1. BLOW MOULD DESIGN

2. Design of Blow Moulded Parts
Chapter – 1
Design of Blow Moulded Parts
Applications of Blow Moulded Parts
Blow Moulded Containers
Blow Moulding Design Parameters
Blow Moulded Part Design Considerations
Corner & Edge Rounding
Volume
Neck, Spouts & other Openings
Closure type & size
Base Design
Attachments
Double Wall Construction
Special Considerations for Bottle Design
Plastics Materials for Blow Moulding

3. Applications of Blow Moulded Parts
Packagings for Milk, Fluids, Medicines, Cosmetics etc.
Automotive fuel tanks, Oil Bottles, Air-Ducts, Seat-Backs etc.
Consumer Products like toys, housewares, sports goods etc.
Drums for chemical industries.
Bellow shaped shields & Double-Walled carrying cases.

4. Applications of Blow Moulded Parts

5. Blow Moulded Part Design Considerations
Design of a blow moulded bottle & other shapes requires consideration
of the following factors :-
Material to be blown
Size & Weight of the product & mould
Contours on the part
Surface texture & engraving
Sharp corners & straight edges
Blow opening available & locations
Parting lines

6. Blow Moulded Containers
The majority of blow moulded part are containers ( a type of package ), serving one or more of the following functions :-
1. To allow transport
2. To protect product integrity
3. As a marketing tool
4. To protect the environment from a spill

7. A Blow Moulded Part : Terminology

8. Corner & Edge Rounding
Wall thinning in corner areas should be considered, as it creates weaker areas in the moulding.

9. Volume Adjustments in Blow Moulded Parts
Volume adjustment can also be done by using changeable inserts in the mould, for side walls. The depth of theses inserts may be changed for adjusting volume.

10. Neck, Spouts & other Openings
Each part must be designed with an opening, which may be utilized to blow it also.
Mostly this opening is utilized as neck or spout.
The important dimensions of a threaded neck finish are shown in fig.

11. Closure type & size
The closure, usually a cap or plug, is fitted to seal the bottle & allow dispensing of the contents.
Closure size can be marketing tools also.
Fig shows how a large diameter closure presents a more massive appearance.

12. Base Design
To avoid the rocking bottom phenomenon, in case of flat bottom parts, the typical solution is to provide a doomed recess in the base, called push-up.
On stretch blown PET bottles/containers, the base must be spherical due to internal pressure. Petaloid type base provides a self-standing container with several egg-shaped feet on which it balances.

13. Attachments
Eyelets can be pressed into a part, in a flange extension, that can later be drilled or pressed-out to provide an attachment site for a pin or insert.

14. Double Wall Construction
Used in the packing or casing for objects such as tools & appliances.
Double wall geometry provides greater stiffness with high cushioning effects
& impact resistance.

15. Special Considerations for Bottle Design
The most important structural & mechanical considerations in a bottle include :-
1.Vertical strength
2. Wall thickness uniformity
3. Highlight deflection
4. Push-up strength
5. Label considerations
6. Rigidity
7. Shape
8. Hot-fill capacity
If the bottle is subjected to vertical loadings, horizontal corrugations or bellows on the part should be avoided.

16. Plastics materials for Blow Moulded Parts
Blow Mouldable Polyolefins
LDPE : Low Density Polyethylene
LLDPE : Linear Low Density Polyethylene
HDPE : High Density Polyethylene
EVA : Ethylene Vinyl Acetate & Ethylene copolymers
PP : Polypropylene & Polypropylene copolymers

17. Blow Moulding Resins Grade

18. HDPE : Blow Moulding Grade
High Density Polyethylene grades are suitable for general purpose extrusion blow moulding applications.
Articles blown from these grades exhibit good stiffness. The resin offers good melt strength, ESCR and impact resistance & typically used for packaging of oil, vanaspati, general purpose containers, jerry can etc.
Physical Characteristics
Property Unit Test Method Value
Density g/cc ASTM D
MFI (2.16 kg) g/10 min ASTM D
Typical Properties
Property Unit Test Method Value
Tensile Strength at Yield MPa ASTM D
Elongation at break % ASTM D
Flexural Yield Strength MPa ASTM D
Flexural Modulus MPa ASTM D
Hardness Shore D ASTM D
Vicat Softening Point °C ASTM D
Processing Parameters
• Melt temperature in range of oC are recommended.
• Normally, temperature of oC will result in optimum ESCR properties.

