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Blow Moulding Process
BLOW MOULD Blow moulding is a plastic moulding
BY
process where a thermoplastic material is
heated to its forming temperature, which is
Dr. P.C.Padhi below the plasticising temperature of the
plastic materials being used to form a
CIPET:IPT Bhubaneswar hollow tube called a parison
Blow Moulding Process Blow Moulding Process
Heated homogeneous plastic material is then
placed between two female mould halves. The mould halves are cooled through
The two female mould halves are then suitable medium through the entire process
closed and compressed air enters via an so that the blown parison when comes in
open end of the parison via a blow pin or contact solidifies immediately.
needle. The two female moulds are then separated
The air blown into the closed female mould and shaped hollow component is then
halves forces the parison to take the internal ejected or allowed to drop out and the cycle
shape of the closed mould thereby forming is repeated again.
the blown component.
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Blow Moulding Process Five Stages in Blow
Moulding Process
1. Plasticising or melting the resin
2. Parison or preform production
3. Inflation of the parison or preform in
a mould to produce the end part
4. Ejection of the part
5. Trimming and finishing of the part
Five Stages in Blow Basic Blow Moulding Process
Moulding Process
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Parts of Extrusion Blow Mould Applications of Extrusion
Blow Moulded Parts
1. Packaging for milk, fluids, medicines,
cosmetics, etc.
2. Automotive fuel tanks, oil bottles, air-
ducts, and seat-backs, etc.
3. Consumer products like toys, house-
wares, sports goods, etc.
4. Drums for chemical industries.
5. Bellow shaped shields and double-walled
carrying cases.
Applications of Extrusion Blow Mould Design Parameters
Blow Moulded Parts
Design of a blow-moulded part involves:
1.The selection of proper plastics
2.Appearance of the product
3.End use properties and
4.Cost economics
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Blow Mould Design Parameters Blow Mould Design Parameters
Design of a blow moulded bottle and other
• The property requirements vary with the shapes requires consideration of the factors
specific application of the product like like:
crack-resistance, impact-resistance,
chemical-resistance, etc. 1. Material to be blown
2. Size and weight of the product and mould
• The appearance of the part covers basic 3. Contours on the part
design along with factors such as gloss, 4. Surface texture and engraving
smoothness, wall-thickness, colour, etc. 5. Sharp corners and straight edges
6. Blow opening available and locations
7. Parting lines
Blow Mould Design Parameters Blow Ratio
• The blow-ratio of a blow moulded part
• Blow moulded articles perform better
gives the amount of stretch from the
with rounded, slanted and tapered
parison size to the part size.
surfaces.
• For cylindrical containers, blow-ratio =
• Squares and flat surfaces with sharp
(Mould or part diameter / Parison
corners should be avoided.
diameter).
• This ratio is usually between 1.5 to 3.0,
it can be maximum up to 7.
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Blow Mould Part Terminology Corner & Edge Rounding in
Blow Mould Part
Corner & Edge Rounding in Neck finish in Blow Moulded Part
Blow Mould Part
1. Rectangular containers : at least
1/3rd depth of mould half.
2. Cylindrical containers : at least
1/10th depth of mould half.
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Base Design in Blow Moulded Part Types of Blow Moulded Container
Design Factors for Container Rib Design in Blow Mould
1. The type of plastic material to be used
2. The size and shape of the container • The round containers are provided with
3. The neck finish size and design horizontal ribs to improve hoop
stiffness, and vertical ribs for
4. Type of thread compression stiffness.
5. The undercuts
6. The parting line location, • The square containers reduce stiffness,
thus losing both top load strength and
7. The surface finish bulge resistance as well.
8. The fill point and weight of the container
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Rib Design in Blow Mould Rib Design in Blow Mould
Consideration for Bottle Design Material Properties for
in Blow Mould Blow Moulding
Important structural and Mechanical
considerations in bottle design includes; 1. Good thermal stability
2. Good flowability of homogenous melt
1. Vertical strength
3. Sufficient stretchability of parison
2. Wall thickness uniformity 4. Excellent repeatability of parison weight and
3. Push-up strength length
4. Label considerations 5. Smooth parison surface
5. Rigidity 6. Compatibility with additives
6. Shape 7. Sufficient wide processing range
8. Excellent lot to lot consistency
7. Hot-fill capacity
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Blow Mouldable Polyolefin Blow Mouldable Polyolefin
Materials Materials
• Melt index describes the flow behaviour of
S. No. Name of Material Melt Index a resin at a specified test temp (190°C),
(g/10min) and a specified test weight (2,160 gm).
1 LDPE – Low Density Polyethylene 1 to 2 Higher value indicates easy flow of the
2 LLDPE – Linear Low Density Polyethylene 1 to 2 melt.
3 HDPE – High Density Polyethylene 1 to 2
4 EVA – Ethylene Vinyl Acetate 1 to 3
• Melt Flow Rate (MFR) describes the flow
5 PP - Polypropylene 1 to 4 (MFR)
behaviour of polypropylene resins at a
specified test temp (230°C) and a specified
test weight (2,160 gm).
