by Alemnew Desalegn debre markos university

1. 54321
Debre markos university
Institute of technology
Mechanical engineering department
(Manufacturing stream)
Tools, jig andfixture design presentation 1
(stretchblow molding die design)
January/04/2018 G-C

2. WELL COME
TO
OUR
PRESENTATION

3. 1. Introduction about stretch blow molding
2. Schematic setup of the machine.
3. Parameters that affect the die.
1. INTRODUCTION
DEBREMARKOS UNIVERSITY
INSTITUTE OF TECHNOLOGY
MECHANICAL ENGINEERING DEPARTMENT
1
This presentation includes:-

4. 4
 Stretch blow moulding is a process on which stretching is done
before blowing.
 The stretch blow moulding method can be applied to both
injection and extrusion blow moulding process.
 Each plastic material has a temperature limit at which it can be
stretched to get optimum orientation and properties.
 Biaxial stretch blow moulding is the method in which the
stretching is done in both longitudinal and transverse direction.
 Biaxial orientation increases the tensile strength, gas barrier
properties, drop impact strength and clarity of plastics.
 The various materials suitable for stretch blow moulding are.
PET,PVC,SAN,POM,PP/polyster, polyvinyl chloride, styrene
acrylonitire,polyacetal, ply olefines./

5. TYPES OF STRETCH BLOW MOULDING
5
 Injection Stretch Blow Moulding.
 Extrusion Stretch Blow Moulding.
INJECTION STRETCH BLOW MOULDING
 The PET preform is injection moulded in the first station and
upon proper cooling, the cavity mould half drops down and the
core rod mould half rises.
 The table indexes 90° to the conditioning station, where the
preform is conditioned by internal and external core-rod
heaters to the proper
temperature for stretch blow moulding.
 The table again indexes 90° to the third station, where the
preform is stretch blow moulded.

6. 6

7. EXTRUSION STRETCH BLOW MOULDING
7
 Suitable for processing of PVC, PET.
PROCESS:-
 Extruding a parison.
 Converting the parison into a preform.
 Blowing and stretching the preform in the
final blow mould.
a) Extrusion
b) Blowing and
conditioning
c) Stretching
d) Blowing
e) ejection

8. 8
 Stretch-blow molding is a process that
allows the forming of hollow parts such
as bottles. In a first step a preform is
injection molded.
 This latter is stored and later re-heated
above the glass transition temperature
of the material, placed into a mold where
forming takes place.
 The forming itself generally results from
three stages:

9. 9
 The preform is first stretched with a rod (low-blow
delay), and then inflated by air at low pressure (pre-blow
at 0.5 to 0.9 MPa) whilst stretching goes on. Finally,
stretching is stopped and pressure is increased up to 40
bars (4 MPa).
 The two first stages define the so-called low-blow period
whereas the last one is the blowing period. The "three-
stage" distinction is not always true in industrial context:
pre-blow often overlaps with stretching to prevent the
touching of the preform with the stretching rod.

10. 10
 As far as bottles are concerned and beside specific
properties required for the liquid that will fill the bottle, the
converter has to guaranty the transparency, the lightness,
the thickness distribution and the mechanical performances
of the container. Poly(ethylene terephthalate) (PET) is one
of the most appropriate materials for this application. For
this polymer the above-mentioned constraints imply that the
preform must be molded and blown in the amorphous state.
Material must exhibit strain-induced crystallization during
blowing while keeping high draw ability as thickness
reduction (ratio of the initial thickness of the preform to the
final thickness of the bottle) can reach values from 8 to 12
during forming.

11. 11
 These preforms are packaged, and fed later (after
cooling) into a reheat stretch blow molding 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.

12. 12
2. Schematic setup of the machine

13. 3.Parameters or factors that affect the
die
13
 Parameters are preform shape, preform temperature,
pressure and flow rate values and timing relationship
between the pressure and stretched rod activation.
Those parameters controls the desired output
characteristics such as material thickness distribution
and the amount of orientation and crystallite with the
final product.
Generally factors are
 Temperature
 Pressure
 Flow rate
 Cooling
 Timing

14. 14
Helpful videos to understand what is stretch blow moulding die design
working

15. 15