19. Design of Extrusion Blow Moulds
Blow Mould Design
Chapter – 2
Design of Extrusion Blow Moulds
Extrusion Blow Moulding process
Extrusion Blow Moulds
Blow Mould Construction
Blow Mould Ancillary Elements
CAD/CAM for Blown-parts & Blow Mould Design
Mould Maintenance Program

20. Blow Moulding Process Fig-1 Fig-3 Fig-2 Fig-4
1). The blow moulding cycle starts with the mould open.
A hollow length of plastic, called a parison, is extruded down between the two halves of the mould.
Fig-3
Fig-2
Fig-4
4). Mould opens and the moulding removed
2). The mould closes over the parison.
3). Compressed air inflates the soft plastic.

21. Blow Moulding Process.
Blow moulding is usually the forming of a hollow object by “blowing” a thermo-plastic molten tube called,
parison in the shape of a mould cavity.

22. Dies for producing Parison
After leaving extruder the molten plastic enter the parison-die-head, where it forms the parison, which emerges out from die-opening.

23. Parison Die Heads for Blow Moulding
Functions of a Parison Die-Head Unit :-
To form the melt into a parison
To maintain the melt at a constant temperature
To meter out the melt at a constant pressure and rate
To form a parison with a desired wall thickness
Divergent Die-Head
Convergent Die-Head

24. Parison Swell Diameter Swell % = { (D – F) / F } * 100 Weight Swell %
Diameter Swell :- In this case the parison balloons outwards from the die, & parison diameter becomes considerably larger than the die diameter.
Weight Swell :- It occurs during the mould open time, when the parison is dropping from the die. The parison may actually shrink in length & become heavier.
Diameter Swell %
= { (D – F) / F } * 100
Weight Swell %
= { (C – A) / A } * 100

25. Parison Programming
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 is utilized
to obtain uniform wall thickness
on the Blow moulded part,
especially when part have profiles
with different diameters.
(varying blow-up ratios).

26. A Programmed Parison designed to fit a particular mould
Fig showing
a Programmed Parison with
heavier wall thickness
for greatest
expansion area
(large blow-up ratio).

27. Parison Programming device

28. A typical Blow Mould

29. Pinch-off Design Recommended Shape of a Pinch-Off with Inserts
The Pinch-Off should not form a groove, which would weaken the bottom of blown part.
A Poor Weld at Pinch-Off
Recommended Shape of a Pinch-Off with Inserts
A Good Weld at Pinch-Off

30. “Double Dam” Pinch-off Design
L = 0,5 to 1 x Parison wall thickness, DPD = 2 to 4 x Parison wall thickness
DL = 1 to 2 x Parison wall thickness,
FW = large enough to hold maximum Parison “flash” after pinch-off
D = 0 to 0,5 mm. Depending on required ease of trimming
DD = D + (0,5 x Parison wall thickness), FD = 1,5 to 2 x Parison wall thickness

31. Pinch-offs Alternate Designs
The parts of the mould that weld the ends,
and the interior portions of the parison
& also cut it or facilitate its removal.

32. Bottom Blowing after spreading the Parison
Parts with Handle
Bottom Blowing after spreading the Parison

33. Needle Blowing the Parison
Parts with Handle
Needle Blowing the Parison

34. Neck Finishing of Blow-Moulded Parts

35. Neck Finishing of Blow-Moulded Parts
Container Necks can be finished during blow moulding cycle, in a process called Pre-Finishing.
Pull-Up Neck Finishing
The neck is finished when blow pin is inserted just before the mould closes on the parison.
At the end of blow-cycle, but before mould opening, the blow pin moves upward to shear the inside diameter of the neck opening.
It is used for light weight & single use containers.
Ram-Down Neck Finishing
The blow pin is inserted into the mould after the mould closes on the parison. The blow pin moves downward to compress the plastic in the neck area & form the neck finish.
It is used when neck strength & rigidity are required.