Blow Mould Materials Blow Mould Cooling Considerations
1. Aluminium Alloy: Aircraft grade aluminium which contains
zinc, magnesium, copper and chromium is most popular 1. The type of plastic being moulded
choice for blow moulds. It has high thermal conductivity,
good machineability, light weight and resistance to 2. Wall thickness of the moulded part
corrosion. 3. Type of mould material used to construct
2. Beryllium-Copper (Be-Cu) Alloy: These alloys are used the mould
extensively due to excellent thermal conductivity, corrosion-
resistance and mechanical toughness. Their drawback is 4. Mould wall thickness between cooling
high cost and poor machineability compared to aluminium. channels and the cavity wall
3. Steel: It is mostly used for blow moulds for PVC or 5. Temperature of the cooling water
engineering resins, due to its corrosion resistance and
extreme toughness. Excellent surface finish can be 6. Volume of mould cooling water
obtained by etching process. 7. Design of mould cooling water zone
4. Miscellaneous Materials: Zinc alloy (Kirksite) can be used 8. Blow air pressure
for casting large moulds or large quantities of small moulds.
It has good thermal conductivity. 9. Surface roughness of mould cavity
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Blow Mould Cooling Blow Mould Cooling Hole Design
Advantages & Disadvantages of Extrusion Blow Moulding Process
Extrusion Blow Moulding
Advantages: It is a process for producing
containers and hollow parts preferred for
moulding high volume containers.
Disadvantages: Uneven wall thickness
components are produced and difficult to
achieve close dimensional tolerances;
relatively low accuracy of surface finishing is
achieved.
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Stages in Extrusion Blow Parison Programming
Moulding Process
• Parison programming is the control
of the wall-thickness, from top to
bottom, of the parison as it
emerges from the die-head during
extrusion
Parison Programming Pinch-off Design
• Pinch parting line is used in the areas
where the parison is to be pinched
together, creating flash.
• Pinch land length is 0.50–0.75 mm.
• Pinch angle of 45 degrees.
• Pinch relief depth is 1.5–2.0 times the
wall thickness.
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Pinch-off Design Pinch-off Design - Types
Venting Venting
Parting Line Venting:
Types of Venting in blow moulds are;
• Parting line venting is used in the areas
of the mould containing flat parting lines.
a.Parting line venting • It is added to only one side of the mould.
b.Cavity venting • Vent depths range from 0.05–0.08 mm
with a land of 6.0 mm.
c.Surface venting
• Beyond the land, vent depth is increased
to 0.25–0.40 mm through channels that
lead to the atmosphere.
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Venting Venting
Parting Line Venting: Cavity Venting:
• Cavity venting is added to areas inside the
cavity containing deep draws and flat
surfaces.
• Slotted vents are used for non-cosmetic
parts. Slot widths should be in the range of
0.40–1.25 mm.
• Pin hole vents are used for cosmetic parts.
• A pinhole vent can consist of one or a group
of holes anywhere from 0.40–1.25 mm
diameter.
Venting Venting
Cavity Venting – Slotted vents Cavity Venting – Pin hole vents
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Venting Venting
Surface Venting Surface Venting
• In order to effectively vent the air from a
mould, the surface of the mould should
be either sandblasted or lightly textured.
• This is necessary to allow the air
contained between the parison and the
mould surface to migrate through the
valleys of the mould surface finish and
exit through the vents.
Process
INJECTION BLOW
MOULDING
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Process Process
• Injection blow moulding machine cost is
• The injection blow moulding is a process
almost similarly with extrusion blow
used for mass production of plastic
moulding machine.
containers ranging from 1 ml to 2 litres
• With injection blow moulding it is possible
capacity.
to produce more bottles per cycle and
• These containers meet the exact more bottles per hour without deflashing,
dimensional tolerance and consistent to trimming, regranulation and remixing of
weight and volume. scrap at a constant weight and with
• It has got wide applications from injection moulding tolerances.
pharmaceuticals to toiletries, automotive • Injection blow moulding does not produce
to household use. a significant amount of scrap polymer like
extrusion blow moulding.
Process Process
Station - 1
• In preform mould, the molten material is
• The injection blow moulding is a injected under low pressure into the
process in which a triangular rotary mould cavity, where it forms a preform /
table indexes in 120° steps. parison around the core rod.
• Core rods mounted on the face of the • In this stage, the neck section is injection
table form the inside of the hot moulded to close tolerances and after
preform, later blown into the finished suitable conditioning, the moulds open
container and the parison is transferred on the core
rod to station 2.
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Process Process
Station - 2 Station - 3
• The parison blow takes place in station 2
and the container is formed as per the
shape and finish of the cavity. • Finally, in the station-3 the
• In this process, the parison is blown with air bottle is ejected from the core
fed internally through the core rod. rod.
• As the blown plastic contacts with the cold
blow mould, the final moulding is produced.
• The mould opens and the finished bottle is
transferred on the core rod to station 3.
Material used for Injection
Blow Moulding Process
• LDPE,
• HDPE,
• PP, STRETCH BLOW
• PS,
• SAN, MOULDING PROCESS
• EVA,
• PVC,
• PC,
• PET
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Stretch blow moulding steps Stretch blow moulding
Injection stretch blow moulding is used for
the production of high quality containers.
The process involves the following steps;
• Injection
• Stretching and blowing
• Ejection
Stretch blow moulding - Stretch blow moulding -
products and applications preform
• Carbonated and soft drink bottles
• Cooking oil containers
• Agrochemical containers
• health, oral hygene products
• Bathroom and toiletry products, etc.
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Stretch blow moulding - Stretch blow moulding –
preform preform design
• Maximum wall thickness 1.5 mm.
• Minimum wall thickness 0.35 mm.
Stretch blow moulding – Stretch blow moulding – preform
preform design neck finish for water bottles
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Stretch blow moulding – preform
neck finish for soft drinks bottles
THANK YOU
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