moves
toward the jet where the
air blows and the product
is obtained after cooling .

21. The
process is
divided
into three
sections
Injection. Blowing. Ejection.
The injection blow molding is used for the production of
hollow objects in large quantities . The main applications
are bottles, jars and other containers.

23. This process is divided into four steps.
Injection : The material is injected as discussed
before.
Stretching : One conditioned to correct temperature ,
the parison is stretched by the blow pin/stretch rod
that stretches it longitudinally .
Blowing : Using two levels of air pressure , the
preform is blown circumferentially.
Discharge : After a set time for cooling the molds open
and the product is removed .
.
Stretch blow molding is also carried out by injection . Used the
production of high quality containers.

25.  Low tooling costs .
 Fast production rates .
 Ability to mold complex parts .
 Little scrap generated .
 Large hollow shape can be produced .
 Produced parts can be recycled .
DISADVANTAGES
• Limited to hollow parts .
• Thick parts cannot be manufactured.

26.  Different types of plastic products can be
manufactured by this process such as:
 Bottles in different shapes and sizes.
 Jars and containers.
 Fluid oil tanks.
 Mugs.
 Toys. etc.