36. Venting Positions on a Blow Mould

37. Venting Positions on a Blow Mould

38. Venting of Blow Moulds Use of Venting Plugs
Standard Plugs used for Venting
Material: Brass & Aluminium
Aluminum Plugs
D-dia
T-thickness
H-height
Slot Width
3.18
2.36
6.35
0.356
4.76
2..36
Brass Plugs
D-dia
T-thickness
H-height
Slot Width
3.18
2.36
6.35
0.254
0.356
4.76
3.96
7.92

39. VENT CLEANER

40. Blow mould design check list
Part Description :
Part Number : Material :
Material Shrinkage : Wall thickness :
Number of Cavitites : Center Line Distance :
Press Size : Platen Size :
Mounting Holes (Size) : Location :
Shut Height of Mould :- Max : Min :
Type of Blow : Blow Pin :- Dia Length
Parting Line Location :
Relief Requirements : Orientation of Part :
Pinch-Off areas : Depth of Relief :
Cavity Construction : Material :
Machined : Cast :
Model Required : CAD :
Type of Cooling : Size, in/out connectors :
Venting :- Parting Line Within Cavity
Inserts : Secondary Action :
Cavity Finish : Texture :
Engraving : General Notes :

41. View of a Closed Blow Mould, Ready to be loaded on the machine.

42. Moving Section Blow Moulds
Step-1
Blowing the parison against
the extended plug
Step-2
Retracting the plug
during the blowing operation

43. Materials for Blow Mould Construction
1). Aluminum alloy : Aircraft grade aluminum
2). Beryllium-Copper (Be-Cu) alloy
excellent thermal conductivity, corrosion-resistance
& mechanical toughness.
3). Steel : for blow moulds for PVC or engineering resins,
AISI-P20 pre-hardened steel is widely used.
For corrosive resins, AISI-420 stainless steel.
4). Miscellaneous Materials : Zinc alloy (Kirksite)

44. Blow Mould Cooling
Cooling of a blow moulded part consists of 3-separate heat transfer mechanisms :-
Conduction of heat in the wall of part
Conduction of heat in mould wall
Convective transfer of heat in cooling fluid

45. Cooling Methods for a Blow Mould
Blow Mould Half with cooling water channels

46. External Cooling Methods for a Blow Mould
It is important to locate the cooling fluid entrance near to bottom of the mould & the exit at a higher level, to eliminate any air trapping.

47. Internal Cooling Methods for a Blow Mould
Venting of blow air to create turbulence inside the part.
Blowing with a cryogenic liquefied gas to quickly cool the inside of the part.
Blowing with a fine mist of water or ice.

48. designed using Autodesk Inventor software
3D Model of a Bottle
designed using Autodesk Inventor software

49. 3D Model of a Blow Mould Cavity
designed using Autodesk Inventor software

50. Machining sequence being generated using Pro/ENGINNER software

51. Cleaning of Blow Moulds
The moulds used to produce PVC and PET bottles containers should always have highly polished cavity surfaces. It is therefore best to polish them once every two weeks.
The mould cavities used to produce PE containers should be sandblasted, because it helps in venting.
With PVC material if venting is not proper, corrosion may result.
Mould cooling lines should be checked for corrosion & flow-restrictions.

52. Mould Maintenance Program
Guide pins and bushings should be replaced at least once a year.
New guide pins & bushings will improve mould life & prevent cavity mismatch.
Whenever mould is shut-down for any length of time, all water-lines should be blown-out with compressed air and all cavities should be coated with a protective agent to prevent corrosion.

53. Designing a Blow Mould for a given part
S.No.
Product Details 1
Name
Bottle for Juice Packing 2
Material
HDPE 3
Capacity / Volume of Bottle 4
Wall Thickness of the part (mm)
0.75 5
Density (gm/cc) 6
Shrinkage (%)
2 - 5 7
Mould Temp (Deg C)
4 - 21 8
Blowing Pressure ((Kg/Sq Cm)
5 - 6 9
Projected Area (Sq Cm) 10
Weight (gms) 11
Required Clamping Force (Tonnes)
Mahine Details
Mould Cooling System
Machine to be Used 17
Type of Cooling 12
Clamping Force Available (Tonnes) 18
No. of Connectors 13
Maximum Day Light (mm) 14
Minimum Mould Height (mm) 19
Mould Lifting Arrangements 15
Platen Size (LengthxWidth) 20
Mould Size ( Height x Width x Length ) mm 16
Blow Pin Diameter (mm) 21
Mould Weight (Kg) 22
Remarks

54. Designing a Blow Mould for a given part
Part designed for a specified Capacity (200ml) in Autodesk Inventor Software

55. Designing a Blow Mould for a given part
Part Drawing :- 2-D view generated from the 3-D solid model.

56. Designing a Blow Mould for a given part
Blow Mould designed in Autodesk Inventor Software

57. Designing a Blow Mould for a given part
Blow Mould Cavity Drawing, generated from the mould design.

58. Design of Injection Blow Moulds
Blow Mould Design
Chapter – 3
Design of Injection Blow Moulds

59. Injection Blow Moulding Process
Station 1:- This is the preform mould. Here, molten material is injected under low pressure into the mould cavity, where it forms a parison around the core rod.
At this stage, the neck section is injection moulded to close tolerances.
After suitable conditioning, the moulds open and the parison is transferred on the core rod to station-2.
Station 2 :- This is where the blow takes place.
The cavity of the mould defines the shape and finish of the container.
The parison is blown with air fed internally through the core rod.
As the blown plastic contacts 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.
Station 3 :- Here, the bottle is stripped from the core rod for packing or filling.

60. Injection Blow Moulding Process

61. Plastics Materials for Injection Blow Moulding
LDPE
HDPE PP PS
SAN
EVA
PVC PC
PET etc.

62. Injection Blow Moulds
Injection blow moulds require :-
1). More complex mould engineering
2). Perform moulds
3). Blow moulds
4). Support tooling
5). Longer lead times for design & fabrication

63. Parison Layout
The outside configuration of the parison is formed by neck-ring
& the parison mould,
while the inside is formed by core-rod.

64. Parison Mould The parison mould consists of two components :-
1). the body
2).the neck-ring.

65. The blow mould forms the final shape of the container.
Injection Blow Moulds
The blow mould forms the final shape of the container.

66. Core Rods
The core-rod forms the internal diameter of the neck and parison,
when sitting in the parison mould.

67. Injection Blow Mould Design
Check-List
Is cavity steel specified right for the part ?
Is type of plating specified ?
Is nozzle size correct ?
Is nozzle seat inserted or air gapped ?
Is heat isolation at neck ring or holding diameter required ?
Is special material required for neck ring ?
Are water ports located at right place ?
Is there a sufficient no. of water ports ?
Has heat treatment been specified ?
Is neck finish correct ? etc…..

68. Design of Stretch Blow Moulds
Blow Mould Design
Chapter – 4
Design of Stretch Blow Moulds

69. Design of Stretch Blow Moulds
Injection Stretch Blow Moulding Process
Producing PET Preform / Bottle
PET Preforms
Preform Molds
Neck Finish on Performs

70. Examples of Stretch Blow Moulded Parts

71. Injection Stretch Blow Moulding Process

72. Typical Plastic Materials Used
Polyethylene-Terephthalate (PET)
Polyolefins (PE) 
PVC

73. PET Preforms

74. Preform Quality requirements
Gate-free preform.
Low preform eccentricity, no more than 0.10mm.
Low weight variation between cavities, +/-0.2g.
Low Acetaldehyde level.
Low preform temperature at exit to avoid preform scratches.

75. Preform Molds

76. Stretch Blow Mould

77. Stretch Blow Mould

78. Stretch Blow Mould

79. Neck Finish for PET Preforms